Fuel Consumption; Fuel Pressure; Power Loss; Fuel Pipe Sizing - Briggs & Stratton 40336 Installation & Start-Up Manual

Fuel Consumption

Estimated fuel supply requirements at half and full load for
natural gas and LP vapor fuels are shown below.
LP Vapor (Propane)
Cu Ft/Hr
Full Load
Gal/Hr (liquid)
BTU/Hr
Cu Ft/Hr
3/4 Load Gal/Hr (liquid)
BTU/Hr
Cu Ft/Hr
1/2 Load Gal/Hr (liquid)
BTU/Hr
Cu Ft/Hr
1/4 Load Gal/Hr (liquid)
BTU/Hr
Cu Ft/Hr
Exercise Gal/Hr (liquid)
BTU/Hr
Natural Gas
Cu Ft/ Hr
Full Load
BTU / Hr
Cu Ft/ Hr
3/4 Load
BTU / Hr
Cu Ft/ Hr
1/2 Load
BTU / Hr
Cu Ft/ Hr
1/4 Load
BTU / Hr
Cu Ft/ Hr
Exercise
BTU / Hr
20kW 16kW 15kW
135 113 109
3.75 3.14 3.03
337500 282500 272500
109 96 90
3.03 2.67 2.5
272500 240000 225000
83 71 68
2.31 1.97 1.89
207500 177500 170000
56 53 51
1.56 1.47 1.42
140000 132500 127500
40 40 40
1.11 1.11 1.11
100000 100000 100000
20 kW 16 kW 15kW
(18 kW) (14.4 kW) (13.5 kW)
260 244 240
260000 244000 240000
240 212 210
240000 212000 210000
187 163 156
187000 163000 156000
135 125 119
135000 125000 119000
99 99 99
99000 99000 99000
Recommended Energy
Content of Fuel
Heating Value:
BTU per gallon (gross**)
Cubic feet (gas)

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.
• NG is 5-7" W.C.
• LP is 11-14" W.C.
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.
LP Vapor Natural
Gas
91,547
2,500 1,000
21