Fuel Consumption
Estimated fuel supply requirements at half and full load for natural gas and LP vapor fuels are shown below.
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18kW | 160 C | 293 C | N/A | N/A |
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| 160,000 B | 293,000 B | N/A | N/A |
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20kW | N/A | N/A | 70.4 C | 141.5 | C |
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| N/A | N/A | 176,825 B | 353,650 B | |
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C = Cubic feet per hour
B = BTU’s per hour
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.
Physical Properties | LP Vapor | Natural |
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Normal Atmospheric State | Gas | Gas |
Boiling Point (in °F): |
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Initial | ||
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Heating Value: | 83,340 | 63,310 |
BTU per gallon (Net LHV*) | ||
BTU per gallon (gross**) | 91,547 |
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Cubic feet (gas) | 2,500 | 1,000 |
Density*** | 36.39 | 57.75 |
Weight† | 4.24 | 2.65 |
Octane Number: |
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Research | 110+ | 110+ |
Motor | 97 |
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* 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”.
NPT | 10ft | 15ft | 20ft | 30ft | 40ft | 50ft | 60ft | 70ft | 80ft | 90ft | 100ft |
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3/4” | 346 | 293 | 240 | 192 | 163 | 145 | 132 | 120 | 113 | 106 | 99 |
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1” | 653 | 549 | 446 | 360 | 307 | 274 | 250 | 230 | 211 | 197 | 187 |
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Natural Gas Pipe Size - Gas Flow chart, in cubic feet per hour, specific gravity=0.65 |
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NPT | 10ft | 15ft | 20ft | 30ft | 40ft | 50ft | 60ft | 70ft | 80ft | 90ft | 100ft |
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3/4” | 277 | 192 | 158 | 126 | 107 | 95 | 87 | 79 | 74 | 69 | 65 |
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1” | 428 | 360 | 293 | 236 | 202 | 180 | 164 | 151 | 139 | 129 | 123 |
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Liquid Propane (LP) Gas Pipe Size - Gas Flow chart, in cubic feet per hour, specific gravity=1.50
Required Propane Tank Size
The required size of the propane tank at various temperatures when kept at least half full is shown below in the chart. Given the gas withdrawal rate and the lowest average winter temperature, an installer can specify the required LP storage tank size.
Withdrawal Rate | 32° F | 20° F | 10° F | 0° F |
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50 CFH | 115 | 115 | 115 | 250 | 250 | 400 | 600 |
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100 CFH | 250 | 250 | 250 | 400 | 500 | 1000 | 1500 |
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150 CFH | 300 | 400 | 500 | 500 | 1000 | 1500 | 2500 |
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200 CFH | 400 | 500 | 750 | 1000 | 1200 | 2000 | 2500 |
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300 CFH | 750 | 1000 | 1500 | 2000 | 2500 | 4000 | 5000 |
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12 | BRIGGSandSTRATTON.COM |
