2.14.7
Regulated Power Supplies
Power supplies shall provide a 24-Vdc linear supply at not less than 2
amperes, with regulation to 0.05 percent of output voltage. Power supplies
shall have a fused input, and shall be protected from voltage surges and
power-line transients. Power supply output shall be protected against
overvoltage and short circuits. Power supply loading shall not be greater
than 1.2 amperes.
2.14.8
Transformers
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NOTE: Indicate a backup transformer connected to an
alternate voltage supply for systems connected to
critical areas where continuous operation is
necessary.
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UL 508 and NEMA ST 1 as applicable. Transformers, other than transformers
in bridge circuits, shall have primaries wound for available voltage and
secondaries wound for correct control circuit voltage.
Transformers shall
be sized so that connected loads equal 80 percent of rated capacity.
Transformers shall be enclosed in rustproof, galvanized steel cabinets with
conduit connections. Disconnect switch shall be provided on the primary
side, and a fuse cutout on the secondary side.
[For systems serving ]
[_____] [or] [as indicated], provide backup power supply including
transformers connected to [the emergency power source] [_____]. [Provide
for automatic switchover and alarm upon failure of primary control circuit.]
2.14.9
Pilot Lights and Manual Switches
Device illumination shall be by light-emitting diode (LED) or neon lamp.
Switches shall have operating levers and index plates showing switch
positions and names of apparatus controlled or other appropriate
designations.
2.15
HVAC SYSTEM CONTROL PANELS
Provide HVAC system control panels.
2.15.1
Panel Assembly
Panel shall be fabricated for bottom entry connection for control system
electric power, control system main air source, control system wiring,
pneumatic tubing, interconnection of control systems, interconnection of
starters, and external shutdown devices. Panel shall have an operating
temperature rise of not greater than 11 degrees C 20 degrees F above an
ambient temperature of 38 degrees C 100 degrees F.
2.15.2
Panel Electrical Requirements
Control panel shall be powered by nominal 120 Vac terminating at panel on
terminal blocks. Instrument cases shall be grounded. Interior and
exterior panel enclosures shall be grounded.
2.15.3
Enclosures
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NOTE: Indicate NEMA class for each panel.
SECTION 15901N
Page 37
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