HomeMy WebLinkAbout14420 ORD - 08/09/1978AN ORDINANCE
ADOPTING THE NATIONAL ELECTRICAL CODE, 1978 EDITION;
MAKING IT UNLAWFUL TO UNDERTAKE THE INSTALLATION OF
ELECTRICAL EQUIPMENT WITHOUT A PERMIT THEREFOR, EX-
CEPT AS OTHERWISE PROVIDED; ESTABLISHING INSPECTION
PERMIT FEES; ESTABLISHING INSPECTION DUTIES AND
AUTHORITY; ADOPTING CERTAIN OTHER REGULATIONS; PRO-
VIDING PENALITIES FOR VIOLATION; REPEALING ORDINANCE
NO. 12570 AND SECTIONS 13 -90 through 13 -136 OF THE
CODE OF ORDINANCES, CITY OF CORPUS CHRISTI, 1976,
AS AMENDED; PROVIDING FOR PUBLICATION; PROVIDING FOR
AN EFFECTIVE DATE FROM AND AFTER SEPTEMBER 1, 1978.
BE IT ORDAINED BY THE CITY COUNCIL OF THE CITY OF CORPUS CHRISTI, TEXAS.
CHAPTER 1 - TITLE AND SCOPE
Section 1 -1: TITLE: The title of this ordinance shall be "The Corpus Christi
Electrical Code," and may be cited as such and it will be referred to in this Ordinance
as "this Code."
Section 1 -2: The "National Electrical Code, 1978," a copy of which is on file
in the office of the City Secretary, is hereby adopted as part of this Code to the
same effect as if copied verbatim herein and shall be in effect except as it may be
in conflict with the provisions of this Ordinance.
Section 1 -3: SCOPE: This Code shall govern all installation of electrical
conductors or equipment hereafter made, and all existing installations which are
altered, or for which the use has changed. Repair and maintenance work shall be
such that if any "electrical conductor or equipment" is removed and later replaced,
same shall be replaced in accordance with the provisions of this Code.
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Section 1 -4: LOW ENERGY CIRCUITS: Permits requirements of this Code shall
not apply to low voltage electrical conductors or equipment installation meeting
the requirements of Article 720 and Article 725 of the National Electrical Code
1978 Edition.
Section 1 -5: OTHER PERMITS: All construction covered by other ordinances
and codes of the city, including all sign structures, sign attachments to buildings,
and /or foundations shall not be initiated until the proper permits have been issued
in compliance with such codes and ordinances.
Section 1 -6: RESPONSIBILITY FOR SAFE WORK: This Code shall not be construed
to relieve from or lessen the responsibility or liability of any person owning,
operating, or installing electrical conductors, devices, appliances, fixtures,
apparatus, motors, or equipment for damages to persons or buildings caused by any
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defect therein; nor shall the City be held liable for damages by reason of the
MICROFILIVf��. , _
enforcement of this Code.
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CHAPTER 2 - DEFINITIONS
Section 2 -1: DEFINITIONS: Words when not otherwise separately defined shall
have meanings which conform to the meanings set out in the National Electrical Code,
1978 Edition, if set out; otherwise, they shall have their usual meanings.
Section 2 -2: BOARD: Board shall mean the Electrical Advisory Board as con-
stituted and appointed by the City Council.
Section 2 -3: CITY: City shall mean the territory within the corporate limits
of the City of Corpus Christi, Texas, or the legally constituted governing bony
thereof, its agents and its officers.
Section 2 -4: CHIEF ELECTRICAL INSPECTOR: The employee of City appointed by
the City Manager.
Section 2 -5: INSPECTOR. Inspector shall mean an individual who has been
designated by the City of Corpus Christi, as an inspector.
Section 2 -6. LICENSED ELECTRICIAN: Licensed electrician shall mean that the
person has made application to the Electrical Advisory Board and has satisfied the
Board that he is qualified to do the work stated in the application; that he has
paid the necessary license fees to date; and that his name is carried in the records
of the Chief Electrical Inspector as a person authorized to do electrical work as
defined in this Code. Licensed electrician shall include any individual licensed
by some other governmental jurisdiction when a license has been issued under the
provisions of the Electrical Licensing Ordinance without examination.
Section 2 -7: MAINTENANCE: Maintenance shall mean the act of keeping in a
state of safe operating condition any conductor or piece of equipment used inside
or outside, attached or connected to any building electrical system by replacement
of units or elements thereof, but shall not include additions to, or replacement
of an existing system or branch thereof.
CHAPTER 3 - ADMINISTRATION AND
ENFORCEMENT
Section 3 -1: RESTRICTION ON EMPLOYEES: No employee of the Building Inspection
Division, except one whose only connection is as a member of a board or committee
appointed by the City Council, shall be financially interested in the furnishing
of labor, material, or equipment for the installation, alteration, or maintenance
of electrical wiring, fixtures, or equipment, or in the making of plans or specifica-
tions therefor, unless said employee is the owner of the property on which the installation
exists or is planned to take place.
Section 3 -2: CHIEF ELECTRICAL INSPECTOR: The Chief Electrical Inspector is
hereby designated as the person responsible for the administration and enforcement
of the Corpus Christi Electrical Code, and who shall discharge the duties and have
the authority hereinafter provided. The Chief Electrical Inspector may delegate
said authority to inspectors and the other employees of the Building Inspection
Division as may be required to carry out his duties. The Chief Electrical Inspector
shall be responsible to the Building Official, the Director of Inspections and
Operations, and the City Manager, each of whom are authorized to act in lieu of
and with the same authority as the Chief Electrical Inspector.
Section 3 -3: POWERS OF INSPECTORS: The Chief Electrical Inspector and
Inspectors shall have the following powers:
(a) To enforce the provisions of this Code and to arrest any person who
violates any of such provisions. For such purpose, the inspectors shall have
the powers of a Police Officer.
(b) To enter any house or premises by due process of law, if necessary,
during reasonable hours, or while any electrical wiring or fixtures or equipment
is being installed; to examine any electric wiring or installation of electrical
wiring, fixtures or equipment therein, in the performance of official duties.
(c) To order electric service disconnected where improper or defective
wiring exists or where electrical construction or equipment has been installed
without a permit as required herein.
(d) To order compliance with provisions of this Code where a change of
occupancy occurs in a building which requires changes or alterations to existing
wiring,;
(e) To disconnect electrical service or services, in cases of emergency
where necessary for safety of persons or property or where electrical equipment
may interfere with the work of the Fire Department.
(f) To attach to electrical equipment or electrical meters any official
notice or seal which might be necessary to prevent the use of electricity; and
it shall be unlawful for any person to use any such seal or break, change, destroy,
tear, mutilate, cover or otherwise deface or injure any such official notice or
seal posted by any Inspector.
Section 3 -5: LIABILITY OF INSPECTORS: Where action is taken by the Chief
Electrical Inspector or other Inspectors to enforce the provisions of this Code,
such acts shall be done in the name of and on behalf of the City, and the inspectors
in so acting for the City shall not render themselves personally liable for any
damage which may accrue to persons or property as a result of any act committed
in good faith in the discharge of their duties, and any suit brought against any
the use of said plant site and the conduct of general operations is such that
the plant site is inaccessible to the general public and the operations on the
plant site involve the assembly, disassembly, reassembly, alterations or im-
provements under the supervision of a Registered Professional Architect or a
Registered Professional Engineer, no permit shall be necessary and no inspection
shall be performed by the City for electrical work in the erection of the plant
or the assembly, disassembly, remodeling, alterations or improvements of the
plant or any portions thereof used in any manufacturing process, pilot plant use,
laboratory testing or use of any mechanical process equipment or laboratory test-
ing of chemical or chemical manufacturing equipment" Any building used principally
as office building, shipping docks, assembly room, restrooms, warehousing, and
not directly related to the manufacturing or testing of equipment or operations,
shall not be exempt under this section from the necessity of obtaining a permit
and any construction or repair of any such building or structure shall be required
to have a permit and shall be permitted only under a permit as for the same type
of building elsewhere within the City limits. In order to qualify for an exemption
of the provisions hereof, an affidavit shall first be filed in the office of the
Building Inspection Division of the City of Corpus Christi, setting forth suffi-
cient facts to show that the affiant is entitled to the exemption requested, on
the form provided by the Building Inspection Division.
(f) Permits and inspections are not required for construction, repair or
alteration of any building which is being used exclusively in connection with
the ranching or agricultural use of any tract of land of ten acres or more in
area, within the City of Corpus Christi, at the time of annexation so long as
the entire premises being used for agricultural or ranching purposes at the
time of annexation is not converted to any other use. Any building for re-
sidential occupancy shall not be exempt under this section from the require-
ments for permits and inspections.
Section 4 -2: PERMIT FEES: Before proceeding with the installation,
alteration of or the addition to any electrical wiring or equipment within the
City, the individual in charge of such proposed work shall first file with the
City an application requesting a permit to carry on such work and the necessary
inspections and pay fees to the City in accordance with the following schedule:
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inspector by reason thereof, shall be defended by the City Attorney until final
termination of the proceedings contained therein.
Section 3 -6: SPECIAL RULING: If a special ruling by the Chief Electrical
Inspector is necessary to govern electrical construction for some particular
occupancy or building not covered by this Code whereby all wiring for similar
types of occupancy or building will be established for the future, a copy of
such ruling shall be approved by the Board before it becomes effective.
Section 3 -7: SPECIAL PERMISSION: The electrical regulations of this Code
may be modified or waived by special permission in particular cases where such
modification or waiver is reasonable, does not differ from the intent of this
Code, and does not create an injustice. Such special permission shall in all
cases be obtained from the Chief Electrical Inspector in writing and shall be
approved by the Board and entered into its minutes prior to starting the work.
CHAPTER 4 - PERMITS AND FEES
Section 4 -1: PERMITS REQUIRED: It shall be unlawful for any person, firm
or corporation to install or cause to be installed, or to permit any person to
install any electrical wiring, fixtures, or equipment or to make any alterations,
additions, changes or repairs within the scope of this Code without first having
procured a permit therefor issued by the Chief Electrical Inspector, except as
provided herein. There shall be one permit for each building for which rough
work for electrical conductors, or electrical equipment is installed. Accessory
buildings, tourist cottages or group houses shall not be considered separate build-
ings when the work is to be installed as one complete project, and at one time;
except where separate switches or meter loops are installed thereon.
Section 4 -2: PERMITS NOT REQUIRED:
(a) No permit shall be required for the installation of electrical conductors
or equipment to be installed where such installation is in accordance with the plans
and specifications approved by the City, and where such installation will be within
and on premises within the control and supervision of the State Highway Department
of Texas, and where such installations will be a part of highway facilities operated,
maintained or controlled by said State Highway Department of Texas.
(c) No permit shall be required for maintenance work performed by a Licensed
Electrician on the premises of his employer.
(d) No permit shall be required of an established refrigeration or air -
conditioning firm or organization for the replacing of a refrigeration or
air- conditioning system motor by another motor of the same horsepower and rating.
(e) Where any industry occupies a site of twenty (20) or more acres and
(a) Permit Fees Required:
Construction Loop ------------------------ --------------------------------- $2.00 ea.
*Circuits -------------------------------
---------- -- ---..................
2.00 ea.
Fixtures, Residential ____________________ _____ ____ ___ _____ __ ____________ 0.20 ea.
Fixtures, (Commercial Building) ___________ __ ______ ___ ___ ________ ____ ___ __ 0.20 ea.
Motor 1 H.P., and smaller __________________ _____ _______ ____________ __ ____ 2.00 ea.
Motor over 1 H.P. to and including 10 H.P. _____________ ____ __ ____________ 4.00 ea.
Motorover 10 H.P. ------------------------------------------------------- 8.00 ea.
Services up to 100 Amperes _________________ _______ _________________ ______ 2.00 ea.
Services 101 to 200 Amperes ________________ __________________ _____ _ ____ __ 6.00 ea.
Services 201 to 400 Amperes -------------- ----- ---- --- ----- -- -- ---- - ----- -10.00 ea.
Services over 400 Amperes .------------------ -- ----- --- -- ---- -------- ----- -20.00 ea.
Services each additional meter ---------------- ------ ------ ----- ------- - -- 2.00 ea.
Appliances ( trash compactors, dishwasher, disposers, etc.) -------- - - - --- 2.00 ea.
Equipment- Heating (Heating and Commercial Cooking
Units and Hot Water Heaters)----------------- ---- -- --------- ----- - - -- - -- 2,00 per 5KW
or fraction
thereof
Equipment-Moving picture projector 10.00 ea.
Equipment -X Ray Machine---------------------------- ------- --- ------ -- - - - -- 10.00 ea. '
Equipment - Welding Machine------------------ ---- ---- ------- -- ----- --- ---- -- 4.00 ea.
(transformer type)
Equipment - Gasoline pump or dispenser----------------- ---- -- --- ----- ------- 4.00 ea.
Equipment - Elevators ------------------------------ --------- -------- - - - - -- -10.00 ea.
Equipment - Swimming Pool__________________
--------------------------_-_-_-_-_-_- _ -_-_-_-_-_-_---_--_--_-_-_-_-_-_-_- _- _- _- _- _-- 4.00 ea. Equipment - Others 10.00 ea.
Si ns -More than 4 transformers
per Transformer)----------------------------- ---------------- - - - - -- - -- 2.00 ea.
General repairs not including any of the above------------- ------- -- - - - --- 4.00 ea.
*The term "circuit" herein shall mean each main feeder, submain or branch
circuit, for electrical services; and each fused or other type of automatic
cutout protected wire of a final branch multiwire circuit. Each such circuit
shall be charged for and considered as a separate cirucit within the terms of
this section.
(b) RESIDENTIAL: An alternate fee schedule for one and two family dwellings,
apartments, townhouses and condominums shall be two cents per square foot of the
main buildings excluding garages.
(c) If the office of the Chief Electrical Inspector has not been notified
within seventy -two (72) hours (Saturday, Sunday and Legal Holidays excepted) after
a specific job is started, then the permit fee shall be doubled. The collection
made is to help defray the additional cost of inspecting work already done and
issuing a permit under such circumstances and is not a penalty and is not pre-
clusive of any remedy otherwise available to the City to enforce this Code.
(d) Permit applications covering the installation of motors on any job shall
specify each motor individually and no grouping of motors per machine, or other
such grouping of horsepower shall be permitted.
(e) In the event the total fees per installation charged are less than Four
($4.00) Dollars then the minimum permit charge of $4.00 shall apply. If such total
fees exceed the sum of Four ($4.00) Dollars the greater amount shall be charged.
(f) In the event that an inspection is made and the resultant discovery is
that work for which a permit is required by this Code has been done but the required
permit has not been issued, then a $10.00 investigation fee shall be added to
the permit fee.
(g) When an inspection is made as required by this Code, and the work
as completed fails to pass so that an additional inspection is required, then
a Five ($5.00) Dollar reinspection fee shall be charged. '
(h) Fees for permits which require inspection outside the City limits
shall be increased by Ten ($10.00) Dollars.
(i) Agencies of the federal, state, county and city governments are
exempt from the payment of fees in connection with the construction or repair
of buildings used, owned, and located on property owned by said governmental
agencies. Permit fees for public schools and other political subdivisions
having ad valorem tax - exempt status, and for church sanctuaries and all other
State constitutionally exempted ad valorem tax entities shall be fifty (50X)
per cent of the regular permit fee.
(j) Fees for permits for installations in buildings or building components
which are manufactured and inspected outside the City limits prior to being
moved into the City may be increased by the Building Official once annually per
manufacturing plant by twenty ($.20) cents per mile plus Twenty ($20.00) Dollars
per 200 miles for the distance between the City and the plant, to allow for annual
in -plant inspections.
Section 4 -4: APPLICATION FOR PERMIT: Application for permits shall be made
in writing upon forms provided by the City for that purpose. When required by
the Chief Electrical Inspector, the application shall include a diagram or plan
showing clearly the character and kind of wiring or installation of fixtures or
equipment work to be done. The plan or diagram shall show the manner in which
the electrical installation is to be made and /or the character of any repairs to
any existing definite scale, showing the point at which service connection is
required, the site of the feeders and sub - feeders, the location of service switches
and centers of distribution, the arrangement of circuits and the number of outlets
connected thereto.
Section 4 -5: PERMITS -- TO WHOM ISSUED: Permits shall be issued to:
(a) Licensed Master Electricians, qualified to secure permits as determined
by Ordinance of the City providing for the licensing of electricians, or their
duly authorized Agents, who shall be certified to the Chief Electrical Inspector
by affidavit stating that said Electrician assumes all and full responsibility
for any permit issued to said Agent. This affidavit shall be kept in file after
it has been approved by the City Attorney.
(b) Property owners for electrical installations or maintenance in single
family dwellings owned and occupied by them as their homes.
Section 4 -6: CHIEF ELECTRICAL INSPECTOR SHALL ISSUE PERMIT: When the
Chief Electrical Inspector finds the application, the diagram or plans and
specifications to be correct and all fees paid, he shall cause the permit to
be issued. Upon receipt of such permit, the electrician may start or cause
to start the proposed job and make the installation described in his applica-
tion, requesting inspection by the Chief Electrical Inspector in the proper
sequence as the work progresses.
Section 4 -7: PERMITS FOR PART JOBS: When one electrician completes the
rough work, in whole or in part, on any electrical wiring or installation of
fixtures or equipment and a second electrician is called upon to complete the
work in whole or in part, then, in that event, a separate permit is required
for which regular fees shall be paid for the work to be done. Each electrician
shall be held responsible only for the work installed by him. Before the second
electrician is issued a permit for the completion of electrical wiring or in-
stallation of fixtures or equipment, the Chief Electrical Inspector shall first
notify the electrician holding the original or first permit, if he can be found,
that the second permit is proposed to be issued. The issuance of the second
permit shall cancel the first permit and no refund of fees paid for such can-
celled permit shall be made.
Section 4 -8: TIME LIMITATION OF PERMITS: If electrical wiring or in-
stallation of fixtures or equipment work authorized under a permit is not
started within sixty (60) days after issuance of such permit, or if the work
is started and then discontinued and the work remains discontinued for a period
of sixty (60) days, the permit shall become void, and no work shall be done on
the premises until a new permit is issued and all necessary fees paid. No re-
funds shall be made for permits that have become void.
Section 4 -9: REVOCATION OF PERMITS: The Chief Electrical Inspector shall
have the right to declare a permit null and void if there has been misrepresenta-
tion of facts or any violation of the provisions of this Code and after any
such declaration no work shall be performed until a new permit is issued, and
all fees have been paid.
Section 4 -10: REFUND OF PERMIT AND INSPECTION FEES: An electrical permit
may be cancelled upon written application by the applicant at any time within
sixty (60) days of the date of its issuance. If no work has been done under such
permit, a refund may be paid when formally requested in writing by the applicant;
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provided that the City shall retain Eight Dollars ($8.00) to cover the cost
of auditing the fee and preparing the request for refund.
CHAPTER 5 - INSPECTIONS
Section 5 -1: INSPECTIONS REQUIRED: It shall be unlawful for any person,
firm or corporation to make connections from a source of electrical energy to
any electrical wiring, devices or equipment on an installation for which a permit
is required, as set forth in this Code, until a Certificate of Approval has been
issued by the Chief Electrical Inspector authorizing such connection and the use
of such wiring devices or equipment.
Section 5 -2: ROUGH INSPECTION: When the rough wiring or installation work
is completed on any premises,the person responsible therefor shall notify the
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Chief Electrical Inspector that the job is ready for inspection, giving proper
identification of the work, address and permit number. The Chief Electrical
Inspector shall then make an inspection of the electric installation. If said
wiring or installation work has been installed in accordance with the terms and
provisions of this Code, the Chief Electrical Inspector shall sign the inspection
card, noting thereon the date of approval of the work. More than one rough.in-
spection may be made without charge when the progress of construction requires
such inspection.
(a) Faulty Work: If the electric wiring or installation of fixtures or
equipment is found to be faulty, or incorrectly or defectively installed, the
Chief Electrical Inspector shall notify the responsible person who installed
such work of the changes necessary to be made in order that the work may con-
form to this Code.
(b) Correction of Faulty Work: The permittee shall within forty -eight
(48) hours from the time of notification make or start to make the changes
ordered and shall proceed with the work until the same is completed. Upon
completion thereof and payment of the Reinspection Fee, permittee shall notify
the Chief Electrical Inspector to the effect that faulty work has been corrected.
The latter shall then cause the reinspection to be made, and if said work is
found to comply with this Code, sign the inspection card noting thereon the date
of approval of the work. If the Chief Electrical Inspector shall again find the
work incorrectly installed, the permittee shall be notified of the necessary
changes, and the permittee shall pay an additional Reinspection Fee. If the
permittee fails to correct the faulty work within a reasonable time, the Chief
Electrical Inspector shall refuse to issue to any such person any further permits
until said work in question is corrected and approved.
Section 5 -3: FINAL INSPECTION: Upon the completion of all electrical
wiring and installation of fixtures or equipment in any building, or any premises,
the permittee shall notify the Chief Electrical Inspector that the work is ready
for final inspection, giving the Electrical Permit Number and Street Address;
and the Chief Electrical Inspector shall then make the inspection, and if any
faulty or defective wiring or equipment is found, the permittee shall be notified
of the changes to be made in order that such work shall comform to this Code. If
such work is found to be correctly installed, replaced or repaired, the Chief
Electrical Inspector shall endorse approval upon the inspection certificate
stating that the wiring or installation work has been installed in accordance
with the provisions of this Code.
Section 5 -4: WORK LEFT OPEN: It shall be unlawful for any person to cover
or cause to be covered any part of a wiring installation with flooring, lath,
wall board or other material until the Chief Electrical Inspector shall have
approved the wiring installation in part or as a whole, except as herein set
forth.
Section 5 -5 INSPECTOR'S REMOVAL REQUEST: It shall be the duty of the
Chief Electrical Inspector to cause all abandoned dead wire, unused poles or
electrical apparatus on the outside of the buildings or in streets or alleys
to be removed at the expense of the owners thereof, by giving the said owners
written notice.
Section 5 -6: INTERFERENCE: It shall be unlawful for any unauthorized
person to in any manner change or alter electrical conductors or equipment in
or on any building. If in the course of the erection of a building or structure,
electrical conductors or equipment have previously been installed in such position
as to interfere with the erection or completion of the structure; notice shall
be immediately given to the authorized person or firm using the electrical con-
ductors or equipment, who shall accomplish this needed change in accordance with
this Code.
Section 5 -7: PERIODIC GENERAL INSPECTION: The Chief Electrical Inspector
shall inaugurate periodic reinspections of installations of all electric wiring,
electric devices, and electric equipment now installed, or that may hereafter be
installed, and within the scope of this code and when.the installation of any:
such wiring, devices or equipment is found to be defective, dangerous or in
an unsafe condition, the person, firm or corporation owning, using or operating
the same shall be notified in writing and shall make the necessary repairs or
changes required to place such wiring, devices, or equipment in a safe condition
within five days, or any longer period specified by the Chief Electrical Inspector
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in said notice. The Chief Electrical Inspector shall immediately order the dis-
connection, or discontinuance of electrical services to such wiring devices, or
equipment until same has been made safe as directed.
Section 5 -8: ELECTRICAL SERVICE CONNECTION: It shall be unlawful for any
person, firm or corporation to make connections from a source of electrical energy
to any electrical wiring device or equipment which has been disconnected by order
of the Chief Electrical Inspector or the use of which has been prohibited for
reasons herein set forth until a certificate of approval has been issued by him
authorizing the reconnection and use of such wiring, devices or equipment.
(a) It shall be unlawful for any unauthorized person, firm or corporation
to disconnect any service, except in cases of emergency.
Section 5 -9: SERVICE OF NOTICE: If tie person to whom any order or notice•
issued pursuant to the provisions of this Code cannot be found after reasonable
search has been made, then such order or notices may be served by posting same
in a conspicuous place upon the premises occupied by said person or the premises
where the defects recited in the order or notice are alleged to exist or on the
premises which may be deemed unsafe or dangerous. Such service shall be equiva-
lent to personal service of such order or notice. An order to comply with the
terms of such order or notice shall be sent by mail in sealed envelope with postage
prepaid and directed to the address of the person performing the electrical work
or the address of the owner, lessee or occupant of the premises where the defects
recited in the order are alleged to exist and shall be equivalent to the personal
services of such order.
CHAPTER 6 - STANDARDS
Section 6 -1: STANDARDS FOR ELECTRICAL EQUIPMENT AND SIGNS: Conformity of
electrical equipment with the applicable standards of the Underwriters' Laboratories,
Inc., shall be prima facie evidence that such equipment is reasonably safe to persons
and property. Only standard parts and materials approved by Underwriters' Laboratories,
Inc., or by the Chief Electrical Inspector as set forth in Chapter 8, herein, shall
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be permitted in electrical repair or maintenance work. Conformity of all types of
electrical signs with applicable standards of the Underwriters' Laboratories, Inc.,
National Electrical Safety Code or electrical provisions of other safety codes
which have been approved by the American National Standards Institute shall be
prima facie evidence that such installations are reasonably safe to persons and
property.
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CHAPTER 7 - LOCAL ENVIRONMENTAL, ATMOSPHERIC AND
SOIL CONDITIONS
Section 7 -1: GENERAL: Due to climatic conditions prevailing in and about
Corpus Christi, certain special rules covering electrical wiring and equipment
installations are set forth herein, and certain exceptions are taken to the
rules and regulations of the National Electrical Code to raise the safety level
of electrical installations and prevent the rapid deterioration of electrical
materials and equipment from severe atmospheric and underground corrosive
action all of which exceptions are set forth in this Chapter 7.
Section 7 -2: UNDERGROUND CONDUIT: All exterior underground installations
of single runs or grouped runs.of conduit shall be nonmetallic. In lieu of
rigid metal conduit for underground wiring in hazardous locations, schedule 80
PVC may be used.
Section 7 -3: ELECTRICAL METALLIC TUBING: Electrical metallic tubing shall
not be installed in any exposed outside location or underground.
Section 7 -4: PROHIBITED CONNECTORS: The use of crimp type connectors and
couplings used with electrical metallic tubing shall be prohibited.
. Section 7 -5: DISTRIBUTION TO AND IN BUILDINGS: Service entrance conductors
and feeders shall run in conduits or raceways. A masthead used for support of,
service drop conductors and extending forty -two inches above the roof shall be
two inch or larger rigid metal conduit:
Section 7 -6: SPECIAL ELECTRICAL CIRCUIT RULES: The following additional,
requirements shall be met for all new construction:
(a) All circuits, except lighting circuits, shall have conductors sized
in accordance with Article 310 of'the.National Electrical Code 1978, to provide
a minimum current capacity of circuit conductors of twenty (20).amperes. Not
more than ten lighting fixtures and general use receptacles (duplex) shall be installed
on a 120 volt branch circuit. Not more than three receptacles (duplex) shall
be installed on each of the two required small appliance circuits in dwellings.
(b) The following listed buildings shall have a minimum of one (1) re-
ceptacle installed for every twenty lineal feet measured horizontally around
the interior wall at the floor level of each room, excluding storage rooms:
Office Buildings Bank Buildings
Store Buildings Mechanical Garages
Restaurants Studios
Taverns
(c) One spare circuit shall be installed for every five (5) circuits in
all new buildings. For each panel a spare one (1 ") inch raceway shall be in-
stalled from the panel to an accessible location.
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(d) If one or more 120 volt receptacles having ground fault circuit
interrupter protection are provided in a garage of a dwelling unit (required
in attached garages), then three additional receptacles may be provided in the
garage without ground fault circuit interrupter protection:
(1) One receptacle (single) for a deep freezer.
(2) One receptacle (single) for a garage door opener.
(3) One receptacle (single) on a separate circuit for the laundry
circuit for the dwelling.
Section 7 -7: Made Electrodes.
(a) Pipe Electrodes: Electrodes of pipe shall be'of brass or copper.
(b) Rod Electrodes: Rod Electrodes °shall be of brass, copper or copper
clad steel and shall be at least 5/8" in diameter.
Section 7 -8: CONSTRUCTION, RAT PROOF: All foundation and exterior wall
openings around electrical cables and conduits shall be protected against the
passage of rats by closing such openings with cement mortar, concrete masonry,
or non - corrodible metal.
Section 7 -9: COMMERCIAL BUILDINGS:
(a) All commercial buildings shall be wired in raceways, except as provided
in Subdivisions (b) and (e) of this section.
(b) The requirements of Subdivision (a) shall not be applicable with regard
to pre- existing wiring in buildings which were originally constructed and used as
single- family, single- story, residential -use buildings, and which are thereafter
converted to commercial usage if, at the time such building is converted to
commercial usage, such pre- existing electrical wiring, fixtures and apparatus in
such building conforms to all other applicable provisions of this Code, including
the requirements that the electrical wiring system shall be effectively grounded
by including or providing a grounding conductor in such wiring system to which
the receptacles, cord connectors, lighting fixtures, wall switches and other
electrical apparatus shall be securely connected. To obtain the benefit of the
exemption granted by this subdivision, the owner or occupant of such building
must obtain an inspection and certificate as required by Subdivision (d).
(c) Any installation of new electrical wiring, fixtures or apparatus installed
in any building which is the subject of the exception stated in Subdivision (b) of
this section, or any rewiring of such building, shall be wired in raceways (including
fexible metal conduit which may be used in otherwise inaccessible areas) as required
by Subdivision (a) of this section.
(d) The exception stated in Subdivision (b) hereof shall be strictly construed.
In order to obtain the benefits thereof, prior to the time that any building is con -
verted to commercial use as specified in Subdivision (b), an electrical inspection
of the electrical wiring, fixtures and apparatus in such building shall be made by
the Chief Electrical Inspector for the purpose of determining whether such build-
ing conforms to all other applicable provisions of this Code at the time such building
is converted to commercial use. If the Chief Electrical Inspector determines that such
building does not conform to all other applicable provisions of this Code, then the
provisions of Subdivision-(b) shall not be applicable.
(e) Temporary buildings, the uses of which are incidental to construction
operations or sale of lots during development being conducted on the same or adjoining
tract or subdivision and which shall be removed upon completion of development,
shall not be requiPed to be wired in raceways.
Section 7 -10: INDIVIDUAL METERING REQUIRED: A building or buildings containing
more than five dwelling units shall provide for individual metering or submetering of
each dwelling unit.
CHAPTER 8 - USE OF ELECTRICAL EQUIPMENT
Section 8 -1: USE OF UNAPPROVED APPLIANCE PROHIBITED: It shall be unlawful for
any person, firm, association, or corporation within City to use any appliance which
has not been endorsed by the Underwriters' Laboratories, Inc., or other nationally
recognized standards association; or without first obtaining approval from the Chief
Electrical Inspector in absence of such evidence of safety approval.
Section 8 -2: APPROVAL GIVEN: The Chief Electrical Inspector shall approve for
use electrical equipment, material, conductors, apparatus, or appliance as are reason-
ably safe to persons and property. Conformity of such equipment and material with the
standards of the Underwriters' Laboratories, Inc. shall be prima facie evidence that
such equipment is reasonably safe to persons and property.
Section 8 -3: SPECIAL APPROVAL: Should any material or equipment be submitted for
approval which is not listed as approved by the Underwriters' Laboratories, Inc., the
Chief Electrical Inspector shall, within ten days of the receipt of written request
for special approval, approve, provisionally approve, or disapprove such electrical
material or equipment.
(a) Approval shall be based on reasonable safety to persons or property and
material and equipment shall be considered as adequate for approval if the standards
of the Underwriters' Laboratories, Inc., and /or provisions of this Code are met.
When material or equipment is approved by the Chief Electrical Inspector, such approval
shall continue until the material or workmanship on the article approved is changed.
When material or workmanship is changed, the article shall be re- examined and approved
prior to use.
(b) When no applicable standard can be used to determine whether an article is
reasonably safe, the Chief Electrical Inspector may grant provisional approval and
allow its use until such time as it can be tested or determined whether the article
is safe to persons or property.
(c) Approval by the Chief Electrical Inspector shall not become final until
concurred by the Board. Denial by the Chief Electrical Inspector may be appealed
to the Board. Unless appealed by any party to the City Council, action by the Board
shall be final.
(d) A complete list of electrical equipment, material, appliances and devices
approved by Underwriters' Laboratories, Inc., provisionally approved, or disapproved
for use within City shall be maintained in the Chief Electrical Inspector's office.
This list shall be available to the public during regular working hours.
CHAPTER 9 - PENALTIES
Section 9 -1: PENALTY FOR VIOLATION OF ELECTRICAL CODE: Any person, firm, cor-
poration or association who violates any of these provisions ofihis Code shall be
deemed guilty of a misdemeanor, and upon conviction thereof, shall be punished by
a fine of not more than two hundred ($200.00) dollars, and each and every day of
continuance thereof shall constitute a distinct and separate offence.
Section 9 -2: VIOLATION: Violation of any of the terms or provisions of this
Code by any corporation or association shall subject the officers and agents actively
in charge of the business of such corporation or association to the penalty herein
provided.
Section 9 -3: CONVICTION: Conviction under the provisions of this Code shall be
deemed just cause for the revocation of any license which said person, firm corpora-
tion or association may have and /or hold under the provisions of this Code or the
Electrical Licensing Ordinance of the City.
Section 9 -4 INJUNCTION: In addition to the penal remedy herein, the City Attorney
shall, upon the direction-of the City Manager, institute any appropriate action or
proceeding, including actions for injunction to prevent, restrain, correct or abate
any act, conduct, work, business, practice or use which is a violation of and illegal
under this ordinance.
CHAPTER 10 - VALIDITY, REPEAL OF CONFLICTING
ORDINANCES, PUBLICATION, AND EFFECTIVE DATE
Section 10 -1: VALIDITY CLAUSE: If for any reason, any section, paragraph, sub=
division, clause, phrase, or provision of this Code shall be held invalid,,it shall
not affect any valid provisions of this or any Code of the City of Corpus Christi to
which these rules and regulations relate.
Section 10 -2: REPEAL OF CONFLICTING ORDINANCES: Ordinance No. 12570, passed
and approved by the City Council on April 1, 1975, is hereby repealed. Division 2,
Sections 13 -90 through 13 -136, of Article III - Electrical, Chapter 13, Code of
Ordinances, City of Corpus Christi, 1976, as amended, is hereby repealed.
Section 10 -3: PUBLICATION: This Ordinance shall be published one time in the
official publication of the City of Corpus Christi, prior to becoming effective,
which publication shall contain the caption stating in summary the purpose of the
ordinance and the penalty for violation thereof.
Section 10 -4: EFFECTIVE DATE: This Ordinance shall take effect from and after
September 1, 1978.
` r
Section 10 -2: REPEAL OF CONFLICTING ORDINANCES: Ordinance No. 12570, passed
and approved by the City Council on April 1, 1975, is hereby repealed. Division 2,
Sections 13 -90 through 13 -136, of Article III - Electrical, Chapter 13, Code of
Ordinances, City of Corpus Christi, 1976, as amended, is hereby repealed.
Section 10 -3: PUBLICATION: This Ordinance shall be published one time in the
official publication of the City of Corpus Christi, prior to becoming effective,
which publication shall contain the caption stating in summary the purpose of the
ordinance and the penalty for violation thereof.
Section 10 -4: EFFECTIVE DATE: This Ordinance shall take effect from and after
September 1, 1978.
That the foregoing ordinance as read for a first time and past to its
second reading on this the of 19 46' _, by the
following vote:
Gabe Lozano, Sr.
Bob Gulley
David Diaz
Ruth Gill
Joe Holt
Tony Juarez, Jr.
Edward L. Sample
That the foregoing ordinance w read for second time and pa sed to its
third reading on this the �h day of 19 7 , by the
following vote:
Gabe Lozano, Sr.
Bob Gulley
David Diaz
Ruth Gill
Joe Holt
Tony Juarez, Jr.
Edward L. Sample
That the foregPi ng ordinanc as readjor the thir time and passed finally
on this the G1 day of , 19.7' , by the following vote:
Gabe Lozano, Sr.
Bob Gulley
David Diaz
Ruth Gill
Joe Holt
Tony Juarez, Jr.
Edward L. Sample
PASSED AND APPROVED, this the_day
ATTEST:
��o ,�/ ��
City Secretary '
APPROVED: p
=DAY OF ,19'
J. BRUCE AYCO , CI Y ATTORNEY
By
Assistagt)ty Attorney
14420
} •
The 1978 edition of the National Electrical Code
contains detailed and comprehensive revisions in a
very wide range of specific NE Code regulations. The
new edition contains completely new articles on equip-
ment never covered by the code before —e.g., power
and control tray cable and intermediate metal
conduit —and has dozens of radically new regulations
and changes in old regulations covering the widest
range*f everyday electrical details involved in the
basiLj1ring of all buildings.
EV,,Jrical construction people everywhere have a
v +al mmediate and awesome task before them. The
-NE, fide •4s •today more' important than it has ever
J,beer.�,05�HA has made it a' mandatory federal stan-
i,'dard,' -'Wa�g under force of legal sanctions. OSHA's
iF%-.1 llication V.LShe -M • Code to all new electrical
c ss�trcc� tionranT,V,modernization and expansion of
existifig.3'ystems /has been deeply and widely felt
throughqut thq-Ltion over recent years. This new
„code will deepen and intensify the government's insis-
tence on maximum safety and effectiveness in elec-
trical work
At the state and local levels, electrical inspection
agencies everywhere are tightening their control over
electrical work and are exercising' stricter enforce-
ment. "Listing" and "labeling" of products by nation-
ally recognized testing labs is a must with inspectors
and engineers. And now the NE Code has many rules
that virtually insist on the use of certified equipment
and materials.
A runaway rate of growth in the use of electrical
energy for light, power, heat, control, signaling and
communications is still another factor that is
promoting greater attention to the code. As the elec-
trical percentage of the construction dollar moves ever-
,L upward, the visibility and universality of electrical
x• SEPTEMBER, 1977 -
usage demand closer, more penetrating concern for
safety in electrical work. In today's sealed buildings,
with the entire interior environments 'totally
dependent on effective electrical usage, the critical
role of electrical systems demands not only concern
for eliminating fire and shock hazards, but also
concern for continuity and ' reliability of electrical
usage as essential to safety of people and property. ;
Another factor that emphasizes the importance of
the NE Code is the highly competitive nature of
construction work. With a constricted electrical
market and the universal concern for energy conserva-
tion, forces in the industry are promoting maximum
economy in such a way, as to jeopardize full attention
to safety. The NE Code is an effective, commendable
barrier against any compromises with basic electrical
safety.
In this issue and in the October and November
issues EC &M's exclusive report delves into the letter
and intent of the code rules. Read and study the
material carefully. Talk it over with your associates;
engage in as much discussion as possible. Iii particu-
lar, check out any questions or problems with your
local inspection authorities. It is true that only time
and discussion will provide final answers on how some
of the new rules are to be interpreted. But now is the
time to start. Do not delay. Use this report to begin a
regular, continuous and enthusiastic program of
updating yourself on this big new code. -
Our illustrated analysis of the 1978 NE Code is most
effectively used by having your copy of the new code
book at hand and referring to each section as it is
discussed. The commentary given here is intended
primarily to supplement and clarify the actual
wording of the code rules as given in the code book
itself.
I
ARTICLE 90'*', INTRODUCTION
Section 90-4
The NE Code has long stipulated that, when ques-
tions arise about the meaning or intent of any code
rule as it applies to a particular electrical installation,
the electrical inspector having jurisdiction over the
installation is the only one authorized by the NE Code
to make interpretations of the rules. The wording of
Section 90-4 has reserved that power to the local
inspection authority along with the authority to
approve equipment and materials and to grant the
special permission for methods and techniques that he
might consider alternatives to those code rules that
specifically mention such "special permission" [for
instance, Section 250- 57(c)]. -
. Up until the 1975 NE Code, Section 90 -4 aimed only
at giving the inspector the right to "interpret" code
rules. But the 1975 NE Code, for the first time,
specifically gave the inspector the authority to
"waive" specific requirements —that is, to disregard
the wording and meaning of individual code rules.
However, use of this authority by the inspector was
allowed (1) only in "industrial establishments and
research and testing facilities" and (2) only where the
inspector is satisfied that the safety objectives sought
by the code rule are achieved by the particular design
and /or installation techniques that are used as alter-
natives to the specifics of the code rule. The 1975 NE
Code referred to the necessity for , "establishing and
maintaining effective safety and maintenance proce-
dures" whenever a rule was "waived" or whenever
Section 90 -4. New balance of enforcement meth-
ods by electrical inspectors
"alternate methods" were accepted.
Now, the 1978 NE Code permits the electrical
inspector to "waive specific requirements or permit
alternate methods" in any type of electrical installa-
tion. The new wording of the last sentence of Section
90 -4 'no longer limits waiver of code rules to industrial
establishments and research and testing facilties. In
residential, commercial and institutional electrical
systems —as well as in industrial —an inspector may
now accept design and /or installation methods that do
not conform to a specific code rule, provided he is
satisfied that the safety objectives of the code rule are
achieved.
ARTICLE 100 - DEFINITIONS
Some of the definitions of terms essential to proper
use of the code have'been revised for clarification;
others have been added.
"Approved for the Purpose"
Because this phrase is used frequently in the NE
Code and has raised questions about the need for
third -party certification (such as UL listing), an
explanatory note was added.
The definition is the same as it was:
Approved for a specific purpose, environment, or applica-
tion described in a particular Code requirement.
But now, the new note answers the question —
"Approved by whom ?" Such approval of equipment or
materials for a specific purpose may be given by "a
nationally recognized testing laboratory" (such as UL,
Factory Mutual, ETL). Or an "inspection agency" may
determine that a piece of equipment or a certain
54
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Fil�u�'`
V,' Sri. • :iti :. "�;t :Fre: "L•5::9
Y DENT
AeQ9 "�` ;sY
PUBL?C'
material is "approved for the purpose." Or any other
organization concerned with product evaluation may
designate approval for a specific purpose.
ELECTRICAL CONSTRUCTION AND MAINTENANCE
tr
Because the new note to the definition includes
reference to the words "Labeled" and "List2d," fieavy
emphasis is placed on UL listing or similar certifica-
tion. It is reasonable to assume that electrical inspec-
tors will base their approval on "listing" and /or
"labeling" by national test labs whenever possible. For
those cases where no test -lab certification covers
approval of a product that a code rule requires to be
approved for a specific purpose, it will be up to the,
electrical inspector to rule on acceptability of the
product.
T,
"Conduit Body" '
_ An added sentence notes that FS and FD boxes —as
well as larger cast or sheet metal boxes —are not
considered to be "conduit bodies," as far as the NE
Code is concerned. Although some manufacturers'
literature refers to FS and FD boxes as conduit
fittings, care must be used to distinguish between
"conduit bodies" and "boxes" in specific code rules.
Distinguish between "boxes" and "conduit bod-
ies" ( "conduit fittings ")
- i:`x't''''Ca'st boz is •o tioz,poot
conduit bad ;an d'ma tonloin�a,
'✓' * ±ia+nspIiciss and /or devices (2ceplutks)
For instance, the last sentence of Section 370 -6(c)
prohibits splicing and use of devices in conduit bodies
with less than three conduit hubs. FS and FD boxes
are not conduit bodies and may contain splices and/or
house devices. Table 370 -6(a) lists FS and FD boxes as
"boxes." "
"Dwelling"
Because so many code rules involve the words
'c "dwelling" and "residential," there have been prob-
lems applying code rules to the various types of
"dwellings " — one - family houses, two - family houses,
apartment houses, condominium units, dormitories,
hotels, motels, etc. The 1978 NE Code includes
changes in terminology to eliminate such problems
and uses new definitions of "dwelling" coordinated
with changes in the words used in specific code rules.
a A "Dwelling Unit" is now defined as "one or more
rooms" used "as a housekeeping unit" and must
contain space or areas specifically dedicated to "eat -
ing, living, and sleeping" and must have "permanent
" provisions for cooking and sanitation." A one - family
house is a "dwelling unit." So is an apartment in an
apartment house or a condominium unit. But, a guest
room in a hotel or motel or a dormitory room or unit is
SEPTEMBER, 1977 -
"Dweiling.Unit" must contain all required facili-
ties
not a "dwelling unit" if it does not contain "perma-
nent provisions for cooking' —which must mean a
built -in range or counter - mounted cooking unit (with
or without an oven). As a result, the rule of, say,
Section 210 -8, which requires GFCI protection of
receptacles in bathrooms of "dwelling units," does not
apply to bathroom receptacles in standard hotel or
motel units or dormitory units, because such units do
not contain "permanent provisions for cooking. "....'. ;
Under "Dwelling," additional definitions cover the
types of buildings containing one or more dwelling
units — "Multifamily Dwelling," "One- Family Dwell-'
ing," and "Two- Family Dwelling."
"Overcurrent" "Overload"
A new definition covers 'Any current in excess of A new definition identifies this as a condition where -
the rated current of equipment or the ampacity of a equipment is operating at current in excess of its
conductor," which may ,result from "overload (see normal, full -load rating. A short circuit or a ground
definition), short circuit, or ground fault." fault is not an overload.
a
ARTICLE 110- REQUIREMENTS FOR
ELECTRICAL INSTALLATIONS
Section 110- 3(a)(3)
A new consideration'for the electrical inspector to
include in his examination to determine suitability of
equipment for safe and effective use is listed as "Wire -
bending and connection space." This new factor was
added because of increasing concern over inadequate
gutter space at conductor terminal locations in enclo-
sures for switches, CBs and other control and protec-
tion equipment. This general mention of the need for
sufficient conductor bending space is aimed at
avoiding poor terminations and conductor damage
that can result from excessive sharp conductor bends
required by tight gutter spaces at terminals. Specifc
Section 110- 3(a)(3). Equipment must be evalu-
ated for adequate gutter space to assure safe
and effective bending of conductors at termi-
nals
Section 110 -9. Equipment must be rated for the
"system" voltage and the value of current it is
"intended to break "
rules that cover this consideration are given in Section
$73 -6 on "Deflection of Conductors" at terminals or
where entering or leaving cabinets or cutout boxes —
covering gutter widths and wire- bending spaces.
Section 110 -9
"Interrupting Rating" of electrical equipment is
now divided into two categories: current at fault levels
and current at operating levels. Equipment intended
56
to clear fault currents must have interrupting rating
equal to the maximum fault current that the circuit is
capable of delivering at the line (not the load) termi-
nals of the equipment.. The internal impedance of the
equipment itself may not be factored in to use the
equipment at a point where the available fault current
on its line side is greater than the rated, marked
interrupting capacity of the equipment.
Equipment intended only for control of load or
operating currents, such as contactors and unfused
ELECTRICAL CONSTRUCTION AND MAINTENANCE
switches, must be rated for the current to be inter-
rupted but does not have to be rated for interrupting
available fault level. However, Section 110 -10 requires
that all equipment be rated to withstand the level of
fault current that is let through by the circuit protec-
tive device in the time it takes to operate — without
"extensive damage" to any of the electrical compo-
nents of the circuit.
Section 110 -10
• The phrase "the component short - circuit withstand
ratings" has been added to this rule. The intent of this
addition is to require all circuit components that are
subjected to ground faults or short- circuit faults to be
capable of withstanding the thermal and magnetic
stresses produced within them from the time a fault
occurs until the circuit protective device (fuse or CB)
opens to clear the fault, without extensive damage to
the components. '.
Section 110 -10. Equipment "withstand "ratings
must be adequate for fault level (i2t and 1,) -
Section 110- 16(a). Increased clearance needed in
direction of access to live parts in enclosures for
switchboards, panelboards, switches, CBs, or
Section 110 -16(a)
In Table 110- 16(a), some of the dimensions of
working space in the direction of access to live elec-
trical parts operating at 600 volts or less have been
increased. All minimum clearances of 21 /2 ft have been
increased to 3 ft. Section 110 -16(d) has required a
working space at least 3 ft deep in front of switch-
boards or motor control centers that have live parts
normally exposed on their front. The minimum of 3 ft
'
was adopted for Table 110 -16(a) to make all electrical
equipment— panelboards, switches, breakers, starters,
etc. — subject to the same 3 -ft minimum to increase
the level of safety and assure consistent, uniform
spacing where anyone might be exposed to the hazard
of working on any kind of live equipment. '
- SEPTEMBER, 1977
- NOTE: M ariy enclosure for eleclrlcel equipment requires rear,,.
�
�access to any live connections or to renewable or adjustable
parts (such as fuses or switches), then these me, work:
clearances would be required at the rear of the enclosure as
shown for the front. Distances must be measured from the`.,-
` live parts If they are exposed, or from the front surface of e-+
'cabinet or housing of enclosed parts. i:7y +�`•�"t S;-'�:ai`,�;'
57
Section 110- 16(c). There must be two paths out Section 110 -16(e)
of the work space required in front of switch- This code rule previously required lighting of all
boards rated 1200 amps or more and over 6 ft work spaces at "switchboards and motor control
wide centers." Because the NE Code gives clear, specific
definitions of those two, types of equipment, the
wording of the rule made work -space lighting neces-
sary only for those types of equipment. Lighting was
not required for work spaces at panelboards or at
individually enclosed switches, circuit breakers, motor
starters, and other equipment that fell outside the
narrow, limited meanings of the two assemblies
mentioned. In fact, a group of combination motor
starters nippled out of an auxiliary gutter would not
technically require lighting of the work space in front
of them —even though such a layout is functionally
identical to a motor control center.
:.'Now Section 110 -16(e) requires lighting of work
space at' "service equipment, switchboards, pan -
elboards or control centers installed indoors.'•' Because
the phrase "control center" is not defined in Article
100, it could be taken to mean any point at which
control is exercised over operation of a circuit —such
as at motor control centers or at individually enclosed
switches, circuit breakers, motor starters, magnetic
contactors, relays, etc. It is possible for any inspector
to put a very broad interpretation on this new wording
of the rule. And with the great concern for the safety
provided by clearly identifying and being able to use
effectively all kinds of disconnects and control devices,
broad interpretation might become common, requiring
lighting at any equipment that could be called a
"control center:'
Section 110 -16(c)
As an added safety measure, to prevent the case
where personnel might he trapped in the working
space around burning or arcing electrical equipment,
the rule here now requires two "entrances" or direc-
tions of access to the working space around switch-
boards and control panels rated 1200 amps or more
and over 6 ft wide. At each end of the working space at
such equipment, an entranceway or access route at
least 24 in. wide must be provided "where reasonably
practicable." That last phrase in the rule is undefined
and leaves final decision up to the inspector. Because
personnel have been trapped in work space by fire
between them and the only route of exit from the
space, rigid enforcement of this rule is likely.
Certainly, design engineers should make two paths of
exit a standard requirement in their drawings and
specs.
58
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 110-16(e) and (f). New listing of eq6ip-
ment that requires lighting and 61/4-ft headroom
at all work spaces around equipment
IK
It should be noted, however, that the chairman of
I
the code-making panel for Article 110 stated that it is
f the intent of the code panel that the phrase "control
center" be taken as "motor control center,"
An important Exception to this revised rule
'excludes "Service equipment or panelboards, in
SEPTEMBER, 1977
dwelling units, that do not exceed 200 amperes" from
the need to have lighting installed at their locations.
But note that the Exception applies only to such
equipment in "dwelling units" —which means in a one ' --
family house or in an apartment within,an apartment
house. The narrow defintion of "dwelling unit". does
not make this Exceptitin applicable to service equip-
ment or panelboards that are in an apartment
building but are located outside any of the "dwelling
units"—such as in hallways, electric closets, and base-
ments.
It should be noted that although lighting is required
for safety, of personnel in work spaces, nothing specific
is said about the kind of lighting (incandescent, fluo-
rescent, mercury-vapor), no minimum footcandle level
is set, and such details as the position and mounting of
lighting equipment are omitted. All of that is left to
the designer and/or installer—with the inspector the
final judge of acceptability.
Z-7
Some type,of lighting
• mu st be provided4t 7 9
� 'rM,
Ior any defined
be
A
it 'I; -�2L. nitis,
work space around ,=at
.the equ! ent
leasf,"�
T,
VP A
'4--
e, �nt',wilchII1z1I17z,
n vice i u me b r 7777777777Z
IVIMr I Ir 1: aster v,.
0 the space on this side of a switchboard is a work space
required by Section 110-16(a)
. . .
. .. as well as the space on this side, then a lighting unit
• here, over only one of the work spaces, would not be
adequate. Another light would be required for the work
space on the other side of the equipmer
,BUT NOTE' F
E
Service equipment or penelbcard
'rated not over 200 amps...
V.
D C
inii
on head
IK
It should be noted, however, that the chairman of
I
the code-making panel for Article 110 stated that it is
f the intent of the code panel that the phrase "control
center" be taken as "motor control center,"
An important Exception to this revised rule
'excludes "Service equipment or panelboards, in
SEPTEMBER, 1977
dwelling units, that do not exceed 200 amperes" from
the need to have lighting installed at their locations.
But note that the Exception applies only to such
equipment in "dwelling units" —which means in a one ' --
family house or in an apartment within,an apartment
house. The narrow defintion of "dwelling unit". does
not make this Exceptitin applicable to service equip-
ment or panelboards that are in an apartment
building but are located outside any of the "dwelling
units"—such as in hallways, electric closets, and base-
ments.
It should be noted that although lighting is required
for safety, of personnel in work spaces, nothing specific
is said about the kind of lighting (incandescent, fluo-
rescent, mercury-vapor), no minimum footcandle level
is set, and such details as the position and mounting of
lighting equipment are omitted. All of that is left to
the designer and/or installer—with the inspector the
final judge of acceptability.
Section 110 -16(f)
. There is no change in this rule on the required
minimum headroom of 6' /4 ft in working spaces
required around electrical equipment; but, as in
Section 110- 16(e), the change is in the type of equip-
ment to which the requirement applies. Where the
1975 NE Code applied the rule to "switchboards or
motor control centers," the 1978 rule applies to "ser-
vice equipment, switchboards, panelboards, or control
centers installed indoors." That wording is the same
as in Section 110- 16(e), and the same Exception is
added that "permits "Service equipment or pan -
elboards, in dwelling units, that do not exceed 200
amperes" to be installed with less than 61/4 ft of
headroom —such as in crawl spaces under single -"
family houses. But the permission for reduced head-
room of the equipment described in the Exception
applies only in "dwelling units" that meet the new
definition of that phrase. In any space other than a
dwelling, unit, all indoor service equipment, switch-
boards, panelboards or control centers must have 61 /a- .
ft headroom in any space around the equipment that
is work space required by Section 110- 16(a).
Section 110 -34
'The Exception to Section 110- 34(a)(3), covering
working space around high - voltage equipment (over
600 volts), has been expanded. As in the 1975 NE
Code, this Exception notes that working space is not
required behind deadfront equipment when there are
.s
Section 110- 34(a)(3). A 30-in.-deep work space is
required behind enclosed high - voltage equip-
ment that requires rear access to "de -ener-
gized" parts
no fuses, switches, other parts, or connections
requiring rear access. But, the_ rule now adds that if
rear access is necessary to permit work on "de-
energized" parts of the enclosed assembly, the work
space must be at least 30 inches deep. This was added
to prohibit cases where switchgear requiring rear
access is installed too close to a wall behind it, and
personnel have to work in cramped quarters to reach
taps, splices and terminations.
ARTICLE 200 -USE AND IDENTIFICATION
OF GROUNDED CONDUCTORS
Section 200 -6(a) '•:.
Exception No. 2 has been added to the basic rule
that requires use of continuous white or natural gray
color along the entire length of any insulated
grounded conductor (such as a grounded neutral) in
sizes No. 6 or smaller. The new Exception permits use
of a conductor of other colors (black, purple, yellow,
etc.) for a grounded conductor in a multiconductor
cable under certain conditions: -
1. That such a conductor is used only where qual-
ified persons supervise and do service or maintenance
on the cable —such as in industrial and mining appli-
cations.
2. That every grounded conductor of color other
than white or gray will be effectively and permanently
identified at all terminations by distinctive white
marking or other effective means applied at the time
of installation.
This permission for such use of grounded conductors
6D '
in multioonductor cable was added to allow the prac-
tice in those industrial facilities where multiconductor
ELECTRICAL CONSTRUCTION AND MAINTENANCE
k d _ •
Section 200- 6(a)(b). In multiconductop cabeo, a
grounded conductor of any color may be used if
identified
changed, and use -of white color is still required to
identify grounded- conductor (usually the neutral)
terminals on equipment and wiring devices. On recep-
tacles, for instance, the terminals for grounded
neutral conductors are whitish- silver in color —which
satisfies the code wording that calls for such terminals
to be "substantially white in color." BUT, an Excep-
tion to that rule now permits field identification of
grounded- conductor terminals by white marking or
"other effective" means applied at the time of installa-
tion. This code permission is, however restricted to
places where only qualified persons work on the equip-
ment and will supervise and maintain such marking or
identification. This code change was made to permit
such use in industrial and mining applications where
conditions require flexibility- in identification and
where the practice is carefully regulated to maintain
safety.
Section 210-4
The basic rule of this Section still requires that
multiwire branch circuits (such as 240 /120 -volt, 3-
wire, single -phase and 3- phase, 4 -wire circuits at
208/120 volts or 480/277 volts) may be used only with
loads connected from a hot or phase leg to the neutral
conductor. But Exception No. 1, which previously
permitted phase -to -phase connected load where a
multiwire branch circuit protected by single pole
protective devices supplies only a "single appliance,"
is now changed to permit phase -to -phase connected
load on a multiwire branch circuit "that supplies only
one utilization equipment." This change was made to
broaden application by permitting use of a multiwire
circuit for a single unit of any type of utilization
SEPTEMBEA,' 1977 " -- ? ' � -' ^ •�� - - -
6.1 _
Section (e) . - . .: • .,_
The revised iced code rules of Section 200 -10(e) and (f) of'
-
the 1975 NE Code are combined now to require that
cord- connected appliances and permanently wired
cables are commonly used — although the rule does not
'appliances have marking to identify the terminal for
limit the use to industrial occupancies.
the grounded circuit conductor where the supply
•
Section 200 -6(b) ...,:.. _ ' - _.
consists of three or more wires.
An Exception identical to the one described above
Section 200-11
under Section 200 -6(a) has been added to the rule that
This section is new and was added to establish a` .
requires any grounded conductor larger than No. 6 to
be either white or gray color for its whole length or to
clear code rule that "No grounded conductor shall he. "•
be marked with white identification (like white tape)
terminations
attached to any terminal or lead so as to reverse
designated polarity." All hookups of wires to termi -� ,
at all at time of installation.
nals on devices and appliances must observe desig -y
•
nated polarities of grounded and ungrounded conduc- ^-
Section 200 -9
tors. This was never specifically and clearly required'
The basic rule of this Section is reworded but not
by any one code rule before.
f - -•; =may
�. '�Y�:i- r;��;.- -;c fir`=,`
.... -..
-- -. �
- - -• .. -_ .h NT -' -- .. ,
ARTICLE 210 - BRANCH CIRCUITS.:. 6
Section 210-4
The basic rule of this Section still requires that
multiwire branch circuits (such as 240 /120 -volt, 3-
wire, single -phase and 3- phase, 4 -wire circuits at
208/120 volts or 480/277 volts) may be used only with
loads connected from a hot or phase leg to the neutral
conductor. But Exception No. 1, which previously
permitted phase -to -phase connected load where a
multiwire branch circuit protected by single pole
protective devices supplies only a "single appliance,"
is now changed to permit phase -to -phase connected
load on a multiwire branch circuit "that supplies only
one utilization equipment." This change was made to
broaden application by permitting use of a multiwire
circuit for a single unit of any type of utilization
SEPTEMBEA,' 1977 " -- ? ' � -' ^ •�� - - -
6.1 _
,L
equipment as well as appliances. The definition of
"utilization equipment," as given in Article 100, is
"Equipment which utilizes electric energy for mechan-
ical, chemical, heating, lighting or similar purposes."
The definition of "Appliance," in Article 100, notes
that an appliance is "Utilization equipment, generally
other than industrial, normally built in standardized
sizes or types ... such as clothes washing, air condi-
tioning, food mixing, deep frying, etc." The change in
wording of Exception No. 1 opens its application to
commercial_ and industrial equipment as well as resi-
dential-2,
it should be noted that the code- making panel
rejected two proposals to change the wording of
Exception No. 2 to permit use of either fused multipole
switches or multipole circuit breakers where loads are
connected line -to -line on multiwire branch circuits.
The intent of the code panel is that line -to -line
Section 210-4. Change in Exception No.1 permits
multiwire branch circuit with single -pole protec-
live devices (fuses or CB poles) to supply any
"single utilization equipment "
d ; >r a
r;!' s*+,v -' • 4 When using single -pole devices <
pp i•. c 4 ;- far branch - circuit protection �L`
f;ra^ �• ? (fuses or single -pole CBs).. .
This basic rule . fy -to- :6� -�^•, "i�.�'E'v.�, `yw.. - k
Is not changed.
i •.���i"aTafi
, �. rt" '�:u'at'�N.`•�aij`;y�FN,F•,�f�.
,,_L_ ti 1 ch-1 s rs PPI1' Y
. ...�multiwire•�branch;clrcuit�s shall su and line- to -;,:
°neutralpconnected loads " ra•;'
�•.t, '9tar'. i' dl.� #'si.-'zr.�•`ki;,1_ �r�"Y'+oL.vs..`�c"i'''«-
, but the first of the tw
following o exceptions has been 'r
t ipanded to recognize all utilization equipment.,',', -.11.
- `.- `'l�°:iw'�.e: {:vk x47sa'_+1`y31�r.;.S:
No,�t: A multiwire branch circuit may supply a single Will izaI-
tion�equlpment with Ilne- to-line and line - to-neutral voltage
'itsingsingIe -pole switching devices In branch - circuit protec -, f
cl2'.N d��t'.'e3.•-= �,'vvix
-yi Single - pollen Cgs a�r fuses,
tl ,.. , -� , .„ , _, ,Singles.:: `This
H' - -s utihzalion•�' Includes- ;`Z
,equipment s.''ia nces;.
17 (fh• d lT� �R^'�,r fitl «�X ,31r•- ' -T'^,• b:
No.2[is multipole CB Is used, loads may be ctinnecled line-
-to-line and /or line- to-neutral. =••'sirc,`. -.- ''K >'� yµa
t•rr
480V 3 pads could be "; J
m. -.
h ly 4e0V -line, but only with
:.
N�° �' _ -_ <• :line -lo -line, but only wuh `
i._.. B �� ' - 0 3-pole CB on branch
;" ;circuu and not wnh a
jjc'�f1YC -i� - :3-pale fused switch
Y a h' ,gip -,.ii : - _ '"w.•..
p- � '�, i� {` ',_'�':''.Tt � >- ia.•:.t- ;�'Tt�'Poe:^t?a:e{',t "a
VW
S. Lout .- �usLJL:.'l— .wr:..:i$VC3S: gLIkY�'nv :K... _
62
f� ya9
connected loads may be used other than in Exceptions'
No. 1, only where the poles of the circuit protective
device operate together, or simultaneously. A multi -
pole CB satisfies the rule, but a fused multipole switch
would not comply because the hot circuit conductors
are not "opened simultaneously by the branch- circuit
overcurrent device."
£
To clarify the correct use of multiwire branch
circuits, a note was added to Section 210 -4 that, "All
,
conductors shall originate from the same pan -
elboard" —that is, the grounded and ungrounded (hots
leg) conductors of any multiwire branch circuit must
come from the same enclosure or panelboard.,
Section 210 -5
A major change in code rules on color coding of
. 4
branch- circuit conductors was made by eliminating
part (c) of Section 210 -5. That rule previously required
that "Ungrounded conductors of different voltages
shall be of different color or identified by other
means." NOW— ungrounded' conductors (the hot or
phase leg conductors) of a branch circuit may all be
the same color or different colors, and any colors or
combinations may be used. By deleting the old rule,
the NE Code rule now ignores or disregards any color
coding for branch - circuit hot legs.
Although the omission of part (c) from Section 210-
5 eliminates the mandatory need to color -code branch
circuit hot conductors, there is, of course, no code
objection to continuing the very effective practice of
color - coding that has always been used for multiwire
branch circuits.
x
No change has been made in the, code rule on
ELECTRICAL CONSTRUCTION AND MAINTENANCE
grounded circuit conductors. Any grounded neutral
conductor or a grounded phase conductor —such as a
leg of a corner - grounded delta system -must be
identified by a continuous white or natural gray color
for the entire length of any conductor up to No. 6 size.
If circuits of different voltage systems are installed in
the same raceway, box or other enclosure, the neutrals
must be differentiated by using white for one neutral
and gray for the other system neutral. For each
additional system neutral in the same enclosure, white
with a color stripe (other than green) running through
it may be used.
No change was made in required color coding for
equipment grounding conductors, which must be green
color or green with one or more yellow stripes —or
such a conductor may be bare.
Section 210 -5. Color coding is no longer required
for ungrounded (hot) conductors of multiwire
branch circuits -
Section 20 -6(a)
Exception No. 1 has several changes in wording of
the conditions under which incandescent lighting in
industrial establishments may be operated above 150
volts to ground and up to 300 volts to ground.
Part "a" notes that such lighting may be used if
maintenance and supervision"is done only by "qual
ified persons." It previously said "competent persons."
The change was made to assure that such persons are
qualified with respect to electrical technology. A
person who knew nothing about electrical matters
could be "competent" —apart from lack of electrical
understanding. -
Part "d ",now permits use of an integral switch in,
say, a 277 -volt incandescent lighting fixture, provided
the switch is not readily accessible. That means that a "
switch is O.K. in the fixture if the fixture is mounted
up oust of reach of persons not qualified in electrical
work and access to the fixture by qualified mainte-
nance personnel would require use of a ladder or some
type of lift or platform.
It should he noted that this new wording of part "d"
permits such use of an integral switch in an inca¢ndes -•
cent fixture, but part "b" of Exception No. 2 has not
been changed and use of an integral "manual' switch
in an electric discharge fixture (fluorescent, mercury
vapor, metal- halide, etc.) is still not permitted. Of ,
course, the word "manual' in part "b" of Exception
No. 2 does limit the prohibition, and remote- control"
switching has been accepted with the relay as a'--,
"nonmanual" switch in the fixture and control exer -'X` ,
cised at low voltage by another switch (manual or
automatic) away from the fixture. Use of multilevel ;
- `r:•.t,
Section 210 -6. Integral switch is permitted in 277 -
volt incandescent fixtures, BUT NOT IN fluorescent `
or other electric- discharge fixtures
MBER, 1877, . -, Gu T J KS
63
than 150 volts between them. Use of split -wired recep-
tacles and 120 /240 -volt duplex receptacles must be
evaluated against the rules of Section 210 -6(c) (1) and
its two Exceptions to determine if they are acceptable
in dwelling -type occupancies as noted in the rule.
Section 210 -6(c). Rule requires careful applica-
tion of split -wired receptacles and two - voltage
receptacles in "dwelling units" and hotol /motel
rooms .
ballasts for different light ~outputs from lamps is
acceptable under this rule if the change in ballast
wiring is done by reconnecting wires in the ballast
compartment. But an integral manual switch for
changing ballast output level in fluorescent fixtures
would violate the rule of part "b ", Exception No. 2.
Section 210 -6(c)
This section has been reworded for clarification, but
there is no change in the rules themselves.'Part (1)
applies to "dwelling unit(s) and guest rooms in hotels,
motels, and similar occupancies." Note that the
wording differentiates between "dwelling unit(s)" and
rooms in hotels, motels and other living or sleeping
units that do not satisfy the new definition in Article
100 on "dwelling unit." This is an important clarifica-
tion that arises in a number of other code rules. Note
that a hotel or motel room or a room in a dormitory is
not a "dwelling unit" and is not subject to those rules
that apply only to "dwelling unit(s)."
The rule of part (1) of Section 210 -6(c) prohibits use
of circuits with over 150 volts between conductors to
supply screw -shell lampholders, receptacles or ap-
pliances in dwelling units and the other specified
rooms, except for permanently connected appliances
and cord - and -plug- connected appliances rated over
1380, watts or 1/4 or more horsepower. The rule limits
incandescent lighting to a .120 -volt rating at all
lighting outlets in those places. But this rule has
caused considerable discussion and controversy in the
past when applied to split -wired receptacles and
duplex receptacles of two voltage levels.
- It has been argued that split -wired general - purpose
duplex receptacles are not acceptable because they are
supplied by conductors with more than 150 volts
between them —i.e., 240 volts on the 3 -wire, single -
phase, 120 /240 -volt circuit so commonly used in resi-
dences. The two hot legs connect to the brass - colored
terminals on the receptacle, with the shorting tab
broken off, and the voltage between those conductors
does exceed 150 volts. The same condition applies
when a 120 /240 -volt duplex receptacle is used —the
240 -volt receptacle is fed by conductors with more
64
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Split -wired receptacles on the two or more 20 -amp
small - appliance circuits required by Section 220 -3(b)
w for the kitchen, dining room and family room of
dwellings might be justified as complying with Excep-
t tion No. 2 of Section 210 -6(c) because such receptacles
supply electric toasters, broilers, fry pans, and other
high - wattage devices. But general- purpose, split -wired
receptacles in other areas of the type of dwelling areas
t specified would' clearly seem to be a violation. And
where a 120 /240 -volt receptacle,is installed in such
dwelling areas, it must be provided for a specific cord:-
connected load of adequate rating, as noted in the rule.
An important indication that the intent of the rule of
Section 210 -6(c) (1) is to prohibit split -wired and two -
voltage receptacles, as discussed here, was the code-
` making panel's rejection of a submitted proposal to
make an Exception to 210 -6(c) (1) that would permit
split -wired receptacles in dwelling units.
Section 210 -7(b)
` This rule requiring grounding of the ground
terminal of receptacles and cord connectors has a new
Exception. It permits receptacles mounted on portable
or vehicle - mounted generators, in accordance with
Section 250 -6, to have their ground terminals left
ungrounded, when the generator frame itself is not
grounded. But where such receptacles are mounted on
portable or vehicle - mounted generators, the grounding
1 terminal of the receptacle mast be bonded to the
generator frame [Section 250 -6(a) (2)J.
SEPTEMBER, 1977
Section 210 -7(b). Grounding is not required for
generator- mounted receptacles
+R�fis s
Section 210 -7(c)
For correlation purposes, a note after Section 210 -
7(c) refers to the use of "quiet grounding" for elec-
trical noise reduction for sensitive equipment, as
covered in Section 250 -74, Exception No. 4.
65
Section 210 -7(d)
On replacement of receptacles, a change in wording
of the Exception clarifies the rule considerably.
Although the basic rule is still the same —that
grounding -type receptacles be used as replacements
for existing nongrounding types —the Exception
requires that a nongrounding type receptacle be used
as the replacement in any case where the box or other
enclosure of the existing receptacle is not grounded
and does not contain an equipment grounding conduc-
tor —as with older installations of nonmetallic
sheathed cable without a ground wire or knob -and-
tube wiring.
Section 210 -7(g)
A new paragraph has been added to this Section to
require that when aluminum conductors are connected
directly to the terminals of any receptacle rated 20
amps or less, the device must be "approved for the
purpose " and must be marked "CO /ALR."
Section 210 -7 (g). Only CO /ALR receptacles for
aluminum wire
'��m+-� 3a��'� ,-,tip•.' ?�;°�iT5+4�- �a;ra�i;3�- ?'aka; -..ry;
• � ','w�.��:L?s_:*�•:v'���'�.�;�.. ..r%xi•.,sunrxa ".All
aluminum wires S
'�: >. "'+`�•` 0 '.i =wp are directly connected to
terminals of a receptacle... ' 1
_ s,.4 „ .?;,;" -� Section 210- 8(a)(1). GFCI protection is required
�o I �� _, for receptacles in garages as well as 'in
E. tµ � � �Y'' +�a=:. bathrooms '
' t. •'P�� I�I �i'�„ -Yy. +;,si :,�.y� „'^ j� PROVIDE THIS PROTECTION.
,r, F'1"> ���� Oh ':..�,;�.�.i�:a:..a... .. r...:s.m:•: ={ _ Single- phose. 120V, ISA wf�s2tf;w'i ' .f.•afir,.'.�t5
F:y ';�'•� .then the receptacle must be 20A receDlacles, ` fir`” ,".;�"'• °"
- <r3.;.. ;•, ^ti1� listed and marked '.' - -� -:.; . • 4�' . �a. n.''ei<' :.:
;'•,�'" -ts; '.kr •,P;_c CO /ALR RECEPTACLE . a `ice "' ' s' " • "•`
.ms. +.— ,�.[�um• -�*v.. -r.TT. —i —r —_ ■ . ;� -Yffi' ° ;. -.r .c.,v:.u... -,
- �Eu9:id.':uiv ".nL:a ktin6 :3ai:�•ui'"i•:a:r;,Srwv.;3.:1 �os.�i`�Set- .u£cu.�,m� ,' - ` •- , ®L �. i:�:
. - `•� - .. ' *` Eithet GFCI CBS' -1 t� 1l'' 5� I - >... a•
In panel or GFCI �. f �.i'..., •-
Section 210-8(a) receptacles I In bathrooms'." r" I In Ga�eges
Part (a) of this Section is now headed "Dwelling at box locations "L - - -;
Units "; and, as a result of the very clear and detailed
definition of those words, as given in new Article 100 ... WHERE CODE REQUIRES ITy' i` ••'• • _ "' *� ::: � '
;t-. - - `,s 3a= !Nluk•e °'r=34'sr.,r: R!j,
of the 1978 NE Code, all of the ground -fault circuit �•• *,• _
For bathrooms- i..p�;tt r • _. 'y3+
interruption rules apply to— ' " to guest rooms" y� �. ;•,
• all one - family houses ` .," For bathrooms
each dwelling unit in a 2- family house anA garages
• each apartment in an apartment house
• each dwelling unit in a condominum
But, the definition now makes it very clear that the
GFCI protection required by Section 210 -8(a) is not Single - family house Apartment units or Hotel, motel
required in bathrooms of hotel or motel rooms or - - Y •• condominium units or dormitory "
dormitory rooms or any other residential occupancy GFCI1 Yes GFCI? Yes b'' CF 2 No
that does not conform to the definition of "dwelling "' " "' " " °";"`'•i' =__' ^r= tg'r t =:
unit' rn
66 ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 210- 8(a)., A "bathroom" is now defined
for application of rule requiring GFCI protection
of receptacles
In part (a), GFCI protection is required for all 120 -
volt, single - phase, 15- and 20 -amp receptacles
installed in BATHROOMS and GARAGES of dwell-
ing units only. The requirement for GFCI protection
in "garages" is new in the 1978 NE Code. It was added
because homeowners do use outdoor appliances (lawn-
mowers, hedge trimmers, etc.) plugged into garage
receptacles. Such receptacles, therefore, require GFCI
protection for the same reason as - "outdoor " - recepta-
cles. In either place, GFCI protection may be provided
either by a GFCI circuit- breaker that protects* the
whole circuit and any receptacles connected to it or the
receptacle may be a GFCI -type that incorporates the
' components that give it the necessary tripping capa-
bility on low -level ground faults.
Although the requirement for GFCI protection in
bathrooms is not new, a lot of the discussion and
controversy that was commonly generated by the
SEPTEMBER, 1977 -
P ' '�'1r•s' =`�� 'f'+C• �= 'LAYOUT OF PLUMBING
+� in separate room ro „�-- FIXTURES IN HOTELt:;;:1
that is MI a F.#,,R,�n`- - :ae AND MOTEL.UNITS'
"baathZoomy �t='•
Guest rooms 16 hotels and motels are required by Section .
- 210 -25(c) to have the same receptacle outlets required by
Section 210 -25(b) for "dwelling units." The requirement for
a wall receptacle outlet at the "basin location" applies to bathrooms; and the anteroom area with only a basin is, by
definition and code intent, a "bathroom." A receptacle at the
basin would, therelore, be required by code. But, Section
210 -8(a), which applies only to bathrooms In "dwelling
-* units," does not apply In hotels and motels —and GFCI
protection Is not required for this receptacle.
question "What is a bathroom? " will now be elimi-
nated because a definition of the word "bathroom" is
added to the Section. A "bathroom" is "an area"
(which means it could be a room or part of another
p 67
Section 210-8(a) (2). For dwelling units, only
outdoor receptacles with "direct grade level
access" require GFCI protection
t basin; and Section 210-8(a) requires that It be GFCI-
Rea;-Piacie on each Idoo'r 91
apartment balcony does not
hove`
M 111
sy and an outdoor receptacle does not require GFCI M
grade -level access,
4F
of "bathroom" refers to the total "area" made up of the
re P
7-
toilet. Although a receptacle Is not required in the "room"
with the tub and toilet, It one Is Installed In that room, It must
room or area) that contains first a "basin" (sometimes
outdoors .,Ih
—ealhervocif
fbi
i' the bathroom," just as the one at the basin location Is "in
r- the bathroom."
one more plumbing fixture—a toilet, a tub, and/or a
s4_
shower. That definition should resolve conflicts about
cover and 11.
�Tavel access.,
68
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Earth
Receptacles fed out of graundY;'Aparttnent balcony receptacles
must be GFCI - protected 0 require GFCI protection ,
4
In'an r placii,
t outdoor dwelling'
E unit, GFCLprotectlon Is not required if there Is nci access to -
thd receptacle from -the grade4evef of ground around the
building.
131 ID
Section 210-8(a). Intent of bathroom GFCI rule �M -
applies to an area (not a room) in, every . . . . . . .
"dwelling unit"
TYPICAL BEDROOM SUIT NE-FAMILY HOUSE OR j 0
p�'Iclocxr.,renpolacr:, n se..nd-11.
APARTMENT I. 'd
: � � ulre GFCI pro in,
'4�,! but receptacle on porch below
Bedroom
�j need GFCI protection.
Outdoor receptacle on this porch might
likely be used to connect appliance used
Basin in vanitory K i- y on ground, and GFCI protection would
outside room with
seem to be required.
il—uh..d Wil
Toilet
IMPORTANT: A hotel, motel or dormitory Is not a "dwelling
T Receptacle t3 unit"
Tub' - I ...
not required
In this room , _7�r�_
ki.
T77-
A'
...... -----
Although this area with basin Is outside room with tub and
toilet, the Intent of Section 210 -25(b) requires a receptacle
t basin; and Section 210-8(a) requires that It be GFCI-
protected. LA
sy and an outdoor receptacle does not require GFCI M
-'- NOTE: 'I't'i's-im'-'p'or—ta'n'i"t"-;—un'je'r'�t7n,i�Fh,-t-ihe coda
protection, even If It does have grade-level access.
of "bathroom" refers to the total "area" made up of the
basin in the alcove plus the "room" that contains the tub and
toilet. Although a receptacle Is not required in the "room"
with the tub and toilet, It one Is Installed In that room, It must
room or area) that contains first a "basin" (sometimes
be GFCI-protected because such a receptacle Is technically `
"in
called a "sink"), and then it must also contain at least
i' the bathroom," just as the one at the basin location Is "in
r- the bathroom."
one more plumbing fixture—a toilet, a tub, and/or a
s4_
shower. That definition should resolve conflicts about
68
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Y.
F!
where GFCI protection is required. Clearly, a small'
room with only a "basin" (a washroom) is not a
"bathroom." Neither is a room that contains only a
toilet and /or a tub or shower.
It should be noted that this new rule on garages
applies to both 'attached garages and detached (or
separate) garages associated with "dwelling units " —
such as one - family houses or multifamily houses'
where each unit has its own garage. BUT, Section 210 -
25(b) requires at least one receptacle only for "at-
tached" garages. A receptacle is not required in a
' detached garage, but if one is used in such a garage, it
must have GFCI protection.
This rule requiring GFCI protection in garages may
cause some difficulties in application. It seems certain
that any 15- or 20-amp receptacle must have GFCI
protection if it is installed in the garage of a one -
family house. But the rule refers to "garages of
dwelling units," which indicates that the "garage" is
restricted to the "unit" and leaves a question about a
large, common -area garage space for many cars in,
say, an apartment house or condominium structure.
Such a large garage area is really not a "garage of a
dwelling unit," The broadest interpretation of the
wording would seem to call for GFCI protection of
receptacles in any garage or auto - parking area that is
associated with any structure containing one or a
number of dwelling units. • - ' '
Part (a) (2) of Section 210 -8, on outdoor receptacles,
has been changed to qualify the need for GFCI protec-
tion of "All 120 -volt, single- phase, 15- and 20- ampere
receptacles installed outdoors" at dwelling units. The
rule now specifies tha£ such protection of outdoor
receptacles is required only "where there is direct
grade level access to the dwelling unit and to the
receptacles ... " The phrase "direct grade level
SEPTEMBER. 1977
access" is not defined, and it seems certain it will lend
itself to many varied interpretations. Because there is
no "grade level access" to apartment units constructed
above ground level, there would be no need for GFCI
protection of receptacles installed outdoors on balcon-
ies for such apartments or condominium units. And
for apartment units above ground level, there could be
no grade -level access to such receptacles on balconies.
Likewise, GFCI protection would not be required for
any outdoor receptacle installed on a porch or other
raised part of even a one - family house provided that
there was not grade -level access to the receptacle —
even though there might be grade -level access to the
"dwelling unit" (the one - family house). This impor-
tant change in the rule on GFCI protection of outdoor
outlets was made to reflect the code - making panel's
conviction that such protection is not needed where
the receptacle cannot readily be used by someone
plugging•in a tool or appliance and making contact -
with earth of any masonry walk or other surface or
grade. ;f
Section 210 -8(b)
There have been major changes in the rules that
concern GFCI protection for all "120 -volt, single-'
phase, 15- and 20- ampere receptacle_ outlets" on '
construction sites. (Note that there are no require-
ments for GFCI protection of 240 -volt receptacles, 3-
phase receptacles, or receptacles rated over 20
amps.)
The basic rule of this Section says that ground -fault
circuit interrupters (either GFCI circuit breakers or
GFCI receptacles) must be used to provide personnel
protection for all receptacles of the designated
rating —that "are not part of the permanent wiring of
the building or structure." That phrase was in the
69
Section 210 -5(b). Assured grounding program of
protection
70
1975 NE Code and excludes from the need for GFCI
protection all receptacle outlets that are intended to
serve the occupants of the building after construction
is completed and are not simply installed as tempo-
rary outlets intended only for use by construction
workers during the course of construction activities.
BUT, THE FIRST BIG CHANGE in that rule in
the 1978 NE Code is the addition of a phrase that
significantly qualifies the need for GFCI protection of
the designated receptacle outlets:
GFCI PROTECTION IS REQUIRED ONLY FOR
THOSE RECEPTACLES THAT "ARE IN USE BY
EMPLOYEES."
That phrase clearly limits required GFCI protection
to receptacles that are actually being used at any
particular time. Receptacles not in use do not have to
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Exception No. 2 eliminates need for GFCI
s
Section 210 -8(b). Three ways to satisfy the
revised basic rule on personnel shock protection
at temporary receptacles on construction sites
be GFCI protected. This change means that poilable
GFCI protectors may be used at only those outlets
being used. There is no need to use GFCI breakers in "
the panel to protect "all" receptacles or to use all
GFCI -type receptacles —as the situation was 'under
the rule in the 1975 NE Code. This change seems to
71
seriously confuse the task or electrical inspection: if all
cord - connected tools and appliances are unplugged'
from receptacles when the inspector comes on the job,
then none of the receptacles are "in use" and none of
them has to have GFCI protection and there is no code
violation. Just how this new rule will be applied is up
to each user on the job site, but the rule itself radically
ieduces the extent of application of GFCI protection
on construction sites and virtually makes evasion of
the rule an easy matter.
Still another option for avoiding use of GFCI
protection on construction sites is given in a new
"Exception No. 2" to Section 210 -8(b). As explained in
the Exception, GFCI protection of receptacles may be
omitted totally if a "written procedure" is established
to assure testing and maintenance of "equipment
grounding conductors" for receptacles; cord sets and
cord- and - plug - connected tools and appliances used on
the construction site. In effect, the NE Code accepts
such an equipment grounding conductor program as a
measure that provides safety that is equivalent to the
safety afforded by GFCI protection. GFCI protection
is not required if all of the following condition's are
satisfied:
1. The inspection authority having jurisdiction over
a construction site must approve a written procedure
for an equipment - grounding program.
. 2. The program must be enforced by a single desig-
nated person at the construction site. -
3. "Electrical continuity" tests must be conducted
on all equipment grounding conductors and their
connections. The requirements on making such tests
are vague, but do call for
a. Testing of fixed receptacles where there is any
evidence of damage.
b. Testing of extension cords before they are first
used and again where there is evidence of damage or
after repairs have been made on such cords.
c. Testing of all tools, appliances and other equip-
ment that connects by cord and plug, before they are
first used on a construction site, again any time there
is any evidence of damage, after any repair, and at
least every three months.
Obviously, those rules are very general and could be
satisfied in either a rigorous, detailed manner or in a
fast, simple way that barely meets the qualitative
criteria. How an assured - equipment- grounding pro-
gram can be fully and realistically enforced by elec-
trical inspectors will only become clear as field experi-
ence develops. It does seem clear that the electrical
contractor who has responsibility for the temporary
wiring on any jobsite is the one to develop, write and
supervise the assured equipment grounding program,
where that option is chosen as an alternative to use of
GFCI protection. This whole NE Code approach to use
of either GFCI or an "assured equipment grounding
program" directly parallels the new OSHA approach
to the matter of receptacle protection on construction
sites.
Section 210- 21(b)(2)
In this rule covering use of receptacle outlets,
previous reference to "portable and /or stationary
appliances" has been changed to "cord- and'plug-
connected load." This is a basic change in code termi-
nology that appears also in the heading for Table 210 -
21(b)(2) and all other places that previously referred
to "portable" and /or "stationary" appliances. The
reason for the change was to more clearly identify the
nature of the load devices covered. Because both
"portable" and "stationary" appliances are "cord- and
plug - connected " —as distinguished from "permanent"
or "fixed" wiring to, "fixed" appliances or other
utilization equipment the new phrase was substi-
tuted for the old one in all applicable places. [See also
Section 210 -23(a) and (b).]
In some cases, reference to "appliances" was
changed to "utilization equipment" to broaden the
application of such code rules and not simply to limit
them to "appliances," which covers a category of ,
basically residential -type load assemblies and does not
include industrial and commercial loads that do not
conform to the definition of "appliances." See Section
210- 22(a), fifth sentence.
72 ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 210 -23 or by -cord-and-plug connection -to a receptacle —but
In part (a), the previous reference- to "fixed the method of wiring connection does not matter now
appliances" has been changed to "appliances fastened in determining "Permissible Loads" on branch circuits
in place" —which makes such appliances easier to "supplying two or more outlets."
identify. The reference to "portable or stationary
appliances" has been changed to "cord- and plug- Section 210 -25(b)
connected appliances not fastened in place." Similar Wording has been revised in the rule requiring at
change in wording is also made in part (b). least one receptacle outlet in each basement and in
With this new wording, a "fixed" appliance becomes each attached garage. First, the rule now applies
one that is "fastened in place" and not simply one that clearly and only to "a one - family dwelling" —which
is fed by "fixed" or "permanent" wiring. A load that is means a one - family house or a one - family unit in a 2-
"fastened in place" may be fed by either fixed wiring family or other multifamily dwelling, where applies-
" ble. Normally, one - family dwellings in apartment
houses (that is, apartment units) do not have indi-
vidual basements or individual attached garages. And
Section 210 -23. Descriptions of appliances have condominiums are the same. But, some duplex apart -
been changed to clarify intent of rules ments in "town houses" or "garden- type" (2 -story)
apartment buildings do have individual basements'
Any "portable" or "statlon.?" appliance y
an garages. In every basement and attached
4,5 is now •'CORD -AND- PLUG - CONNECTED" f �,4l garage —where associated with a one - family dwell-
appliance not fastened in place.
`a ''a;k „s:; ing —at least one receptacle outlet must be installed
p• .t�"sfii :,:,r? :. °: _t ,:. for each such area.
Another important clarification in this rule now
requires a receptacle outlet in a basement in addition
to any receptacle outlet(s) that may be provided as the
• py "»K? ,; •• �. , - required receptacle(s) to serve a laundry area in the
ry” 0:• - }: � `tt
BROILER S; 7 basement. This point was not clear in the 1975 NE
,�; �•:,�„ .^
BROILERS, „ .' FANS '
COOKERS Code, which left the possibility p
possibili that one rece tacle in
iREF RIGERATORS � i '` .. - •
_ - FREEZERS �i'.Y"s�.f}`- _ �,�^?a a� { .v •-��;' - .. ,_:. -: ., . «•.. -� .. =i.,, '-,-
r �,' _. Section 210- 25(b). Required receptacles for
[: �;,;"' - „j_•;' RADIOS,TVs ,,, "laundry” and "basement" must be separate,
individual receptacle "outlets ".
v.3Z • is _� s_ . "� `.
° -y CLOTHES WASHERS, "L;. BUILT -IN DISH
=N DRYERS- `^''xj PERMANENT, N
SEPTEMBER, 1977 - �+'«• ••- j•'7'.
Y
' • - ..73
- y`- ryas °:.:,� is;i.�M.:�s.;:•w :. -�s - - :r :r_ _ .�i t' ._ .._ . - -- � _� �: s- _ �," r;'': : p
.ti - .*.:X= �. }`.3�.s:r°:.• ;;�?+: %:4 <tis�F':m.' ,. ,�.;.'tw. ^" . -. �• _ - _ _ _ �s;�;^. _ ' ~ --
the basement at "the laundry area located there could need "to minimize the use Hof cords across doorways,
satisfy as both the required 'laundry" receptacle and fireplaces and similar openings" —and the heated air
the required "basement" receptacle. Now, a separate outlet along a baseboard heater is a "similar opening"
receptacle has to he provided for each requirement to that must be guarded.
satisfy the code rule. '- -
Section 210- 25(b), New Exception Section 210- 25(b). New exception permits recap-
At the end of part (b) of Section 210 -25, a new Moles in heaters as required spaced recepta-
Exception is added to the rule that "The receptacle ties
outlets required by this section shall be in addition to
•` ^'R`�Doorwu ""t.t^-f?r�•..s�ify"'.. +4^.I:GS.?a�S
an receptacle that is art of an lighting fixture or
• y:€ =:w
Y P P Y g 1; ml of dwelling umt
appliance...: ' In spacing receptacle outlets so that - �, *, .`},; ' :x' ; � "-'sue "r.,. ;:�;=;r- ':r„�•,;��:�
Ino floor point along the wall space of the rooms
designated by Section 210 -25(b) is more than 6 feet
from a receptacle, a receptacle that is part of an :x ^'. a,. :� BOTH OF THESE OUTLETS
appliance could never be counted as one of -the a ,- �; SATISFY SPACING RULES
required spaced receptacles. Now, the new Exception
states that a receptacle that is "factory installed" in a
:,� ,.x.�.a,,;;,y..- �:r' ^.3%^ ;.sue- sw8:�.c,`;,:,_+�= m',•_n
"permanently installed electric baseboard heater" (not �• � �,,,�,�„��,. � . „� r
a portable heater may be counted as one of the. s T � eta
required spaced receptacles for the walls ace occupied ''i': ; �/ ^ Nat more than 12FC
by the heater. Or a receptacle "provided as a separate t th- sn,. Peceptacle outlet in N. toanexi o itei f f'
ermanentl Installed
assembly by the manufacturer" may also be counted a
electric baseboard on cantinaous -
'-4 "?'t< °c; heater (at end or
wall space
as a required spaced receptacle. BUT, such receptacles ,
must not be connected to the circuit that supplies the ( ', .• _ at middle)
electric heater. Such a receptacle must be connected to NOTE: This change In the new Exception of Section;210 =25 ; •
M
�:, b was made to eliminate the need for use of wall _mounts
another circuit. 666.1 1 "
• •receptacles that might be required above a long baseboard • � a
Because of the increasing popularity of low- density -',heater to satisfy requirements on 'spaced receptacles- This
electric baseboard heaters, their lengths are frequent- was added because UL requires a warning on baseboard
ly so long (up to 14 feet) that required maximum heaters that receptacles are not to be located above the
heater units. c ^M
spacing of receptacles places receptacles above heaters i
• .- and produces the undesirable and dangerous condition i• Bur warcH THist..:< * -, 41r
where cord sets to lamps, radios, TVs, etc., will drape Separate circuiting required for heater and receptacle.: y x
over the heater and might droop into the heated -air ` _ ' '• " r > xr' : ' ;ate ' �„� �}`
outlet And UL rules prohibit use of receptacles above E y3 ^ ^ 240Vcircuit "p80 seboard 4- a
electric baseboard heaters for that reason. Receptacles 1 a } to healer assembly •; s
in heaters can afford the required spaced receptacle _ry
° '/'L 120V circuit xemer siemens
units without mounting any above heater units. They 1 toreoeplaale• ;- �4. „;..
satisfy the UL concern and also the - preceding note N aunetlst • ,x ,. r < ' ».. '« ,•_ 5 :.;
near the end of Section 210 -25(b) that calls for the
74 - ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 210 -26(a)
A change has been made in wording of the basic
rule that requires "at least one wall switch controlled
lighting outlet" in rooms, halls, stairways and at
outdoor entrances. The word "bathrooms" has been
added in the basic rule because various building codes
do not include bathrooms under their definition of
"habitable rooms." So the word "bathroom" was
needed to assure that the rule covered bathrooms.
A new note clarifies that "A vehicle door in an
attached garage is not considered as an outdoor
entrance." This now makes it clear that the code does
not require such a light outlet at any garage door that
is provided as a vehicle entrance because the lights of
the car provide adquate illumination when such a door .
is being used during darkness. But the wording of this
new note does suggest that a rear or side door that is -
provided for personnel et,�ry to an attached garage
would be "considered as an outdoor entrance" because
the note only excludes "vehicle" doors. Such personnel
entrances from outdoors to the garage would seem to
require a wall - switched lighting outlet.
Section 210- 26(a). Revised rule eliminates need
for lighting outlet at garage `vehicle" door '
.ystorage,oi coriteIn equlpmeiii•tlia4 -re quires- serWcing. � _?
9
Section 210- 26(a), Exception No. 1: Change - in
wording does not change intent of rule 7�,x.
`q
Kitchen and all bathrooms— •,s -,
Each must have at least one lighting outlet that is wall-
switch - controlled (not pullchain or switch In fixture or -
:3 canopy) ,
o`t 1
2 75
Section 215 -2. Feeder conductors need not be larger than service - entrance conductors when
higher ampacity of Note 3, Table 310 -16 is used
76
Of; A Tultllamlly dwelling
Itng might be fed Ilke this =' '
z ��'- •L- '9i,- ��`"'� Y':t``';3'�.f:ldn -...�f �r ':''..• -�` S'q:•
sA� +'sY f�fYZ •ear "•'" ., W 3" -..
� ih'-`' iii .i�;x " " -�' �`' �L.'.u�T/t�i��'•� `
'i" i =- '•�:: <:s: + �-n :�ri � ' Feeder to•� =;,u..
each aPYF k'�fi F4t_
Each set or }``'�`` - ... the set of
:;G: _:.
feeder conductors - service- entrance a
need not be ' wr`l ,<- "
z:, •,'._A;a conductors that {
larger than ... •4„ r +sr'ri'} supptydt
away, diversity on the feeder conductors should give
them the same reduced heat - loading that enables the
service conductors to be assigned the higher ampacity.
This new rule simply extends the permission of Note 3
to those feeders that carry the whole service load and ,
is applicable for any such feeder in a one - family
dwelling or for mobile home feed. -
. ELECTRICAL CONSTRUCTION AND MAINTENANCE
Another change has been made in Exception No. 1
.T'"°";,�'�"�` -' .-
�' q
of Section 210- 26(a). The word "bathroom" has been
,F;'
removed from this Exception that permits use of a
ti? _.r ° -'.: ;1T•,3
wall - switched receptacle as an alternative to use of a
wall- switched lighting outlet, because a "bathroom" is '
not a "habitable room." But, the meaning and intent r
g
-t
'n
ea
of this Exception has not been changed. In dwelling
<. • `,
units, every bathroom and every kitchen must have
'
at least one wall - switch controlled lighting outlet, and
those rooms may not use a wall switch controlled
receptacle outlet as an alternative to the lighting
�-
outlet: But in -all other rooms, use of a switch-
tom
controlled receptacle (to feed aplugged -in lamp) is,an _
Y
acceptable alternative. All of these changes in Section '
VI
210 -26(a) are really clarifications and, aside from the
note about "vehicle" doors, do not present new re -• '
quirements.
'ARTICLE 215 - FEEDERS
Section 215 12
selected in accordance with the higher- than - normal
In this section, added sentences note that it is never
ampacities permitted by Note 3 to Table 310 -16 for s
necessary for feeder conductors to be larger than the
services to residential occupancies. If the service
service- entrance conductors (assuming use of the
conductors are brought in to a single service discon -. F
same conductor material and the same insulation). In
nett (a single fused switch or circuit breaker) and `
particular, this is aimed at those cases where the size
load -side feeder conductors carry the entire service
of service - entrance conductors for a dwelling unit is
load to a switchboard or panelboard some distance e
Section 215 -2. Feeder conductors need not be larger than service - entrance conductors when
higher ampacity of Note 3, Table 310 -16 is used
76
Of; A Tultllamlly dwelling
Itng might be fed Ilke this =' '
z ��'- •L- '9i,- ��`"'� Y':t``';3'�.f:ldn -...�f �r ':''..• -�` S'q:•
sA� +'sY f�fYZ •ear "•'" ., W 3" -..
� ih'-`' iii .i�;x " " -�' �`' �L.'.u�T/t�i��'•� `
'i" i =- '•�:: <:s: + �-n :�ri � ' Feeder to•� =;,u..
each aPYF k'�fi F4t_
Each set or }``'�`` - ... the set of
:;G: _:.
feeder conductors - service- entrance a
need not be ' wr`l ,<- "
z:, •,'._A;a conductors that {
larger than ... •4„ r +sr'ri'} supptydt
away, diversity on the feeder conductors should give
them the same reduced heat - loading that enables the
service conductors to be assigned the higher ampacity.
This new rule simply extends the permission of Note 3
to those feeders that carry the whole service load and ,
is applicable for any such feeder in a one - family
dwelling or for mobile home feed. -
. ELECTRICAL CONSTRUCTION AND MAINTENANCE
ARTICLE 220 BRANCH CIRCUITAND'
FEEDER CALCULATIONS
Section 220-2
Section 220 -3(c). No "other outlets" are permit-
, Throughout the many parts of this Section covering
ted on 20 -amp circuit required for laundry recap-
computation of branch- circuit loads, and other
tacle(s)
• - Sections in the code, all reference to "dwelling occu-
pancies" have been changed to "dwelling units" and
^"Ligiitinq.outlel�,[ ,a;.r7�,,." c•y';- � -
are must be taken to apply all rules on the basis of
for laundry; oreo!��t'�,��,,$ " viol AnoNt
the now meaning of the phrase "dwelling
Laundry circuit may
Vii;': ' not supply lighting
unit" —which is a living accommodation that includes
; "'T� or
:;�_ •, ry
'"'••`z'-
"�
permanent provisions for cooking (a kitchen area) and
- yf;3t�Z` '*k''*
'r•'p,oiechon ksck i3` +- '
any other lighting °
ma and '•
sanitation (a bathroom). Hotel, motel and dormitory
roled cl 20A tags';
outlets.
<
units that do not have permanent cooking equipment
M'Ff fir'
are not "dwelling units" and are subject to the various
"`
"rE
XReceplacle eLworFtiench
:"
•
rules only where specifically mentioned.s
+; •�` 7,7' 'Q
f r�r
,'.Cis-- •oralhe"r loiulian "4aY�y`„
In Table 220 -2(b), the listing of "Dwellings (Other
as `.:cOn Rgie,
�Ai least oneesmgle of M�
Than Hotels)" has been changed to "Dwelling Units"
duplex receptocle,within 6f1
'ci
n
r +b is ,WKW; °T:
(which o not include
ci
laundry:equipmenInimumreq
' ired branch circuit
capacity remains as
...laundry circuit may #5�j
it was, at 3 watts per sq ft.,'
not supply receptacles
c6�y °i.�"�v° more than B ft from
-----
jyj;Yi laundry or not intended
a- Section 220 -3(c) ^; •:
«s5 w +> for laundry.. • -,, -• .,
7
' This rule, which requires at least one 20 -amp
branch circuit to supply the receptacle outlet(s).
- -
• required at the laundry location of a dwelling unit, has'
been modified by a new sentence that prohibits the use
20 -amp general- purpose receptacle outlets. Such load
of that laundry circuit for supplying outlets that are
is considered sufficiently covered by the load capacity
not at the laundry area. And laundry outlets are still
provided for general lighting.) But in other than -
' required by Section 210 -25(b) to be within 6 feet of the
dwelling units, where a load of 180 voltamperes of
intended location of the appliance. It would seem that
feeder capacity must be provided for all general-
any receptacle outlet more than 6 feet from laundry
purpose 15- and 20 -amp receptacle outlets, a demand
• equipment could not be connected to the required 20-
factor may be applied to the total calculated recep-
* amp laundry circuit.
facie load as follows:; .t.
Fbe
1. The demand factors in Table 220 -11 may
Section 220-13
applied to the total load of general - purpose receptacle
This rule has been revised to perinit two possible
outlets for the particular type of occupancy. (That was
• approaches to determine the required feeder apacity
the only provision for use of demand factors on
to supply receptacle loads in "other than dwelling
receptacle loads, in the 1975 NE Code.)
units." (In dwelling units and in guest rooms of hotels
2. As an alternative to the foregoing use of demand
and motels, no feeder capacity is required for 15- or
factors from Table 220 -11, the 1978 NE Code permits
;^.:SEPTEMBER, 1977
0
y •«
1�
I ake the ioiaii7umtiar or genera,- purposa receptacle out -
' meted by a -given feeder.:' c,C3 :r°•lq-
. - ILS ' :x.'i :-R Y .It•�9 +f>•x'*,,�-,•m -.
—
• 500'receplo_cks,+�l/ -���; � ��-, 1, Q ;;�+" w¢Q❑', ,
i '�S;,s ��Sw'�T•�p�- �5�:,•. 3 ^��`.° -$ 500
Y_§-= mulOplythetotal by- 180�voltamperes . - +•s,- ,, .fi ;3•'• -;_•
[raqulred load of section 220 -2(c) (4) for each recepta-
-- clel-;�j a s:� ��&•±�i�"`'k'� s ivti.:"ar'sS' ,�': "�c.;?
��;= K. �" en��> r�n�- n#r�',••°^t'�rn.::�3'��.,�4 �'-y 1,•.
�SOdx�180VA,��' 90,000'VR�
and take4he result as a load of unity power factor. (This '
�• 0¢,fs' riot mentioned (n the code rulaj° +".�f� ,�= r'ta?�°,,�x ;,: ` y�i.��," tip? y3. �', 4�? t,; f, �� _ ? +Cz.'.:Xt�:A`-.'�3y7- aa;7.•
-,Theti applyahe demand factors from�Table 220- 13:' " * "i _
` Flrst 10'kw orless @ 100%- demand �,:; .= 10,000 watts'.-
-- Remaindero`ver 10 kw @ 50% demand s °`�'"• "' �' _ -• `
? v =.(90,000 = 10,000) x 50 %-•vi3. `:=" =•r Y.� ?+rte• -++� .
d X80,000 'U.5
+'^ °c G 40,000 walls " -
Minimum demand -load total = - 60,000 watts
Thereforeahe feeder -must have a capacity of 60 kw for the;":
'total receptacle load: Required minimum ampacity for that
load is then determined from the voltage and phase - makeup
-(single- or 3- hase'of the feeder.:"'- "-'.'°' "iD ° "" "'
use of demand factors as given in new Table 220 -13.
Those demand factors apply to any "nondwefling",
occupancy. It should be noted that the total receptacle
load, obtained by multiplying the total number of
receptacles by 180 voltamperes, comes out in "voltam-
peres." Yet, the new Table 220 -13 refers to the "Re-
ceptacle Load" in "wattage." It must be assumed that
the " voltampere" load is taken as unity power factor
so that the load then becomes the - same value in
"watts."
Section 220 -17
Revised wording of this rule makes clear that a
"fixed appliance" is one that is "fastened in place."
But the basic rule itself is not changed —a demand
'factor of 75% may be applied to the sum of the
nameplate load ratings of ' four or more appliances
fastened in place" in determining the required
ampacity of a feeder that supplies all of the
appliances.
Section 220 -32
This section has a new heading that designates it
for use with "Multifamily Dwellings" - instead of
"Three or More Multifamily Dwelling Units."
78,
g a ee er o we ng Lint .
It notes that if calculation of suchl feeder according
to the basic long method of calculating given in Part B
of Article 220 exceeds the minimum load ampacity
permitted by Section 220 -32 for three identical
dwelling units, then the lesser of the two loads may be
used. This rule was added to eliminate the obvious
illogic of requiring a greater feeder ampacity for two
dwelling units than for three units of the same load
+, makeup. Now "Optional Calculations" provide for a
feeder to one dwelling unit, two dwelling units or three
or more dwelling units.
Section 220-34
The optional calculation for feeders and service -
entrance conductors for a school has been clarified.
Feeders "within a building or structure" must be
calculated in accordance with the standard long
calculation procedure established by Part B of Article
220, BUT the ampacity of any individual feeder does
not have to be greater than the minimum required
ampacity for the whole building, regardless of the
calculation result from Part B.
To be continued next month.
• ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 220 -13. New method uses Tati[e 220`13 to.
Section 220 -33
t
calculate feeder demand load for general-
This is a new section that provides an optional
purpose receptacles
• calculation for sizin f d to "tw d
lli •ts "
I ake the ioiaii7umtiar or genera,- purposa receptacle out -
' meted by a -given feeder.:' c,C3 :r°•lq-
. - ILS ' :x.'i :-R Y .It•�9 +f>•x'*,,�-,•m -.
—
• 500'receplo_cks,+�l/ -���; � ��-, 1, Q ;;�+" w¢Q❑', ,
i '�S;,s ��Sw'�T•�p�- �5�:,•. 3 ^��`.° -$ 500
Y_§-= mulOplythetotal by- 180�voltamperes . - +•s,- ,, .fi ;3•'• -;_•
[raqulred load of section 220 -2(c) (4) for each recepta-
-- clel-;�j a s:� ��&•±�i�"`'k'� s ivti.:"ar'sS' ,�': "�c.;?
��;= K. �" en��> r�n�- n#r�',••°^t'�rn.::�3'��.,�4 �'-y 1,•.
�SOdx�180VA,��' 90,000'VR�
and take4he result as a load of unity power factor. (This '
�• 0¢,fs' riot mentioned (n the code rulaj° +".�f� ,�= r'ta?�°,,�x ;,: ` y�i.��," tip? y3. �', 4�? t,; f, �� _ ? +Cz.'.:Xt�:A`-.'�3y7- aa;7.•
-,Theti applyahe demand factors from�Table 220- 13:' " * "i _
` Flrst 10'kw orless @ 100%- demand �,:; .= 10,000 watts'.-
-- Remaindero`ver 10 kw @ 50% demand s °`�'"• "' �' _ -• `
? v =.(90,000 = 10,000) x 50 %-•vi3. `:=" =•r Y.� ?+rte• -++� .
d X80,000 'U.5
+'^ °c G 40,000 walls " -
Minimum demand -load total = - 60,000 watts
Thereforeahe feeder -must have a capacity of 60 kw for the;":
'total receptacle load: Required minimum ampacity for that
load is then determined from the voltage and phase - makeup
-(single- or 3- hase'of the feeder.:"'- "-'.'°' "iD ° "" "'
use of demand factors as given in new Table 220 -13.
Those demand factors apply to any "nondwefling",
occupancy. It should be noted that the total receptacle
load, obtained by multiplying the total number of
receptacles by 180 voltamperes, comes out in "voltam-
peres." Yet, the new Table 220 -13 refers to the "Re-
ceptacle Load" in "wattage." It must be assumed that
the " voltampere" load is taken as unity power factor
so that the load then becomes the - same value in
"watts."
Section 220 -17
Revised wording of this rule makes clear that a
"fixed appliance" is one that is "fastened in place."
But the basic rule itself is not changed —a demand
'factor of 75% may be applied to the sum of the
nameplate load ratings of ' four or more appliances
fastened in place" in determining the required
ampacity of a feeder that supplies all of the
appliances.
Section 220 -32
This section has a new heading that designates it
for use with "Multifamily Dwellings" - instead of
"Three or More Multifamily Dwelling Units."
78,
g a ee er o we ng Lint .
It notes that if calculation of suchl feeder according
to the basic long method of calculating given in Part B
of Article 220 exceeds the minimum load ampacity
permitted by Section 220 -32 for three identical
dwelling units, then the lesser of the two loads may be
used. This rule was added to eliminate the obvious
illogic of requiring a greater feeder ampacity for two
dwelling units than for three units of the same load
+, makeup. Now "Optional Calculations" provide for a
feeder to one dwelling unit, two dwelling units or three
or more dwelling units.
Section 220-34
The optional calculation for feeders and service -
entrance conductors for a school has been clarified.
Feeders "within a building or structure" must be
calculated in accordance with the standard long
calculation procedure established by Part B of Article
220, BUT the ampacity of any individual feeder does
not have to be greater than the minimum required
ampacity for the whole building, regardless of the
calculation result from Part B.
To be continued next month.
• ELECTRICAL CONSTRUCTION AND MAINTENANCE
ARTICLE .234-SERVICES
Section 230 -2
A new Exception (No. 7) has been added to the basic
rule requiring that any "building or other structure"
must be supplied by "only one set of service drop or
service lateral conductors." Exception No. 7 adds an
important qualification of that rule as it applies only
to Section 230-45 covering service - entrance layouts
where two to six service disconnects are fed by one
drop or lateral and are installed in separate individual
enclosures at one location, 'with each disconnect
supplying a separate load. As described in Section 230-
45, such a service equipment layout may have a
separate set of service: entrance coriductors' run to
"each or several" of the two-to -six enclosures. New
Exception No. 7 notes that —"where a separate set of
underground conductors of size 1/0 or larger is run to
each or several of the two -to -six service •disconhects,
the several sets of underground conductors are consid-
ered to be one service lateral, even though they are
connected together at their supply end (at the'trans-
former on the pole or in the pad -mount enclosure or
vault) but not connected together.at•their load ends.
The several sets of conductors are taken to be "one
service lateral" in the meaning of Section 230 -2,
although they actually function as separate circuits.
Although Section 230 -45 applies to "service
entrance conductors" and service equipment layouts
fed by either a "service drop" (overhead service) or a
"service lateral" (underground service), Exception No.
'is addressed specifically and only to service "lateral"
, O ER, 1977 .
conductors because of the need for clarification based
on the code definitions of "service drop,". "service
lateral," "service- entrance conductors, overhead sys-
tem," and "service- entrance conductors, underground
system." (Refer to these definitions in the code book to
clearly understand the intent of new' Exception No. 7
and its relation to Section 230 -45). The matter
involves these separate but related considerations:.: ,
1. Because a "service lateral" may (and usually
does) run directly from a transformer on a pole or in a
pad -mount enclosure to gutter taps where short tap
conductors feed the terminals of the service discon-
nects, most layouts literally do not have any "service
entrance conductors" that would he subject to the
application permitted by Section 230 -45 —other than
the short lengths of tap conductors in the gutter or
box where splices are made to the lateral conductors.
- 2. Because" Section 230 -45 refers only to sets, of
"service- entrance conductors" as being acceptable for
individual supply circuits tapped from one drop or
lateral to feed the separate service disconnects, that
rule clearly does not apply to "service lateral" conduc-
tors, which by definition are not "service- entrance
conductors." So there is no permission in Section 230-
45 to split up "service lateral" capacity. And the basic
rule of Section 230 -2 has the clear, direct requirement
that a building or structure be supplied through only.
one lateral for any underground service. That is, a
service lateral must be either a single circuit of one set
of conductors or,-if circuit capacity requires multiple
` 55
Section 230- 2,,Exception No. 7. This clarifies application.ol /Section 230-45 to underground services.
I•i�',:(9{ti.' ='>_;, r�,.'•;..;� -,"_•" �s r",'�d ; r� ^ ""y }. H�" _ _ S � • >sT`7i t47.,.t_v.y'�: - ie4 Sjv���;; a,,`....,r.��J,r� a
rr' !'' ^: .. '•.5 ..� ...,. ..+ }�7 ,j- ,i -•lS,s %rte- •`_c`�:4� ° _ -. •• .: .. .. _. ',- °••:`�..n.,. {: _:. r. •... ... :i ..S.« -�.`? .`y'�
�uSectlori 23045 can be applied to overhead services, as But the 1975 NE code had this Ilmltatlon on service �^
shown here . - = % ': ; ';, ,- _ y'r� - la:ara!s (and this Is still acceptab!e)- - -
pi
Ulil
.5.;1a : :.v ;;,aF- ,•.�is'a'ilt� -'.fv s,! 'vfir- •_��sti5= .•:.'.;Tsj -i: >` :mil n , - •� .�' a f:�"?.i Sr . L�rw
iiy:
;S ?! c•�,_- ,J.,c -
;��� +,i Dole' - . �_< e ` • E''. - '• - -•; _- {eZ :. :�!
•1,,:1"'sa:,:,LyEs_';''" =„ i:o:�,T• - » -:. d Tronsformer in pad -
:. .r °'- = - • �' ' mounted enclosure
or mat installation
;'M,,';,z , %rv: =t• .. .Commercial or - • ,3
!ng from/ ..industrial bldg ^with - - - -
Y ?', ^- 'point of drop -. • - single lendncy - = j - '.... ' �J
' •3 v, CanneC110n -� 2; { •• 'i: '--.:;: f
°Service lateral° . Each service disconnect fed by
(conductors in cable short length of "se(vice- enlronce'
• >''�'�- %4i�:cr'3#r�. LTwo to six'service- disconnects, .aracewoy);3
conductors", that lop Yulerol "'+:.,, _
�, i .�•r „• •, uw•-�T h• �, ...g '• ',conductors in gullet
�'S.a; each fed by a separate set of ,..:� •: +, <` = .5r `. •:.:, ,,.�.: ^:_:,xw ?iw..::•r.x: �k�a.•isi.6i;.1. ,
Sr- SE conductors . ; ervice lateral conductors are not "service entrance” c
:s;o xur - , •.fit �;' _. ,. ,'( conductors and were, therefore, not applicable to the
i, subdivision permission of Section 230-05. The requirement
FROM TWO To SIX separate sets of service-entrance - t of Section 230 -2 for "one set of service lateral conductors"
conductors may be supplied by a single servke drop for demanded one circuit of single- conductor or parallel- '
,k either single• or - multiple- occupancy buildings. Disconnects _'; conductor makeup. %•j
can be of same or different ratings, and each set of service-
.t entance, conductors can be installed using any approved
wiring method. Now, Exception No. 7 considers this type of hookup to be :(
_crsa ; -cu''r `s�, °s=•�,,r-SS�s�.:-�:.c;,;,r c:.,;t - "one sat of service lateral conductors " - - •ti • J
- e�'- ii'' �T... r.. i'. ���'`° �'' i,•' �. a-'"'"".-.. t' �` r' ��= ?s "�:x�a`,"r'G�S<.'�v:,:i:.x<.'r s "" ,- _ - - ':�
. ar other layouts may be used to correspond to Section • i !
230 -45 wording of "service- entrance conductors" to supply t Service laterals ••'',.' �- Two to six separate
"each or several" service equipment enclosures. connected together - service disconnects sup-
, #•,z. s„�: >, ^.nl.� -c, :,.c.,�,..,�.�- ,•,:,., •,_-,: of common supply Point fxouped' plying seporala loads
.FNr -b: -C:•?-t:, .F...r ry,g. e,.r... • i -
but not at of one
Service drop ,- ��:1;•.5.� �,;.. -, :,�;;';, Service drop load ends ' tacalion'
w. F :' Service- entrance' 1
LL _• conductors- r-{ i
cM i _ . , rf( r
Service disconnects - ) jj )(?() , , -•.i
andOCprotecl!on
a;; z; Y.; rxi,,. ?,,•' tc< It „' >, =Jr'-,�- w:;;.,if;,;:,,,;r: _ -,�; Underg
round sets ofconductors- eoch one
. - "�
' <yc -• ^r " +f ^” ri =.. 1; _ aseparale circuit of conductors not smaller' i
y' Service drop : y :; Service drab than size 1/0 — • }
Service- entrance
�- conductors This Is one service lateral, In the meanin of the basic rule of '
Service disconnects_ > 1 y > y Section 230 -2.
yea•-:
ts:°s:ais.�'�:'. -. cis' "r�:::2�::. " >::�"`t..�._..= .ate,,,., -_ -.3 :- '._..:, :.�c ,.,.. _..... ...a�•, °.:s..- r= 4'iYr'�'' %�
conductors per phase leg, the lateral must be made up
of sets of conductors in parallel — connected together
at both the supply and load ends —in order to consti-
tute a single circuit (that is, one lateral).
3. New Exception No. 7 now alters the intent of
Section 230 -2 to permit "laterals' to be subdivided
into separate, nonparallel sets of conductors in the
way that Section 230 -45 permits such use for "service -
entrance conductors" —but only for conductors of 1/0
and larger and only where each separate set of lateral
conductors (each separate lateral circuit) supplies one
or several of the two -to -six service disconnects.
A major reason given in support of adding Excep-
tion No. 7 to the 1978 NE Code was the importance of
subdividing the total service capacity among a number
of sets of smaller conductors rather than a single
parallel circuit (that is, a number of sets of conductors
connected together at both their supply and load
5s
ends). The single parallel circuit would have much
lower impedance and would, therefore, require, a
higher short- circuit interrupting rating in the service
equipment. The higher impedance of each separate set
of lateral conductors (not connected together at their
load ends) would limit short - circuit current and
reduce short- circuit duty at the service equipment,
permitting lower IC (interrupting capacity) -rated
equipment and reducing the destructive capability of
any faults at the service equipment. This point was
made in the "Supporting Comment' that accompanied
the proposal in the Preprint to add this clarification
of Exception No. 7. The comment read:
Presently a service requiring over 400 -amp capacity
requires one or more sets of conductors in parallel (if cables
are used), because a single service drop or underground
ELECTRICAL CONSTRUCTION AND MAINTENANCE
" lateral is required. This causes a maximum Available
short-c cuitcurrent. Example: 208 /120 -volt service, 500 -kva
transformer, infinite primary supply, 1400 -amp service, 100-
ft length, conductors in parallel, four 500MCM cables in
pa1'a11eL -• - •
Available short - circuit current = 22,000 amps (paralleled).
i_•,.•.
- -; IE our separate service drops or laterals were permitted to
be four disconnect switches all grouped at one location, then
the cable impedance would be four times as great. Overall
impedance would reault in the following:
Available short - circuit current = 12,500 amps (four single
- ;cables)•':::.' \ -
,....
Presently up to six switches are allowed at a service. Why
::not let a separate feeder to each with all joined up at the
' transformer secondary terminals instead of at the building
;side? ?r
AN-
y°
Section 230 -30
Rewording of Exception No. 4 now makes clear that,
-for underground service lateral conductors, an indi-
Section 230 -30, Exception No. 4. Bare aluminum
or copper -clad aluminum grounded conductor
must be covered in cable assembly.
OCTOBER, 1977 '- -
' f
vidual grounded conduct (such as a grounded
neutral) of aluminum or copper -clad aluminum
without insulation or -covering may not be used in
raceway underground.
The way this rule was worded in the 1975 NE Code, .
an individual bare aluminum neutral (along with
individual- insulated aluminum • phase legs) of an
underground service lateral appeared to be permitted
if the circuit was installed in conduit or other raceway,
and that interpretation was common. Under that ,
same rule, however, a bare aluminum neutral of a
lateral directly buried in the ground had to be "part of
• cable assembly approved for the purpose and having j
• moisture- and fungus - resistant outer covering."
The new wording of Exception No. 4 permits an
'aluminum grounded' conductor of an underground
service lateral to be without individual insulation or
covering "when part of a cable assembly approved for'
the purpose" where the cable is directly buried or run i
in a raceway. BUT, .if an individual 'aluminum
grounded neutral conductor of an underground service
is used in a raceway, it MUST NOT he bare. Even in
a raceway, the code permits an aluminum grounded
conductor to be bare only if it is,included in a cable
assembly approved for the purpose with a moisture -
and fungus - resistant outer covering on the cable
assembly. Of course, a lateral made up of individual
insulated phase legs and an insulated neutral is
acceptable in underground conduit or raceway..:. z.
Section 230-40
The same change in wording has been made in
Exception No. 4 of Section 230 -40(a) as described
above for Section 230 -30. In this section, the reference '
is to "service entrance conductors' instead of "service -
lateral conductors:' But, again; a -bare individual: •.. ;`
aluminum or copper -clad aluminum grounded conduc=
for (grounded neutral or grounded phase leg) may not
be used in raceway or for direct burial. Any such bare ,
conductor is acceptable only when enclosed in an
approved, jacketed cable assembly — whether installed
as a direct burial cable or in a raceway. =
Section 230-43 - - -
The list of wiring methods that are acceptable for-'...
use with service entrance conductors has been -:
expanded to include "INTERMEDIATE METAL
CONDUIT" (IMC, Article 345) and "TYPE MC
CABLE" (Metal -clad cable, Article 334). And a note _ 2.
was added at the end to recognize use of cable tray to
support cables that 'are listed in Section 240 -43 as
suitable for service entrance conductors. -
Section 230-50
In part (a), "INTERMEDIATE METAL CON-
DUIT" and "TYPE MC CABLE" were added to the
list of acceptable physical protection for service
entrance conductors. "where installed in exposed
places near driveways or coal shutes ..:' etc.
Section 230 -72 (a), Exc, 'ion No.^ 2. Permits
remote installation of of two -to -six service
disconnects to protect Fire -pump circuits (typ-
ica) layouts).
I more
K disco
=to five normal ce disconnects
y grouped at main
service location or
u? In common enclosure
Water pump that `
also serves as
fire- protectlon
water supply
Olt-
Single normal aj
service disconnect
Installed remote • "':
from main location
:,fir t�:�r.�r'��•� � �:�
Two to five service disconnects, each fed by a separate set
of SE conductors
'r.,:.,` c.k•'; ".n?L":`�^ err- �..°' �� ".�.'"� =��z?;.F� =.?'is�i':Wx.
liO, „w,._�..•.. -y!%,. ,�.+,� S. OR, remote disconnect
ixr .One or more ”. could be fed by
-' conduit risers`;.` lateral circuit
,one or more; #� from main location ; •,
laterals an pole
• ' r ,'�,F `. Y 4�.��' `lCc, � �;- ••••IIII g7'/'i�^4i }''fir'
.'U A� �T''s• rt �i �:.a J r .r� Z.• }:min ^; :, -�`�'1
�;.•' -•s^ti �; r'�.- �One'to FiveSS.... ,� 4„�r:✓,c' ' -�, -"
'service disconnects :; �c ;�; =�s' '''i•'" -`
-
a; 1. one lateral to i One lateral run
` ,:.1:
,,n•I grouped disconnects . a directly to remote or separate lateral v - disconnect for -
' to each disconnect ^ 'r� ,.= water pump >
t.t ::Y.. ^�� .^,- -�r� r -STr� +N,rc..- ,.r•„ f +fir'. v'
'NOTE: Many layouts are-possible, depending upon capacity
••, of circults and type of metering required. Disconnects may
- be Indoors or outdoors.
58
Section 230
The basic. . of this section has not been changed
and still requires that, where more than one switch or
CB is used for the service disconnect means (up to a
maximum of six switches or CBs in a common enclo-
sure or separate enclosures), all of the disconnect
devices must be grouped together. That rule is a _
follow -up to Section 230- 71(a), which permits use of
either a single switch or CB as the service disconnect
or up to six switches or CBs in either a common
enclosure'or in separate, individual enclosures. The
idea behind the basic rule of Section 230 -72(a) is to
group all of the service disconnects together at one
location so the service conductors can he readily
disconnected from all loads at one place.
A new Exception No. 2 has been added to Section
230 -72(a) to permit one of the two -to -six service
disconnects to be located remote from the other
disconnecting means that are grouped in accordance
with the basic rule — PROVIDED THAT the remote
disconnect is used only to supply a water pump that
is also intended to provide fire protection. In a
residence or other building that gets its water supply
from a well, a spring or a lake, the use of a remote -
disconnect for the water pump will afford improved
reliability of the water supply for fire suppression in
the event that fire or other faults disable the normal
service equipment. This new Exception was needed to
tie into the rule of Section 230- 72(b), which permits
remote installation of a fire -pump disconnect switch
that is permitted to be tapped ahead of the one -to -six
switches or CB's that constitute the normal service
disconnecting means (see Section 230 -82, Exception
No. 5). The new Exception provides remote installa-
tion of a normal service disconnect when it is used for
the same purpose (water pump used for fire fighting)
as the emergency service disconnect (fire pump)
covered in Section 230- 72(b). In both cases, remote
installation of, the pump - disconnect is permitted to
isolate the critically important pump circuit from
interruption or shutdown due to fire, burndown or any
other fault that might knock out the -main (normal)
service disconnects.
A wide variety of layouts can be made to satisfy the
code permission for remote installation of a wateir-
pump disconnect. The accompanying illustration
shows three typical arrangements that would basically
provide the isolated fire -pump disconnect. - -
. ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 230-95
A number of important changes have been made in
this Section, regulating use of ground -fault protection
at services:
1. For the first time, the code rule requiring ground -
fault protection for any service disconnect rated 1000
amps or more (on 480/277 -volt services) now specifies
a maximum time delay of one second' for ground -
fault currents of 3000 amps or more. Previously, the
NE Code did not mention "time delay."
The maximum setting of any service ground -fault
protection hookup is still 1200 amps, but the time -
current trip characteristic of the relay must assure
opening of the disconnect in not more than one second
for any ground fault current of 3000 amps or more.
This change in the code was made to establish a
specific level of protection in GFP equipment by
setting a maximum limit on in of fault energy.
The reasoning behind this change was explained in
the Preprint as follows:
- The amount of damage done by an arcing fault is directly
proportional to the time it is allowed to-burn. Commercially
available GFP systems can easily meet the one second limit.
Some users are requestingtime delays up to 60 seconds so all
downstream overcurrent devices can have plenty of time to
trip thermally before the GFP on the main disconnect trips.
However, an arcing fault lasting 60 seconds can virtually
destroy a service equipment installation. Coordination with
downstream overcurrent devices can and should be achieved
by adding GFP on feeder circuits where needed. The code
should require a reasonable time limit for. GFP. 3000
amperes is 250% of 1200 amperes. 250% of setting is a
calibrating point specified in ANSI 37.17. Specifying a
maximum time delay starting at this current value will allow
OCTOBER. 1977
Section 230 -95. New n , warns of improper
operation of GFP equipment when used with
emergency supply system.
jr 3. This GF current coming, back on neutral goes through
GFP sensor and Is not sensed as fault current.
GFP
.Servicro hookup,` f •.
In �`�Trancier'
'r' -• '��swi /lah •`r �s.r 7�� -.,{� Gene�ialor•
��. + -"✓' ?� 3 1. Phase Adevelops'e:•'(
lyµY.,'Z ground fault to '
or
_s enclosure oni,e°
bad side of Ec ^Lo
transfer switch -
NOTE: And even under normal (non - faulted) conditions,
neutral current due to normal load unbalance on the phase
legs can divide at common neutral connection In transfer
switch, with some current flowing toward generator and
returning to service main on the conduit — Indicating falsely
that a ground fault exists and causing nuisance tripping of
GFP.
either flat or inverse time delay characteristics for ground -
fault relays vntli approximately the same level of protec-
tion.
• • r ' }
' =:•'�;R:.
GF torrent .=
,•
_ in conduit and` ^c.
t:u.`� • 7:: x,. `r• t:- -(
enclosures. :y.f`•�hi`
7yA��..C.twf:!u;:�.��::e.�`.i
GF current goes
„t to neutral here
J-;
E Ground fault ' -�„ .
end returns over
current divides a ; ; =!
;' neutral to service,
here r : " "" •
through GFP sensor.
��. + -"✓' ?� 3 1. Phase Adevelops'e:•'(
lyµY.,'Z ground fault to '
or
_s enclosure oni,e°
bad side of Ec ^Lo
transfer switch -
NOTE: And even under normal (non - faulted) conditions,
neutral current due to normal load unbalance on the phase
legs can divide at common neutral connection In transfer
switch, with some current flowing toward generator and
returning to service main on the conduit — Indicating falsely
that a ground fault exists and causing nuisance tripping of
GFP.
either flat or inverse time delay characteristics for ground -
fault relays vntli approximately the same level of protec-
tion.
2. A new Exception has been added to Section 230-
tional or increased hazards» The idea behind that is
95(a) to'exclude from GFP requirements any service
to provide maximum protection against service outage
installation serving "a continuous industrial process
for such industrial processes. With highly trained
where a aonorderly shutdown will introduce addi-
personnel at such locations, design and maintenance
of the electrical system can often accomplish safety
objectives more readily without GFP on the service.
Section 230 -95 (a). New rule specifies maximum
Electrical design can account for any danger to
energy let- through for GFP operation.
personnel resulting from loss of process power versus
r^'«,•..sw- .-:. -� `:�.,•r. .,,.,,,,,.,;,.�, fi;,,..,_: ; .,,,�,,,
(•'r•^�L~n' fV
damage to electrical equipment. ,
°- �•Tli°f
• .JL Yr AA
"° Maximum �" Tlmecurrent
-
•. as t
Y200•amp �. •,1 operating curve ;
band • -�
- -
;F' or must not
'`'. ` ': �,' •' .. 1:' %�`� pass through
r[erenn, tl'xfsq, •. °. 1 y1.3•�N` �r1f;; t4 p �:::i� Shaded area
YT %lYf ill Sit~,_, ^ °i ;a�e = s�(•i:; �'-' ;��� �- .�
_
tR' l .:t�'� -- .•. ;s1.y_.
}�.. r ' -4i ■�� j: +> •�•, F'Si.
.0 -
OEM Cp EM
lam mum ,' I
'7,001 - - •,l
��^x`i:5h`' ','::, �'.; si'�.�: "•',`S qty � o O•; :t%�`'•�, :�
yY,t;:sj �;LLrteM(ampeiea)�;� �,•�°� �'� ;-:F^
,5 TyplcalGFP '•
lf�' �'..: �• ";���': �� h "+"� relay curve '
s a ^~ ,rj`",•?' dry^ }. -•�i that satisfies
%'�t ^ c'-t 4- ,,•,., > "5i��.� x; L?1 Sae lion 230.95(a)
E`r.::,a. - .eflS:1 J��".'w�i51 i.:��..^k• °yY �= �'.a:= `�•'.x. -.i
-a
Time -delay setting of GFP relay must not exceed Y second,
at 30011 amps. _
F. Y:. ��";' is :_wy'.i.��„�:'."r,'����•ay,:��. wae_.�..,c -?$r.. ,..�:;:1
CONTINUOUS INDUSTRIAL PROCESS operations are now exempted from
the GFP rules of Section 230 -95(8) where the electrical system Is under the
supervision of qualified persons who will effect orderly shutdown of the
system and thereby avoid hazards, greater than ground fault itself, that
would result from the nonordady, automatic Interruption that GFP would
produce In the supply to such critical continuous operations.
3.'A new note has been added to Section 230 -95(b) to
warn about potential de- sensitizing of ground -fault
sensing hookups when an emergency generator and
transfer switch are provided in conjunction with the
normal service to a building. The note applies to those
SELECTIVE COORDINATION between ground -fault protection and cases where a solid neutral connection from the
conventlonat protective devices (fuses and CBs) at main and leader circuits . normal service is made to the neutral of the generator
Is now a very dear and specific task as a result of rewording of Section 230- - .tIIrOU h a
95(a) that calls for a maximum time delay of 1 second at arty ground-fault g 3 -pole transfer switch. With the neutral
current value of 3000 amps or more. t grounded at the normal service and the neutral
60 ELECTRICAL CONSTRUCTION AND MAINTENANCE
Ri}
h111'
CONTINUOUS INDUSTRIAL PROCESS operations are now exempted from
the GFP rules of Section 230 -95(8) where the electrical system Is under the
supervision of qualified persons who will effect orderly shutdown of the
system and thereby avoid hazards, greater than ground fault itself, that
would result from the nonordady, automatic Interruption that GFP would
produce In the supply to such critical continuous operations.
3.'A new note has been added to Section 230 -95(b) to
warn about potential de- sensitizing of ground -fault
sensing hookups when an emergency generator and
transfer switch are provided in conjunction with the
normal service to a building. The note applies to those
SELECTIVE COORDINATION between ground -fault protection and cases where a solid neutral connection from the
conventlonat protective devices (fuses and CBs) at main and leader circuits . normal service is made to the neutral of the generator
Is now a very dear and specific task as a result of rewording of Section 230- - .tIIrOU h a
95(a) that calls for a maximum time delay of 1 second at arty ground-fault g 3 -pole transfer switch. With the neutral
current value of 3000 amps or more. t grounded at the normal service and the neutral
60 ELECTRICAL CONSTRUCTION AND MAINTENANCE
grounded to the generator frajne, ground -fault current
on the load side of the transfer switch can return over
two paths, one of which will escape detection by the
GFP sensor. Such a hookup can also cause nuisance
tripping of the GFP due to normal neutral current
being diverted from the sensor, which then senses the
condition as a ground fault. The new note points out
that "means or devices" (such as a 4 -pole, neutral -
switched transfer switch) "may be needed" to assure
proper, effective operation of the GFP hookup.
But, watch out for the change in Section 250 -5(d) that
permits a nonbonded generator neutral with a 3 -pole
transfer switch.
connection between the facilities of the serving utility
and the premises' wiring." All equipment on the load -
side of that point is subject to NE Code rules. Any
equipment on the line side is the concern of the power
company and is not regulated by the code. In any
particular installation, identification of that point can
be made by the utility company and design personnel.
The new definition was added to clarify that the
property line is not the determinant as to where NE
Code rules must begin to be applied. This is particu-
larly important in cases of multibuilding industrial
complexes where the utility has distribution circuits
on the property.
Section 230 -20M NE Code rules apply on toad side
of "SERVICE POINT" —not from property line.
MANDATORY GFP TESTING Is now required when any GFP system
required by the code Is "first Installed" and a written record must be kept
with the system to verily such factors as GF current pickup and time delay.
New Section 230 -95(c) Is a short, simple ruts.
4. Because of so many reports of improper and /or
unsafe operation (or failure to operate) of ground -
fault protective hookups, a new part (c) has been
added to Section 230 -95 and requires (a mandatory
rule) that every GFP hookup be "performance tested
when first installed." This rule requires that such
testing be done according to "approved instructions
... provided with the equipment" A written record
must be made of the test and must be available to the
inspection authority..•
Section 230 -200
A new definition has been added here to clarify the
basic rule on high - voltage services that the provisions
of Article 230 apply only to equipment on the load -side
of the "service point." Because there has been so much
controversy over identifying what is and what is not
"service" equipment in the many complicated layouts
of outdoor high - voltage circuits and transformers, the
new definition defines "Service- point" as the "point of
Section 230 -201
A very important change has been made in this
Section, which establishes whether the primary or
secondary circuit of a service transformer must be
considered as the "service conductors" for the installa-
tion. This whole matter has long been a difficult area
of code application, but the addition of condition No. 5
of Section 230- 201(a) will clarify many common situa-
tions involving use of load - center unit subs located
indoors, fed by a high - voltage utility line from
outdoors, and operating at not over 600 volts on the
secondary.
In the 1978 NE Code, Section 230- 201(a) is almost
the same as it was in the 1975 NE Code. But now, new
condition No, 5 says that, if the transformer serving
the facility is located "inside the building or other
structure" and is "in metal - enclosed gear," then the
secondary conductors from the transformer —not the
primary conductors to the transformer —are the
service conductors to the building. As this was covered
by condition No. 4 in the 1975 code, the secondary
conductors were the service conductors when the
serving transformer was "inside the building or other
OCTOBER, 1977 61
Section 230 -201 (a).. The secondary is the "ser-
vice" for any indoor transformer "in metal -
enclosed gear" and fed by utility line.
structure served where in a locked room or other
locked enclosure and accessible to qualified Persons
only."
Under the wording of condition No. 4, if a load -
center unit substation that handles the electrical load
for a building was in a locked room in the building and
was fed, say, by an underground high - voltage (over
600 volts) utility line from outdoors, then the
secondary conductors from the transformer of the unit
sub were the "service conductors" to the building. And
the switching and control devices (up to six CBs on
fused switches) in the secondary section of the unit
sub constituted the "service equipment" for the build-
ing. Under such a condition, if any of the secondary
section "service disconnects" were rated 1000 amps or
more, at 480/277 volts grounded wye, they had to
comply with Section 230 -95, requiring ground -fault
protection for the service disconnects.
However, under the wording of condition No. 4, if
the same unit sub was inside the building but not in a
locked room, then the primary conductors would be
the service conductors; and the primary switch or CB
would be the "service disconnect " In that case, no
ground -fault protection would be needed on the "ser-
vice disconnect" because Section 230 -95 applies only
up to 600 volts, and there is no requirement for GF
protection on high - voltage services. Also, in that case,
there would be no need for ground -fault protection on
the secondary section disconnects, because they would
not be "service disconnects" —and those are the same
disconnects that would be subject to Section 230 -95 if
the unit sub was in a Iocked room.
To eliminate this inconsistency, condition No. 5 was
added in the 1978 NE Code and adapts the concept of
condition No. 4 to "metal- enclosed gear," which covers
load- center subs and any other assembly in which the
transformer is actually in metal - enclosed gear. Under
condition No. 5, any load- center sub inside a building
and used for service to the building would always have
the secondary conductors from the transformer
section as the "service conductors," and the secondary .
control and protection section must satisfy "all code
rules on service equipment — including any service
ground -fault protection as required by Section 230-
95.
In applying Section 230 -201, care must be taken to'.
distinguish between "secondary conductors" that are
"not over 600 volts (such as a 480/277 -volt unit sub
secondary) and "secondary conductors" that are over
600 volts (such as 34 kv stepped down to 4160/2400
volts). In the latter case, all of Part K of Article 230
applies to the secondary.
Section 230- 202(b)
A new paragraph has beer' added to this Section
that specifies the wiring methods that are acceptable
for use as service entrance conductors where it has
been established that primary conductors (over 600
volts) are the service conductors or where the
secondary conductors are the service conductors and
operate at more than 600 volts.
The new paragraph points out that cable -tray
systems are also acceptable for high - voltage services,
provided that the cables used in the tray are "ap-
proved for use as service- entrance conductors."
Section 318 -2(a) recognizes "multiconductor service -
entrance cable" for use in tray, for cables rated up to
600 volts. Now, high - voltage (over 600 volts) service -
entrance cables may be used if the cables are "ap-
proved"— which, in today's strict usage, virtually
means that such cable must be listed by a nationally
recognized test lab (UL, etc) as suitable for the
purpose. Article 338 on "Service- Entrance Cable" does
not refer to any high - voltage cable for service-
entrance use.
Section 230 -205
This rule covering the electrical fault characteristics
has been revised. It now requires that the service
disconnect be capable of closing, safely and effec-
tively, on a fault equal to or greater than the
maximum short - circuit current that is available at the
line terminals of the disconnect. A new sentence notes
that where fuses are used within the disconnect or in
conjunction with it, the fuse characteristics may
contribute to fault- closing rating of the disconnect.
The idea behind this rule is to assure that the discon-
nect switch may be safely closed on a level of fault
that can be safely interrupted by the fuse.
ELECTRICAL CONSTRUCTION AND MAINTENANCE
ARTICLE. 240 - OVERCURRENT'
PROTECTION
Section 240-3, Exception No. 5
A number of clarifications were made by additions
to the Exceptions to the basic code rule that conduc-
tors must be protected at their allowable ampacities
' from NE Code Tables 310 -16 through 310 -19.
- A new sentence has been added at the end of
Exception No. 5 to clearly and emphatically state that
the secondary conductors from a transformer may not
he protected by overcurrent protection on the primary
side of the transformer— EXCEPT for a transformer
with a 2 -wire secondary. That has long been the
intent of the code, but much discussion and controver-
sy has regularly concentrated on this matter because
the code has not previously had the simple prohibition
against secondary protection by a primary CB or set of
fuses. The whole issue of transformers and overcur-
rent protection is now firmly established as follows.
The basic way to provide overcurrent protection for
a dry-type transformer rated 600 volts or less is to use
fuses or CBs rated at not more than 125% of the
transformer primary full -load current (TPFLC) to
protect both the transformer and the circuit conduc-
tors that supply the transformer primary. [This is
presented in Section 450- 3(b).] These circuit conduc-
tors must have an ampacity of not less than the rating
of the overcurrent protection or must have an
ampacity such that the overcurrent protective device
is "the next higher standard device rating" above the
conductor ampacity, as described in Exception No.1 of
Section 240-3.
But the primary circuit protection is not accept-
able as suitable protection for the secondary conduc-
tors—even if the secondary conductors have an
ampacity equal • to the ampacity of the primary .
conductors times the primary/secondary voltage.
ratio.
When primary devices are used for protection of 3-
and 4 -wire transformer secondaries, it is possible that
an unbalanced load may greatly exceed the secondary
conductor ampacity, which was selected assuming
balanced conditions. Because of this, the NE Code does
not permit the protection of secondary conductors by
overcurrent devices operating through a transformer
from the primary of a transformer having a 3 -wire br
4 -wire secondary.
However, Section 240 -3, Exception No. 5, recognizes
such primary protection of the secondary conductors
of single- phase, 2 -wire to 2 -wire transformers if the
primary OC protection complies with Section 450 -3
OCTOBER, 1977
Section 240 -3, Exception No. 5. New sentence
clearly resolves long- standing controversy.
(e.g., not over 125% of rated primary current) and
does not exceed the value determined by multiplying
the secondary conductor ampacity by the secondary-
to- primary trpnsformer voltage ratio. In such applica-
tions, the lengths of the primary or secondary conduc-
tors are not limited.
•Section 240-3, Exception No. a.'
"
This is a new exception to the basic rule and
represents a new concept;in code application. When
Section 240-3, Exception No. 8. It "overload protec-
tion" creates a hazard, it may be eliminated. . -
conductors supply a load to which loss of power would
create a hazard, this exception states it is not neces-
sary to provide "overload protection" for such conduc-
tors, BUT "short- circuit protection" must be provided.
By "overload protection," this exception means "pro-
tection at the conductors' ampacity" —that is, protec-
tion that would Prevent overload.
Several points should be noted about this excep-
tion.
1. Use of this exception is reserved only to applica-
tions where circuit opening on "overload" would be
more objectionable than the overload itself, "such as
in a material handling magnet circuit." In that
example mentioned in the exception, loss of power to
such a magnet while it is lifting a heavy load of steel
would cause the steel to fall and would certainly be a
serious hazard to personnel working below or near the
lifting. magnet. To minimize the hazard created by
such power loss, the circuit to it need not be protected
'at the conductor ampacity. A higher value of protec-
tion may be used — letting the circuit sustain an over-
load rather than opening on it and dropping the steel.
because such lifting operations are usually short -time,
intermittent tasks, occasional overload is far less a
safety ' concern that the dropping of the magnet's
load.
2. The permission to eliminate only "overload
protection" is not limited to a lifting magnet circuit,
which is mentioned simply as an example. Other
electrical applications that present a similar concern
for "hazard" would be equally open to use of this
exception. • '
3. Although.the exception permits elimination of
overload protection and requires short - circuit protec-
tion, it gives no guidance on selecting the actual rating
of protection that must be used. For such circuits,
fuses or a CB rated, say, 200 -400% of the full -load
operating current would give freedom from overload
opening. Of course, the protective device ought to be
selected with as low a rating as would he compatible
with the operating characteristics of the electrical
load. And it must have sufficient interrupting capacity
for the circuit's available short- circuit current. .
4. Finally, this exception is not a mandatory rule
but a permissible application. It says "... overload
protection shall not be required..: ; it does not say
that overload protection "shall not be used." Overload
protection may be used, or it may be eliminated.
Obviously, careful study should always go into use of
this exception.
Section 240-4
The change in this rule is basically editorial and
aims to pull together a number of rules to clarify code
intent on protection of flexible cords and fixture wires.
The basic rule still says that No. 16 or No. 18 fixture
wire or cord is adequately protected by the protective
device of the branch circuit it is connected to when
such a device is rated at 15 or 20 amps. Of course, use
of fixture wire must also satisfy all other code rules
that apply —as in Article 400 on cords, Article 402 on
fixture wires, and Section 725 -16 on fixture wires for
control circuits.
A tabulation is given to show the minimum sizes of
flexible cords that may be used on circuits rated at 20, .
30, 40, and 50 amps. A similar tabulation is given for
fixture wire. The tabulation for flexible cord is the
same as it was in the 1975 NE Code. The tabulation
for fixture wire shows the minimum AWG conductor
sizes of fixture wire permitted on each circuit rating.
This eliminates the confusion that previously resulted
from cross- referencing Section 240-4 to amp ratings of
tap conductors given in Exception No. 1 of Section
210- 19(c). The new format is clear and straightfor-
ward
Section 240 -6
The content of this Section is a listing of the
"standard ampere ratings" of fuses and circuit
breakers for purposes of code application, and that has
not been changed. Although other ratings of devices
are available in- between the values given here, the
code relates its rules on protection to these "standard"
ratings. But a new Exception has been added to
designate "Additional standard ratings" of fuses at 1,
3, 6,10 and 601 amps. These values apply only to fuses
and not to circuit breakers.
The 601 -amp rating was added to give code recogni-
tion to use of Class L fuses rated less than 700 amps.
The Preprint comment on this was as follows:
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 240-6. Lower "standard ratings" of fuses will affect motor - circuit loading.
F� cat~. :i..t..�....- ..-- �,:Y_,.�.:..zi �:�1:...?:: -fn .''CL�u yr- _ _ _ ..3.. -•"7 ."�`
I
in the 1975 NE Code, several motors could be supplied In ,. BUT In the 1978 NE Code, 15 amps Is not .&' "next higher"
d
actor ante with Section 430 -53(b) like this
t•. 46OV, 3d circuit"
d.
:L' F OL protection
(. - Fi�A�• fit•- Motorfufi -'-
��... •- `- load current 3.4A _ I A
G:��,'xti..' �r:-- +.,•tire' -;.S'' f: >' -- Ma I /2hp I/2h1
15 -amp, -pole F °.,.,.r ."e•' - _ p,
F 2hP.'i z.:.
CB was the keys.- f'%''�* ':•-/,.. ., - :..
3ff squlrret -wge malors
Section 430 -53(b) requires branch-circuit protection•to
"• not higher than the maximum amps set by Section 430 -52 c
Y for the lowest rated motor of the group. f
N
L; From Section 430 -52 and Table 430 -152, that maximum
protection rating was 250% x 1 amp (the lowest rated
motor) or 2.5 amps. But, 2.5 amps Is not a "standard rating" "
n of protective device, from Section 240-8; and the third
li paragraph of Section 430 -52 permits use of the "next Cf
_ higher" rating of standard protective device.
Because, 15 amps Is the lowest standard rating, It Is the
It "next higher" device rating above 2.5 amps and could be }'
used as the rating of the branch - circuit protection. !,
•• Such application permuted use of several motors up to -°
Ft circuit capacity, based on Section 430 -24 and 430 -53(b) and kl
on starting torque characteristics, operating duly cycles of
the motors and their loads and the time -delay of the CB.:
Such application greatly reduced the number of CB poles, �I
k, number of panels and the amount of wire used in the total
�'. system. One limitation was placed on this practice In the last i
sentence of Section 430 -52, as follows:
i "Where maximum branch - circuit protective device ratings
are shown In the manufacturer's overload relay table for use -
# Wth a motor controller or are otherwise marked on the
f equipment, they shag not be exceeded even 11 higher values •6�
are allowed as shown above." '-
• ewe'- ti-. �,�.>..`�.i.5'- iv?al- �,r";L'e%� Lisv: ,::i:�
An examination of fuse manufacturers' catalogs will show
that 601 amperes is a commonly listed current rating for the
Class L nontime -delay fuse. Section 450-52 (Exception f) also
lists this current rating as a break point in application
rules.
Without a 601 ampere rating, the smallest standard fuse
which can be used in Class L fuse clips is rated 700 amperes.
Since the intent of Table 430 -152 and Section 430 -52 is to
encourage closer short - circuit protection, it seems prudent to
encourage availability and use of 601- ampere fuses in combi-
nation motor controllers having Class L fuse clips.
Because ratings of inverse time circuit breakers are not
related to fuse clip size, a distinction between 600 and 601
amperes in circuit breakers would serve no useful purpose.
Hence, inverse -time circuit breaker ratings are listed sepa-
rately. Such separation also facilitates recognition of other
fuse ratings as standard.
rating above 2.5 amps .. .
_ - •. . ,.�. >::••: :_.; :ms'..,µ.
.. standard fuse ratings of 1, 3, 6 and 10 amps are now
Included In Section 240 -6 .. .
tv
Table 430 -152 sets a maximum of 300% when fuses
1- are used (300% x 1 amp 3 amps)
_ .,.=:. w._^• �f- i _...,.,- -..Y...•- r,- .,,r- ..._.- .:BFI -�;`rn l
.. and the maximum rating of branch-circuit protection
. fuse .�'. ., - ;i*? <`••tt�
' (:. •'�- • :3 AMPS "'• :•.r_.YxC
•
Then 1h9 three motors above -would be circultedKlike
i' this-
]
46OV,3g circuit' i 46b circuit,;
3 -amp)' -= ;� =5:` !t•?�..t''
fuse E s�i1!''•- i:,:.::;;. -y:
T
fuse f�3,4A
IA IA
-- - M M _ 3.4 amps ;;;;�• M
bq • 10.2 amps) r r r'"' `
• 4 I /2hp `I /2hp
NOTE: Only fuses, not circuit breakers, can satisfy the rules
of such application. But Interpretations by local Inspection
authorities will be necessary to determine it circuit breakers
are excluded as circuit protection where their minimum
! standard rating of 15 amps is In excess of 400% times the
motor full -load current —the specified maximum- In the
Exception to section 430 -52. - • - •• _
ry
The smaller sizes of fuses (1, 3, 6 and 10 amps) were
added as "standard ratings" to provide more effective
short- circuit and ground -fault protection for motor
circuits —in accordance with Section 430 -52, Section
430 -40, and UL requirements for protecting the over-
load relays in controllers for very. small motors. The
Preprint comment was as follows:
Fuses rated less than 15 amperes are often required to
provide short circuit and ground -fault protection for motor
branch circuits in accordance with Section 430 -52. ' -
Tests indicate that fuses rated 1, 3, 6 and 10 amperes can
provide the intended protection in motor branch circuits for
motors having full load currents less than 3.75 amperes (3.75
X 400% = 15). These ratings are also those most commonly
shown on control manufacturers overload relay tables. Over-
load relay elements for very small full load motor currents
OCTOBER, 1977 _ -
G5
have such a high resistance that a bolted fault at the
controller load terminals produces a short- circuit current of
less than 15 amperes, regardless of the available current at
the line terminals. An overcurrent protective device rated or
set for 15 amperes is unable to offer the short circuit or
ground fault protection required by Section 110 -10 in such
circuits.
An examination of fuse manufacturer's catalogs will show
that fuses with these ratings are commercially available.
Having these ampere ratings established as standard should
. improve product availability at the user level and result in
better overcurrent protection.
Sins inverse time circuit breakers are not readily avail-
able in the sizes added, it seems appropriate to list them
separately..
The addition of those smaller fuse ratings will have
a significant effect on use of several small motors
(fractional and small- integral- horsepower sizes) on a
single branch circuit in accordance with Section 430 -
53(b). When applying the third paragraph of Section
430 -52 in the 1975 and previous codes, it was possible
to put, say, 5 or 6 motors on one branch circuit because
the lowest standard rating of fuse or CB was 15 amps,
from Section 240 -6; and Section 430 -52 is the basis for
sizing the maximum permitted branch - circuit protec-
tive device in Section 430- 53(b). With the change in
Section 240 -6 of the 1978 NE Code, application of the
third paragraph of Section 430 -52 will frequently
require use of those low -rated fuse's for the branch -
circuit protection because they are "standard" values;
and use of a 15 -amp CB dr 15 -amp fuses will not be
permissible for a branch circuit supplying two or more
motors in accordance with Section 430- 53(b).
It is likely that inspectors will apply Section 430 -52
as requiring use of fuses instead of circuit breakers
for those cases where the low -rated standard fuses can
satisfy the maximum protection ratings specified in
Table 430 -152.
Section 2404
The Exception to this code rule has been expanded
to recognize both circuit breakers and fuses for use "in
parallel" IF they are "factory assembled in parallel"
and are "approved for the purpose."
Section 240-12
This is a completely new' Section on". "Electrical
System Coordination" and is aimed at 'Industrial
locations" where hazard to personnel would result
from disorderly shutdown of electrical equipment
under fault conditions. The purpose of this rule is to
eliminate unknown or random relation between oper-
ating time of overcurrent devices connected in series.
The new Section recognizes two approaches to the
task of "orderly shutdown."
One is selective coordination of the time- current
characteristics of protective devices in series from the
service to any load —so that, automatically, any fault
Section 240 -12. Time - current characteristics of
protective deevices in series provide coordinated
protection, as required.
will actuate only the short - circuit protective device
closest to the fault on the line side of the fault, thereby
minimizing the extent of electrical outage due to a
fault.
The other technique is "overload indication based on
monitoring systems or devices." A note- to this new
Section gives very brief descriptions of the two
approaches and establishes only a vague or'general-
ized understanding of "overload indication:' It seems
sure that effective application of this new Section will
depend upon developing field experience.
- It should be noted, however, that in this new
Section, it says that the two techniques for orderly
shutdown "shall be permitted" —but does not require
either or both of the techniques. Although it could be
argued that the wording implies a mandatory rule,
consultation with electrical inspection authorities on
this matter is advisable.
Section 240 -21
This Section has been reworded to clarify the
minimum required ampacity of feeder tap conductors
not over 10 feet long. The intent of the rule has not
been changed. Where conductors are used to tap from
ELECTRICAL CONSTRUCTION AND MAINTENANCE
larger size feeder conductors, without overcurrent
protection at the supply end of the tap conductors,
those tap conductors must not be longer than 10 feet
and must have ampacity of—
Not less then the rating of the "device" supplied by
the top conductors, ;
or
Not love than the rating of the overcurrent device
(fuses or CB) at the termination of the tap conductors.
Section 240-61
.The listed data covering classification of cartridge
fuses and fuseholders has been revised and expanded
to bring the information up to date with developments
in fuse availability.
A sentence was added to this section noting that
any fuse may be used at its voltage rating or at any
voltage below its voltage rating. The two exceptions
of this section recognize fuses larger than 6000 amps
when "approved for the purpose" and fuses of voltages
other than those designated.
Section 240 -83(d)
This is a new part -of the code rule on required
marking of circuit breakers and refers to those appli-
cations where panelboard circuit breakers are used for
ON -OFF control of fluorescent lighting —a practice that
has been very popular in commercial and industrial
electrical systems. Any CB used to switch 120 -volt
fluorescent lighting must be "approved for the
purpose" and shall be marked 'WD-"
The new code rule presented here is actually the
same requirement noted in the Electrical Construc-
tion Materials List of the Underwriters Laboratories
under the heading of "Circuit Breakers." The rule has
already been a code requirement under the 1975 NE
Code, even though not specifically covered by Section
240 -83 in that code, because Section 110 -3(b) of the
1975 (and the 1978) NE Code gives all application
requirements of UL the force of NE Code rules.
Section 240- 83(d). Circuit breakers used for
switching lights must be "SWD" type.
Yra: any CB used for i=1' �t _
oN-w control must
F` = ty
be marked "SWD" lr -;`i'v;' ='I`
~n . if It switches 120 -volt
fluorescent Iuminaires
Under this rule, only those breakers bearing the
designation "swu" (switching duty) may be used as
snap switches for lighting control. Type "swn"
breakers have been tested and found suitable for the
greater frequency of ON -OFF operations required for
switching duty than for strictly overcurrent protec-
tion, where the breaker is used only for genet'ally
infrequent disconnect for circuit repair or mainte-
nance.
Section 240 -100
These rules have been revised to clarify code intent
on protection of high - voltage feeders (above 600
volts).
A high - voltage feeder -
1. must have a "short- circuit protective device in
each ungrounded conductor," OR-
2. it may he protected by a circuit breaker equipped
with overcurrent relays and current transformers in
only two phases and arranged as described in Section
230- 208(d)(2) or (d)(3), which covers overcurrent
protection of high - voltage service conductors.
The requirement on maximum value of high-voltage:
overcurrent protection has been rewritten, although
not changed—
A FUSE must be rated in continuous amps at not
more than THREE TIMES the ampacity of the circuit
conductor.
A CIRCUIT BREAKER must have a long -time trip
element rated not more than SIX TIMES the
ampacity of the feeder conductor.
Section 240 -101
- The change in this rule is similar to change in
Section 240 -100. A high - voltage branch circuit must
be protected by a short - circuit protective device in
each ungrounded conductor OR it may be protected by
a circuit breaker _with relays in only two phase legs, as
described in Section 230- 208(d)(2) or (d)(3).
ARTICLE 250 - GROUNDING
Section 25"(b), Exception No. 3
A new exception to the basic rule requiring
grounding of one conductor of ac electrical systems
recognizes use of ungrounded control circuits derived
from transformers.
According to the rules of this section, any 120 -volt,
2 -wire circuit must normally have one of its conduc-
tors grounded, the neutral conductor of any 240/120-
volt, 3 -wire, single -phase circuit must be grounded,
and the neutral of a 208 /120 -volt, 3- phase, 4 -wire
circuit must be grounded. Those requirements have
often caused difficulty when applied to control circuits
derived from the secondary of a control transformer
that supplies power to the operating coils of motor
starters, contactors and relays. For instance, there are
Section 250 -5(b), Exception No. 3. 120 -volt control
circuits may be ungrounded to avert unsche-
duled shutdown.
-i If primary Is rated
[ d not over ioDo volts .. ;
cases where a ground fault on the hot leg of an
ungrounded industrial control circuit can cause a
hazard to personnel by shutting down a process. A
metal- casting facility was cited in the Preprint as an
example of such an installation. Although circuit
designers have often wished to operate such 120 -volt
control circuits ungrounded, the NE Code rule of this
section literally prohibited such usage. Now, new
Exception No. 3 permits ungrounded control circuits
under certain specified conditions:
A control circuit may be.operated ungrounded
when all of the following exist:
1. The circuit is derived from a transformer that
has a primary rating less than 1000 volts. •
2. Whether in a commercial, institutional or Indus-
trial facility, supervision will assure that only persons
qualified in electrical work will maintain and service
the control circuits.
3. There is a need for preventing circuit opening on
a ground fault —that is continuity of power is required
for safety or for operating reliability.
4. Some type of ground detectors are used on the
_ ungrounded system to alert personnel to the"presence
of any ground fault, enabling them to clear the ground
t it `; v : .,;iw Ga: >•.: ,-.2Q. s fault in normal
( ??=' +_f a1 ^
-.and secondary supplies ~ - downtime of the system.
F -,� •_._; + on control circuits where `I This new exception permitting ungrounded control
E ' j ^•'v loses of power to motors or other load circuits is primarily significant only for 120-volt
.. conditions cause objectionable co . ) „= • control circuits, which have
_ -, previously always been
required to be grounded. Past editions of the NE Code
4aov,s8 have long permitted 240 -volt and 480 -volt control
circuits operating ungrounded, and the 1978 NE Code
—
�,: continues that ruling for circuits of those voltages.
Application of this new exception can be made for
i`4 `4rc . '% >_”` ° • F; r, any 120 -volt control circuit derived from a control
�� ; r • -°?x �t•'r�,�: � ` transformer in an individual motor starter or for a
• � T,^ _ ��s ; •, separate control transformer that supplies control
power fora number of motor starters or magnetic
' 'i then It Is not ?:-
Unecessary to ground
. `
contactors. • -
-
• one side of
`'?C''.',
circuit, but protection ,_-- ?;�'�.•r
nt
Section 250 -5(b), Exception No.4
ymust be used In both
comrol ";
:.: >,: :!
This simply recognizes that isolated (ungrounded)
ungrounded legs ; ,::;_. ,-
circuits as required in Articlo 517 are permissible.
P
Y' NOTE: Although, the new code exception does not 11 It' or
the secondary voltage, this application Is
Section 250 -5(d)
yjj specity primarily ..
because 240
A very important change in the grounding require-
d related to 120 -volt control circuits, -volt and
:, 480-volt control circuits may always be operated '•
ments for emergency generators in buildings has been
#i ungrounded. Of course, the new exception could also be
made by the addition of a clarifying phrase in the
7 used to permit ungrounded 277 -volt control circuits under
basic rule requiring grounding of "separately derived
the same conditions.
r i
- systems." The details of this change involve several
Q 37 ...� - _.,, s:'...•... "_., .r .,- x. .,i
steps as follows:
as ELECTRICAL CONSTRUCTION AND MAINTENANCE
} 1. Section 250 -5(d) is the basic rut. that covers
grounding of "separately derived .systems" —which
has always been understood to refer to generator
output circuits and transformer'secondary circuits
because such systems are "derived" separate from
other wiring systems and have no conductor connected
to the other systems.
2. Fqr a separately derived system, if the voltage
and hookup required grounding as specified in Section
250 -5(b), then such systems have to be grounded and
bonded as described in Section 250 -26.
3. With respect to 2- winding transformers (that is
Section 250 -5(d). Ground and bond generator
neutral onlywhen "separately derived ".
Wlth 3-Pole transfer switch ~'�.... - A'.:%,
a %$
lood
• generolor �;�;
By ±
c
N
single -phase or polyphase transformers that are not
autoti'ansformers and have only magnetic coupling
from the primary to the secondary), there is no
question that the secondary circuits.are "separately
derived," and grounding must always be done as
required by Section 250 -5(b) and Section 250 -26.
4. But, when the rule of Section 250 -5(d), as worded
in the 1975 NE Code, was applied to 208 /120 -volt or
480/277 -volt generators'used for emergency power in '
the event of an outage of the normal electric utility
service, difficulties arose. The 1975 NE Code wording,
of that rule required such an emergency generator to
have its neutral bonded to the generator housing and
to be connected to a grounding electrode —both as
spelled out in Section 250 -26. Such generators were
tied into the automatic transfer switch that is also fed
from the normal service equipment —with a solidly
connected neutral conductor running from the service
equipment, through the transfer switch, to the gener-
ator neutral terminal; and the neutral is bonded and
grounded at both the normal service and at the
generator.
5. Section"250 -21 prohibits grounding connections
that produce objectionable flow of current over
grounding conductors or grounding paths. But the two
grounding connections -at the service and at the
generator, as described in 4 can produce objectionable
current flow under both normal and fault conditions:
Under normal conditions, neutral current of the
connected. load in the building has two paths of
current flow from the common neutral point in the
transfer switch back to the service neutral terminal.
One path, of course, is over the neutral conductor from
the transfer switch to the service equipment. The
other path as over the neutral conductor from the
transfer switch to the generator, at which point the
current can flow back to the service equipment over
the grounding conductor (the conduit and enclosure
interconnections) that runs between the service equip-
ment and the generator.'
Under ground -fault conditions, a similar double
path for current flow can cause - desensitizing of
ground -fault protective equipment —as discussed and
shown previously under Section 230 -95, when a 3 -pole
transfer switch is used.
6. Prior to the 1978 NE Code, elimination of the
desensitizing of service GF protection could be accom-
OCTOBER, 1977 -
�°. -c,- • e switch
Because there Is
q direct neutral
Bonding and connection between
grounding' normal and
required here emergency supplies .. .
saF ,:1f :•4F. _ 'h7 = ``} ... this generator Is
not a "separately derived
�..K system" and bonding and
'.;�;; �• grounding of generator
neutral Is not required
plished by the use of a 4 -pole transfer switch that
Section 2513-6(a). "Ungrounded" generator frame
prevented a solid neutral connection from the service
is acceptable grounding electrode.
" equipment to the generator.
7. NOW grounding n the 1978 NE Code, the oundin re-
) When frame of portable
quirements of Section 250 -5(d) apply to a generator
generator Is left ungrounded '• >' ? ;. <? : +'; _` °, t
only where the generator "has no direct -electrical
' . as permitted In Section 250 -e . - .
connection, including a solidly grounded circuit
conductor" to the normal service. The rule would
the generator frame
apply to a generator that fed its load without any tie-
=..y,••
�y i ?.
" x`
...
Is a suitable grounding
in through a transfer switch to any other system. If a
�j
" ': '':' c: ' ` Y' electrode for cord - connected
generator does have a solidly connected neutral from
t., ,'.
Q E)
^. tools and appliances with
grounding -type cord and caps 11
- it to the service through a 3 -pole, solid- neutral
plugged Into generator
transfer switch, then that generator is not a sepa-
%
receptacle Z
rat ely derived system and Section 250 -26 does not
y,
; "r
"r- _ °�"l??"::r
apply. The code does not require the generator neutral
.
°'4 �'""
to be bonded to the frame or to be grounded to a
i" . • =i. - , a r_s;:�� , `��. a "� s % ats,�a;ifxi
'.-grounding electrode. . .
The effect of the rule of Section 250 -5(d) on transfer
Switches is as follows: '
3 -POLE TRANSFER SWITCH —If a solid neutral
section requires the neutral conductor of. the generator
connection is made from the service neutral, through
output to be bonded to the frame of the generator
the transfer switch, to the generator neutral, then
-when it is'not used as an emergency source connected
bonding and grounding of the neutral at the generator
to a transfer switch.
sre not required because the neutralis"already bonded
and grounded at the service equipment. And if
bonding and grounding were done at the generator, it.
Section 250 -6(b) ,
When the frame' of a vehicle is used as the
be considered a violation of Section 250- 21(a)-
Founding electrode for a generator mounted on the
,could
and would have to be corrected by Section 250- 21(b).
vehicle, grounding terminals of receptacles on the
Without bonding and grounding at the generator,
generator must be bonded to the generator frame,
desensitizing and other problems with GF protection
which must be bonded to the vehicle frame.
are avoided. -
4 -POLE TRANSFER SWITCH— Because there is
Section 250 -6(c)
no direct electrical connection of either the hot legs or
A change in the wording of this rule was made to
the neutral between the service and the generator, the
bring application of portable and vehicle- mounted
generator• in such a hookup is a "separately derived
generators into compliance with the concept described
system" and must be grounded and bonded to the
above in Section 250 -5(d) on grounding and bonding of
generator case at the generator.
the generator neutral conductor. A generator neutral
It should be noted that the 4 -pole transfer switch
must be bonded to the generator frame when the
came into use to eliminate problems of GFP desensi-
tizing that were caused by use of a 3 -pole transfer
"
switch when the neutral of the generator was
VV U
bonded to the generator housing. By eliminating
u
that bonding requirement for emergency generators,
{
s��YrK'y2
Section 250 -5(d) now makes possible use, of 3 -pole
�i'r: ?sr;i aw.•iii ?�,.rA
- ��� �•�' ' ,f :; ,;; .
transfer switches without disruption of service
`-
°c..
6 ground -fault protection.
Section 250 -6(a)
A clarification in part (a) points out that, where a
portable generator is used with its frame not
grounded, the frame is permitted to act as the
grounding electrode for any cord- connected tools or
appliances plugged into the generator's receptacles.
This change was needed to assure that tools and
appliances that are required by Section 25045 to be
grounded do satisfy the code when plugged into a
receptacle on the ungrounded frame of a portable
generator. It should also be noted that part (c) of this
70
ELECTRICAL CONSTRUCTION AND MAINTENANCE
i
Section 250 -6(c). Revised rule clarifies bonding of
.generator neutral.
j.1 °xPortable generator= - -•�_ "•'
1 supplying premises wiring i;
240/120V
service service disconnect I'f" generator tie to ;•
(: �,
Tor norrhel alternate power�source, neutral does
r supply ,+ - !• r`�not have to be bonded to frame
r N
ikpSolid neulral`g';�.�b %�s.Sr "' •_ _;`.a
connection between•; tttx v` _ _ r.•�4��• _;,�= �;;��• "-
,iwg sources
Portable rvehlcM vehicle � r�_�, � _ - T� - ,�•{'+
orator
2 gon as sots source �'_' •. ?.��' -': `•s'•
�- - generator Is an Independent •sup -�"'
•;, �� ply, Its neutral must be bonded to 1%
the frame },
•• grounding
.. bonded
to frame'
-N >•�4.i nfi- ,con sAn ...r
generator is the sole source of power to•the loads it
feeds and is not tied into a transfer switch as part of a
NORMAI,EMERCENCY' hookup for feeding the load
normally from the utility service and from the gener-
ator on -an emergency or standby basis. A note to this
section refers to Section 250 -5(d) for grounding and
bonding of portable. generators that supply a fixed
wiring system on a premises. In such a case, bonding
of the neutral to the generator frame is not required if
there is a solid neutral connection from the utility
service, through a transfer switch to the generator.
Section 250 -23(a)
A very important revision of this rule on grounding
connections for Be systems will eliminate confusion
and controversy about connection of the grounding
electrode conductor when a building is fed by service
conductors from a meter on a yard pole.
OCTOBER, 1977
The rule of this seetion still says that the grounding
electrode conductor required for grounding both the
grounded service conductor (usually a grounded
neutral) and the metal enclosure of the service equip-
ment must be connected to the grounded service
conductor within or on the supply side of the service
disconnect. BUT NOW, the rule further requires that
the connection of the grounding electrode conductor
must be connected at the load end of the service
drop or lateral.
Section 250- 23(a). New rule covers grounding
when outdoor meter is distant from building
service disconnect.
As a result of that new requirement, if a service is
Section 25D -42. "Fixed" equipment is now clearly
fed to a building from a meter enclosure on a pole or
and readily identified for grounding rules.
-other structure some distance away and an overhead
„_ • .:... -t. •: ,:; . .j h - -y;-
or underground run of service conductors is made to
__.
"' " +-' _ '•: `'
the service disconnect in the building, the grounding
Nailed ,screwed,bolted EQuipmenlposilionedon';..
'or clamped to structural ' J but not fastened to fbor,',,;•
electrode conductor may not be connected to the
_ surface or member ; ' matt or other support
neutral in the meter enclosure but must be connected
`
at the load end of the underground or overhead service
' ` '" �` -•
conductors. And, as the rule states, the connection
"preferably" `within"
should be made the' service
In residential and nonresidential occupancies,
disconnect enclosure.
=,sue: •
.,
:,1�; s�;.�y:.�C - - -- :s` �i
Section 250 -28
o {i, :n• o"
A rewording of parts of this section was done to
clarify the intent of the rules without changing the
rules themselves. One important clarification calls for
bonding and grounding of a transformer secondary
neutral "at the source of the separately derived
system" —which seems to insist that the bonding
jumper and the connection of a grounding electrode
conductor be made right at the transformer and not
thin the enclosure for the disconnectin means
It equipment Is I%•
fastened In place, k`
' {' It's "tlxed equipment" -
`_ 1 — whether fed by 1 `
i ? permanent wiring or
cord- and -plug connected._
it equipment Is not
fastened In place, but
fs fed by "permanent
widng,' It's "fixed
equlpment ".
m g
immediately fed by the transformer secondary circuit.
-
wording may call for the inspectors interpretation.
The latter point of connection was permitted by some
inspectors on the basis that such connection was ,
Section 250-42,43
° "ahead of any system disconnecting means." The new
The word "fixed" as applied to equipment requiring
grounding now applies to "Equipment fastened in
place or connected by permanent wiring." And that
Section 250 -26. Transformer secondary bonding
usage is consistently followed in other code sections.
and grounding must be "at the source ".
Section 250- 45(c)(d) '
In residential and nonresidential occupancies,
-: •. :+ Bonding and grounding must t "r� =,• .
k-
gFj,a , . be done at the transformer, '
'. which Is "the source" of the
aquarium equipment, snow blowers and portable hand
Iamps have been added as cord- and plug - connected
.5j --- secondary system .. - " " "`
equipment that must be operated with a grounding
[,..Primary racew �xTransformer'�, r'y: = se ndary 33
type cord and plug if not of the approved, double-
"portable"
/• ' ' + ` >•' roceway, .. `
°'jL
insulated type. The word was removed
after the word "Listed" in the beginning of the Excep-
P ,;
..cf: - "; t» ij:;lE;;} •9.
`?
• : -
Enclosum-
rne
tion to Section 25045(c) and was removed before the
"tools" in Exception No. Section 250- 45(d).
-•s
; •,
'.'s, - -
, ;
'
+ea e, •
Irons ormer
:
word I of
_+
�•�a. rY.�»
ri'31l•Y�Y ,.�,
ry•d
1.1."��i".iy �,:"
•�::3
"i
_
', ', .
'
f'�•�l
aYs- '_r°.' „.G.,t,�
;is. *:r.,
J
•i ;,�,yi�; ?-
_ -.
Section 250-50 • . "': • -
i
:,.,•,�
^;f':r
,'
� ••�45�;
Rewording clarifies the required points of connec-
��,;_�
�;;.i; "s;,';'.`k; #tt --•
�r,_;?•�f;:'; "-
'" ` >'4 r.,;:' eti--
:Bondiig^jumper
tion to $r oundtid neutrals or other legs le s for
•
Yyr;,;;i�4
,qrm' -- „• "• t'
_ ,sited by sec. 250-79te) �'
7
equipment grounding conductors at services or at
,", :a•�F= G:cf.:,c',
''fit
connect neutral .r
” to metal case .,,.:; .'•r`i
,.arr.Ft:`:p'Y;;i' � -.
separately derived systems. -
% #;.,•tr7;;ix:4:,.r
+Vx=s ^S =-
_
�*� . • i�.,'• ;,. •..• • ,Yr;
t ° :'i. ; i..t.'x'•_-.�4:...,...t.. i.'; .:
Section 250 -57(b)
_
.Grounding elecuodee` .r:
be: : e,,�% ;
:
i • • • end oot at
a
The rule now makes clear that an equipment
shall -, i4•�
a Nearest available
gqrounded structuroI `'
,;;'.:,;.
; <t ^= the as, fused switch,
• paneiboard or r
grounding conductor" for "fixed" equipment —where
'buitaingsteet,or .:
- 0';-•t� switchboard fed by j
other than conduit, other raceway or an enclosure
• 2Neurcst grounded
'•I the transformer : i
serves as the grounding conductors —may be "bare,
metal woler pipe,or'-
3.Olherisecs.250-
-"sr.; ;': _•; :- 1
_ s� I -
,
covered or insulated." '
'•' •81 a 83) -
•
rounding electrode conductor..
New Exception No. 3 permits specific on- the -job
„: - • • .
�,,,,,,�;_, eo.,: „ • =`; r;
t, --
=sized by 250-946) for the
3 secondary phase conductors,'
to o grounding electrode • .S
identification of an insulated conductor used as an
equipment grounding conductor in a multiconductor
--
S :i•`:�- :- t'•,':�':•' -<;';
•'run _
as near as possible and
s
—cable. Such a be
i,.`p, ;r ';,.iY •., };i
' ?
preferably in the same area
conductor, regardless of size, may
_ _
identified in the same manner permitted by Exception
1 ;v +� _ • ,,:; 1; _' �'s,. •.,•.• , -` r` =- - • <'i
r
No.1 of that section for conductors larger than No. 6
Section 250- 58(a). Watch out for grounding to metal racks or structures or to building steel
'" .:zuc,�i z:;,�:k,•.•.u.i= .c.`�x . ::rte, •';r:i�
r This Is now parm lit
ed
- _.. .'> i _ .t!r - '.IS:x'y 41•'�„•:e: Y- ,•?•;`e z
�^E'°- .�K.'ra :•:" J•_ Si:: aC'; laG�tisys 'FM.�:`t�c�'!dsu�.:..tt...
3. Metal rack is, therefore, 1
` _ "� • -j,' ; • grounded by conduit as jt 1
required by Section 250.58(a) � I l
and Section 250 -57(a) [,
!i•'` kktt "::�'r. `a, -', Boned or raided)
2. Metal enclosure Is 't�.in•. r,1 ";
supporting the equipment, the metal enclosure of the
equipment is considered suitably grounded by connec-
tion to the metal rack PROVIDED THAT the metal
rack itself is effectively grounded by metal raceway
enclosing the circuit conductors supplying the equip-
ment or by an equipment grounding conductor run
with. the circuit supplying the equipment.
A long - standing controversy has been settled by the
second sentence of Section 250 -58(a) which now
clearly' prohibits using structural building steel as an
equipment grounding conductor for equipment
mounted on or fastened to the building steel —IF THE
SUPPLY CIRCUIT TO THE EQUIPMENT OP-
ERATES ON ALTERNATING CURRENT. BUT,
structural.building steel that is effectively grounded
and bonded to the grounded circuit conductor of a de
supply system may Ge used as the equipment
grounding conductor for the metal enclosure of do
operated equipment that is conductively attached to
the building steel.
It is important to understand the basis for the code
rules of Section 250 -57(b) and Section 250 -91(b) and
their relation to the new concept of. Section 250-
58(a); ;
Note that Section 250 -91(b) refers very clearly to an
equipment grounding conductor run with or enclosing the
circuit conductors. Except for do circuits [Section 250- 57(b),
Exception No. 2) and for isolated, ungrounded power sources'
[Section 517 -86) an equipment grounding conductor of any
+ type must not be run separately from•the circuit conductors.
The engineering reason for keeping the ground return path
and the phase legs in close proximity (that is, in the same
raceway) is to minimize the impedance of the fault circuit by
placing conductors so their magnetic fields .mutually cancel
each other, keeping inductive reactance down, and allowing
sufficient current to flow to "facilitate operation of circuit
protective devices ' as required by Section 250 -51.
The new second sentence of Section 250 -58(a)
applies the above concept of ground -fault impedance
to the metal frame of a building and prohibits its use'
as an equipment grounding conductor. As shown in
the bottom of the 3 -part illustration of Section 250 -
58(a), use of building steel as a grounding conductor
provides a long fault return path of very high impe-
dance because the path is separated from the feeder
circuit hot legs— thereby violating Section 250- 51(c).
The new first sentence of Section 250 -58(a) accepts
a limited variation from the basic concept of keeping
circuit hot legs and equipment grounding conductors
physically close to each other. When equipment is
grounded by connection to a "metal rack or structure"
that is specifically provided to support the equipment
and is grounded, the separation between the circuit
hot legs and the rack, which serves as the equipment
grounding conductor exists only for a very short
— length that will not significantly raise the overall
impedance of the ground -fault path.
Section 250 -60. Neutral may be used to ground
circuit box as well as appliance trame. .
Section 250 -60
Wording of the rule that permits frames of ranges
and clothes dryers to be grounded by connection to the
grounded neutral conductor of their supply circuits
has been expanded to permit the same method of
grounding of outlet or junction boxes serving such
appliances. The revised rule permits grounding of an
outlet or junction box, as well as cooking unit or dryer,
by the circuit grounded neutral. That practice has
been common for many years but has raised questions
about the suitability of the neutral for such grounding.
Now, the revised rule makes clear that such grounding
of the box is acceptable.
Section 250- 71(c). Bonded terminals for conduit or
armor of grounding electrode conductor , ,
OCTOBER- 1977
Section 250 -71(c) '
Rewording of this part of the rule on `bonded
connections" for all interconnected service equipment
makes clear that bonded terminations must be used at
Section 250- 79(c). Sizing a copper bonding jumper
for aluminum service conductors '
_ ;•- :�•ne- y�x1y -s7
: �- rYi,` �v�'' tF.•. �i. 3�- ���t : ^.�tin`v-- �i'•�:Iv'- •y[�::. ^�".i: }� �t �:�°T
Each service phase lag has -
a cross - section area of
-�i3 X 750MCM 2250MCM
= , i %('cc .,pq• ", "L.�s.
aluminum G.',....: , _ : •5:c.....:Y; ,r.31
-•enclosure•^ _r
•z'._� }; - `.:' - "•: , °4'' +- `%�`Equipmenl'ground *Vi �; Y,
_ ' " "• `- �` ._honded to service,nGosure�,
,,;....✓a .ice
i.
-. ^,' ' r..•'4t
~Co•er
~
Busbnrs
.bonding
- - -
r:. _,
7,as: k'�•
M1�•'
"-jumper ^ -
,:3rkr�
P�,
_ ends of conduit (rigid metal conduit, IMC or EMT) or
=D '''• 3' ...�•
'
o j(u'"
s; `�
;o s v u'i
. cable armor• that encloses a grounding electrode
-):• -.. -.• •H::.
,
:':a�.:'
::�
:a•c•. ='
;,;.
'a• •p �•.; -'shg
conductor. That means that connection of conduit or
cable armor must be made using a bonding locknut or
s +,.: ;;:,::6:�g _, :� ' ; : d:';. , ; ;;_o 'i ; n: �? : a °•
bonding bushing (with a bonding jumper around
un unched concentric or eccentric rings left in any
} Bonding bushing service'°
with terminal lu - conduit: =° �t '° _ z
knockout be to
on each conduit ,r• _ ;. i,}'w
sheet metal or must connected a•
IF attaching -. _ _�;� „• ^•
threaded hub or boss
bonding jumper "'” '•�., , -
Section 250 -92 (a), first sentence of second para-
'h M1.
• - } Copper bonding jumper 1
graph, requires a metal enclosure for a grounding
Three 4-in. conduits mus(be sized as if
electrode conductor to be electrically in parallel with
' • stubbed up under swbd, r phase legs were copper, '
the grounding electrode conductor. As a result, a
each carrying four 750 MCM . with per -phase ampacity
-THW aluminum conductors a to that of three
metal conduit or EMT used to enclose a grounding
of o parallel service of ; • 750MCM THW aluminum `f
:- three 750 MCM ° er p hose -° r• :"
electrode conductor— whether or not such conduit or
_ - _ ;,`- _ conductors f
EMT is mechanical protection required by Section
F,•;:;,; z��•'° �ws;;k
�'`""'"'�'
250 -92(a) —forms "part" of the grounding electrode
conductor. In fact, such conduit or EMT has a much -
Mutton k
lower impedance than its enclosed grounding electrode
�; 1. Each 750MCM THW aluminum has ampacity of 38s € -
- conductor (due to the relation of magnetic fields) and
amps.
-' 2. The smallest copper conductor of at lea st that ampacityts
is, therefore, even more important than the enclosed
..i 600MCM THW copper (420 amps). -
conductor in providing an effective path for current to
= 3 Three 600MCM THW copper provides spar -phase cross--
:' section area of 3 X 600 - 1800MCM. j
• the grounding electrode. Because of that importance,
i' 4• Because that value Is In excess of 1100MCM copper, sec. A
the new wording of Section 250 -71(c) requires "bond-
. ' 250 -79(c) requires the copper bonding jumper to have a es
ing" connection of such raceway to any service enclo
1=t cross - section area not less than 121/:% of 1800MCM . #�
; 8. 0.125 X 1800 - 225MCM (250 Is the next standard
sure.
Section 250 -79(c)
- The second sentence sets minimum sizes of Copper:
Therefore- copper bonding jumper must be 250MCM :.
and aluminum service entrance conductors above
1. size r
which a service bonding jumper must have a crosssec-
w La�
tion area "not less than 121/:% of the area of the
largest phase conductor." And the rule now states that
if the service conductors and the bonding jumper are
of different material (i.e., service conductors are
EXAMPLE: If an aluminum bonding jumper is
copper, say, and the jumper is aluminum), the
used at a service fed by copper service entrance
minimum size of the jumper shall be based on the'
conductors in conduit and if the service feeder is made
assumed use of phase conductors of the same material
up of, say, four sets of conductors in four conduits,
as the jumper and with an ampacity equivalent to that
-with four 500MCM THW copper conductors per phase,
of the installed phase conductors:
then the size of the aluminum bonding jumper must ,
76
ELECTRICAL CONSTRUCTION AND MAINTENANCE
be selected as if the service were 7r, -,1e up using
' `" x, '• "'" '',,�� +fit ¢ : _
' aluminum instead of copper,, and the assumed size of
the aluminum phase conductors must be such that
they have an ampacity not less than 380 amps per
IL
"`" °'` ''�`ii'Ky: ?': •� , �,a.:f
conductor (the ampacity of each 500MCM THW
`�' °; ;° '��t� =" a�"
iY. .rY
copper phase leg). From Table 310 -16 (this Table is
also substantially revised, as will be described later
A,
an aluminum THW conductor with ampacity at least
•� 1s f i u.� .V^ J 4
equal to 380 amps is 750MCM size (385 amps). Four
` r aM`r-4',L* {4
750MCM conductors per phase is a total of 4 x
' 750MCM = 3000MCM of cross- section for each phase
le of the service. Because that is larger than
g g
1750MCM aluminum, as noted in the new rule of
Section 250- 79(c), the bonding jumper must have a
minimum cross- section area, of not less than 12/2%
'
times 3000MCM. The result of the calculation is 0.125
X 3000 = 375MCM, minimum size of the aluminum
bonding jumper. The illustration for Section 250 -79(e)
, 7'
shows a sample calculation for the opposite combina-
tion of conductor materials— aluminum service con -;
-
ductors and a copper bonding jumper. The calculation
is clear and similar, following the steps of the code
_
rule.
,*
Section 250 -79(e)
•.:
This is a new permission in the code and follows the
r
_ °
1,�
thinking that was described above for external
grounding of equipment attached to a proper) y
grounded metal rack or structure, under Section 250-
_
58(a). A short length of flexible metal conduit,
liquidtight flex or any other raceway may, if the
raceway itself is not acceptable as a grounding condue-
y
tor, provide grounding by a "bonding jumper" (note, .
not an equipment grounding conductor) run either
'
inside or outside the raceway or enclosure PRO-
VIDED THAT the length of the equipment bonding
jumper is "not more than 6 feet and the jumper is
routed with the raceway or.enclosure.
t '
Note that this is a new permitted application that
"
has limited use for the conditions specified and is a -
-
�•
special variation from the concept of Section 250- ,
,' 57(b), which requires grounding conductors run inside
raceways. Its big application is for external bonding of
°
short lengths of. liquidtight or standard flex, under
those conditions where the particular type of flex "
:v
itself is not suitable for ' providing the grounding _
'
"continuity required by Section 350 -5 and Section
351 -9.
In addition to those code rules, required bonding of
'
s
flex must correlate to application rules in the UL's
"Electrical Construction Materials List" (the green
book). UL notes•than any listed liquidtight flex in 11/4
r
in. and smaller trade size, in a length not over 6 feet, is
EE
satisfactory as a grounding means through the flex
and does not require a bonding jumper (or equipment
grounding conductor) either internal or external. .
For liquidtight flex larger than 11/4-in, size, there
possib]e application conditions:
t • OCTOBER, 1977 - _
77
Section 25D- 79(e). New rule applies to bonding jumpers for flex and liquidtight.
1. If a length of liquidtight flex larger than 11 /4-in. ing -type connectors at the ends of the flex, ari external
is short enough to permit an external bonding jumper - .bonding jumper may be used. BUT WATCH OUT!
not more than 6 feet long between external- ground- - The rule says the jumper, not the flex, must not
78 ELECTRICAL CONSTRUCTION AND MAINTENANCE
exceed 6 feet in length AND the jumper "shall he
routed with the raceway" —that is, run along the flex
surface and not separated from the flex. '
i If any length of flex is over 6 feet, then the flex is
not a suitable grounding conductor, regardless of the
trade size of the flex. In such cases, an equipment
grounding conductor (not a "bonding jumper" —the
phrase reserved for short lengths) must be used to
provide grounding continuity and IT MUST BE RUN
INSIDE THE FLEX, NOT EXTERNAL TO IT, IN
ACCORDANCE WITH SECTION 250- 57(b)..
Standard flex is not listed by UL as suitable for
grounding in itself. Section 350 -5 of the NE Code,
however, permits flex to be used without any supple-
mental grounding conductor when any length of flex
in a ground return path is not over 6 feet and the
conductors contained in the flex are protected by
overcurrent. devices rated not over 20 amps. Use of
standard flex with the permission given in Section -
_ 250 -79(e) must be as follows:
1. If a length.of.flex is short enough to permit a
bonding jumper not over 6 feet long to be run between
external grounding type connectors at-the flex ends,
while keeping the jumper along the flex, such an
external jumper may be used where equipment
grounding is required —as for a short length of flex
with circuit conductors in it protected at more than 20
amps. Of course, such short lengths of flex may also be
"bonded" by a bonding jumper inside the flex instead
of external.
2. Any length of standard flex that would require a
bonding jumper longer than 6 feet may not use an
external jumper. In the new code sense, when the
length of such a grounding conductor exceeds 6 feet, it
is not a BONDING JUMPER BUT IS AN EQUIP-
` MENT GROUNDING CONDUCTOR AND MUST
BE • RUN ONLY INSIDE THE FLEX, AS
j- OCTOBER, 1977
REQUIRED BY SECTION 250- 57(b). Combining UL
data with the rule of Section 250 -79(e) and the Excep-
tion to Section 350 -5, every length of flex that is over
6 feet must contain an equipment grounding conductor
run only inside the flex.
In all cases, sizing of bonding jumpers for all flex
applications is made according to Section 250- 79(d),
which requires the same minimum, size for bonding
jumpers as are required for equipment grounding
conductors. In either case, the size of the conductor is
selected from Table 250 -95, based on the maximum
rating of the overcurrent devices protecting the circuit
conductors.
Section 250-80
This section on bonding of piping systems in build-
ings has been divided into two parts -metal water
piping and other metal piping.',,.
Part (a) requires any "interior metal water piping
system' to be bonded to one of the following. the -
service equipment enclosure; the grounded conductor -
(usually, a neutral) at, the service; the grounding
electrode conductor where it is sized from Table 250 -• -
94;.OR to the one or more grounding electrodes used.
This rule applies where the metal water piping system
does not have 10 feet of metal-pipe buried in the earth
and is, therefore, not a grounding'electrode. In such
cases, though, this rule makes clear that the water,
piping system must be bonded to the service
grounding arrangement. And the bonding jumper
used to connect the interior water piping to, say, the
grounded neutral bus or terminal (or to the ground
bus or terminal) must be sized from Table 250 -94
based on the size of the service conductors. The
jumper is sized from that table because that is the
table that would have been used if the water piping
had 10 feet buried under the ground, making it suit-
able as a grounding electrode.
79 1
Part (b) requires a bonding connection from other
metal piping systems that "may become energized" to
the grounded neutral, the service ground terminal, the
grounding electrode conductor or to grounding elec-
trodes. BUT, for these other piping systems the
bonding jumper is sized from Table 250 -95, using the
rating of the overcurrent device of the circuit that
may energize the piping. And where a particular
circuit poses the threat of energization to•a piping
system, the equipment grounding conductor for. that
circuit (which could be the conduit or other raceway
enclosing the circuit) may be used as the means of
bonding the piping back to the service ground point.
The considerations involved in applying the rules of
Section "250 -80 should be carefully weighed when
designing and installing a suitable "grounding elec-
trode system " —as required by the new concepts of the
substantially revised Section 250 -81.
Section 250-81
The basic rules on grounding electrodes have been
altered in such a way as to downgrade the water pipe
electrode and to require a "grounding electrode
system" made up of more than one grounding elec-
trode, with effective bonding together of all of the
electrodes. The several requirements set by this
revised section and the conditions established for
application of the new rules can be best understood by
considering the steps involved in making the necessary
provisions for typical- installations.
First, take the case of a building fed by an under-
ground water piping system with at least a 10 -ft
length of metal water pipe buried in the earth ahead
of the point at which the metal pipe enters the
building. Such buried 'pipe is a grounding electrode,
and connection must be made to the underground pipe
by a grounding electrode conductor sized from Table
250-94-and run from the grounding point in the service
equipment. But now, a number of other factors must
be accounted for, as follows:
1. EVEN THOUGH THE WATER PIPE IS A
SUITABLE GROUNDING ELECTRODE, SECTION
250 -81(a) REQUIRES THAT AT 'LEAST ONE
MORE GROUNDING ELECTRODE MUST BE
PROVIDED AND MUST BE BONDED TO THE
WATER PIPE ELECTRODE. A water pipe, by itself,
is no longer an adequate grounding electrode and must
be supplemented by another electrode to provide a
"grounding electrode system." ,
2. The additional electrode may be-
e The metal frame of the building provided the frame
is effectively grounded (embedded in earth and /or in
buried concrete).
• OR, a concrete- encased electrode within and near
the bottom of a concrete foundation or footing in
direct contact with earth. The electrode must consist
of at least 20 feet of one or more steel reinforcing bars
Section 250 -81. New approach to system grounding provides variety of grounding electrode
arrangements. ;
In buildings without grounded metal frame���':
1. i -... �:- W�...":#:..x�.ti `_i: �' �L�siw�:.°C'a:.�.i; =- `;e�,.•f °, k^,,:.�
• Case ; ` Grounding electrode conductor sized from Tabiel•.
250 -94 must connect bonded service neutral
EY ?M;^ = clamp on water -pipe electrode. • • PI
`, :-:. ::j.�r'^•'F- °,:- q'�- <. •'E•�;'r:;,c:- rz ^;:r:"a'.. j—7
Because the underground tanks are not a `mode '..'
=''''• �eleclrode, this grounding electrode •conduciormustbe ,.�
_ sexed from Table 250-94 —ond not simply No.6 copper.
'a =l. °r' •. +•� '•:.;:" • or equivalent as c '
Meler wish''. ="_
,p tamper ,: S
Ti; ;ea 250-94 "'r'.
no, le
More than loft of ° - :�
metal pipe in eorihX • •
vva[er pipe is an F• :- - -. in building • e
electfodebut% •:Tib >.a'e.:aa`r,: +ms's. :a'�'..:r..,:- -
• must be
su lemdnted by!
another P. -in SE ..;., .y, 4' *'f= ``;:;,i,a+ '
enclosure ,
electrode .i „„ hooded to �„° ° Tanks
.`,}::. e`s.�•':r- "+C:6�ii- '+uwiS:ovi+L t.� ».Lis .Se_t�34. ;�.w::. ,: ")
7
Because building does= not have grounded metal
frame or either of the electrodes descdbed In Section 2
,'.'• 250 -81(c) and (d), the last sentence of Section 250 -�
•' 81(a) requires that one of the electrodes of Section
250 -83 be used to supplement the water'plpe elec-
trode—such as metal piping to underground metal
tanks.+
or rods of not less than 1 /2-in. diameter, or it must
consist of at least 20 feet of bare solid copper
conductor not smaller than No. 4 AWG.
• OR, a "ground ring encircling the building or strue-
ture," buried directly in the earth at least 21/2 feet
down. The ground ring must be "at least 20 feet" of
bare No. 2 or larger copper conductor. (In most cases,
the conductor will have to be considerably longer than
e2
Section 250- 91(a), Exception No. 2
An addition was made to this rule that covers the
use of a main grounding electrode conductor with taps
from it to provide system grounding in each separate
service enclosure where two to six service disconnects
are used in separate enclosures. New wording of the
Exception r8quires. the main grounding electrode
conductor to be sized from Table 250 -94, but does not
-_.,tell on what basis that Table is used. The main
grounding electrode conductor might be sized for the
ELECTRICAL CONSTRUCTION AND MAINTENANCE
20 feet in order to "encircle" the building or strue-
'
ture.)
gr g piping or other
• OR,' under ound bare metal as g
metal underground piping or tanks.
Imo` w
o OR, a buried 8 -ft ground rod or pipe or a plate
electrode.
Sections 250 -81 and 250-83. list the acceptable elec-
trodes and describe_ installation requirements.
3. As worded. in Section 250 -81, any of the four
types of grounding electrodes mentioned there must be
"
rr;
$J,' 4,{
bonded together IF THEY ARE PRESENT. Note
-.• „No- .:i; J"::
_ that the rule does not state that any of those electodes
must be provided. But if any or all of them are
D
present, they must be bonded together to form a
f`�'
"grounding electrode system,” sizing such bonding
,jumpers from Section 250- 79(c). And where a water
pipe electrode, as described, is present any one of the
-
' three electrodes in Section 250 -81 may be used as the
IR
required "additional electrode."
'nonmetallic
In the case of a building fed by a
y
'underground piping system or one where there is not
_
10 feet of metal pipe underground, the water piping
system is not a grounding electrode— HOWEVER,
THE INTERIOR METAL WATER PIPING SYS-
TEM MUST BE BONDED TO THE SERVICE
�'�
- GROUNDING, as described above under Section 250-
• 'sit
�• q. ,�= 4- -- �.w:'� -' �<fi
:.80(a). P P grounding
But when the water pipe is not a
electrode, another type of electrode must be provided
'
to accomplish the service grounding. Any one of the
- .. .
other. three electrodes of. Section 250 -81 ((b), (c) or
(d) ) may be' used as the required grounding`electrode'.
of the electrodes from Section 250 -83 MUST BE
For instance, if the metal frame of the building is
USED. Note that any type of electrode other than a
effectively grounded, a grounding electrode conductor,
water pipe electrode MAY BE USED BY ITSELF AS
sized from'Table 250 -94, and run from the bonded
THE SOLE ELECTRODE., '
service neutral or ground terminal to the building
A very important sentence of Section 250 -81(a) says
frame, may satisfy the code. Where none of the four
that "Continuity of the grounding path or the bonding
electrodes described in Section 250 -81 is present, one
connection to interior piping shall not rely on water
meters." The intent of that rule is that a bonding
-
jumper always MUST BE USED around a water
x. =s,� "v p
'i: -e
meter. this has been added because of the chance of'
-.loss
•
- ii�w �'�r� �
of grounding' if the water meter is removed or
;; ' •� } p'! ii ^,'r.
replaced with a nonmetallic water meter. the bonding
;;)
Jumper around as meter must be sized in accordance
4{
t
with Section 250 -79(c) 7which is based on Table 250-
?i+`�s
94, but may call for a conductor even larger than the
grounding electrode conductor ruri to the grounding
electrode (i.e., 121/2% of service phase leg cross - section
area ) - •
e2
Section 250- 91(a), Exception No. 2
An addition was made to this rule that covers the
use of a main grounding electrode conductor with taps
from it to provide system grounding in each separate
service enclosure where two to six service disconnects
are used in separate enclosures. New wording of the
Exception r8quires. the main grounding electrode
conductor to be sized from Table 250 -94, but does not
-_.,tell on what basis that Table is used. The main
grounding electrode conductor might be sized for the
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 250- 91(a), Exception No: 2. New rule on
sizing main and taps of grounding electrode
conductor at multiple- disconnect services
sum of the cross - section areas of the total number of
conductors connected to one hot leg of the service
drop. Or, the main grounding electrode conductor
could be sized from Table 250 -94 on the basis of the
size of one hot leg of a service of sufficient size to
handle the demand load fed by the two to six service
disconnects. -
The rewording of the rule does, however, make clear
that the size of the grounding electrode tap to each
separate enclosure may be determined from Table
250 -94 on" the basis of the largest service hot leg
serving each enclosure.=.
• Section 250 -91(b)
Some clarifications were made to cover the accept-
able types of equipment grounding conductors:
• For Type MC metalclad cable (the so- called "inter- '
locked armor cable "), the metal sheath may serve as
the equipment grounding conductor. Or, the combina-
tion of the metal sheath and enclosed grounding -
conductor(s) may serve that purpose. -
• A new conduit called "flexible metallic tubing" has -
been added in the Exception that permits limited
grounding through "flexible metal conduit." Now both
standard flex (Greenfield) and the new "flexible metal
tubing" may be' used without a bonding jumper or
internal equipment grounding conductor under the
following conditions:
1. The total• length of either type of raceway is not
OCTOBER, 1077 -
i
over 6 feet long "in any ground return path." That last
phrase is -intended to prohibit use of more than one
six -foot length in a run of raceway. But, the "total
length" of 6 feet could be made up of, say, a 2 -ft length
and a 4 -ft length in a raceway run..
2. The circuit wires in either raceway must be
Protected at not more than 20 amps. -
3. Approved grounding -type fittings must be used.
Exception No. 2 in this section covers liquidtight
flexible metal conduit in a similar rewording.
Liquidtight Rex in VA -in. and smaller trade size may
be used without a bonding jumper inside or outside
provided that the "total length" of that flex -"in any
ground return path" is not over 6 feet. Thus, two or
more separate 6 -ft lengths installed in a raceway run
would not be acceptable with the - bonding jumper
omitted from all of them. In such cases, one 6 -ft
length or more than one length that do not total over 6
feet may be used with a bonding jumper, but any
additional lengths 6 -ft or less in the same raceway run
must have an internal or external bonding jumper
sized from Table 250 -95.
Although UL gives the same grounding recognition
to their `listed" liquidtight flex, this code rule covers
liquidtight that the UL does not list, such as high -
temperature type.'
Section 250 -92(a)
Protection of a grounding electrode conductor may
be provided, as'required, by "rigid metal conduit,
intermediate metal conduit, electrical metallic tubing,
or cable armor." Use of IMC must satisfy Article 345;
rigid metal conduit, Article 346; and EMT, Article
348.
the aluminum size has been raised from 1000MCM to %<, i ,'w:::,.:: } ground rod
1200MCM.
Section 250 -112 '
Rewording of this rule has added a'requirement
that many inspectors have requested as essential to + _i, .-z '«
safe application. • The rule now requires that the
connection of a grounding electrode conductor to the
grounding electrode "shall be' accessible." Inspectors
want to be able to see and/or be able to get at any
connection to a grounding electrode. But because there
• are electrodes permitted in Section 250 -81 and Section
250-83 that would require underground or concrete- •.�,�
encased connections, an Exception was added to the
basic rule to permit inaccessilile connections in such
cases. This section now places the burden on the ` `� -^ • r
• fi,•� sac •�K
installer to make such connections accessible wherever ;t
possible.
To be continued next month.
T•' _ �; Buried
r connection
"' *.• 'j Is O.K. {
sleet r'
d 11
on Till
Bond g
bushing : '. •. : ,'f ,
Grade
No
bond
�
Welds '1
i graend.lerminal
Bonding
Section 250 -112. Whenever possible, connections to grounding electrodes must be "accessible."
•
rpr tx. -+4.7( •,�••.y ;e,- .-i,�µ u
't'�:� •se- �Uki �+e+: v;• t'1 .e JC''ii'r •,?r'�V i�
, "r`XXwAfP`.TUb:.�+�l:.i
N..- .- ;,nw..1_L'�^w.n. 7PY:-SS: i(t z[.ir
±p 3�F �LI�_•r"�T$T'?tY'.�.'�, �:"/._ t'y�•: �y i�
T.._c %SSI,i i✓ �1L✓ �+'�xf�ta�� >.'.`•JCf.'�."P:�]iC F%
'l� grounding; •./ •• '
":: iAaYeeYl��'�,'w i_ a.; �....: �l =w'' >..�' J
:i1f.L�i�f.SLSA
"' _ .� ... must be accessible 1 I I ; -; ,,., :'• - No. 4/0
%h„ r:; ; J bond
• Connections to interior metal _:
'. ` 's
nut, encased and /or burled connections may he used
'
rj�'•, water -pipe grounding electrodes .. R l' ,;, ja.y ;• ; J
.•%
i where needed `
..
.".. ,ys•c;f..- ..clrod� p r�;.'j•.:5::'%iici:}`i�s•. :���W,'`.k::'.
" f5a
?- .C;^°.'r.*°,•,a .^r;�Y-'•�,'s1.
E.o} ;F:',s� fyw :r
S
":•4.;-
oundingelee`: - Y,•)
'conductor
;�� > ° 'To,groundterminalr' ?'�'
-' (plus canduih?• , ...end to i
i .. , :; - • r, in a ui m n =_ •`:'.'`S7%:rm
9 D e
',it used as proleclion) ., �:, "t ry grounded metal tram's' :�•
,f,
n
of buitdµng _„;••: _ �i
•
G de:; D, %:e '� 3
• : Grbunding
•: ^ ` •�'Pr.�b,y
•
ushng ; .„. •s-•
¢ -A :b.,\- H:.• ^- $••,•:r-�- S y- kJumPer os.� F•.,.
,tor?
electrode condtictor
': t •� connected by fusing or
,,!•., '
}'; %ta >: : ;..s• < .• -:,Gf• needed
° t`
_
-
mechanical connector to
'r
-
eS ^ .s: n: z y5 =.2 =a :' • Z I '
=;y
: _' . 9 reinforcing steel In
t
.,'$ =r; Y r _
t,7Z" `' �' "-
f ,t underground concrete
.�!• " '
! l
Lr�fl�� M ^ ,• ' ) `
r' footing or foundation
. °;' :j
;
a - "•` _;1
)i:. `�:. = _�''_°=
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'- b:'�4•,V %Z
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.:ait�,•.•t- ,` • .�i,`' p
7y, i Ja a�;,.y...sr.'y; }c�
- �= • ; At Ieosl 20fi one more
"'. •V J; F' `r4...p.•b��: >;' . sleet reinforcing bars or rods of
3; • 1pf nol less lhan l /2-in. diameler
• �
iti i�''.`i Y.%v .. __- s'��,vS�`�f'�%r::�.•. i- ,id�.+%fY:ri ',�i� +.:,I
_. i'i+_.�..e�:.'::: i .. .........::£4i4 �1• iP• �. .i ":�.Yi:'rl':.:.��.�d•.?•_i�3.
the aluminum size has been raised from 1000MCM to %<, i ,'w:::,.:: } ground rod
1200MCM.
Section 250 -112 '
Rewording of this rule has added a'requirement
that many inspectors have requested as essential to + _i, .-z '«
safe application. • The rule now requires that the
connection of a grounding electrode conductor to the
grounding electrode "shall be' accessible." Inspectors
want to be able to see and/or be able to get at any
connection to a grounding electrode. But because there
• are electrodes permitted in Section 250 -81 and Section
250-83 that would require underground or concrete- •.�,�
encased connections, an Exception was added to the
basic rule to permit inaccessilile connections in such
cases. This section now places the burden on the ` `� -^ • r
• fi,•� sac •�K
installer to make such connections accessible wherever ;t
possible.
To be continued next month.
T•' _ �; Buried
r connection
"' *.• 'j Is O.K. {
sleet r'
d 11
on Till
Bond g
bushing : '. •. : ,'f ,
Grade
No
bond
�
Welds '1
i graend.lerminal
Bonding
"4 /
y.+, �i''::,>»i � - ,,tr..i .A,•:5 -.b "oA ;•f�.m:$: y. bushing
_
�hfr'- S•,r "i:i sq�:fi .tw .1�.% T' •! �.•�� �
No. "
t <: j':z ti:, w�i�.:.:`_'�.,MS'+ \.
-
5 +��'a.5:.? Stiv. La" �. Jt'. y ..aJ..w_i..,._•,J.u.u..- �...... .:
'l� grounding; •./ •• '
r..
a d••�... �
"' _ .� ... must be accessible 1 I I ; -; ,,., :'• - No. 4/0
%h„ r:; ; J bond
�;�.•....
�'•):
�,� .- .- �'.'•L�y!�r. ':F- •'�•r•'!ffr T.iY±�:a��`? F-�� •:.�Z•F.le .•.3 . -. -...,. '�J.
the aluminum size has been raised from 1000MCM to %<, i ,'w:::,.:: } ground rod
1200MCM.
Section 250 -112 '
Rewording of this rule has added a'requirement
that many inspectors have requested as essential to + _i, .-z '«
safe application. • The rule now requires that the
connection of a grounding electrode conductor to the
grounding electrode "shall be' accessible." Inspectors
want to be able to see and/or be able to get at any
connection to a grounding electrode. But because there
• are electrodes permitted in Section 250 -81 and Section
250-83 that would require underground or concrete- •.�,�
encased connections, an Exception was added to the
basic rule to permit inaccessilile connections in such
cases. This section now places the burden on the ` `� -^ • r
• fi,•� sac •�K
installer to make such connections accessible wherever ;t
possible.
To be continued next month.
T•' _ �; Buried
r connection
"' *.• 'j Is O.K. {
sleet r'
d 11
on Till
Bond g
bushing : '. •. : ,'f ,
Grade
No
bond
�
Welds '1
Section 250-95
"4 /
In Table 250 -95, associated with this section, the N
No. "
size of aluminum equipment grounding conductor has b
'l� grounding; •./ •• '
been increased for two of the sizes of overcurrent
a d••�... �
protection listed in the left -hand column. For 2500- >
�;�.•....
{ r
r•
from 500MCM to 600MCM. For 5000 -amp protection, °
°''.
T•' _ �; Buried
r connection
"' *.• 'j Is O.K. {
sleet r'
d 11
on Till
Bond g
bushing : '. •. : ,'f ,
Grade
No
bond
�
Welds '1
WIRING METHODS AND, MATERIALS
Article 300— Wiring methods
Section 3oo-1. Scope. Rewording of the exceptions in
this section indicates clearly that not all of the general
requirements in Article 300 apply to remote control
circuits, to signal circuits, to low- energy circuits, to
fire- protective signaling circuits, and to communica-
tions systems.
As indicated in the exceptions, only those sections of.
Article 300 that are referenced in Article 725, in
Article 760 and in Article 800 apply to the types of
circuits covered by those articles. In effect, not all of
the regulations on wiring for general - purpose power
and light circuits apply to the specialized circuits
covered by Articles 725, 760 and 800.
Section 300-3. Conductors of different systems. A
number of editorial revisions in this section were
made to better express the intent of the code on
applications where circuits of different voltage are
installed in common enclosures. . , , :, ._
In Section 300 -3(a), the words `cable or raceway"
were added after the words "wiring enclosure" to
clearly indicate that it is the intent of the code that
circuits of different voltage up to 600 volts may occupy
the same wiring enclosure, cable or raceway provided
all of the conductors are insulated for the maximum
voltage of any circuit in the enclosure, cable or race -
NOVEMBER, 1977,
way. Although that change may appear as a simple
editorial revision, it was the intent of the code panel to
indicate clearly that motor power conductors and
motor control conductors be permitted in the same
conduit. This was changed to resolve a long - standing
controversy about the use of control- circuit conductors
in the same conduit with power leads to motors.
• For a long time it has been argued that Section 300 -
3(e) in the 1975 code required a separate raceway for
each motor when the control conductors were run in
the raceway with the' power conductors. This was
supported by Section 725 -15, which also indicated that
Class 1 control conductors may be run only in the
raceway for the power conductors which the control -
conductors actually control.
It was the intent of the change in Section 300 -3(a)
to permit a common raceway to contain a number of
motor -power circuits along with a number of motor -
control circuits. It is no longer necessary to use a
separate conduit for each motor power- plus - control
hookup.
But Section 725 -15 still requires that control
conductors used in a raceway with power conductors
must be "functionally associated" with the power
conductors. Thus, separate raceways are required if
motor power supply conductors are run in a raceway
with motor control conductors (Class 1 conductors,
from Article 725) where the motors are individual
5
Section 300 -1 Revised wording intends permission to uae control and power wires for more than
one motor m common raceway.
motors rather than a number of motors as part of,
say, a multimotor machine. But, where several motors
are actually functionally associated, that is, their
operation is interrelated one to the other, power and
control wires for all of the motors may he run in a
single raceway. it is now stated that conductors.
In Section 300 -3(b),
operating at more than 600 volts must not occupy the ' -
same equipment wiring enclosure, cable or raceway
with conductors of 600 volts or less. .
The editorial revision of Section 300 -3 now lists
h (m [not to paragraph
(a)]. Exception No. 3 is intended to apply to enclo-
sures, not raceways, such as used for high - voltage
motor starters, permitting the high- voltage conduc-
tors operating at over 600 volts to occupy the -
controller housing as the control conductors operatin@
at less than 600 volts.
three exceptions to paragrap
_ - ELECTRICAL CONSTRUCTION AND MAINTENAN
Section 3110 -4(a). New clearance for cable holes
through wood studs . , Z.
Section 300-4. Protection against physical damage. In
Section 3004(a), a change has been made in the
clearance from the edge of a hole in a wood member to
the edge of the wood member. Where the 1975 NE
Code required a minimum of 11/2 in. from the edge of a
cable hole in a stud to the edge of the stud, the 1978
NE Code now requires only 11 /e in. This change was
made to permit realistic compliance with the code rule
when drilling holes in studs that are 31/2 -in. deep. It
also was taken into consideration that the nails
commonly used to attach wall surfaces to studs were
of such length that the 11 /, -in. clearance to the edge of
the cable hole afforded entirely adequate protection
against possible penetration of the cable by the nail.
Section 3005. Underground installations. A new
Exception No. 2 recognizes that raceways run under
concrete slabs or under buildings have sufficient
protection against digging and are not required to be
subject to the burial depth requirements given in
Table 300 -5. Where raceways are so installed, the rule
requires that the slab or building extend at least 6 in.
beyond the underground raceway. This new exception
applies only to conduits or other raceways and not to
direct - buried cables.
Exception No. 8, also new, recognizes reduced burial
depth for low- voltage landscape lighting circuits and
supply circuits to lawn sprinkler and irrigation valves.
Change was made in recognition of the reduced
hazards and safety considerations for circuits oper-
ating at not more than 30 volts. The rule requires that
Type OF cable or other approved cable must be used
for such circuits and that the burial depth does not
have to exceed 6 in.
In Section 300 -5(f), a new paragraph was added to
specifically require that backfilled trenches must
contain any necessary protection for raceways or
i
NOVEMBER, 1977 _
Section 300 -5. New Exception No. 2 eliminates
burial depth requirements for direct - buried
"raceways" under specified conditions.
Burial -depth requirements of Table 300 -5 do not apply
to raceways Installed like this.
raceways" but not to direct - burled cables:; ;3,N,4:
Any direct - burial cabie•ruh under a building m
Installed In raceway, as required by Section 300 -5 (1
the raceway may be installed In the earth, lmmediately
the bottom of the building= without any earth cover:
Y 2. Any direct - burled cable under a slab Is subject
24 -in. minimum burial -depth requirement of Table 300
burial depth may be reduced as permitted by Fxceptlr
4, 5, 6, and 8: Application of Exception No. 1 to reduce
burial -depth under a grade -level slab Is quest[
because that exception calls for, "concrete -pad" pro
to be "in the trench over the underground Installatior
cables buried in the trench. It specifies that sand or
suitable running boards of wood or concrete or other
protection must he afforded in those cases where
backfill consists of heavy stones or sharp objects that
Section 300-5, Exception No. 8. Reduced burial
depth for low- voltage landscape lighting and
lawn- sprinkler controls
otherwise would present the possibility of damage to
the cable or raceway.
In Table 300 -5, intermediate metal conduit has been
added, and the minimum burial depth is given at 6 in.,
the same as thatfor rigid metal conduit.
as
��
Section 300-6. Protection against corrosion. This
section has been reworded to effect a positive recogni-
tion of the use of ferrous or nonferrous metal race-
ways and fittings in concrete or in direct earth burial.
The change also was intended to indicate that galvan-
izing on conduits is a form of corrosion protection and'
that when conduits are directly buried or are placed in
concrete in accordance with UL regulations, they are
suitable for such use.
Throughout the 1978 NE Code this same change
was made in all rules applying to the use of metal
raceways in the earth or in concrete. .. .
Section 300 -19. Supporting conductors in vertical
raceways. In Table 300- 19(a), the vertical line in the
right margin indicates simply that the word "thru"
has replaced the word "to" in all lines of the table.
This was done to more accurately specify the range of
conductor sizes that apply to each of the support
spacings indicated in the table. Thus, "No. 18 thru No.
8" makes it clear that both No. 18 and No. 8 are
included.
Section 300 -22. Wiring in ducts, plenums, and other
air - handling spaces. Section 300 -22(c) was reworded to
tighten up code rules on the use of wiring methods in
air- handling ceilings above suspended ceiling tiles. In
listing the wiring methods permissible in air handling
Section 300- 22(c). "Only' the wiring methods
listed may be used in air - handling ceilings.
ceilings, the word "Only" was inserted in the first
sentence to make clear that only the indicated wiring
methods may be used. Previous wording accepted a
number of wiring methods but did not clearly exclude
wiring methods not mentioned.
The listing of raceway methods, acceptable now
includes flexible metallic tubing, which is a new
raceway recognized by the NE Code and covered in
new Article 349. But flexible metallic tubing may be
used in air - handling ceilings only in single lengths not
over 6 ft long. The same length limitation applies to
liquidtight flexible metal conduit used in air - handling
ceilings.
Article 305— Temporary wiring
Section $05-1. Scope. Two new words, "mainte-
nance" and "repair," were added to Section 305 -1(a).
This indicates that the less rigorous methods of
temporary wiring may he used and that all rules on
temporary wiring must he observed wherever mainte-
nance or repair work is in process. This expands the
applicability of temporary wiring beyond new
construction or remodeling work.
Splices are now permitted to be made in temporary
wiring circuits of cord or cable without the use of a
junction box or other enclosure at the point of splice or
tap [Section 305- 2(h)]. But this new permission applies
Section 305 -2(h). Splices may be used without
boxes for cord and cable runs on construction
sites.
56
ELECTRICAL CONSTRUCTION AND MAINTENANCE
only to nonmetallic cords arid cables. A box must be
used when a change is made from a cord or cable
circuit to a raceway system or to a metal -clad or
metal- sheathed cable.
New regulations in Section 305 -2(i) require protec-
tion of flexible cords and cables from damage due to
pinching, abrasion, cutting, or other abuse.
Article 310 — Conductors for general wiring
Section 310-2. Conductors to be Insulated. Although
the basic rule of this section has not been changed, a
note has been added to refer to Section 250 -152 on the
Section 310 -2. A new note refers to neutral
conductors of solidly grounded high - voltage
systems [Section 250 -152].
High voltage :,•%C�''� 'A„�, �'y: phi
(over 600 volts') ??• • „i?$irr:;� 'be
system derived• . yo-, �• ,� for
from solidly-
Solidly grounded neutral conductor must have Insulation
3 rated for at least 600 volts, although a bare copper
? neutral may be used for BE conductors or for direct-
, buried feeders, and bare copper or aluminum may be
i used for overhead parts of outdoor circuits.
use of solidly grounded neutral conductors in high -
voltage systems. As an exception to the general rule
that conductors must be insulated, Section 250 -152
does permit a neutral conductor of a solidly grounded
"Y" system to have insulation rated at only 600 volts.
It also points out that a bare copper neutral may be
used for service- entrance conductors or for direct -
buried feeders, and bare copper or copper -clad
aluminum may be used for overhead sections of
outdoor circuits.
Of course, for such high - voltage systems, the phase
legs —the ungrounded conductors —must be insulated
for the circuit phase voltage. It is interesting, however,
that there is no specific code rule that requires insula-
tion of any circuit to be rated for. phase -to -phase
voltage. Code rules do not distinguish between phase -
to -phase voltage or phase -to- neutral voltage on
grounded systems, with respect to insulation. Thus,
the use of circuit conductors with insulation rated only
for phase -to- neutral voltage would not constitute a
violation of any specific code rule, and such practice is
used on high - voltage systems. . ,
Section 310.4. Conductors in parallel. A new excep-
tion was added after the first paragraph of this
NOVEMBER, 1977 _
section to clearly indicate long -time code acceptance of
paralleling conductors smaller than No. 1/0 for use in
traveling cables of elevators, dumbwaiters, and
similar equipment. This permitted use is not new in
the code but was never specifically indicated in Section
310 -4 as an exception to the basic minimum size of
conductor for parallel circuit makeup.
Section 310 -10. Conductor identification. Section 310 -
10(a), Exception No. 5 now recognizes the use in
multiconductor cables of a grounded conductor that is
not white throughout its entire length provided that
only qualified persons will service the installation. The
rule requires that such grounded conductors be
identified by white marking at their terminations at
the time of installation.
Similarly, a grounding conductor in a 'multicon-
ductor cable may be identified at each end and at
every point where the conductor is accessible by strip-
ping the insulation from the entire exposed length or
by coloring the exposed insulation green or by
marking with green tape or green adhesive labels
[Section 310- 10(b), Exception No. 2]. .
Section 310 -11. Marking. Anew cable, power- limited
tray cable (PLTC), has been added to the list in
Section 310 -11(b) of the conductors and cables
required to have surface marking. This cable, intended
for use in power- limited circuits, is referenced in other
Articles of the code covering use of such cable.
Section 310 -15. Ampacity. Tables 310 -16 through
310 -19 and accompanying Notes 1 through 12,
covering the maximum continuous ampacities for
copper, aluminum, and copper -clad aluminum conduc-
tors, have been completely revised.. The tables have
been altered in format from previous code editions.
For instance, Table 310 -16 now covers both copper
conductors and aluminum or copper -clad aluminum
conductors rated up to 2000 volts where not more than
three conductors are installed in a raceway or cable or
are directly buried in the earth —based on an ambient
temperature of 30C. ,
Table 310-17 covers both copper conductors and
aluminum or copper -clad aluminum conductors up to
2000 volts where conductors are used as single conduc-
tors in free air based on an ambient of 30C.
Tables 310 -18 and 310 -19 now apply to conductors
rated 110C to 250C, used either in raceway or cable or
as single conductors in free air. Care must be taken in
using these tables and in noting references to them
throughout the code.
In Note 3 to Tables 310 -16 through 310 -19, it is now
clearly indicated that the higher allowable ampacities
for residential occupancies using 3 -wire, single -phase
services also may be applied to 3 -wire, single -phase
feeders in those cases where the feeder conductors
from the service equipment to a sub -panel or other
distribution point carry the total current supplied by
the service conductors. This permission was added to
logically permit the feeder conductors to have the
same elevated ampacities as are allowed for service
conductors in those cases where the service conductors
and the feeder conductors are carrying the identical
load. '
Note 11 to the ampacity tables is new and makes it
clear that an equipment grounding conductor, which
under normal conditions is carrying no current, does
not have to be counted when determining ampacities
of conductors when more than three conductors are
used in a raceway or cable. As a result, equipment
grounding conductors do not have to be factored into
the calculation of required derating of ampacities
specified in Note 8. `
Section 310 -31. Construction of conductors for over
600 volts. Revisions have been made in Tables 310 -31•
through 310 -37. In particular, Table 310 -34 has been
expanded to cover a wider range of voltage ratings and
required insulation thicknesses.
Section 310 -38. Ampacity. Revisions also have been
made to the tables showing allowable ampacities of
high - voltage conductors. Tables 310 -39 and 310-40
have been expanded to cover conductors rated up "to
35,000 volts. Ampacities of high - voltage cables now -
extend through Table 310 -54. Care should be exercised
in using these tables and relating this data to selection
of high - voltage cables under the application conditions
given at the head of each of the tables.
Article 318 —Cable trays '
Section 318 -2. Uses permitted. Section 318 -2(d) now
specifically uses the word "only" when referring to
cable types that are permitted to be used in cable trays
in hazardous locations. Previous wording was more
open -ended and permitted specific cables without
limiting use to only such cables.
Section 318 -5. Installation. This section has been
revised to cover use of both high - voltage and low -
voltage cables in the same cable tray. Section 318 -5(e)
now notes that any multiconductor cables rated 600 "
volts or less may be used in the same cable tray.
Section 318 -5(f) points out that although cables rated
over 600 volts must not be installed in the same cable
tray with cables rated 600 volts or less, there are two
exceptions to that rule. High - voltage cables and low- -
voltage cables may be used in the same tray if a solid,
noncombustible, fixed barrier is installed in the tray
to separate high - voltage cables from low - voltage
cables. Where cables are Type MC, it is not necessary
to have a barrier in the cable tray, and MC cables•
operating above 600 volts may be used in the same
tray with MC cables operating less than 600 volts. But
$a
Section 318 -5(e) and (f). New rules clarify use of
cables in cable tray.
for cables other than Type MC, a barrier must be used
in the tray to separate high - voltage from low - voltage
cables.
Section 318-8. Number of multiconductor cables,
rated 2000 volts or less, in cable trays. This revised head
now limits application of these rules to multiconductor
` ELECTRICAL CONSTRUCTION AND MAINTENANCE
cables rated 2000 volts or less. For cables rated 2001
volts or higher, the number permitted in a cable tray
is now covered in Section 318 -11.
Section 318-9. Number of single- conductor cables,
rated 2000 volts or less, in cable trays. As in the
preceding section, this revised head limits application
of single - conductor cables to those rated 2000 volts or
less. The permissible number of single- conductor
cables rated over 2000 volts is now given in Section
318 -11. - - . • , " .
Section 318 -10. Ampacity of cables rated 2000 volts or
less in cable trays. A revision of this section now limits
its coverage to the ampacity of cables rated 2000 volts
or less —both multiconductor and single- conductor
cables. '
Section 318 -11. Number of Type MV and Type MC cablea
(2001 volts or over) In cable trays. This new section
covers MV and MC cables in cable trays. Type MV
cable is a high - voltage cable now covered by new
Article 326. Type MC cable is the metal -clad cable
operating above 2000 volts —a cable assembly long
known as interlocked armor cable. -
Section 318 -12. Ampacity of Type MV and Type MC
cables (2001 volts or over) in cable trays. This is also a
new section, covering the ampacities of MV and MC
cables operating above 2000 volts in cable trays —both
single - conductor and multiconductor.
Article 326— Madium voltage cable
Section 326-1. Definition. This first section of this
new article defines the medium voltage cable now
blown as Type MV. Because the code now has an
article and cable designation for cables operating
above 2000 volts up to 35,000 volts, it may be expected
that electrical inspection authorities will insist that all
cables in that voltage range must be Type MV to
satisfy the NE Code.
Great care should be exercised in determining the
attitude of local inspection authorities toward the
meaning of this article. In particular, the relationship
of Section 110 -8 to Article 326 should be determined.
Section 110 -8 states that 'only wiring methods,
recognized as suitable are included in this code." The
question to be answered is: Will electrical inspection
agencies require all high - voltage conductors ' to be
Type MV? Or will inspection agencies accept high- .
voltage conductors -not specifically designated Type
MV? In other words, because the code now has an
accepted type of high - voltage cable, will it be permis-
sible to use high - voltage cables that are not of this
accepted type?
The remaining sections of Article 326 spell out the
basic code rules on use of medium - voltage cables.
NOVEMBER, 1977
Article 333— Armored'cable `
Section 333-1. Definition. This section identifies Type
AC cable, which is the cable assembly long used and
known as BX cable. All of the regulations on use of
Type AC cable are given in the balance of the sections
of this new code article. The rules on armored cable
are not new and were contained in Article 334 on
metal -clad cable in the 1975 NE Code and earlier
codes. Now Type AC armored cable, the commonly
used BX cable, is covered by an article of its own and
is separated on application and code enforcement from
the use of metal -clad cables, which are now covered in
Article 334. ,
Section 333 -8. New Exception recognizes BX.
cable for limited use in hazardous locations. .
® _ hazozdo
Type AC cable may be used for wiring of Intrinsically safe
equipment, such as Instruments or signals in which the
electric circuit Is not capable of releasing enough energy
under any fault condition, to cause Ignition of the
hazardous atmosphere.
NOTE: This same permission is also given for t,
cable, Type NMC cable, Type OF cable, rigid i
conduit, surface raceways, multioutlet assembly,
raceways, cellular metal floor raceways, wireway
59
Fy
Article 334 —Metal -clad cable Article 336 — Nonmetallic- sheathed cable
Section 334 -1. Definition. This section defines this
type of cable assemblies covered by this article. The
definition for metal -clad cable — "a factory assembly
of one or more conductors, each individually insulated
and enclosed in a metallic sheath of interlocking tape,
or a smooth or corrugated tube" —also covers Type
ALS and Type CS cables. Both of these cables had
articles of their own in the 1975 code, but now all
metal -clad cables —Type MC, Type ALS, and Type
CS —are covered in the single Article 334.
Because the rules of these three cable types have
been compiled into a single article, use of any one of
the Type MC cables must be evaluated against the
specific rules that now generally apply to all such
cables. The code no longer contains the designations
Type ALS and Type CS. They are included now along
with interlocked armored cable as Type MC cables.
Section 336 -3. Definition of "first floor" clarifies
use of NM cable in buildings "not exceeding
three floors above grade."
Section 336 -3. Uses permitted or not permitted.
Because the code rule limiting use of Types NM and
NMC cables to buildings not exceeding three floors
above grade has produced difficulties in interpreta-
tion, a clarification on this matter was added. The
problem arises when buildings are built on hillsides or
sloping grades, where the building will have three
floors above grade on the uphill side and four floors
above grade on the downhill side. The question then is:
Is this a 3 -story building or a 4 -story building, and is
use of Type NM cable permitted?
In an effort to clarify the issue, Section 336 -3 now
defines the first floor of a building and attempts to
establish a basis for applying the code rule. Whether
or not a particular building will be considered as a 3-
story building or a 4 -story building when installed on
sloping grade depends upon the definition now given
for the first floor of a building. The code spells out
that the first floor shall be that floor designed for
human habitation which is level with or above
finished grade of the exterior wall line of 50% or more
of its perimeter: As shown in an accompanying sketch,
this determination can readily be made based on the
actual ground conditions as the grade changes along-
side the building. - . ° ' = : "
As shown, if the bottom floor has anything over
5o% of its floor line level with or above adjacent
finished grade, then the bottom floor is the first floor.
If that bottom floor is the first floor in a building with
four stories or four floors, then the building is a 4-
story building and use of Type NM or Type NMC cable
is prohibited. But as can he seen, a bulldozer or back -
hoe could be used to alter the actual steepness of the
grade to create the required conditions that would
exclude the bottom floor as the first floor of the
building and would thereby permit use of nonmetallic-
sheathed cable. Application of this rule in the field
remains for determination by local electrical inspec-
tors. a ;
In the second paragraph of Section 336 -3(a), the
word "adobe" was added to prohibit the use of nonme-
tallic- sheathed cable imbedded in the chases in adobe
brick, a material commonly used in the southwest part
of the United States. Adobe is a sun -dried brick
material used for building construction. Because it is
brittle and because boxes embedded in it tend to
become loose, the use of nonmetallic - sheathed cable
offers no support for 'such boxes. As a result, this
whole change prohibits the cable from being run in the
adobe or in the chases between the adobe brick's. -
Article 34o— 'Power and control tray cable
Section 340-5. Uses not permitted. Although this
section has the effect of prohibiting the use of Type
TC tray cable directly buried in the earth, the rule has
ELECTRICAL CONSTRUCTION AND MAINTENANCE
section 340-5. Type TC (Power'and Control Tray
Cable) is recognized for direct earth burial.
been modified by addition of the phrase "unless
approved for the purpose." The result of this change is
to permit Type TC cable directly buried in the earth
where the cable is approved for the purpose by the
local electrical inspector. This permission for direct
burial was added because the cable assembly was
designed to withstand such application and because
Type TC cable has been successfully and effectively
used directly for many years in a good number of
installations. '
The proposal adding this change to the 1978 code
argued that such cable had been listed for direct earth
burial by UL, and that the performance record has
been excellent. '
Article 345— Intermediate metal conduit
Section 345-3. Uses permitted. Section 345 -3(a) has
been revised to give it a positive rather than negative
focus on use of IMC, although there was no change in
basic code intent.
Sections 345 -3(a), 346 -1(b) and 348 -1. Use of
aluminum fittings and enclosures with steel
raceways is specifically recognized.
An exception no v permits the use of aluminum
fittings and enclosures with steel intermediate metal
conduit. This permission also has been added in
Article 346 on rigid metal conduit and Article 348 on
electrical metallic tubing. Tests have established that
aluminum fittings and enclosures create no difficulty
when used with steel raceways. The exception was
added in the code to counteract the implication of that
phrase that cautions against use of dissimilar metals
in a raceway system to guard against galvanic
action.
Rewording of Section 345 -3(b) was done to make
clear that the galvanizing or zinc coating on the IMC
does give it the measure of protection required when
used in concrete or when directly buried in the earth.
The last phrase, "judged suitable for the condition,"
refers to the need to comply with UL regulations such
as those contained in UL's Electrical Construction
Materials List, advising how and when steel raceways
and other metal raceways may be used in concrete or
directly buried in earth.
The UL data points out that there are soils where
some difficulties may be encountered, and there are
other soil conditions that present no problem to the
use of steel , other metal raceways. The phrase
"judged suitble for the condition" implies that a
correlation was made between the soil conditions or
the concrete conditions at the place of installation and
the particular raceway to be used. This means that it
is up to the designer and /or installer to satisfy himself
as to the suitability of any raceway for use in concrete ,
or for use in particular soil conditions at a given
geographic location. Of course, all such determinations
would have to be cleared with the electrical inspection
authority to be consistent with the meaning of code
enforcement.
NOVEMBER, 1977 61
Article 346 —Rigid metal conduit
Section 348 -1. Use. An exception in Section 346 -1(b)
now indicates acceptability of use of aluminum fitting
conduit bodies and other enclosures in steel rigid
metal conduit systems.
Section 346 -7(b). Threading. The rule requiring 9/o-
in.-per-foot taper has been made mandatory. It
previously was a note at the beginning of Article 346.
Section 346 -7. Threading taper for rigid metal
conduit is now mandatory.
Article 348— Electrical metallic tubing
Section 348 -1. Use. Again, as in Articles 345 and 346,
permission is given for use of aluminum fittings and
enclosures with steel electrical metallic tubing.
Section 348 -7. Threads. Here, the rules have been
reworded to clarify code intent. Threading of electrical
metallic tubing is prohibited, but integral couplings
used on EMT shall be permitted to be factory
threaded. Such equipment has been used successfully
in the past and has been found satisfactory. The
revised code rule recognizes such use. But it should be
noted that this applies to EMT using integral fittings,
that is, fittings which are part of the EMT itself.
Article 349 — Flexible metallic tubing
Section 349 -1. Flexible metallic tubing is a new
NE Code raceway for use in lengths up to 6 ft, for
limited application —as in air - handling ceilings.
Article 347 —Rigid nonmetallic conduit _
Section 347 -8. Supports. In this section, Table 347 -8,
giving the maximum distance between supports for
rigid nonmetallic conduit, has been revised to permit
greater spacing. For each size of rigid nonmetallic
conduit, a single maximum spacing between supports,
in feet, is given for all temperature ratings of conduc-
tors used in rigid nonmetallic conduit raceways.
Section 347 -8. Change in support - spacing for
rigid nonmetallic conduit
62
Section 349 -1. Scope. 'The first section of this new
article defines this new NE Code raceway. The rule
indicates that flexible metallic tubing is intended for
use where "not subject to physical damage" and gives
use above suspended ceilings as an example. Although
this wording does not limit its use to air - handling
` ELECTRICAL CONSTRUCTION AND MAINTENANCE
ceilings, it does raise some questions for electrical
inspectors with respect to accepting flexible metallic
tubing as a general- purpose raceway. 'r .: r; - .
The meaning of the phrase, "not subject to physical
damage," is not clear. When the proposal was made to
add flexible metallic tubing to the code as a suitable
raceway, it was indicated that it had been designed for
certain specific applications and not for general use. It
was specifically intended for use as the fixture whip
on recessed fixtures where high- temperature wire is
run from the branch - circuit junction box to the hot
wiring compartment in lighting fixtures, an applica-
tion long filled by flexible metallic conduit.
Section 349-3. Uses permitted. Although flexible
metallic tubing is liquidtight without a nonmetallic
jacket, Section 349 -3(a) appears to limit its use to dry
locations, and Section 349 -3(d) appears to limit its use
to branch circuits. The problem of interpretation
arises from the wording. The first sentence of Section
349 -3 indicates where flexible metallic tubing shall be
permitted to be used, but it does not say that other
uses would he prohibited. For instance, it is permitted
to be used in dry locations, but nowhere in the article
is it prohibited from being used in wet locations —
except for direct earth burial or embedding in poured
concrete or aggregate (Section 349 -4]. .
Section 349-4. Uses not permitted. Section 349 -4(e)
limits use of flexible metallic tubing to lengths not
over 6 ft long. That limitation has the effect of ruling
out flexible metallic tubing as a general - purpose
raceway and limiting its use to short interconnections
so commonly made with flexible metal conduit or
liquidtight flexible metal conduit. But it does not
appear that flexible metallic tubing, in spite of its
resistance to moisture or liquid penetration, is an
alternative to the use of liquidtight flexible metal
conduit in wet locations.
Article 350- Flexible metal conduit'
Section 350-5. Grounding. The second sentence of this
basic rule now notes that an equipment bonding
jumper used with flexible metal conduit may be
installed inside the conduit or outside the conduit
when installed in accordance with the limitations of
Section 250 -79. Rewording of the exception to this rule
makes clear that flexible metal conduit when used as
an equipment grounding conductor in itself is
Permitted only where a length of not over 6 ft is
inserted in any ground- return path. The wording
indicates that the total length of flex in any ground -
return path must not exceed 6 ft. That is, it may be a
single 6 -ft length. Or, it may be two 3 -ft lengths, three
2 -ft lengths, or any total equivalent of 6 ft. If the total
length of flex in any ground -return path exceeds 6 ft,
the rule appears, to require an equipment grounding
NOVEMBER" 1977 -
Sections 350 -5 and 351 -9. New wording empha-
sizes importance of proper bonding. -
Where bonding of standard or liquldtight flex is flatly
required, as In Class 1, Div. 2 and Class H. Div. 2
locations ... .
...an Internal or external bonding jumper must be
used at all times, for any size and any length of the flex
and must conform to Section 250 -79(e) as noted in
Section 501 -16(b) and Section 502- 16(b).
conductor to be run within or outside any length of -
flex beyond the permitted 6 ft that is acceptable as a,
ground- return path in itself.
Article 351 — Liquidtight flexible metal conduit
Section 351 -8. Supports: A new Exception No. 2 now
permits a length of liquidtight flexible metal conduit
not over 3 ft long to be used at terminals where
flexibility is required without any need for clamping
or strapping. Previous code wording did not contain
this permission and in effect required every piece of
liquidtight flexible metal conduit to he clamped within
12 in. of every outlet box or fitting. Obviously, the use
of flex requires this permission for short lengths
without support. . . -
Section 351 -8. Unsupported length of liquidtight
flex is OK at terminations.
A length not over 3
may be used for flexibility r?,
t%v at terminations. P.
_ "_kr�•,',,.SY'� 'n''�'+,,.,- �`'^.;� y rm``T°. c' "7e.�i°-"� �^r�j`a?� -fwf is ,a
:`�,��y.. F "•Yt No clamp o'j
''� "G °` • 'mother iupporl ,. - :•F'��
olong length {' A:
'oth Uidlight
°�
63
Section 351 -9. Grounding. Revision of this rule
permits internal or external bonding of liquidtight
flex as covered previously for standard flex and spelled
out under Section 250 -79. A similar change in the
wording of the exception also focuses on a maximum
total length of 6 ft in any equipment ground -return
path where the liquidtight flex itself is used as the
equipment grounding conductor. UL application data
in the Electrical Construction Materials List (the
green book) does not make that limitation to a "total
length" of 6 feet. But it appears that any UL- listed
liquidtight flex must also follow the "total length"
concept.
Section 351 -10. Bends in concealed work. This new
rule was added to set the same requirement on
liquidtight flex as Section 350 -6 establishes for stan-
dard flex.
Section 351 -10. Limitation on bends in concealed
places now applies to liquidtight as well as ordi-
nary flex (Greenfield).
Article 352 — Surface raceways
Section 352 -4. Number of conductors in [metal] race-
ways. The rules of conductor fill may now be applied to
surface metal raceway in very much the same way as
standard wireway. This rule applies such conductor
fill and ampacity determination to any surface metal
raceway that is over 4 square inches in cross - section.
Section 352-4. New rule permits conductor fill of
metal surface raceway without ampacity derat-
ing of wires.
As with wireway, if there are not more than 30
conductors in the raceway and they do not fill the
cross - section area to more than 20% of its value, the
conductors may be used without any ampacity
derating from Note 8 of Tables 310 -16 through 310-
19. y,
Article 370 — Outlet, switch and junction boxes,
and fittings r
Section 370-3. Nonmetallic boxes. A new second
paragraph of this section recognizes the use of nonme-
tallic boxes with metal raceways or metal- sheathed
cables. In the 1975 and previous code editions, nonme-
tallic boxes were permitted to be used only with open
wiring on insulators, concealed knob- and -tube wiring,
nonmetallic- sheathed cable, and approved rigid non-
metallic conduit. But there was no permission to use
nonmetallic boxes with metal raceways. .
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Growth in the application of nonmetallic boxes over
past years has stimulated the.addition of the new
paragraph, which regulates the conditions under
which nonmetallic boxes may• be used with metal
raceways or metal- sheathed cable. The need and popu-
larity of these boxes developed out of industrial appli-
cations where corrosive environments dictated their
use to resist the ravages of various punishing atmo-
spheres.
Section 370 -3. Larger nonmetallic boxes are now
recognized for use with metal raceways and
metal - sheathed cable. I - • •
`q yam. and the enclosure contains
b on ding means between all raceway
F and cable enlrles" —with such
.. bonding "manufactured" Into the box .. .
.,r.
worded, the manufacturer of the nonmetallic box must
provide the necessary bonding means for all raceway
and /or cable entries into the box.
Section 370-6. Number of conductors in switch, outlet,
receptacle, device, and junction boxes. Although NE
Code rules have long regulated the maximum number
of conductors permitted in metal wiring boxes [such as
given in Table 370- 6(a)], there was no regulation on
the use of conductors in nonmetallic device boxes. Now
Section 370 -6(b) requires that nonmetallic boxes be
durably and legibly marked by their manufacturer
with their cubic -inch capacities to permit calculation
of the maximum number of wires that the code will
permit in the box. Calculation of the conductor fill for -
these nonmetallic boxes will be based on the marked
box volume and the method of counting conductors set
forth in Section 370 -6(a). The conductor volume will
be taken at the values given in Table 370 -6(b), and
deductions of space as required for wiring devices or
for clamps must be made in accordance with the rules
of Section 370 -6(a). This requirement for marking of
nonmetallic boxes arises from the wording of Section
370 -6(b), which refers to boxes other than those
described in Table 370 -6(a). Because Table 370 -6(a)
refers only to metal boxes, nonmetallic boxes are then
"boxes other than those described in Table 370- 6(a)."
The indirect wording then becomes a clear mandatory
Section 370 -6(b). Marking is required to assure
safe conductor fill in nonmetallic boxes.
In many applications it was desirable to use nonme-
tallic boxes along with plastic- coated metal conduits
for a total corrosion- resistant system. However, the
code prohibition in Section 370 -3 presented a serious
problem. The need for such application is now
recognized by the code, although a limitation is placed
requiring internal bonding means in such boxes. The
permission applies only to nonmetallic boxes suffi-
ciently large —that is, over 100 cubic inches. PVC
boxes, fiberglass boxes, or other nonmetallic boxes or
enclosures may be used with metal raceway or metal -
sheathed cable, but the bonding means between all
raceway and cable entries must be manufactured into
the box. That is, the grounding continuity from each
raceway entry to each other raceway entry must be a
Part of the provisions of the box itself. That require-
ment was placed in the code rule to assure the safety
of effective equipment grounding where metal
raceway systems are used with nonmetallic boxes. As
NOVEMBER, 1977
65
. ;za-.
code rule on calculating safe conductor fill for nonme-
tallic device boxes. .
Section 370 -6(c) now permits splicing in C and L-
type conduit bodies. As previously worded, the rule
prohibited splicing in any conduit bodies having provi-
sions for less than three conduit entries. In the new
rule, types C and L conduit bodies are excluded from
that prohibition if they comply with the provision of
Section 370 -6(b) —that is, if they have their internal
volume marked in cubic inches and if the conductor fill
of the fitting is calculated in accordance with Section
Section 370 -6(c). Change in wording now rec-
ognizes splicing in "C" and - -L" conduit bodies.
370 -6(a) using the wire volumes of Table 370 -6(b).
Use of splices in type C or L conduit bodies is clearly
limited as a result of this wording to those cases where
the conduit body does have its volume marked by the
manufacturer. Further, the rule requires that where
such fittings are used, they must be supported in a
rigid and secure manner. Because Section 370 -13
establishes 'the correct methods for supporting of
boxes and fittings, it must be observed.
The last two paragraphs of Section 370 -13 describe
code- approved supporting of threaded boxes or fittings
not over 100 cu in. in size. Use of type C or L conduit
bodies for splicing must comply with the requirements
of Section 370 -13. Accompanying diagrams show how
this change in code rules would make permissible
certain arrangements that were objectionable under
the more limited wording of the 1975 NE Code.
Section 370-7. Conductors entering boxes or fittings.
Section 370 -7(c) now requires that, where nonmetal-
lic- sheathed cable is connected to nonmetallic boxes,
the cable must enter through a knockout opening
provided for nonmetallic- sheathed cable, and not
through a hole made at any point on the box. At least
1/4 in. of the cable sheath must be brought inside the
box.
Another very important limitation, in this code
Section 370 -7(c). New restrictions apply to instal-
lation and connection of NM cable in nonmetallic
boxes.
ELECTRICAL CONSTRUCTION AND MAINTENANCE
section applies to"the need for clamping nonmetallic -
sheathed cable at a knockout where the cable enters
anything other than a single -gang box. The code has
always accepted the use of nonmetallic- sheathed cable
without box clamps where the cable is stapled within 8
in. of the box. The cable is then brought into the box
through a NM cable knockout on the box, without any
kind of a connector at the K.O.
But the intention of the revised code rule is that
boxes or enclosures other than single -gang boxes must'
be provided with a clamp or connector to secure
nonmetallic - sheathed cable to such boxes. Only single -
gang nonmetallic boxes may be used without a cable
clamp at the box knockouts. Where the code permits
elimination of a cable clamp if the cable is clamped to
the stud within 8 in. of the box, the rule specifies that
the 8 -in. length he measured along the cable and not
simply from the point of the cable strap to the box
edge itself.
Section 370 -13. Supports. Where boxes contain nails
that are used to mount the box to a wooden stud or
wooden joist, the code rule now specifies that such
mounting nails within the box must not be more than
1/4 in. from the back of the box to prevent the nails
from constricting the interior box volume and pre-
senting an obstruction to devices mounted within the
box. - , -
Section 370 -13. Mounting nails must not obstruct
box interior space.
Article 380 — Switches
Section 380-3. Enclosure. A new sentence has been
added to require adequate wire - bending space at
NOVEMBER. 1977 -
Section 380 -3. Terminating and gutter space in
switch enclosures is now specified.
terminals and in side gutters of switch enclosures. In
this section and in other sections applying to wiring
space around other types of equipment, it is now a
mandatory code requirement that wire- bending space
and side gutter wiring space conform to the require-
ments of Table 373 -6(a) in the code. That table estab-
lishes minimum distance from wire terminals to
enclosure surface or from the sides of equipment to
enclosure side based on the size of conductors being
used. '
This whole concern for adequate wiring space in all
kinds of equipment enclosures reflects a repeated
theme in many code sections as well as in Article 110
on general installation methods. One of the most
commonly heard complaints from constructors and
installers in the field is the inadequacy of wiring space
at equipment terminals. This change in Section 380 -3
is designed to assure sufficient space for the necessary
conductors run into and through switch enclosures.
Section 3811.8. Position of knife switches. Although it
has long been a basic requirement in the NE Code that
knife switches be so mounted that gravity will tend to
open them rather than close them, a change in the
1978 code recognizes use of an upside -down or reverse-
mounted knife witch where provision is made on the
67
Section 380 -6. Upside -down knife switches may
be used if properly equipped.
contingent upon the switch being approved for such
use, which virtually means UL- listed for that applica-
tion.and also upon the switch being equipped with a
locking device that will prevent gravity from closing
the switch. Actually, this change in Section 380 -6 for
single -throw knife switches is the same as the 1975
NE Code permitted for double -throw knife switches..
The wording in Section 380 -6 now requires that
single -throw knife switches of the inverted type must
be approved for use in the inverted position. Double -
throw knife switches, however, are recognized for
vertical' mounting or horizontal mounting. The only
requirement is that a locking device shall be provided
so that,the blades remain in the open position when
the switch is in the open position.'
Section 380-9. Faceplates for flush- mounted snap
switches. A new last sentence in this rule requires that
such faceplates must be installed to cover the wall
opening completely and to seat against the wall
surface. The purpose of this addition was to assure
that the box behind the faceplate is properly covered
and to prevent any openings that could afford penetra-
tion to energized parts.
switch to prevent gravity from actually closing the
switch contacts. This change was made in recognition
of the much broader use of underground distribution,
with the intent of providing a switch that could have
its line terminals fed from the bottom and its load ,
terminals-connected at the top. With such a configura-
tion, an upside -down knife switch would provide the
necessary locations of such terminals, that is, "line" at
bottom and "load" at top. However, use of any knife
switch in the reverse or upside -down position is -
Section 380 -14. Hating and use of snap switches.
Section 380- 14(a)(4) now requires snap switches rated
20 amps or less to be of the CO /ALR type and so
marked when directly connected to any aluminum
circuit conductors.
Article 384— Switchboards and panelboards
Section 384-3. Support and arrangement of busbars
end conductors. A new sentence at the end of this code
rule requires that all service - switchboards have a
barrier installed within the switchboard to isolate the
service busbars and the service terminals from the
Section 384 -3(a). In switchboards, service bus
must be isolated from rest of switchboard.
Section 384 -7. Ceiling clearance no longer re-
quired for enclosed switchboards.
remainder of the switchboard. Because it is commonly
impossible to kill the circuit feeding a service switch-
board, it has become very common practice for
mechanics to work on switchboards with the service
bus energized. The hazard associated with this has
caused concern and is the reason for this addition to
the code.
Switchboard manufacturers in many parts of the
country have been supplying switchboards with these
barriers in place; this code rule aims at making such
protection for personnel a standard requirement. With
a barrier of this type installed in a service switch-
board, mechanics working on feeder devices for other
sections of the switchboard will not be exposed to
accidental or surprise contact with the energized parts
of the service equipment itself.
Section 384 -3(g) now makes it mandatory that wire -
bending space at terminals and gutter spaces in`
panelboards and switchboards must afford the room
required in Section 373 -6. This is a repeated require-
ment throughout the new code and is aimed at,
assuring safe termination of conductors as well as
adequate space in the side gutters of panelboards and
switchboards for installing the line and load conduc-
tors in such equipment. This concern for adequate
wire- bending space and gutter space is particularly
important because of the very large size cables and
conductors so commonly used today in panelboards
and switchboards. Sharp turns to provide connection
to terminal lugs does present possible damage to the
conductor and does create strain and twisting force on
the terminals themselves. Both of those objections can
be eliminated by providing adequate wiring space.
NOVEMBER, 1977
Section 384-7. Clearance from ceiling. Although it ,
has long been a code rule that a clearance of at least 3
ft be provided from the top of a switchboard to a
nonfireproof ceiling above, an exception has been
added in this section to exclude totally enclosed
switchboards from this rule. The original rule
requiring a 3 -ft clearance was based on open -type
switchboards and did not envision totally enclosed
switchboards. The sheet metal top of such switch-
boards provides sufficient protection against heat
transfer to nonfireproof ceilings. As a result.of this
exception, there now is no minimum clearance
required above totally enclosed switchboards.
Section 384- 18.Overcurrenl protection. An important -
revision of Section 384- 16(a), Exception No. 2,
completely eliminates the need for individual overcur-
rent protection of lighting and appliance branch-
circuit panelboards used as service equipment in
supplying an individual residential occupancy. The
exception no longer prohibits the use of 15- and /or 20-
amp protective devices as main disconnects in such
panels. In the 1975 and previous codes, the rule
permitted a service panel for a residential occupancy
to have up to six main disconnect devices but stipu-
lated that none of the main devices could be rated at
15 or 20 amps. For any panel —a standard single -
section -bus panel or a split -bus panel — previous codes
required that any bus supplying 15- or 20 -amp protec-
tive devices must be provided with a main disconnect
device for the bus itself. .
Now a lighting and appliance panelboard containing
six single -pole breakers or six 2 -pole breakers (or even
six 3 -pole breakers or fuses) may be used as residen-
tial service equipment without a main protective
device ahead -Iii split -bus panelboards, where it was
69
Section 384- 16(a). Change in Exception No. 2
- Hminafaa nand rnr main in residential service
Section 384- 16(e). Use of so- called "delta break-
er" is now a code violation.
previously permitted to use six main devices in the
section fed by the service conductors, it is now permis-
sible to use 15- and /or 20 -amp protective devices in
that main section. Of course, 15- and /or 20 -amp
protective devices may still be used in the bottom
section of the panel, which is protected by one of the
mains in the top part of the panel. -
Section 384 -16(e) is a new rule prohibiting the
installation of any 3 -phase disconnect or 3 -phase over -
current device in a single -phase panelboard. It is now
required that any 3 -pole disconnect or 3 -phase protec-
tive device supplied by the bus within a panelboard
may be used only in a 3 -phase panelboard. The effect
of this new rule . is to outlaw the so- called delta
70
breaker, which was a special 3 -pole circuit breaker
with terminal layouts designed to be used in a single -
phase panel where the loads served by the panel were
predominantly single - phase, but where a single 3-
phase motor or 3 -phase feeder was needed and could
readily be supplied from this type of delta breaker.
This change was made because the use of delta
breakers has been found hazardous. When a delta
breaker is used in a single -phase panel and the main
disconnect for the single -phase panel is opened, there
is still the high hot leg supplying the delta breaker.
This has caused confusion to personnel who were
surprised to find the energized conductor and have
been subjected to shock hazards.,, ;
'- ELECTRICAL CONSTRUCTION AND MAINTENANCE
EQUIPMENT FOR GENERAL USE
Article 400— Flexible cords and cables
Section 400-8. Uses not permitted. The first sentence
of this rule has been rewritten to clearly and unmis-
takably indicate that flexible cords and cables may be
used only under the specific conditions permitted in
Section 400 -7. The use of flexible cords and cables as
substitutes for fixed wiring methods has caused objec-
tions from inspectors in the field. A slight rewording
of this code rule, along with specific mentions of
acceptability for certain types of cords and cable
connections, such as in Section 410- 30(e), is aimed at
resolving any confusion about the acceptable extent of
usage of cords and cables for equipment hookups.
Article 402— Fixture wires
Section 402 -5. Ampacity of fixture wires. Table 402 -3,
giving the ampacity values for each size of fixture
wire, has been expanded to include No. 12 and No. 10
fixture wires with their maximum ampacities of 23
amps and 28 amps, respectively.
Article 410 — Lighting fixtures, lampholders, lamps,
receptacles, and rosettes
Section 410-4. Fixtures in specific locations. The rules
on use of lighting factures in commercial and indus-
trial ducts and hoods for ranges and other cooking
devices have been revised and expanded: Section 410 -
4(c) spells out the conditions for using fixtures and
their associated wiring in all types of nonresidential
cooking hoods.
Section 410-A Connection of electric - discharge light-
ing fixtures. Two new paragraphs at the end of this
code rule expand coverage of the use of wiring
methods suitable for supplying electric- discharge
lighting fixtures. The next -to -last paragraph notes
that such fixtures are permitted to be supplied from
busways as described in Section 364 -12. The last
Paragraph provides for cord connection of a lighting
fixture where the cord is equipped with a connector
body at its lower end for insertion into a flanged inlet
recessed in the lighting fixture housing. This method
Of cord supply to electric discharge lighting fixtures
Presents an alternative to the other method recognized
in this section using a cord from the fixture with a
Plug -cap on the other end of the cord for insertion into
a receptacle mounted in a box directly above the
NOVEMBER, 1877
71
fixture. The new permission for use of a connector
body and flanged inlet supply affords greater ease in
maintenance of the fixture, since maintenance people
can disconnect the fixture at the lower end of the cord
to remove it for cleaning or repair.
Section 410 -14. Rule now recognizes a second
method of cord supply to suspended fixtures.
Section 410.30. Connections, splices, and taps. A new
rule in Section 410 -30(e) recognizes the use of fixed
cord connection for energy supply to lighting fixtures
that require aiming or adjustment after installation.
Use of a cord supply to lighting fixtures has been a
Section 410- 30(e). New rule permits fixed -cord
connection of certain fixtures.
recurring controversial issue, although Section 400 -7
has permitted cord supply to lighting fixtures for a
long time. Section 410 -14 has required that electric
discharge lighting fixtures, if suitable for supply by
cord, must make use of plug- and - receptacle connection
of the fixture to the supply circuit. The new rule
permits floodlights —such as those used for outdoor
and indoor areas for sporting events, for traffic
control, or for area lighting —to have a fixed -cord
72 _ ELECTRICAL CONSTRUCTION AND MAINTENANO
connection from a bushed -hole cover of the branch -
circuit outlet box to the wiring connection compart-
ment in the lighting fixture itself. This new rule gives
adequate recognition to the type of cord connection
that has long been used on floodlights, spotlights and
other fixtures'used for area lighting applications.
Section 410 -31. Expanded use of fixtures as race-
ways provides better control for conservation. ,
This
' ''.'•t / °7-. +Ai'R• Only one 2 -wire or multiwire branch
_ +�•.; •
circuit supplying only fixtures In the row
'k: t .1 was permitted to be run through the
1 1ia,c fixtures by the 1975 NE Code.
Now the code rule accepts one more circuit—only a 2-
wire circuit —run through the row. But this additional
circuit must supply one or more of the fixtures in the row,
such as night lighting by, say, every fifth fixture, to enable
the others to be turned off for energy conservation:
Section 410 -31. Fixtures as raceways. This code rule
has long stated that fixtures shall not be used as a
raceway for circuit conductors. Exceptions No. 1 and
No. 2 have permitted variations from that rule. Excep-
tion No. 1 still permits fixtures to be used for circuit
conductors if the fixtures are approved for use as a
raceway, and Exception No. 2 still permits limited use
Of fixture wiring compartments as a raceway provided
that the fixtures are designed for end -to -end assembly
to form a continuous raceway or the fixtures are
connected together by recognized wiring methods
(such as rigid conduit and EMT).
However, this exception noted that such fixture
layouts may carry only conductors of either a 2 -wire
NOVEMBER, 1977 . -
or a multiwire branch circuit where the wires of the
branch circuit supply only the lighting fixtures
through which the circuit conductors are run. Thus, it
has been permissible to use a 3- phase, 4 -wire branch
circuit through fixtures so connected, with the total
number of fixtures connected from all of the phase
legs to the neutral, that is, with the fixture load
divided among the three phase legs. But the tole did.
limit such use to a single 2 -wire or multiwire branch
circuit.
Now in the 1978 code, a new Exception No. 3
permits one additional 2 -wire branch circuit to be run
through such fixtures (connected end -to -end or
connected by recognized wiring methods) in addition
to the 2 -wire or multiwire branch circuit recognized by
Exception No. 2, and this additional 2 -wire branch
circuit may supply one or more of the connected "
fixtures throughout the total fixture run supplied by
the other branch circuit run through the raceway. '
This new permission was added to permit separate
control of some of the fixtures fed by'the additional
branch circuit, providing the opportunity to turn off
some of the fixtures for energy conservation during
the night or other times when they are not needed.
Section 410- 35(a). High- temperature wire rating
must be marked on fixture, if needed.
Section 410- 35(a). Fixture rating. An added sentence
in this section now specifically requires that any
fixture he suitably marled to indicate the need for
supply wires rated higher than 90C to withstand the
heat generated in the fixture, Such marking must be
prominently made on the fixture itself and also on the
shipping carton in which the fixture is enclosed.
73
Section 410 -42. Portable lamps. This revised section
contains requirements for both portable lamps and
portable hand lamps. These rules were covered in
Sections 410 -42 and 410 -43 in the 1975 code.
Section 410 -42. New rules aim at greater safety in
use of portable lamps and portable hand lamps.
not trapped in this space. Free circulation of air must
be provided with this 3 in. spacing. If, however, the
fixture is approved for installation with thermal
insulation on closer - spacing, it may be so used.
Section 410 -66. Clearance of recessed fixture•
from thermal insulation is greatly reduced.
Section 410 -42(a) requires portable lamps to be
wired with flexible cord approved for the purpose and
to be equipped with polarized or grounding -type
attachment plugs. An exception to the rule indicates
that nonpolarized attachment plugs shall be permitted
until January 1, 1980, but after that date, plug -caps on
the cords for portable lamps must be either'grounding
type or polarized type to permit a single orientation of
the plug for insertion in the receptacle outlet. Such
polarizing of the plug will provide for connecting the
grounded conductor of the circuit to the screw shell of
the lampholder in the lamp.
In Section 410 -42(b) four specific rules are given on
the use of portable hand lamps. This data is shown in
an accompanying • illustration. The requirements of
Section 410 -42(a) calling for polarized or grounding -
type attachment plugs also are made applicable to
portable hand lamps.
Section 4111-66. clearance. When recessed fixtures',
are used with thermal insulation in the recessed space,
thermal insulation must have a clearance of at least 3
in. on the side of the fixture and at least 3 in. at the
top of the fixture and shall be so arranged that heat is
74
Section 410 -73. General. Rewording of Section 410 -
73(e) makes clear that the thermal protection required
for ballasts of fluorescent fixtures installed indoors
must be within the ballast. Previous wording
permitted the interpretation that the supplementary
protection for the ballast could be in the fixture and
not necessarily within the ballast. .
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Article 422 — Appliances
[ Section 422-8. Flexible cords. New rules on the
r hookup of kitchen garbage disposers, dishwashers, and
trash compactors are given in new Section •422 -8(d).
The rules cover the type of cords that are acceptable,
the lengths of the cords, receptacle locations, and
grounding requirements.
section 422 -8(d). New rules assure effective
grounding for kitchen garbage disposers.
n;
physical da�M must t accessible fl abe c and located to avoid
physical damage to the flexible cord
C , Cord must be Type S, So, ST, STO, SJO, SJT, SJTO or
I SPT -3 -3- conductor, terminated with a grounding -type
_:l plug. Cord must be between 16 and 36 in. long.
NOTE:, Double- insulated,^- Olaposers� do not- have `to I
Hookup of dishwashers and trash compactors is the
s i same, except that the cord must be 3 to 4 N long.
• sa.; ..�::z:5.:�"t�. Esc .v~......F.z;.•.W.:::.:rr.�:.�
NOVEMBER, 1977 -
Section 422 -22. Disconnection of cord- and plug.
connected appliances. Where household electric
ranges are supplied by cord - and -plug connection to a
range receptacle located at the rear base of the range,
Section 422 -2(b) permits such a plug and receptacle to
serve as the disconnecting means for the range if the
connection is accessible from the front by removal of a
drawer.
Section 422 -26. Disconnecting means for motor-driven
appliances. Although the basic rule requires that a
switch or circuit breaker serving as the disconnecting
means for a permanently connected motor -driven
appliance of more than 1/s hp must be within sight
from the motor controller, an exception has been
added to that rule.
The branch - circuit switch or circuit breaker serving
as the other disconnect required by Section 422- 24(a),
(b), (c) or (d) is now permitted to be out of sight from
the motor controller of an appliance that is equipped
with a unit switch that has a marked OFF position and
disconnects all ungrounded conductors of the supply to
the appliance.
Section 422 -26, Exception. Disconnect for motor -
driven appliance may be "out of sight from the
motor controller."
Section 422 -27. Overcurrent protection. Section 422 -
27(f) covers electric heating appliances using resist-
ance -type heating elements. It requires that, where
the elements are rated more than 48 amps, the heating
elements must be subdivided. Each subdivided load
shall not exceed 48 amps and shall be protected at not
more than 60 amps. That part of the rule is not new.
The rules of this section are generally similar to the
rules contained in Section 424 -22 for fixed electric
space heating using duct heaters as part of heating,
ventilating, and air - conditioning systems above sus-
pended ceilings. But new Exception No. 2 applies to
commercial kitchen and cooling appliances using
sheath -type heating elements. This exception permits
such heating elements to be subdivided into circuits
not exceeding 120 amps and protected at not more
than 150 amps under the conditions specified.
76
z�4__-
Exception No. 3 of this same section permits a
similar subdivision into 120 -amp loads protected at
not more than 150 amps for elements of water heaters
and steam boilers employing resistance -type immer-
sion electric heating elements contained in an ASME-
rated and stamped vesseL
Article 424 —Fixed electric apace heating
equipment
Section 424 -19. Disconnecting means. Extensive revi-
sion and expansion of the rules in this section have
been made. The basic rule requires disconnecting
means for the heater, motor controller(s) plus supple-
mentary overcurrent protective devices for all fixed
electric space - heating equipment. It also points out
that the disconnecting means may consist of more
than one device. In such cases, they must be grouped
and identified
Section 424 -19(a) applies to heating equipment
provided with supplementary overcurrent protection
(such as fuses or circuit breakers) to protect the
Section 424 -19. Extensive revisions of rules on
disconnects for heating equipment demand
careful study for HVAC systems with duct
heaters and supplementary overcurrent protec-
tive devices.
subdivided resistance heaters used in duct heating.
Section 424 -19(b) applies to heating equipment
without supplementary overcurrent protection. -
Care must be taken to evaluate each of the specific
requirements in this code section to actual job details
involved with electric heating installations.
Section 424- 22(e). Conductors for subdivided
heater circuits must fully match overcurrent
device rating.
76
Section 424- 22.Overcurrent protection. 'A new rule in
Section 424 -22(e) requires that the conductors used for
the subdivided electric resistance heat circuits speci-
fied in Section 424 -22(c) must have an amp rating not
less than 100% of the rating or setting of the overcur-
rent protective device protecting the subdivided
circuit(s). Exception is made for heaters rated 50 kw
or more where under the conditions specified it is
permissible for the conductors to have an ampacity
not less than the load of the respective subdivided
circuits, rather than 100% of the rating of the protec-
tive devices protecting the subdivided circuits.
Section 424 -37. Clearances of branch - circuit wiring in
walls. When electric heating panels are mounted on
interior walls of buildings, any wiring within the wails
ELECTRICAL CONSTRUCTION AND MAINTENANCE
Section 424 -37. Wiring in walls behind heating
panels must have ampacity corrected for more,
than 30C.
Electric heating Panel ` 33�iS �'�,`�• �s•
s3S; mounted against wallb:1 ;i.x3
a s.w
Interior all �s:•�� q„4: _�k�3'1<z�:. ^'y+v:k�- i'��ryr' _ i'�
of building
• VIEW
" 2
P,IANwM.
c 1111
a
Wiring run In this space must have '�, Amblent In
ampacity derated for elevated ambient— this space Is ,�
using temperature correction factors ;1; taken to be
from Tables 310 -16 through 310 -19. _. 40C (104F).
behind the heating panel is considered to be operating
in an ambient of 40C rather than the normal 30C for
which conductors are rated. Because of this, the
ampacity of such conductors in wall space behind
electric heating panels must be reduced in accordance
with the correction factors given as part of Tables 310-
16 through 310 -19 [Section 424- 37(b)].
Section 424 -43. Clarification permits cutting of
nonheating leads for "panels."
Nonhealing
t'•? ,;,ik -b a _ I_ • _ .'_S,`� ':k leads may
` -;i f'Rr•s" �i•• "a't`r :.>'ytA ba cut to
`= 'z��'�it'r_- s�..,,'•a length Tor
connectin g
tocircuit.
EleMriece; ling heating panel';1;
Section 424 -43. Installation of nonheating leads of
cables and panels. Section 424 -43(d) is a new rule
permitting excess nonheating leads of heating panels .
to he cut to the required length for connecting to the
supply circuit. Section 424 -43(c) has always and still
does prohibit cutting of the excess lead of heating
cables. Any excess nonheating leads of heating cables
must be secured to the underside of a ceiling and '
embedded in plaster or other approved material.
Section 424 -72. Overcurrent protection (for resist-
ance-type boilers). New Section 424 -72(e) ,specifies
that the ampacity of conductors used for the subdiv-
ided heating circuits within such boilers must not he
less than 100% of the rating or setting of the overcur-
rent protective devices protecting the circuit conduc-
tors from their point of application to the heating
elements. Again, however, an exception is added for •
heaters rated 50 kw or more under certain given
conditions. '
Article 426 —Fixed outdoor electric de -icing and
snow- melting equipment
Section 426-3. A single heating cable may be fed
by a circuit of any rating.
°"��;�; - �r �Cable•2
�•' i... :ms,'J:" -' - b :arcs
Branch - circuit Fes, ¢ ur. } • y pnc -Y; g
overcurrent•device 'r`f... N3•'�.�;,,; §z' ' -',
must be rated 15, .r�'�"�`:1: �' • - -'?
20, 25, 30, 40, or , , when circuit supplies more than
50 amps ... one heating cable. .
�gt;:f `6UT�,' � .:W 'r5��': .r:'c�x'T1•.r''ao� � °�"
t ;�''
.4th S .r��+7�a+� . � �'•3 . »�
A circuit of is ... may supply a single cable
any rating ... assembly.
Section 426-3. Branch circuit requirements. This basic
rule still requires that, where more than one electric
de -icing or snow - melting cable is connected to a
branch circuit, the rating of the branch circuit must be
15, 20, 25, 30, 40 or 50 amps. However, a new exception
notes that an individual branch circuit shall be
permitted to supply any load to a single heating cable.
That is, the rating of the branch circuit may be any
value higher than 50 amps as necessary to supply a
single heating cable that requires the higher circuit
rating.
NOVEMBER, 1977 77
y `s
EQUIPMENT FOR GENERAL USE Continued . -
Article 430— Motors, motor circuits, and con-
trollers
Section 430.44. Orderly shutdown. In recognition of
the needs of many industrial applications, this section
(as well as a number of other sections) permits alter-
natives to automatic opening of a circuit in the event
of overload. The permission -for elimination of over-
load protection given in Section 430-44 is similar to
the permission given in Section 240 -12 to eliminate
overload protection when automatic opening of'the
circuit on an overload would constitute a more serious
hazard than the overload itself. As the rule notes:
If immediate automatic shutdown of a motor by a
motor overload protective device(s) would introduce addi-
tional or increased hazards) to a person(s) and continued
motor operation is necessary for safe shutdown of equip-
mentor process,
then automatic overload opening is not required..
However, it is necessary that the circuit be provided
with a motor overload sensing device conforming with
the code requirement on overload protection to indi-
cate, by means of a supervised alarm, the presence of
the overload. Overload indication, instead of auto-
matic opening, will permit corrective action for an
orderly shutdown to resolve the difficulty. But, as is
required in Section 240 -12, the short - circuit protection
on the motor branch circuit will take care of those
n-PURFR 1977
Section 430-44. Running overload protection may
be eliminated to prevent hazard.
5. "- _-, •s Overload relays hooked Into �la'r'm'yE�<ri. -w -
o-':. instead of motor starter coil F' -,'I
tFr[l, 50L - _ >4ti :,_`� -•✓:' �:'ti : i'- ^="` �(-�
eL
Sudden, unexpected
shutdown of this
r motor would produce '
coil >c,� a serious hazard
1 : to persons —as In
• slop start - - _ mining operations
} - - Supervised alarm -
V t• or annunciator to �_f•`3
a warn of overload ..
Alarm ' and permit -safe,
_ - volloge5
source - ` orderly shutdown 1
See Section 240 -12.
NOTE: Section 445-4 has a new exception that permits this'
some use of an alarm Instead of overcurrent protection
where It Is better -to have a generator fall than stop operating..•
iii
t
high -level ground faults and short circuits that would
be more serious in their hazardous implications than
simple overload. -
Section 430.62. Acting or setting —motor load. A revi-
sion has been made in the second paragraph of Section
430- 6'2(a) to provide more effective and accurate sizing
of motor feeder protection in accordance with the
basic rule stated in the first paragraph
In,the 1975 code, the second paragraph said:
where two or more motors of equal horsepower rating
are the largest in the group, one of these motors shall be '
considered as the largest for the above calculations.
Because Table 430 -152 recognizes many different
ratings of branch - circuit protective devices (based on
use of fuses or circuit breakers and depending upon
the *particular type of motor), it is possible for two
motors of equal horsepower rating to have widely
different ratings of branch - circuit protection. If, for
instance, a 25 -hp motor was protected by nontime-
delay fuses, Table 430 -152 gives 300%. of full -load
motor current as the maximum rating or setting of the
branch- circuit device. Thus, 250 -amp fuses would be
used for a motor that had a 7 8-amp full -load rating.
But another motor of the same horsepower and even
of the same type, if protected by time -delay fuses,
could use fuses rated at only 175% of 79 amps, which
would be 150 -amp fuses.
The problem could even be more complicated if the
two 25 -bp motors were of different types, one being a
wound -rotor motor and the other being a squirrel -cage
induction motor. Obviously, the statement in the 1975
code that one of these motors shall be considered as
the largest (for purposes of calculation) presents a
possibility that the one selected could have the lower -
rated branch - circuit protective device.
To eliminate confusion that can be created by
focusing on horsepower ratings of motors, the second
paragraph of Section 430 -62 now bases selection of the
feeder protection on the largest rating or setting of a
branch - circuit protective device, even when a number
of branch - circuit protective devices fed by the feeder
might have the same rating or setting. Of course, it
still is possible for motors of different horsepower
ratings to have the same rating of branch - circuit
protective device, again depending upon the type of
motor and the type of protective device. But the
concept of "equal horsepower rating" as presented in
the 1975 code was definitely misleading. .
Section 43D- 62(a). Revision clarifies rule on maxi-
mum rating for motor feeder protection.
•ssy.. ��:::z�<_. ~:.may a.
2. ff both 25-hp ; £ : "y 11. Feeder protection must not; s
motors had is ,_;, jt a berated more than the largest j
150 -amp time- ;� . +: F� x. , rating of branch- clrcult device-;I
..y delay fuses for Feeder •Plus sum of full -bad currents
a branch - circuit of other motors fed. li
y, ., protection , . -• v..n :1
ra protection. A,:t - i` r " o
then feeder ..,,� *;; .'`iNontime -delay
Vprotection must ' ' . -'' r -r fuses roted
trot exceed l' = —T--r' -�� -.at 300%
150 + 78 t 32 3 w _ x78A =234A t�+
+ 18 amps. :.supply /�Osed 250A "
_ 4fuses�
r . •- `t• „�,, 6mnch Time -delay
Circuits T z fuses rated of
?' All motors rated ..I,, ry,_ : O U .� 175 % x78A i
200V, 3¢ 136A-Used 3q -, SHP I32A 78A 270A
i•^ IBA 32A 78A 70A 150A (uses -•j
%i But -11 ditterent - 3. Revlsed rule relates feeder
u' fuses are used /or - - protection to actual rating of
< the two 25 -hp 1 largest branch - circuit device
motors— used -250 + 78 + 32 +
i _ - ;19 amps. li
Section 430 -72. New rules on proteuttng coil
circuit conductors of magnetic starters
Section 430- 72.Overcurrent protection. Practically all
of this section has been revised, and the changes are
significant.
Exception No. 1, as now worded, indicates that the
branch - circuit protective device may serve as suffi-
cient protection for control circuit conductors where
the control conductors do not actually leave the enclo-
sure of a magnetic motor starter, such as when the
sTAaT -sTor pushbutton station is in the cover of the
starter housing. But the rule now adds that this is
permissible only where the branch- circuit protective
DECEMBER, 1977
device has a rating not over s00% of the ampacity of
the control circuit wires. Obviously, this requires that
the size and amp rating of control circuit wires must
be known and evaluated against the rating of the
branch - circuit protective device before it can be
assumed that protection for the control circuit is not
required within the starter. And, if such protection for
the internal control circuit is required, a suitable fuse
block and fuse must be inserted in the controller
housing.
In Section 430- 72(b), the rules on use of overcurrent
protection where a control transformer is provided
have been altered. An exception now notes that
control- circuit protection may be provided on the
primary side of a control transformer as permitted in
Section 240-3, Exception No: S. This exception covers'
those cases where a transformer has a 2 -wire primary
and a 2 -wire secondary, and it is permissible to protect
the primary conductors, the transformer itself, and
the secondary conductors all by a single overcurrent
device (or set of overcurrent devices) on the primary
side in accordance with the turns ratio of the trans-
former to afford correct protection to conductors on
both sides of the transformer. This permission could
apply to a control transformer installed within the
starter enclosure as well as to an external control
transformer fed by a separate supply from that
feeding the power circuit through the motor control-
ler.
Section 430 -74. Disconnection. In recognition of the
unusual and complex control conditions that exist in
many industrial applications — particularly process
industries and manufacturing facilities — Exception
No. 1 to Section 430 -74(a) now alters the rule that
disconnecting means for control circuits must be
located immediately adjacent to each other. When a
piece of motor - control equipment has more than 12
Sebtton 430 -74. Exception added to permit
remote mounting of control circuit disconnects
Is aimed at safety in industrial applications..,
motor - control conductors associated with it, remote
locating of the disconnect means is permitted under
the conditions given in Exception No. 1. This permis-
sion is applicable only where qualified persons have
access to the live parts and sufficient warning signs
are used on the equipment to locate and identify the
various disconnects associated with the control- circuit
conductors. = '
. Exception No. 2 presents another instance in which
control- circuit disconnects may be mounted other than
'immediately adjacent to each other. It notes that
where the opening of one or more motor - control
circuit disconnects might result in hazard to personnel
or property, remote mounting may be used where the
conditions specified in Exception No. I exist; i.e., that
access' is limited to, "qualified persons and that a
warning sign is located on the outside of the equip-
ment to indicate the location and the identification of
each remote control- circuit disconnect.
Section 430 -102 Out of sight disconnect. A new
exception has been added to the rule that basically
calls for a disconnecting means to be installed within
sight from a motor controller location. Exception No.
2, recognizing that many multimotor machines have
structural arrangements that often obscure the view
of a disconnect from some or all of the controllers
located among the various structural elements of the
machine, now permits a single disconnect to he not
within sight of all of the controllers. This exception,
however, applies only to the case where a single
disconnect switch is used for a'group of interrelated
controllers that are adjacent to each other on a
multimotor machine assembly. The word "adjacent"
indicates that the controllers are physically close to
the disconnect even though the disconnect is not
literally "in sight from some or all of the.:
controllers."
Section 430 -102. New Exception permits "out -of-
sight" disconnect for multimotor machines.
A single disconnect may - '.•`
• be mounted "adjacent" to - - !:y;;.. i 3
a group of controllers ..° - ' '•
�• ,t�s�,- �� f�;=+`•': :-;.��'ir;ti %air: r''•v'' •.'�
{
on a multlmotor continuous n,
process machine.
Section 430 -113. Energy from more than one source.
The basic rule of this section still requires a discon-
necting means to be provided for each source of
electrical energy input to the equipment, and each
source is permitted to have separate disconnecting
means. But a new exception to the code rule now states
that where a motor receives electrical energy from
more than one source (such as a synchronous motor
receiving both alternating current and direct current
energy input), the disconnecting means for the main
power supply to the motor shall not be required to be
immediately adjacent to the motor — provided that the
controller disconnecting means, which is the discon-
nect ahead of the motor starter in the main power
circuit, is capable of being locked in the open position.
If, for instance, the motor control disconnect can be
locked in the open position, it may be remote; but the
disconnect for the other energy -input circuit would
have to be adjacent to the machine itself.
Section 430 -113. Lock -open disconnect may be
used with motor having multiple energy
sources.
Disconnect for '` .. but If the disconnect ahead T
one source must of the controller for the
be adjacent to ; main supply can be locked open
motor ... , .. .w It may be remote from motor.
0•
Energy _ - - •-
.' input No.l —► Conlroller • "'Energy input .
•---- No.2
Motor receiving energy
• from Iwo or more sourcesr;'' -
ELECTRICAL CONSTRUCTION AND MAINTENANCI
Article 450 — Transformers and transformer vaults
Section 450 -1. Scope. A new Exception No. 8 notes
that liquid -filled or dry-type transformers used for
research, development, or testing are exempt from the
requirements of Article 450 provided that effective
arrangements are made to safeguard any unqualified
persons from contacting high - voltage terminals or
energized conductors. Again, in the interest of the
unusual conditions that frequently prevail in indus-
trial occupancy, this rule recognizes that transformers
used for research, development, or testing are
commonly under the sole control of entirely competent
individuals and exempts such special applications
from the normal rules that apply to general - purpose
transformers. The rule recognizes a difference
Section 450 -1. New exception covers certain
types of transformers. '.
If a transformer is used for
research, development or testing .. .
_ -• . It Is exempt from the rules of Article i
.' 450— provided unqualified personnel are i
protected from energized parts. L 'i
DECEMBER. 1977 - - .
between test transformers and those used for distribu-
tion within buildings and for energy supply to utiliza-
tion equipment, controls, signals, communications,
and the like.
Section 450 -23. High- fire - point, liquid - insulated trans-
formers. This new section covers transformers
designed to replace askarel- insulated transformers.
Because askarel transformers have become objec-
tionable from an environmental standpoint, they have
been phased out of electrical work. And, because oil -
filled transformers used indoors require a transformer
vault, the high - fire -point insulated transformer offers
an alternative to the oil -filled transformer, without
the need for a vault.
Section 450 -23. Requirements for new liquid -
filled transformers to replace askarel type.
_ - •w �:5 ?�j', _ tip.- t, --..g
o
�
57
Section 450 -42. Transformer vault requires only
1 -hour rated construction it automatic sprinkler,
water spray, or carbon dioxide is used.
t::::..•%>%c::zr.••+�a:.:�a:�4 � >;
Common -
'r�Readly vented
to outside without ',
recommendations '
r flues or ducts (where practicable)
on thickness of
sF -
tvr
cp r r ,wX
4%
walls and-root
(not code
requirements):
.
�
-'
1. 6-1n. reinforced
NS- , �°
F t;y '. t
``.F
„
• '.'
t�
concrete, or
2. 8 -In. brick, or
3 12"In.
. Baring
the or blocks—
with Inside
.'
-,
coating of
`
��
✓"
`=l'i'..� ^'x.
" ''• "'
3/44n.-thick
(" i
cement or
L
,v'etr•.
gypsum plaster -
iy.,.rrla�xti.:.'.'a`J C °"' ^�.q -,^•_ Minimum floor -
. t F i.. •!
Door sill or curb to contain �a t�., , thickness: 4 -in. ;
transformer oil — minimum concrete when In '
t: of 44n. p t;; " :I contact with earth• .
liM,:'•:`? s _F j;4a".'C " ";;F''• Approved minimum 3 -hr
Ore -rated door with lock
' =i ' =�• c =Q• :.•,. to exclude unqualified persons
Section 450 -42. Walls, roof and floor [of transformer
vaults]. An exception to the basic regulations estab-
lishing the construction standards for transformer
fireproof vaults now notes that the transformer -vault
fire rating may be reduced where the transformers are
protected with automatic sprinkler, water spray, or
carbon dioxide. The usual construction standards for
transformer vaults (such as 6-in.-thick reinforced
concrete) provide a minimum fire - resistance rating of
3 hours. Where automatic sprinkler, water spray, or
carbon dioxide is used, a construction rating of only
one hour will be permitted.
SPECIAL OCCUPANCIES
Article 501 —Class I locations
Section 501-4. Wiring methods. Threaded steel inter-
mediate metal conduit has been added to the wiring
methods suitable for use in Class I, Division 1 loca-
tions listed in Section 5014(a). This permission, plus
recognition by other sections of the code, gives IMC
full recognition as a general - purpose raceway equiva-
lent in application to rigid metal conduit.
Section 5014(b) adds power- limited tray cable
(Type PLTC) to the list of wiring methods permitted
in Class I, Division 2 locations, in accordance with the
provisions of Article 725 covering remote - control,
signaling, and low- energy circuits.
The last paragraph of Section 501 4(b) has been
revised to make clear that high- voltage circuits (i.e.,
circuits over 60b volts) may employ the wiring
methods covered in the first part of Section 5014(b)
Section 501 -4(a). "Threaded steel intermediate
metal conduit' is now OK for hazardous areas.
and, where protected from physical -damage, may be
made up using metallic - shielded, high - voltage cable in
cable trays when installed in accordance with Article
318.
Section 501 -5. Sealing and drainage. The basic rule of
Section 501- 5(a)(1) requires a seal fitting in every
conduit run entering an enclosure for equipment that
may produce arcs, sparks, or high temperatures. That
is, at enclosures for switches, circuit breakers, and
similar devices, a seal fitting must be placed as close
as practicable and not more than 18 in. from such
enclosures. But questions have always arisen about
the acceptability of boxes or fittings between such seal
fittings and the enclosure being sealed. This section of
the 1978 code identifies.the devices that may be used
r
'• jai / /ia / /aii / /aoi /tiff /a /iaiioiii /aioi
i
i
i
Conduit length In hazardous area must not contain
union, coupling, box, or other fitting within the hazer
' area and for 12 In. beyond each boundary.
.� .:Fs`i'?- �'rt*.?rrt±.:s -e -: ,.'w.^r..- -,�..- rrr•�r:rs -
NOTE This does not apply to Gass I, Div. 2 looatloris. ?'
between the seal and the enclosure. Explosionproof
unions, couplings, elbows, capped elbows, and conduit
bodies similar to L, T, and cross type shall be the only
enclosures or fittings permitted between the seal
fitting and the enclosure. The rule goes on to note that
any conduit body used in that position must be of a
size not larger than the trade size of the conduit with
which it is used. This revision clearly rules out the use
of a box or any similar large- volume enclosure
between the seal fitting and the enclosure being
sealed.
The fittings listed as acceptable for use between, the
DECEMBER, 1977
seal and the enclosure were selected on the basis that
their internal volume was sufficiently small as to
prevent the accumulation of any dangerous volume of
gas or vapor. Acceptability was based on limiting the
volume of gas or vapor that may accumulate between
the seal and the enclosure being sealed. It was on this
basis also that conduit bodies are prohibited from
being of a larger size than the conduit with which they
are used. If they were permitted, they would present
the opportunity for accumulation of a larger volume of
gas or vapor, which is considered objectionable.
The Exception to Section 501- 5(a)(4) covers the case
where a metal conduit system passes from a nonhaz-
ardous area, runs through a Class I, Division 1
hazardous area, and then returns to a nonhazardous
area. Such a run is permitted to pass through the
hazardous area without the need for a seal fitting at
either of the boundaries where it enters and leaves the
hazardous area. The new wording of this exception.
requires that such conduits, in order to be acceptable,
must not contain a union, coupling, box, or fitting in
any part of the conduit run within the hazardous area
or in any part of the conduit run extending 12 in. into
each of the nonhazardous areas involved. In the 1975
NE Code, the exception merely referred to "unbroken
rigid -metal conduit" that passes through the hazard-
ous area. The effect of the change is to clarify the
meaning of the word " unbioken."
It is important to note that a similar exception to
Section 501- 5(b)(2) covers the use of an "unbroken
metal conduit" passing through a Class I, Division 2
location. That exception does not have the same
wording prohibiting unions, couplings, . boxes, or
fittings that are spelled out in the exception after
Section 501- 5(a)(4). The difference in wording
between the two exceptions appears to indicate that in
a Class I, Division 2 location, the same prohibition
against unions, couplings, etc, is not applicable.
Section 501- 5(a)(1). Big clarification on use of
boxes and fittings between seal and enclosure.
t��� � _...s g.�.:. .wt_, -� • ;;<Ft�yyn,.'+rt��,z � s„
rAAS51 DIV Y-,
LOCATION" -:.
:.,`..
•Sealin { VIOLATIONI —This box
fining•.•`` or any similar encbsure re
_ 9 •_ - must not be used between :(
the seat fitting and the
switch enclosure
-Rule ;•'�'.. _
corers - -. mac.'• - ;,7:
Explasior' r < -c
Ibis
is length __A_ proof
Junction'.'
`[ box , BUT —an exptosionproof union,
!, coupling, elbow, capped elbow,
" • ' - or a conduit body (like the "L,'• x'•
_ "T" and "cross" type) maybe
used In this position. But, a
Explosion-proof - conduit body must not be €,
;>� , tumbler switch enclosure for
'� larger than the conduit size. -
- .. qtr
59
ARTICLE 517- HEALTH CARE FACILITIES
Article 517 — Health care facilities*
.'This Article has been revised extensively, both
editorially and technically. It now contains ten parts.
These are listed in the new code as A— General; B—
Wiring Systems, General; C— Clinics, Medical and
Dental Offices, and' Out- Patient Facilities; D—
Nursing Homes and Residential Custodial Care Facili-
ties; E— Hospitals; F— Patient Care Areas; G— Inhal-
ation Anesthetizing Locations; H— Communications,
Signaling Systems, Data Systems, Fire Protective
Signaling Systems, and Low - Voltage Systems; J—
Therapeutic High Frequency Diathermy Equipment;
and K —X -Ray Equipment. Much of the content of
this Article remains the same, although it has been
relocated to conform with the new 10 -part format.
A. General -
.This part is concerned primarily with definitions.
An important addition in the scope is contained in
Section 517 4(c). This paragraph now requires appli-
cation of respective parts of Article 517 not only to
single - function buildings but also to multifunction
buildings with respect to occupancy. Simply stated,
the appropriate paragraphs for a clinic will apply not
only to a building containing only a clinic but also to a
clinic in a building with other types of occupancy.
. The new definitions included are: exposed conduc-
tive surfaces, hazard current, hospital, isolated
power system, isolation tranV'ormer, nursing home,'
residential - custodial care facility, therapeutic high-
frequency/ diathernny equipment, and wet location,
health -care facilities. '
The following definitions that appeared in the 1975
NE Code have been deleted: continuous power
system, critical patient care area, critical system,
and life support branch.
Revised definitions include anesthetizing location,
flammable anesthetizing location, health -care facili-
ties, patient grounding point, patient vicinity, refer-
ence grounding point, and room bonding point. An
anesthetizing location is now an area that is intended
for use rather than one that is used. The same change
I is found in the definition for flammable anesthetizing
location. The change in definition of health -care facil-
ities was a further clarification and aided in the
formation of Section 517 -1(c) as noted above. The
remaining revised definitions were changed to further
clarify and avoid confusion in the meanings and
intent.
S. Wiring systems — general
Most of the requirements of this part existed in the
previous edition of the code. Section 517 -11, Ground-
ing, has been rewritten and replaces the old Section
517 -3. It is broken into two paragraphs —one for
receptacles and fixed equipment, the other for
portable equipment. The section now refers only to
parts, equipment, etc. likely to become energized
rather than all conductive surfaces. Also, the refer-
ence is to areas used for patient care rather than
locations for occupancy by patients as stated in the
previous code. This clears up the confusion of what to
do in patient waiting rooms, admitting offices, patient
dining rooms, etc.
It should be noted that throughout Article 517 the
requirements for stranded conductors have been
deleted.
C. Clinics, medical and dental offices,
and out - patient facilities
This new part applies the wiring. methods and
grounding requirements of Sections 517 -10 and 517 -11
to those specific health -care facilities listed, which
were not covered in previous editions of the NE
Code.'
D. Nursing homes and residential
custodial care facilities
This is a new part, bringing all requirements for
nursing homes and residential custodial care facilities
under one part. Most of these requirements appeared
in the previous edition of the NE Code in various other
paragraphs, but there are some significant changes
Section 517 -40 permits a nursing home or' facility tc
derive its essential electrical system supply from tbal
of a hospital when it is contiguous to the hospital.
Section 517 -44(c) permits the use of a Singh
transfer switch for the entire essential electrica
system rather than a separate transfer switch for eacl
branch in small facilities. Separate transfer switches
I are required only if dictated by load considerations
For small facilities, the typical emergency electrica
system consists of the life safety branch and thl
*This summary important changes Article 517 was prepared critical branch. For larger facilities, the critica
by Marvin J. Fischer, Assistant Vice President-Facilities Planning,
and Engineering Services, Brookdale Hospital Medical Center,. branch is divided into three separately define)
Brooklyn, N.Y. - branches for patients, heating, and sump pumps-
ELECTRICAL CONSTRUCTION AND MAINTENANCI
Minimum electrical system for typical small
nursing homes and residential custodial care
facilities
_ Normal sources •. Alternate source
-Service Generator
enhance
vercu
Cpp'" Nonessential
f` loads . r • ax. : '' - ' a� '.
t+ .�_7d >r Jz Lomolie Delayed
switching outomotic F
equipment swilching
eq
Ufa safety Critical
�* �! branch branch
s`•- .•''.j i,i ' EMERGENCY SYSTEM
a. jx
alarms. The emergency system and its branches have
been renamed to be consistent with those of a hospital
electrical system. New Diagrams 51742(1) and 517-
42(2) have been included in the code to illustrate
typical installations.
Typical large electrical system for nursing homes
and residential custodial care facilities .
Section 517 -45(b) is new and describes the' switching
arrangements for night transfer of corridor lighting.
It insures that some lighting will always be provided
in the corridor regardless of the mode of operation.
New Section 517 -47 requires any home or facility
that provides inpatient hospital care to comply with
the requirements for hospitals.
E. Hospitals
As stated in Section 517- 60(a), "Part E applies to
hospitals and other health -care facilities serving
patients who are unable to provide for their own
safety." It thus puts all requirements specifically
intended for hospitals in this part.
The Emergency System of the Essential Electrical
System now consists of only two parts —the Life
Safety Branch and the Critical Branch. All reference
to the previously noted Life Support Branch has been
deleted. Basically, the two remaining branches include
all items that were included in the three branches in
the previous edition of the NE Code, and therefore,
with the exception of renumbering, there are similari-
ties between the two editions.
Exception No. 3 of Section 517 -61(d) permits sepa-
rately derived low - voltage signaling, communication,
and alarm circuits to be run without metal conduit,
even though they are connected to the essential elec-
trical system — provided they comply with Articles
725, 760, and 500.
Section 517 -61(g) permits use of a single transfer
switch, rather than multiple transfer switches, for the
Minimum electrical system for typical small
' hospital
•ra,.q.iw.•,�- •r::H.;..r: srx- <z.Y =., .;,;.: a....__. -h.. -, ...v- ,- .....,. =' `-_'�;
ourca,t�l '';� ,Alternate source. ~Norm at sources
r _ tt
^'$lfVloe enirOnee :. r t; S'. • F$eivice -
�•• entrance'
Overcunenl ' - f• j :, .Overcurreni
protect* Y�.:i`,<,� `,' _ - "--, fitt, Protections -
.r`
ion,'
oulomolic
switching equipme i _
• , T
•1+ 1 1 .1'
!*ads"
Delayed
F,
No gantlet ,_ ;,•,' „ .
- .
,�
equipment
Life safety •.
�'.
5 -; branch
+ Nonessential Equipment
Patient
bads system
�.
Critical
Sump pumps,
branches
1•'
alarms
Heating -
_E
- Automatic
Manual
switching
?
swilching;
EMERGENCY SYSTEM equipment
equipment
�;,•
Delayed
F,
automatic"• -'
switching .-
,�
equipment
+ Nonessential Equipment
bads system
i
source
Automatic
Life safety Critical
branch branch
EMERGENCY SYSTEM
DECEMBER, 1977 61
Essential Electrical System in' the same manner as
previously described for nursing homes and residential
custodial care facilities. New Diagrams- 517 -60(1)
and 517 -60(2) have been included to illustrate typical
arrangements.
New Section 517 -62(b) has been added describing
the night -light switching arrangements permitted in
corridor lighting of hospitals. These are similar to
those previously described for nursing homes and
residential custodial care facilities.
Section 517 -63(b) adds corridors in general patient
care areas to the task illumination and selected recep-
tacles to be served by the Critical Branch of the
Essential Electrical System. The receptacles thus
served must be identified.
Section 517- 64(e)(3) has been revised to permit the
supply and exhaust ventilating systems for certain
areas to be served only from the normal system,
provided they have windows that open to the outside.
Those areas include all labor suites, infant nurseries,
recovery rooms, emergency rooms, and "other areas
designated by the hospital." Supply and exhaust venti-
lating systems for all laboratory fume hoods, surgical
suites, and obstetrical delivery suites are required to
be connected to the essential electrical system, regard-
less of inclusion of openable windows in the design.
Section 517 -64(g) permits fire pumps to be connect-
ed to the equipment system if there is sufficient
capacity, or they may be connected to it separate,
alternate source of power.
A new last paragraph has been added to the mate-
Typical large electrical syatern for hospitals
late'
'y4,f
Si
•local }
anch
EMERGENCY SYSTEM
rial described in Section 517- 66(b), which covers
switching of emergency service. This is a mandatory
requirement for the provision of a 15- minute
minimum time -delay setting for the re- establishment
of the normal power source. This is done to avoid
erratic, short -time re- establishments of the normal
power source and subsequent reconnection to the
essential electrical system. The rule's intent is to
insure at least a 15- minute stable condition of the
normal power source before its re- establishment.
F. Patient care areas
Part F has undergone some major changes in termi-
nology, criteria, intent, and definitions. The fine -print
note in Section 517 -80 has a sentence added that, deals
with the control of electric shock hazard by the
limitation of current flow through the patient. It
delineates the means of achieving this: (a) by raising
the resistance of the conductive circuit (including the
patient); (b) insulating exposed surfaces that might
become energized; (c) reducing the possible potential
difference between exposed conductive surfaces; and
(d) any combination of the three.
Section 517 -80(b) reclassifies Patient Care Areas
into two categories, General Care Areas and Critical
Care Areas, rather than the three that appeared in
previous editions of the code. There are, however, nc
definitions included in the new code for either a
Critical Care Area or a General Care Area. The desigr
of these areas, including wet locations in accordance
with the type of patient care anticipated, is the
responsibility of the governing body of the facility.
The maximum permitted potential differena
between any two exposed conductive surfaces it
Patient Care Areas under normal operation at
frequency. of 1000 Hz measured across a 1000 -ohn
resistance is now given in Section 517 -81 as 50
millivolts for General Care Areas and 100 millivolt
for Critical Care Areas. There no longer is a perform
ance criteria for a line -to- ground fault —only fe
normal operations.
It is the feeling of some that the requirement for a
isolated power supply in a critical care area has no,
been eliminated with the removal of the line-t(
ground -fault criteria. The performance criteria fc
normal operation can be met using more convention,
methods other than isolated power supplies.
Section 517 -82, listing items that are exempted fro
the grounding requirements, has been expanded 1
include bedside stands, over -bed tables, chair
portable IV poles, and small portable nonelectric
devices such as trays, pitchers, and bedpans.
The branch - circuit arrangement for General Ca
Areas has been revised to require at least one circt
to be served from the normal system [Section 51
83(b)]. All branch circuits in a patient bed locati
-tee served by the normal system must originate from t
same panelboard, with the exception of speci:
ELECTRICAL CONSTRUCTION AND MAINTENAN
purpose outlets (such as those serving portable X -ray
equipment).
In Critical Care Areas, all receptacles in a patient
bed location served from the normal power system
must be supplied from a single panelboard, and all
receptacles on the Emergency System must be
supplied from a single panelboard. At least one branch
circuit must be supplied from the Emergency System.
Emergency System receptacles must be identified and
must indicate the panelboard and circuit number
supplying them [Section 517- 84(b)].
The Patient Grounding Point may now be grounded
directly to the Reference Grounding Point or "by
means of a conductor permanently connected to the
grounding conductor of a nearby power receptacle"
[Section 517- 84(c)].
Exposed conductive* surfaces in a patient vicinity
may now he connected to conductive building struc-
tural members having conductivity at least equal to
- that of AWG No. 10 copper wire. Otherwise, they
must be connected to the room bonding point or
reference grounding point. This new option of
connecting to conductive building structural members
eliminates the need to install miles of extra green
grounding wires to bond exposed conductive surfaces
to ground when a perfectly good grounding system is
available in the structural steel. Small wall- mounted
conductive surfaces such as soap dispensers and
mirrors are exempted from the grounding require-
ment [Section 517- 84(f)].
Section 517 -85 now states that when a grounded
distribution system is used, grounding of the feeder
conduit has to be assured by means of a grounding
bushing and a connection from the grounding bushing
to the grounding bus in the panelboard. Previously, all
metallic raceways required this assurance. •
An.important deletion is noted in Section 517 -90.
The isolated power system is no longer referred to as a
system to improve safety. This removes the problem of
a hospital being accused of not putting in the safest
• possible system if isolated power supplies are not
installed. The use of this type of system is now left
solely to the designer and the hospital authorities.
Similarly, rewording of the requirements for recepta-
cles supplying wet locations [Section 517 -92] now
places dependence of design on the new definition for
wet locations and on the hospital authorities.
G. Inhalation anesthetizing locations -
The major changes in this part involve renumber-
ing, but a few important changes should be noted.
Section 517 -100 now separates the applicable re-
quirements for hazardous Iocations from those for
other - than - hazardous locations. It allows for a third
category to be used —that of "above- hazardous loca-
tions." The new code thus covers wiring and equip-
ment requirements applying to anesthetizing locations
in three sections: Section 517 -101 (within- hazardous),
DECEMBEa, 1977
Section 517 -102 (above - hazardous), and Section 517-
103 (other- than - hazardous) locations.
Many of the requirements for safety in the above -
hazardous'anesthetizing locations are not required in
other - than - hazardous locations. For example, rigid
conduit, electrical metallic tubing, and IMC are the
only raceways permitted in above - hazardous anesthe-
tizing locations [Section 517 -1021 whereas any type of
rigid raceway (surface metal raceway, rigid nonme-
tallic conduit, etc.) is permitted in other -than-
hazardous locations. The reader is specifically referred
to Sections 517- 102(b), (c), and (d) whose require-
ments are not repeated in Article 517 -103.
Section 517- 104(d)(2) now requires isolated circuit
conductors to be' identified by brown and orange
colors. Section 517- 104(e)(1) clarifies the line isolation
monitor alarm values and now specifies 1.7 milliam-
peres as the lower limit of alarm for total hazard
current. Previous limits are still included.
Section 517- 104(f)(1) requires that a general -
purpose lighting circuit, connected to the normal
grounded service, be installed in each operating room.
Section 517- 104(g) permits components of an isolated
power center and its grounded primary feeder to be
installed above a hazardous location or in an other-
than-hazardous location.
H. Communications, signaling systems,
data systems, fire protective signaling
systems, and low- voltage systems
This part has been rewritten and the requirements
expanded; most of it is new. Protection in patient care
areas for these systems is equivalent to that required
for the electrical distribution system. Requirements
are now set forth for signal transmission between
appliances, including proper grounding and'outdoor
signal transmission. '
J. Therapeutic high - frequency
diathermy equipment
The requirements for this part were in Article 665,
Part E, in the 1975 NE Code. They have not been
changed. However, the definition of "therapeutic
high- frequency diathermy equipment" (previously
given in Section 665 -2 and now in Section 517 -1), has
been made much more general.
K. X -ray equipment ' s
This part is also a hew addition to Article 517. Most
of it was derived from Article 660 and still appears in
Article 660.'A special grounding requirement is set
forth for the frame of the patient support and the
stationary portion of the system for permanently
installed X -ray equipment. The requirements repeated
here are for grounding of permanently installed
X -ray equipment, individual branch circuit require-,
ments for portable, mobile and transportable equip-
ment, and the rating of supply conductors and over -
current protection:
SPECIAL EQUIPMENT
Article 680— Swimming pools, fountains, and
similar installations
Section 6804 Definitions. Since there are differences
in the requirements for "permanently installed" pools
and "storable' pools, there has been some confusion in
the past as to just what a "storable" pool was. The
1975 code defined a "storable swimming or wading
pool" as follows:
One that is so constructed that it may be readily
disassembled for storage,and reassembled to its original
integrity.
Apparently disagreement over the word "readily"
has resulted in rather large above - ground pools being
classed as "storable" pools simply because they could
be disassembled. The definition of "storable swim-
ming or wading pool" was changed in the new code to
read as follows:
A pool with a maximum dimension of 15 feet and a
maximum wall height of 3 feet and is so constructed that
it may he readily disassembled for storage and reassem-
bled to its original integrity.
Thus, the introduction of the limiting dimensions now
serves to differentiate storable pools from perma-
nently installed pools.
Section 680-5. Transformers and ground - fault- circuit
Interrupters. Exception No. 1 to Section 680 -5(c) has
been revised. In the 1975 code, when a ground- fault-
circuit interrupter (a GFCI breaker) was used in a
panelboard to supply swimming -pool circuits, it was
necessary to use supplementary insulation (such as
nonmetallic sleeving or tubing) on the GFCI conduc-
tors in the panelboard gutter to protect these conduc-
Section 680 -5(c). New Exception No. 7 eliminates
need to put insulating sleeving on GFCI conduit
conductors run in panelboard gutter.
Aside from the panelboard it
- - ' gutter, conductors on the bad i
' - i, side of a GFCI must not be
breakers •: used In any raceway or other ' a
c; In pdnel - enclosure containing conductors
that are not GFCI - protected
r. }GFCI•.' .r:^ -' `LUr.: =� °i �•:�t
"Ge°y"r'� - _ - : "Y ,;.fir -f �`; ,; -:•.i
These conductors on load side of
GFCI no longer require
supplementary insulation Qnsulating
sleeving or tubing) to Isolate them
from conductors of other circuits
which do not have GFCI protection.
tors against excessive leakage due to capacitive
coupling to the other conductors in the gutter. Exces-
sive leakage was considered a problem because of the
sensitivity of ground- fault - circuit interrupters, espe-
cially when used in conjunction with such wet or damp
applications as swimming pools. .
New Exception No. 1 has eliminated the need for
insulating sleeving on the GFCI circuit conductors in
panelboard gutters. It was concluded that such insula-
tion did not offer sufficient protection against the
problem of leakage.
Section 680 -6. Revised rules set mounting
heights for lighting fixtures or outlets in space
- around pools.
`a Lights In this space around
pool must have GFCI protection ' -
k��"'' -;' r' and must be rigidly attached
to structure. f,
?An II -hts of or
e abov p
Po _
,: • .. deck In lhts area must be - ;, s
at least 12 it above water
t,=N° and do not need GFCI protection.
:;. :F-�= ,y��• "'+' GFCI
-:. -s t
A3,- - w•g' _ - ';g, =�•'' no
fwed µ
, v //n 121[above lights
N: :r max. water:-:...+;•_..:.r ipoa
level 7.
{ 5tt—I a
It above 5tl N51t
mox.roler level �• "loft
IG`_'T?^•.rPool vrole
Exception: *•=
Any existing lighting fixtures or lighting outlets are t
permitted In this space around the pool If rigidly attached
to the existing structure and protected by a GFCI in the
branch circuit supplying the fixtures. But new (not
.:'existing ") lights are not permitted In this �•:
space around a pool. - t
. t' t.- s.' a+' 4::" v% i?i�' �s7: c2c_ isa"n 13;" n -'�.- p.,:i»A'.•'.it.°"- S`I� -:': E.r""S,. ;�"l'.': ..
IECEMBER, 1977 -
Section 680 -6(a). New rule and new Exception
cover use of receptacles at pools. '
. 7 I�rece [sties locafed3" : 2.,allo accessible y V-,,
P ''r•-,'` receptacles permitted
j between 10 and 15 ft of " • p p i �
_ Inside walls of pool C,- ' , within 10 ft of the Inside g
must be protected by walls of the pool i•f
. ,
! aground- feultcircuit
( _ Interrupter.; • v, -y,`I
I _ _ _ �;;{:''r.;e�= , � A .� • Via::; � .
i _ I :.y .�,.._; �: ,.. _ter; 'C` -c ,. ,:. �,-• _;� ! 1 - J
Permanent ..✓,!^! -.. I •- • -`' �
_- Pool ; "-: '15ft
5 ft
11511 - _ 1 _ I
.ruj . -'" '-�' °• - - , 4. A receptacle for the
_ ` 3. For a pool installed •: '- cord connection of the
at an existing dwelling, - -- pool recirculating pump );, t '
'- at least one receptacle L ' • may be Installed not less -
' must be Installed within t -::' than 5 it from Inside wall
the 10-to-15-ft band of the pool, but it must
around the pool and must be a single locking and v„
Y be protected by a GFCI S.i grounding -type device Ei; '
r ` device. ' " and it must be protected . ,<
by a GFCI device.
F _ •»: � st�:1•t ii'f"f'u'^t:;�:^.= xr_ f:v-c;?r_ _
Section 680 -6. Receptacles, fighting fixtures, and
lighting outlets. A new requirement in Section 680 -6(a)
calls for at least one receptacle to be installed not less
than 10 ft and not more than 15 ft from the edge of a
swimming pool for those cases where a swimming pool
is installed at an existing dwelling. This rule was "
added to assure that a receptacle will be available at `•
the pool location to provide for use of cord- connected
equipment. It was found that absence of such a .
requirement resulted in excessive use of long extension
cords to make power available for appliances and
devices used at pool areas.
A new exception to thi0 general rule permits the
installation of a receptacle for a swimming -pool recir-
culating pump as close as 5 ft from the inside wall of
the pool. Normally, receptacles are prohibited from e
installation anywhere within the 10 -ft boundary
around the edge of the pool. However, because swim-
ming -pool pump motors are commonly cord - connected
to permit their removal during cold weather in areas
where freezing may damage it, this change was made
to allow provision for a receptacle for the pump motor.
Such a receptacle,.thougb, must be a single receptacle
of the locking and grounding type.
65 .
As shown in an accompanying sketch, rules on
locations of lighting fixtures and lighting outlets
around pools have been revised. The rules distinguish
between existing lighting fixtures and those installed
during or after the pool construction. These new rules
and the ones on the use of GFCIs are considerably
different than those in the 1975 code. Great care
should be exercised in applying these new rules.
Section 680 -20. Underwater lighting fixtures. An
SPECIAL CONDITIONS
Article 700— Emergency systems
Section 700-6. A change has been made in Section
700- 60)(2) regarding the operating -time capabilities
of a fuel supply for internal combustion engines used
for emergency power. The 1978 code calls for an on-
site fuel supply capable of operating the prime mover
at full demand load for at least two hours.
Section 700- 6(b)(2). New rule requires greater
'fuel supply for engine - generator sets
Fuel
lank =!
r�. R{ J„a; ^;, .- .....•:.,..r. Fuel
EE '
L;< " "'�'�'` `_ '';lE:` . ;ce,• + r�'T;= t fLeI supply must be -
i=''i;;�_ -_ :.4 +'k4 ^.:n'nX capable of running
f'- _ - „ �'; ••;r .LL. engine for 2 hours • j
tt °rte` z'Arri'M. ;,j at fuq demand load f
E>"r ^�:`.°` _f,,:s�,l },'r.:.%r. Lei. ;�!- i,rhy.'f;,;n,- Fr'`v:��•a•Y -• _
"` `" }: - �.:: � 'F;''i't:. ^'ivr'`3✓.,at t �... • d . F,. +12:• - •; ', ,,ggff
f.- Nuum l975 NE Code+required fuel supply for only I -k hours.
Article 710 —Over 600 volts, nominal
Section 710-3. Wiring methods. Cable tray and inter-
mediate metal conduit have been added to the list of
suitable raceways for high - voltage circuit conductors
in above - ground applications.
66
interesting requirement has been added on the use of
wet -niche lighting fixtures. The rule here requires
that some type of low -water cutoff or other approved
means be provided to protect wet -niche lighting
fixtures against overheating when such fixtures
depend on submersion in water for their safe opera-
tion. The question arises —is it necessary to use a float
switch or some similar liquid -level indicator to control
the energy input to the light fixture? It would seem
that some such device is called for.
A note to Table 710 -3(b) has been moved inti
Section 710 -3(b). It requires that unshielded cable
(i.e., cable without electrostatic shielding on the
insulation) shall be installed in rigid metal conduit, if
IMC, or in rigid nonmetallic conduit encased in no
less than 3 in. of concrete. One effect of this rule i
that unshielded (or nonshielded) cables may not b
used directly buried in the earth.
Section 710 -6. Insulation shielding. A rewording o
this regulation now makes clear that the need fo
shield termination using stress cones or similar termi
nating devices applies to "semiconducting insulation
shielding as well as to metallic -tape or metallic -wir
insulation - shielding systems.
ELECTRICAL CONSTRUCTION AND MAINTENANC
Section 710 -21. Circuit- interrupting devices. An
intensive revision and expansion of regulations on
high- voltage circuit- interrupting devices have been
made. Use of such equipment must be checked against
;he new and more - detailed requirements. The regula-
tions cover circuit breakers and fusible switches along
with the devices not previously covered in detail -
7ower fuses and fuseholders, distribution cutouts, and
)il -filled cutouts plus fuses.
3eetion 710 -21. Extensive additions to code rules
on "circuit- interrupting devices" cover equip-
ment specs and circuit design for high - voltage
applications. .
• -�- �# Diseanm
type mo
(lrftllit ( .,
POWER FUSES [S
DISTRIBUTION CUT
Section 710 -24. Metal- enclosed power switchgear and
industrial control assemblies. A major expansion of
this section includes a specific requirement that warns
about the hazards of energy backfeed through fuses
used in certain high- voltage circuit configurations
[Section 710- 24(o)]. The rule notes that where fuses
can be energized by backfeed, a warning sign must he
placed on the equipment to protect personnel against
accidental contact with the energized parts.
Section 710 -24. Detailed new Section on high -
voltage switchgear has many new rules, includ-
ing warning against "backfeed" that energizes
fuses.
,.;t om: =r ::�; ; y f t! - f^'�a Y•?.1 _
t7, :!' ^a-r
'Ke- interlock.
Section
- i 'must be opens
r- .Hole for • " t 710 -24( °) Y break -er can be
'•'- hook- slick, F= requires.;r
;i" - =?• operation i:•' warning sign`'
:r. - - -=
-T�t� - •' i r- - 1 . .w
Primary'
tiriq ..'s'; - f ?,;.''• , Supply
�•'f - �,n ;'�46 �,' _- Fused load-
`. inlerrupler
DANGER switch -
Nole: Switch
blades and Luse
Power �' - terminals are
f - fuse : _' i`' energlxed - d:
'in open
_- - '�_r.,`•?"' '_ with switch • � � ���-�k _
•''• "�'�;•'•Dischaige filter _ - -• i - =-
_�ar condenser _ . _ _ ; ,, • f
Or this may be done—
Ion 710- 21(b)] ° l'
OUTS [Section 710.21(c)] - Add a reverse - connected switch
here to Kell all terminals In main
I switch under emergency
generator feed conditions,
_. with key interlock.
- '•;z �;� -%.-
- here lorolote'-
�•.�;"
�'�'F ^""^-
bracket' -
•switching :��_- - "z
foonfing
mechanisms = % ".'•
for. at
Filloil herA;
use lorsolidlink "
J
sedlinrotaling • ; .
ssembly which •' `�
-.
This is a wiping]
ridges contocl pasts
• sleevelfor lead '
-'
"`Line or load •-'�• Load or line'
•i - Non - polarized
.-
.:1.:• �:.:.•. -: terminals
�:r`rt:;i.�ssz;itiw:- ..�:.;.r.•�•w�,":�ri;,•�.._
M
.. +. nx:- n +>- ..:_..
OIL- FILLED CUTOUTS [Section 710- 21(d)] '
t
ECEMBER• 1977 - -
x
used ;'e•_� 480V.
_ �' _'.•emergence
generator
losup
=•�J Wdgs,
�' londi
' = Feeders •,'f
for
step -dow
lui
Illustrated Changes in
the 1978 National Elec-
trical Code is a 320 -page,
2 -color book presenting all
the text and drawings of.
our September, October,
November, and December
articles on code changes.
Its handy 43 /s- by -7 -in. size
makes it easy to carry to
the jobsite for ready refer-
ence. Copies are now avail-
able from EC &M for $7.00
each. See the ad on page 46
for quantity prices.
67
4 •
S.
i
i
1 -
l
• � C
PUBLISHER'S AFFIDAVI':
STATE OF TEXAS, 18s:
ref;ounty of Nueces.
Before 16e, the undersigned, a Notary Public, this day personally came ....... �......_._.__._....
DIVINA PULIDO who being first duly sworn, according to law, says that he is the
- - - - .... ..................... ....................
` ............ of the Corpus Christi Caller and The Corpus Christi Times,
` Daily Newspapers published at Corpus Christi, Texas, in said County and State, and that the publication of
. — LEGALS.... NOTICE._. QF... pil SA. Q�Q} TIANCE_ Nf2._. L442Q ...AAOP.TZNP...THE..NATSbDIAL. "
ELECTRICAL CODE... `
of which the annexed is a true copy, was published in ._.......G.ULF L- TIMES .._.........__.._.._..._____._. �.
on the.....1A. day of ............ UM'S iii .......... _.._ ... _ .......
tke1
udaothmm....... .............. ...............................
_...... ...._ .......... Times.
$35.70........ .......... "753vinid . ............... accoun£ing
Subscribed and sworn to before me this... 16.__ .......... day o£._...._ APZI A;3 t .............................. 18...7.8—..»
Lois Winn���
Not Public, Nueces County, Texas
OF
TO
EQUIPMENT '+ —" i
A PERMIT
EXCEPT A5
e "4
STAB LISHING IN-
'ECTION DUTIES AND AU•
1ORITY; ADOPVNG CER-
AIN OTHER
EGULgTIONS; PROVID•
IG PENALTIES FOR Vil
1TION1 REPEALING ORDI-
ANCE NO. 14570 AND
:rrinuc i1m Tuoni v:u iz
�
ICES, CITY OF CORPUS]
RISTI, 1976, AS]
'TEMBER 1, 1
PASSED AN
Meeting held on August 9
M at 4;00 p.m, and prov
It it shall . in full force e
fect, as specified in the and ,
me, after passage and pub
anon one time in the official
t1cation of the City of Corpus
irist4 Texas.
ISSUED UNDER MY HAN
4D SEAL of the, City of Cor
s Christi, Texas this 1014 day
August, 1M.
- s•BIII G. Read
City etery