![D. ADJUSTING OR CHECKING FURNACE INPUT](/images/new-backgrounds/70961/7096129x1.webp)
FIGURE 14
FIGURE 15
MANIFOLD PIPE
D. ADJUSTING OR CHECKING FURNACE INPUT
–Natural Gas Line Pressure 5″ - 10.5″ W.C.
–LP Gas Line Pressure 11″ - 13″ W.C.
–Natural Gas Manifold Pressure 3.5″ W.C
–LP Gas Manifold Pressure - 10″ W.C.
Supply and manifold pressure taps are located on the gas valve body 1/8″ N.P.T. and on the manifold.
Use a properly calibrated manometer gauge for accurate gas pressure readings.
Only small variations in the gas flow should be made by means of the pressure regulator adjustment. Furnaces functioning on LP gas must be set by means of the tank or branch supply regulators. The furnace manifold pressure should be set at 10″ W.C. at the gas con- trol valve.
To adjust the pressure regulator, remove the regulator cap and turn the adjustment screw clockwise to increase pressure or counterclockwise to decrease pressure. Then replace
the regulator cap securely.
Any necessary major changes in the gas flow rate should be made by changing the size of the burner orifices. To change orifice spuds, shut off the manual main gas valve and remove the gas manifold.
For elevations up to 2,000 feet, rating plate input ratings apply. For high altitudes (elevations over 2,000 ft.), see conversion kit index
Check of input is important to prevent
Cu. Ft. Per Hr. Required =
Heating Value of Gas (BTU/Cu. Ft.) x 3600
Time in Seconds (for 1 Cu. Ft.) of Gas
Start the furnace and measure the time required to burn one cubic foot of gas. Prior to checking the furnace input, make certain that all other gas appliances are shut off, with the exception of pilot burners. Time the meter with only the furnace in operation.
IMPORTANT NOTE FOR ALTITUDES ABOVE 2,000 FEET (610 METERS): The main burner orifices in your furnace and in these kits are sized for the nameplate input and intended for installations at elevations up to 2,000 feet in the USA or Canada, or for ele- vations of 2,000 - 4,500 feet (610
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