UFC 3-520-01
June 10, 2002
5-10
5-7.3
Disconnect switches can be used as a means to satisfy circuit lockout
requirements. For example, a disconnect switch can be installed between a transformer
and an MCC to allow for an OSHA-recognized positive means of deenergizing the MCC
for maintenance.
5-7.4
All disconnect switches must be lockable.
5-7.5
Rate disconnect switches for motor applications for the horsepower rating of
the associated motor.
5-8
CIRCUIT LOCKOUT REQUIREMENTS. Circuit breakers, disconnect
switches, and other devices that meet the OSHA definition of energy-isolating device
must be lockable. OSHA has determined that lockout is a more reliable means of
deenergizing equipment than tagout and that it is the preferred method to be used. An
energy-isolating device is considered capable of being locked out if it meets one of the
following requirements:
·
It is designed with a hasp to which a lock can be attached.
·
It is designed with any other integral part through which a lock can be affixed.
·
It has a locking mechanism built into it.
·
It can be locked without dismantling, rebuilding, or replacing the energy isolating
device or permanently altering its energy control capability.
5-9
INFORMATION SOURCES. The following references provide additional
information regarding circuit breaker selection and sizing:
5-9.1
ANSI C37 Series--provides several standards related to switchgear and
circuit breakers and should be used as a reference source when preparing
specifications.
5-9.2
IEEE 141--provides an application overview of switchgear, breakers, and
other switching devices.
5-9.3
IEEE 241--provides an application overview of switchgear, breakers, and
other switching devices.
5-9.4
IEEE 1015, IEEE Recommended Practice for Applying Low-Voltage Circuit
Breakers Used in Industrial and Commercial Power Systems (IEEE Blue Book)--
provides detailed application guidance for low voltage power circuit breakers and
MCCBs.
5-9.6
NEMA AB 3, Molded Case Circuit Breakers and Their Application--provides
guidance for the application of MCCBs and molded case switches. IEEE 1015 should
be used preferentially as a reference document.