NFPA 79
Electrical Standard for
Industrial Machinery
2007 Edition
NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471
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, 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.
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