UFC 3 -520-01
June 10, 2002
with other overcurrent protective devices. By incorporating downstream GFP, the
overall facility coordination can often be improved so that a single ground fault event is
less likely to deenergize the entire facility. Verify that the service entrance GFP is set
high enough to allow coordination with downstream devices.
Ensure eq uipment 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.
Install service equipment in an equipment room of sufficient size to allow
proper maintenance of the equipment. If electrical equipment is located in a joint
electrical/mechanical equipment room, reserve adequate space for the electrical
equipment, including provi sions for future modifications. Do not allow piping, ducts, and
other equipment unrelated to the electrical equipment to pass through or over the space
reserved for electrical equipment. When fluid systems are located near electrical
equipment, furnish the equipment with splash-shields and water-resistant enclosures.
Design the system with the capability to disconnect all ungrounded
conductors in a building or other structure from the service-entrance conductors.
Ensure the disconnecting means pla inly indicates whether it is in the open or closed
position and install it at a readily accessible location nearest the point of entrance of the
service-entrance conductors. Each service disconnecting means must simultaneously
disconnect all ungrounded co nductors.
Clearly and permanently mark all circuit disconnect devices, including
switches and breakers, to show the purpose of each disconnect.
Place barriers in all service switchboards such that no uninsulated,
ungrounded service busbar or service terminal will be exposed to inadvertent contact by
persons or maintenance equipment while servicing load connections.
Depending on the facility design, consider p roviding the following metering
with the service entrance equipment: voltmeter, ammeter, kW meter, kVAR or power
factor meter, and kWh meter with peak demand register and pulse generator for future
connection to energy monitoring and control systems.
SWITCHGEAR AND SWITCHBOARDS GENERAL CRITERIA.
Select switchgear and swi tchboards of the dead-front, floor-mounted,
freestanding, metal-enclosed type with copper bus and utilizing circuit breakers or
fusible switches as circuit protective devices. Space-only cubicles and appropriate bus
provisions should be installed for future protective device additions, as necessary to
accommodate planned load growth. Ensure switchboards are designed in accordance
with NEMA PB 2, Deadfront Distribution Switchboards. The term switchgear is used
here to describe the assembled equipment of switching, interrupting, control,