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10 BRIGGSandSTRATTON.COM
When the initial test runs are completed, the manometer
is removed and the port is plugged. A typical final fuel
connection assembly is shown here, where (A) is the fuel
supply and (B) goes to the home generator.
Fuel Pipe Sizing
The tables below provide the maximum capacity of pipe in
cubic feet of gas per hour for gas pressures of 0.5 psi or
less and a pressure drop of 0.3 in. water column. Specific
gravity of gas is shown.
Listed values compensate for a nominal amount of
restriction from bends, fittings, etc. If an unusual number of
fittings, bends, or other restrictions are used, please refer to
federal and local codes.
Fuel Consumption
Estimated fuel supply requirements at half and full load for
natural gas and LP vapor fuels are shown below.
B
A
Natural Gas LP Vapor
1/2 Load Full Load 1/2 Load Full Load
18kW 160 C 293 C N/A N/A
160,000 B
293,000 B N/A N/A
20kW N/A N/A 70.4 C 141.5 C
N/A N/A 176,825 B 353,650 B
C = Cubic feet per hour
B = BTU’s per hour
NPT 10ft 15ft 20ft 30ft 40ft 50ft 60ft 70ft 80ft 90ft 100ft
3/4” 346 293 240 192 163 145 132 120 113 106 99
1”
653 549 446 360 307 274 250 230 211 197 187
Natural Gas Pipe Size - Gas Flow chart, in cubic feet per hour, specific gravity=0.65
NPT 10ft 15ft 20ft 30ft 40ft 50ft 60ft 70ft 80ft 90ft 100ft
3/4” 277 192 158 126 107 95 87 79 74 69 65
1”
428 360 293 236 202 180 164 151 139 129 123
Liquid Propane (LP) Gas Pipe Size - Gas Flow chart, in cubic feet per hour, specific gravity=1.50
Physical Properties LP Vapor Natural
Gas
Normal Atmospheric State Gas Gas
Boiling Point (in °F):
Initial
End
-44
-44
-259
-259
Heating Value:
BTU per gallon (Net LHV*)
BTU per gallon (gross**)
Cubic feet (gas)
83,340
91,547
2,500
63,310
1,000
Density*** 36.39 57.75
Weight† 4.24 2.65
Octane Number:
Research
Motor
110+
97
110+
* LHV (Low Heat Value) is the more realistic rating.
** Gross heat value does not consider heat lost in the form of water
during combustion.
*** Density is given in “Cubic Feet of Gas per Gallon of Liquid”.
† Weight is given in “Pounds per Gallon of Liquid”.