However, the recent increase in bandwidth required by
Lighting and Receptacle Panelboards. Lighting and
the latest IT equipment has been accompanied by the use
receptacle panelboards shall be circuit breaker type.
of CAT 6 cables and fiber optic cables. Neither of these
Provide minimum 30 poles for 100 amps panelboards
cables can tolerate the proximity to the power cables or
and minimum 42 poles for 225 amp panelboards.
the sharp bends from the header ducts to the cells to the
Conduit Systems. The specification shall list the various
outlets, which significantly deminshes the practical use of
types of conduit systems which are approved for use on
these systems.
the project and the specific raceway applications for which
they are to be used, as follows:
Panelboards
RSC Rigid galvanized steel conduit ANSI C80.1
Panelboards shall be constructed to comply with the
Exposed outdoors
requirements of UL 67 and UL 50.
RAC Aluminum conduit (with steel elbows) Indoor
All panelboard interiors shall be constructed using hard-
feeders exposed and/or concealed
drawn copper of 98% conductivity, with AIC bracing
IMC Intermediate steel conduit ANSI C80.6 Indoor
greater than the calculated available fault current.
feeders exposed and/or concealed
Minimum short circuit rating for 208/120v panelboards
EMT Electrical Metallic Tubing (compression fittings)
shall be 10,000 amperes symmetrical. Minimum short
ANSI C80.3 Branch circuit wiring, exposed and/or
circuit rating for 480/277v panelboards shall be 14,000
concealed
amperes symmetrical. A 200% neutral shall be provided
FMC Flexible steel conduit connections to recessed
for panelboards serving office loads served from the
lighting fixtures and concealed in movable and/or
secondaries of K-rated transformers or harmonic
dry wall partitions
canceling transformers. A full size copper ground bus for
connecting ground conductors shall be bonded to the
LFMC Flexible steel conduit with PVC jacket. Connections
steel cabinet. Provide isolated ground bus where required.
to vibrating equipment (motors, transformers, etc.)
Branch circuit breakers shall be bolt-on designed for
PVC Underground feeders encased in concrete
replacement without disturbing adjacent units. Breakers
envelope. Indoors and outdoors. Transition to
shall comply with the requirements of UL 489, thermal
steel or aluminum when exposed.
magnetic type with short-circuit rating greater than the
calculated available fault current. Panels shall be
specified with "door-in-door" trim.
Power Distribution Panels. In general, circuit breaker
type panels will be the standard of construction for
federal buildings. With the exception of lighting and
receptacle panel boards, fusible switches may be
considered if specific design considerations warrant their
application, such as in electrical coordination of electrical
over-current devices.
199
ELECTRICAL
ENGINEERING
6.10
Branch Wiring Distribution Systems
Revised March 2005 PBS-P100
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