Rheem RESIDENTIAL GENERATOR SYSTEM GEN12S - Manual (Page 13)

11
Fuel Comparison Chart
The fuel comparison chart shown below is provided for your
reference.
Size of Propane Tank Required at Various
Temperatures When Kept at Least Half Full
Given the gas withdrawal rate and the lowest average winter
temperature, an installer can specify the required LP storage
tank size. The table below provides guidance on tank size
selection.
Required Propane Tank Size (Lowest Average Winter Temperature), in Gallons
Fuel Comparison Chart
Withdrawal Rate 32°F 20°F 10°F 0°F -10°F -30°F -40°F
50 CFH 115 115 115 250 250 400 600
100 CFH 250 250 250 400 500 1000 1500
150 CFH 300 400 500 500 1000 1500 2500
200 CFH 400 500 750 1000 1200 2000 2500
300 CFH 750 1000 1500 2000 2500 4000 5000
Physical Properties Propane Natural Gas
Normal Atmospheric State Gas Gas
Boiling Point (in °F):
Initial -44 -259
End -44 -259
Heating Value:
BTU per gallon (Net LHV*) 83,340 63,310
BTU per Gallon (Gross**) 91,547
Cubic Feet (Gas) 2,500 1,000
Density*** 36.39 57.75
Weight† 4.24 2.65
Octane Number:
Research 110+ 110+
Motor 97
*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".