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3.10.3.1 Interior Electric Power Distribution
3.10.3.1.1 Buildings should be served from main switchboards in the
electrical rooms at 480/277 volt, 3-phase, 4-wire for lighting, power
and mechanical loads. DEPMED should be provided with 208/120
volt, 3-phase, 4-wire power supply.
310.3.1.2 Verify and coordinate the size of the main electrical room
and closets with the architect.
Figure 3-12
3.10.3.1.3 Conductors for feeders should be sized to prevent a
USARC, Camp
voltage drop exceeding 3 percent at the farthest outlet of power,
Parks, California
heating, and lighting loads, or combinations of such loads and where
the maximum total voltage drop on both feeders and branch circuits to
the farthest outlet does not exceed 5 percent, should provide
reasonable efficiency of operation.
3.10.3.1.4 The main switchboard and the distribution panels should
have circuit breakers. The combination starters should be provided
with fusible switches to serve motors in HVAC equipment. Branch
circuit panels should be circuit breaker panelboard type with plug-in
breakers.
3.10.3.1.5 Interior conductors should be type THHN/THWN or
THW conforming to UL83 or RHW conforming to UL44. All
conductors should be copper. All conductors should be routed in
conduit. Minimum conductor size should be #12 AWG, except
conductors for fire alarm system should be #16 for initiation circuits. A
separate green ground conductor, size per N.E.C. Article 250
"Grounding," should be installed in all conduits containing receptacle
and lighting circuits, and should be installed in all feeders from main
switchboard to panelboards and motor/equipment.
3.10.3.1.6 The main electrical service switchboard ground bus shall
be connected to a Grounding Electode System in accordance with
NFPA 70, ART 250.50. The computer room grounding and
equipment should be connected directly to the building service
ground.
3.10.3.1.7 The following minimum loads should be assumed to
determine the preliminary size of electrical service to the building:
Lighting Load26.9VA/sq m
Site Lighting 465 VA per fixture
HVAC Load 64.6 VA/sq m
Elevator
40 HP/elevator
UFC 4-171-05
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