UFC 3 -520-01
June 10, 2002
For services greater than 600 volts, use metal-enclosed, manually operated,
fusible load interrupter switches or power circuit breakers. For services 600 volts and
less, use molded case breakers, low voltage power circuit breakers, or fusible
disconnect switches. Low voltage power circuit breakers should be selected only where
the added cost incurred by their use can be justified by operational considerations.
Provide a single disconnecting means for each facility. Avoid multiple disconnects
unless major economies can be realized in large capacity services or if multiple service
voltage requirements exist. Ensure equipment ampacities are adequate for the
estimated load demands plus a contingency of 10 percent to 20 percent for future load
growth. A larger reserve contingency can be applied if a specific need for future load
growth can be documented. Equipment must be capable of safely performing all
interrupting functions based on the availa ble system capacity and characteristics.
Provide energy usage and demand meters in accordance with paragraph 8 -6.
Equipment room space required by major items of equipment such as
systems, and batteries should be designed in accordance with the NEC. Ensure that
equipment can be removed and replaced without interference with other systems or
equipment, and without requiring building modifications. Provide ventilation as
necessary to permit equipment to operate within normal ambient temperature
limitations; otherwise, derate the equipment accordingly for a lower capability and
potentially shorter service life. Provide separate air-conditioned electronic equipment
rooms as required. Refer to paragraph 8 -1 for additional requirements regarding
Design electrical distribution systems that require high reliability power to
comply with ANSI C84.1, Electrical Power Systems and Equipment--Voltage Ratings
A voltage limits. Facilities that
do not have high reliability requirements
can be designed to ANSI C84.1 Range B limits.