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Fuel Consumption
Estimated fuel supply requirements at half and full load for
natural gas and LP vapor fuels are shown below.
LP Vapor (Propane)
20kW 17kW 15kW
Full Load
Cu Ft/Hr 135 118 109
Gal/Hr (liquid) 3.75 3.28 3.03
BTU/Hr 337500 295000 272500
3/4 Load
Cu Ft/Hr 109 99 90
Gal/Hr (liquid) 3.03 2.75 2.5
BTU/Hr 272500 247500 225000
1/2 Load
Cu Ft/Hr 83 74 68
Gal/Hr (liquid) 2.31 2.06 1.89
BTU/Hr 207500 185000 170000
1/4 Load
Cu Ft/Hr 56 54 51
Gal/Hr (liquid) 1.56 1.5 1.42
BTU/Hr 140000 135000 127500
Exercise
Cu Ft/Hr 40 40 40
Gal/Hr (liquid) 1.11 1.11 1.11
BTU/Hr 100000 100000 100000
Natural Gas
20 kW
(18 kW)
17 kW
(14.4 kW)
15kW
(13.5 kW)
Full Load
Cu Ft/ Hr 260 248 240
BTU / Hr 260000 248000 240000
3/4 Load
Cu Ft/ Hr 240 218 210
BTU / Hr 240000 218000 210000
1/2 Load
Cu Ft/ Hr 187 170 156
BTU / Hr 187000 170000 156000
1/4 Load
Cu Ft/ Hr 135 128 119
BTU / Hr 135000 128000 119000
Exercise
Cu Ft/ Hr 99 99 99
BTU / Hr 99000 99000 99000
Recommended Energy
Content of Fuel
LP Vapor Natural
Gas
Heating Value:
BTU per gallon (gross**)
Cubic feet (gas)
91,547
2,500 1,000
Fuel Pressure
Both LP vapor and natural gas fuel supply pressure at the
generator’s fuel inlet port should be between the following
levels at full load with all gas appliances turned on
and operating.
t /(JTw8$
t -1JTw8$
Ensure that all gas line shutoff valves are OPEN and that
adequate fuel pressure is available whenever automatic
operation is desired.
Power Loss
Air density is less at high altitudes, resulting in less available
engine power. Specifically, engine power will decrease 3.5%
for each 1,000 feet (300 meters) above sea level and 1% for
each 10° F (5.6°C) above 77°F (25°C). Make sure you and
your installer consider these factors when determining total
generator load.
Fuel Pipe Sizing
There are numerous on-line or otherwise-published
references for fuel pip sizing. For example, NFPA 54-Natural
Fuel Gas Code, 2006 (Item #: 320-6031-06) is a
common resource.
The installer should consider the specific gravity of gas and
compensate for a nominal amount of restriction from bends,
fittings, etc. If an unusual number of fittings, bends, or other
restrictions are used, refer to federal and local codes
for guidance.