NFPA 79
Electrical Standard for
Industrial Machinery
2007 Edition
NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471
An International Codes and Standards Organization
The Standard is downloaded from www.bzfxw.com Standard Sharin
, IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPA DOCUMENTS
NOTICE AND DISCLAIMER OF LIABILITY CONCERNING THE USE OF NFPA DOCUMENTS
NFPA codes, standards, recommended practices, and guides, of which the document contained herein is one, are de-
veloped through a consensus standards development process approved by the American National Standards Institute.
This process brings together volunteers representing varied viewpoints and interests to achieve consensus on fire and
other safety issues. While the NFPA administers the process and establishes rules to promote fairness in the develop-
ment of consensus, it does not independently test, evaluate, or verify the accuracy of any information or the soundness
of any judgments contained in its codes and standards.
The NFPA disclaims liability for any personal injury, property or other damages of any nature whatsoever, whether
special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance
on this document. The NFPA also makes no guaranty or warranty as to the accuracy or completeness of any information
published herein.
In issuing and making this document available, the NFPA is not undertaking to render professional or other services
for or on behalf of any person or entity. Nor is the NFPA undertaking to perform any duty owed by any person or entity
to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate,
seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances.
The NFPA has no power, nor does it undertake, to police or enforce compliance with the contents of this document.
Nor does the NFPA list, certify, test or inspect products, designs, or installations for compliance with this document.
Any certification or other statement of compliance with the requirements of this document shall not be attributable to
the NFPA and is solely the responsibility of the certifier or maker of the statement.
The Standard is downloaded from www.bzfxw.com Standard Sharin
,ADDITIONAL NOTICES AND DISCLAIMERS
Updating of NFPA Documents
Users of NFPA codes, standards, recommended practices, and guides should be aware that
these documents may be superseded at any time by the issuance of new editions or may be
amended from time to time through the issuance of Tentative Interim Amendments. An offi-
cial NFPA document at any point in time consists of the current edition of the document
together with any Tentative Interim Amendments and any Errata then in effect. In order to
determine whether a given document is the current edition and whether it has been amended
through the issuance of Tentative Interim Amendments or corrected through the issuance of
Errata, consult appropriate NFPA publications such as the National Fire Codes® Subscription
Service, visit the NFPA website at www.nfpa.org, or contact the NFPA at the address listed
below.
Interpretations of NFPA Documents
A statement, written or oral, that is not processed in accordance with Section 6 of the Reg-
ulations Governing Committee Projects shall not be considered the official position of NFPA
or any of its Committees and shall not be considered to be, nor be relied upon as, a Formal
Interpretation.
Patents
The NFPA does not take any position with respect to the validity of any patent rights
asserted in connection with any items which are mentioned in or are the subject of NFPA
codes, standards, recommended practices, and guides, and the NFPA disclaims liability for
the infringement of any patent resulting from the use of or reliance on these documents.
Users of these documents are expressly advised that determination of the validity of any such
patent rights, and the risk of infringement of such rights, is entirely their own responsibility.
NFPA adheres to applicable policies of the American National Standards Institute with
respect to patents. For further information contact the NFPA at the address listed below.
Law and Regulations
Users of these documents should consult applicable federal, state, and local laws and reg-
ulations. NFPA does not, by the publication of its codes, standards, recommended practices,
and guides, intend to urge action that is not in compliance with applicable laws, and these
documents may not be construed as doing so.
Copyrights
This document is copyrighted by the NFPA. It is made available for a wide variety of both
public and private uses. These include both use, by reference, in laws and regulations, and
use in private self-regulation, standardization, and the promotion of safe practices and
methods. By making this document available for use and adoption by public authorities and
private users, the NFPA does not waive any rights in copyright to this document.
Use of NFPA documents for regulatory purposes should be accomplished through adop-
tion by reference. The term “adoption by reference” means the citing of title, edition, and
publishing information only. Any deletions, additions, and changes desired by the adopting
authority should be noted separately in the adopting instrument. In order to assist NFPA in
following the uses made of its documents, adopting authorities are requested to notify the
NFPA (Attention: Secretary, Standards Council) in writing of such use. For technical assis-
tance and questions concerning adoption of NFPA documents, contact NFPA at the address
below.
For Further Information
All questions or other communications relating to NFPA codes, standards, recommended
practices, and guides and all requests for information on NFPA procedures governing its
codes and standards development process, including information on the procedures for
requesting Formal Interpretations, for proposing Tentative Interim Amendments, and for
proposing revisions to NFPA documents during regular revision cycles, should be sent to
NFPA headquarters, addressed to the attention of the Secretary, Standards Council, NFPA,
1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.
For more information about NFPA, visit the NFPA website at www.nfpa.org.
The Standard is downloaded from www.bzfxw.com Standard Sharin
, 79–1
Copyright © 2006 National Fire Protection Association. All Rights Reserved.
NFPA 79
Electrical Standard for
Industrial Machinery
2007 Edition
This edition of NFPA 79, Electrical Standard for Industry Machinery, was prepared by the
Technical Committee on Electrical Equipment of Industrial Machinery, and acted on by
NFPA at its June Association Technical Meeting held June 4–8, 2006, in Orlando, FL. It was
issued by the Standards Council on July 28, 2006, with an effective date of August 17, 2006,
and supersedes all previous editions.
This edition of NFPA 79 was approved as an American National Standard on August 17, 2006.
Origin and Development of NFPA 79
This standard was first submitted at the 1961 NFPA Annual Meeting under the title Electrical
Standard for Machine Tools and was tentatively adopted subject to comments. It was extensively
revised and resubmitted at the 1962 Annual Meeting, where it was officially adopted. In 1965 a
revised edition was adopted, reconfirmed in 1969, and in 1970, 1971, 1973, 1974, 1977, 1980,
1985, 1987, 1991, 1994, 1997, and 2002, revised editions were adopted.
In September 1941, the metalworking machine tool industry wrote its first electrical stan-
dard to make machine tools safer to operate, more productive, and less costly to maintain,
and to improve the quality and performance of their electrical components. That particular
standard served as an American “War Standard.”
To study the special electrical problems involved with machine tools, in 1941 the Electrical
Section of the National Fire Protection Association sanctioned a Special Subcommittee on
Wiring, Overcurrent Protection, and Control of Motor-Operated Machine Tools. This Sub-
committee, cooperating with machine tool builders, manufacturers of control equipment,
and Underwriters Laboratories Inc., conducted tests and investigated the peculiar conditions
involved with machine tools that might warrant exception to certain specific National Electrical
Code® requirements. This investigation resulted, on August 4, 1942, in a Tentative Interim
Amendment and first appeared in a 1943 supplement to the 1940 edition of the National
Electrical Code as Article 670, “Machine Tools.” It remained essentially unchanged through the
1959 edition.
Meanwhile, manufacturers of other types of industrial equipment erroneously began to
follow the specialized practices permitted by Article 670. Late in 1952, a Technical Subcom-
mittee on Fundamentals of Electrically Operated Production Machinery and Material Han-
dling and Processing Equipment for Fixed Locations was organized to attempt to group the
special requirements of this broad field into one article. The extremely broad scope intro-
duced so many problems that, in December 1956, this Technical Subcommittee was reorga-
nized into an NFPA Committee whose scope was limited to machine tools and whose objective
was the preparation of this NFPA standard with corresponding revisions in Article 670 in the
National Electrical Code.
Modern machine tool electrical equipment may vary from that of single-motor machines,
such as drill presses, that perform simple, repetitive operations, to that of very large, multimo-
tored automatic machines that involve highly complex electrical control systems, including
electronic and solid-state devices and equipment. Generally these machines are specially
designed, factory wired, and tested by the builder and then erected in the plant in which they
will be used. Because of their importance to plant production and their usually high cost, they
are customarily provided with many safeguards and other devices not often incorporated in
the usual motor and control application as contemplated by the National Electrical Code.
The Standard is downloaded from www.bzfxw.com Standard Sharin
Electrical Standard for
Industrial Machinery
2007 Edition
NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471
An International Codes and Standards Organization
The Standard is downloaded from www.bzfxw.com Standard Sharin
, IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPA DOCUMENTS
NOTICE AND DISCLAIMER OF LIABILITY CONCERNING THE USE OF NFPA DOCUMENTS
NFPA codes, standards, recommended practices, and guides, of which the document contained herein is one, are de-
veloped through a consensus standards development process approved by the American National Standards Institute.
This process brings together volunteers representing varied viewpoints and interests to achieve consensus on fire and
other safety issues. While the NFPA administers the process and establishes rules to promote fairness in the develop-
ment of consensus, it does not independently test, evaluate, or verify the accuracy of any information or the soundness
of any judgments contained in its codes and standards.
The NFPA disclaims liability for any personal injury, property or other damages of any nature whatsoever, whether
special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance
on this document. The NFPA also makes no guaranty or warranty as to the accuracy or completeness of any information
published herein.
In issuing and making this document available, the NFPA is not undertaking to render professional or other services
for or on behalf of any person or entity. Nor is the NFPA undertaking to perform any duty owed by any person or entity
to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate,
seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances.
The NFPA has no power, nor does it undertake, to police or enforce compliance with the contents of this document.
Nor does the NFPA list, certify, test or inspect products, designs, or installations for compliance with this document.
Any certification or other statement of compliance with the requirements of this document shall not be attributable to
the NFPA and is solely the responsibility of the certifier or maker of the statement.
The Standard is downloaded from www.bzfxw.com Standard Sharin
,ADDITIONAL NOTICES AND DISCLAIMERS
Updating of NFPA Documents
Users of NFPA codes, standards, recommended practices, and guides should be aware that
these documents may be superseded at any time by the issuance of new editions or may be
amended from time to time through the issuance of Tentative Interim Amendments. An offi-
cial NFPA document at any point in time consists of the current edition of the document
together with any Tentative Interim Amendments and any Errata then in effect. In order to
determine whether a given document is the current edition and whether it has been amended
through the issuance of Tentative Interim Amendments or corrected through the issuance of
Errata, consult appropriate NFPA publications such as the National Fire Codes® Subscription
Service, visit the NFPA website at www.nfpa.org, or contact the NFPA at the address listed
below.
Interpretations of NFPA Documents
A statement, written or oral, that is not processed in accordance with Section 6 of the Reg-
ulations Governing Committee Projects shall not be considered the official position of NFPA
or any of its Committees and shall not be considered to be, nor be relied upon as, a Formal
Interpretation.
Patents
The NFPA does not take any position with respect to the validity of any patent rights
asserted in connection with any items which are mentioned in or are the subject of NFPA
codes, standards, recommended practices, and guides, and the NFPA disclaims liability for
the infringement of any patent resulting from the use of or reliance on these documents.
Users of these documents are expressly advised that determination of the validity of any such
patent rights, and the risk of infringement of such rights, is entirely their own responsibility.
NFPA adheres to applicable policies of the American National Standards Institute with
respect to patents. For further information contact the NFPA at the address listed below.
Law and Regulations
Users of these documents should consult applicable federal, state, and local laws and reg-
ulations. NFPA does not, by the publication of its codes, standards, recommended practices,
and guides, intend to urge action that is not in compliance with applicable laws, and these
documents may not be construed as doing so.
Copyrights
This document is copyrighted by the NFPA. It is made available for a wide variety of both
public and private uses. These include both use, by reference, in laws and regulations, and
use in private self-regulation, standardization, and the promotion of safe practices and
methods. By making this document available for use and adoption by public authorities and
private users, the NFPA does not waive any rights in copyright to this document.
Use of NFPA documents for regulatory purposes should be accomplished through adop-
tion by reference. The term “adoption by reference” means the citing of title, edition, and
publishing information only. Any deletions, additions, and changes desired by the adopting
authority should be noted separately in the adopting instrument. In order to assist NFPA in
following the uses made of its documents, adopting authorities are requested to notify the
NFPA (Attention: Secretary, Standards Council) in writing of such use. For technical assis-
tance and questions concerning adoption of NFPA documents, contact NFPA at the address
below.
For Further Information
All questions or other communications relating to NFPA codes, standards, recommended
practices, and guides and all requests for information on NFPA procedures governing its
codes and standards development process, including information on the procedures for
requesting Formal Interpretations, for proposing Tentative Interim Amendments, and for
proposing revisions to NFPA documents during regular revision cycles, should be sent to
NFPA headquarters, addressed to the attention of the Secretary, Standards Council, NFPA,
1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.
For more information about NFPA, visit the NFPA website at www.nfpa.org.
The Standard is downloaded from www.bzfxw.com Standard Sharin
, 79–1
Copyright © 2006 National Fire Protection Association. All Rights Reserved.
NFPA 79
Electrical Standard for
Industrial Machinery
2007 Edition
This edition of NFPA 79, Electrical Standard for Industry Machinery, was prepared by the
Technical Committee on Electrical Equipment of Industrial Machinery, and acted on by
NFPA at its June Association Technical Meeting held June 4–8, 2006, in Orlando, FL. It was
issued by the Standards Council on July 28, 2006, with an effective date of August 17, 2006,
and supersedes all previous editions.
This edition of NFPA 79 was approved as an American National Standard on August 17, 2006.
Origin and Development of NFPA 79
This standard was first submitted at the 1961 NFPA Annual Meeting under the title Electrical
Standard for Machine Tools and was tentatively adopted subject to comments. It was extensively
revised and resubmitted at the 1962 Annual Meeting, where it was officially adopted. In 1965 a
revised edition was adopted, reconfirmed in 1969, and in 1970, 1971, 1973, 1974, 1977, 1980,
1985, 1987, 1991, 1994, 1997, and 2002, revised editions were adopted.
In September 1941, the metalworking machine tool industry wrote its first electrical stan-
dard to make machine tools safer to operate, more productive, and less costly to maintain,
and to improve the quality and performance of their electrical components. That particular
standard served as an American “War Standard.”
To study the special electrical problems involved with machine tools, in 1941 the Electrical
Section of the National Fire Protection Association sanctioned a Special Subcommittee on
Wiring, Overcurrent Protection, and Control of Motor-Operated Machine Tools. This Sub-
committee, cooperating with machine tool builders, manufacturers of control equipment,
and Underwriters Laboratories Inc., conducted tests and investigated the peculiar conditions
involved with machine tools that might warrant exception to certain specific National Electrical
Code® requirements. This investigation resulted, on August 4, 1942, in a Tentative Interim
Amendment and first appeared in a 1943 supplement to the 1940 edition of the National
Electrical Code as Article 670, “Machine Tools.” It remained essentially unchanged through the
1959 edition.
Meanwhile, manufacturers of other types of industrial equipment erroneously began to
follow the specialized practices permitted by Article 670. Late in 1952, a Technical Subcom-
mittee on Fundamentals of Electrically Operated Production Machinery and Material Han-
dling and Processing Equipment for Fixed Locations was organized to attempt to group the
special requirements of this broad field into one article. The extremely broad scope intro-
duced so many problems that, in December 1956, this Technical Subcommittee was reorga-
nized into an NFPA Committee whose scope was limited to machine tools and whose objective
was the preparation of this NFPA standard with corresponding revisions in Article 670 in the
National Electrical Code.
Modern machine tool electrical equipment may vary from that of single-motor machines,
such as drill presses, that perform simple, repetitive operations, to that of very large, multimo-
tored automatic machines that involve highly complex electrical control systems, including
electronic and solid-state devices and equipment. Generally these machines are specially
designed, factory wired, and tested by the builder and then erected in the plant in which they
will be used. Because of their importance to plant production and their usually high cost, they
are customarily provided with many safeguards and other devices not often incorporated in
the usual motor and control application as contemplated by the National Electrical Code.
The Standard is downloaded from www.bzfxw.com Standard Sharin
