KS 3-2010
Page 1
Section 1
GENERAL
1.1 Scope
NEMA Standards Publication KS 3 sets forth, for use by qualified personnel
1
, a number of basic
procedures that may be used for the inspection and preventive maintenance of switches used in industrial
and commercial applications rated up to and including 600 V 50/60 Hz ac or ac/dc.
NOTE—Consult the manufacturer for other manufacturer-specific ratings.
The National Electrical Code
®
defines several switch types: General Use Switch, Isolating Switch, Motor-
Circuit Switch, and Double-Throw Switch. In most cases, a switch is capable of interrupting/disconnecting its
rated current at its rated voltage. An Isolating Switch does not have an interrupting rating and is actuated
after the circuit has been opened by some other means. A Motor-Circuit Switch is rated in horsepower and is
capable of interrupting the maximum overload current of a motor with the same horsepower rating.
The methods outlined may be used to verify specific characteristics of a switch that was originally built and
tested in compliance with the requirements of NEMA Standards Publication KS 1. These methods are
intended for field application and are, therefore, non-destructive in nature. Accordingly, these methods
cannot be used to verify all performance capabilities of a switch since verification of some capabilities
requires tests of a destructive nature.
Many tests, including those of a destructive nature, as defined in KS 1, are performed on representative
samples of switches by the manufacturer, as part of a routine program of factory inspection.
The KS 3 Standards Publication is not intended, nor is it adequate, to verify proper electrical performance of
a switch that has been disassembled, modified, rebuilt, refurbished, or handled in any manner not intended
or authorized by the original manufacturer. Such switches should be removed from service.
1.2 Referenced Standards
In this publication, reference is made to the latest edition of the standards listed below. Copies are available
from the indicated sources.
National Fire Protection Association
1 Batterymarch Park
Quincy, MA 02169
NFPA 70 National Electrical Code
®
NFPA 70B Recommended Practice for Electrical Equipment Maintenance
NFPA 70E Standard for Electrical Safety in the Workplace
1
For purposes of these guidelines, a qualified person is one who has skills and knowledge related to the construction and operation of
the electrical equipment and installation and has received training to recognize and avoid the hazards involved. In addition, the
person is trained:
—and authorized to test, energize, clear, ground, tag, and lockout circuits and equipment in accordance with established safety
practices.
—in the proper care and use of protective equipment such as rubber gloves, hard hat, safety glasses or face shields, and flash
resistant clothing, in accordance with established safety practices.
—in first aid.
© Copyright 2010 by the National Electrical Manufacturers Association.
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