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University of Wisconsin-Extension
An
emergency source of power is important for any farm with mechanically
ventilated production facilities, bulk milk handling equipment,
mechanical feeding equipment or facilities requiring constant
and continuous heat (such as brooders). On such a farm, a
standby electric generator is a good investment, possibly
preventing costly losses during a power failure.
During
disasters such as flood or tornado, relief agencies may provide
generators to farmers on an emergency basis.
Standby
generators are either engine driven or tractor driven. Either
type can be stationary or portable. Engine driven units can
be either manual or automatic start. Gasoline-, LP gas- (bottled
gas) and diesel-fueled engines are available.
Generators
must provide the same type of power at the same voltage and
frequency as that supplied by power lines. This is usually
120/240 volt, single phase, 60 cycle alternating current (AC).
An air-cooled engine is often used for generators up to 15
kilowatts. A liquid-cooled engine is necessary for generators
larger than 15 kilowatts. Engine capacity of 2 to 2 1/4 hp
with the proper drive system must be available for each 1,000
watts of generator output.
A
full-load system will handle the entire farmstead load. Automatic
engine-powered, full-load systems will begin to furnish power
immediately, or up to 30 seconds after power is off. Smaller
and less expensive part-load systems may be enough to handle
essential equipment during an emergency.
Power-take-off
(PTO) generators are about half as costly as engine-operated
units. Under a part-load system, only the most essential equipment
is operated at one time. For most farms, this type of system
is adequate, provided the generator is sized to start the
largest motor. For example, the milk cooler or ventilation
fan would need to be operated continuously, but the operation
of the silo unloader and mechanical feeding system could be
postponed until the milking chores are completed. PT units
can be mounted on a trailer.
Wiring
and equipment must be installed in accordance with the National
Electrical Code, local ordinances and the requirements of
your power supplier. It is essential that you have the proper
equipment for disconnecting the generator from public utility
lines. Most companies require the installation of a double-pole
double-throw transfer switch or its equivalent for this purpose.
Check with your electrician or power supply representative
for installation, installation instructions and inspection.
- Large
engine generators should be located in a building, preferably
a heated building.
- Inlet
and outlet air ducts must be large enough to carry off excess
heat. They should be open at least a half a square foot
for each 1,000 watts of generator capacity.
- Combustion
fumes must be carried outdoors safely. Exhaust pipes must
be at least 6 inches from combustible material.
An
automatic standby unit should start automatically when power
fails, and stop when power is restored. When using an engine-driven
generator with a manual start, or when using a tractor driven
unit, follow this procedure when power fails:
- Call
your power supplier and advise them of the conditions.
- Turn
off or disconnect all electrical equipment.
- Position
the tractor or engine for belt of PTO drive.
- Start
the unit and bring the generator up to proper speed (1,800
or 3,600 rps). Check on arrangement to carry off exhaust
fumes. Be sure there is no danger of fire. The voltmeter
will indicate when the generator is ready to carry the load.
- Put
the transfer switch in the generator position.
- Start
the largest electrical motor first, adding other loads when
each is up to operating speed. Do not add too much too fast.
If the generator cuts out for any reason, repeat the second,
third and fourth steps above.
- Check
the voltmeter frequently. If voltage falls below 200 volts
for 240 volt service or below 100 volts for 120 volt service,
reduce the load on the generator by turning off some electrical
equipment.
- When
commercial power is restored, put the transfer switch in
normal power position. Then stop the standby unit.
- Keep
the unit clean and in good running order at all times so
it will be ready for immediate use. Dust and dirt accumulations
on the motor can cause it to overheat when operated.
- Follow
maintenance instructions in manufacturer's manual. A short
operation at set intervals will keep the engine in good
operating condition. Regularly scheduled warm-ups are necessary
to keep a standby engine in working order.
Additional resources:
Your county agricultural agent
Related publications:
UW-Extension publications-
"Standby Electric Power Equipment for the Farm and Home," (AF2273);
"Electrical Systems for Agricultural Buildings," (checklist), (A8NE846);
"Electrical Systems for Agricultural Buildings," (recommended practices), (A8NE845).
"Standby Power," Illinois Farm Electrification Council, Fact Sheet #2.
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NASD Review: 04/2002
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