6.12 Emergency Power Systems
locations heaters can reduce moisture collection in the
generator windings. Critical silencers are required for all
generators. Acoustical treatment of the generator room
shall be provided if necessary. Temperature and
Emergency power systems must be designed to comply
ventilation shall be maintained within the manufacturer's
with the requirements of NFPA 110, Emergency and
recommendations to assure proper operation of the unit.
Standby Power Systems. See Chapter 7: Fire Protection &
Calculations to support the size of the intake air supply
Life Safety for additional requirements. Unless otherwise
for combustion, cooling and radiation as well as exhaust
specifically authorized by the Contracting Officer all
piping, and exhaust paths shall be provided by the design
facilities shall be provided with a standby generator to
engineer.
supply power to the facility in the event of a sudden loss
of power.
Radiators shall be unit-mounted if possible. If ventilation
is restricted in indoor applications, remote installation is
Generator Systems
acceptable. Heat recovery and load shedding shall not be
considered. Remote location of radiators shall be designed
The system shall consist of a central engine generator
to avoid excess pressure on the piping seals.
and a separate distribution system with automatic transfer
switch(es), distribution panels, and 480/277V lighting
Provide permanently installed load bank sized at 50% of
panel (if applicable) with dry-type transformers feeding
generator rating. Load bank shall be factory mounted to
208/120V panels as required. Effort must be made to
the radiator.
ensure proper coordination of mechanical engineering
elements of the generator systems design.
approximately 110 percent of design load; ideally it shall
Service Conditions. If the unit is to be installed outdoors,
run at 60 percent to 80 percent of its rated capacity after
it shall be provided with a suitable walk-in acoustic
the effect of the inrush current declines. When sizing the
enclosure and jacket water heaters to ensure reliable
generator, consider the inrush current of the motors that
starting in cold weather.
are automatically started simultaneously. The initial
voltage drop on generator output due to starting currents
When installed at high altitudes or in areas with very
of loads must not exceed 15 percent. Day tanks shall be
high ambient temperatures, the unit must be derated in
sized for a minimum capacity of four hours of generator
accordance with manufacturers' recommendations.
operation. Provide direct fuel oil supply and fuel oil
Operation of starting batteries and battery chargers must
return piping to the on-site storage tank. Piping shall not
also be considered in sizing calculations. In humid
be connected into the boiler transfer fuel oil delivery "loop".
201
ELECTRICAL
ENGINEERING
6.12
Emergency Power Systems
Revised March 2005 PBS-P100
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