With Power and Gas On:
2. Put furnace into heating cycle and turn on all other gas
consuming appliances.
Inlet Gas Pressure
Natural
Min. 5.0" W.C., Max. 10.0" W.C.
Propane
Min. 11.0" W.C., Max. 13.0" W.C.
Figure 34
Inlet Gas Pressure
Note: Inlet Gas Pressure Must Not Exceed the Maximum
Value Shown.
If operating pressures differ from above, make necessary
pressure regulator adjustments, check piping size, etc.,
and/or consult with local utility.
Gas Line
Gas Shutoff Valve
Gas Line
To Furnace
Open To
Atmosphere
Drip Leg Cap
With Fitting
Manometer Hose
Manometer
Figure 35
Measuring Inlet Gas Pressure
(Alternate Method)
Gas Manifold Pressure Measurement and Adjustment
NOTE: The gas manifold pressure must be measured with
the burners operating.
Connect a “U-Tube” manometer having a scale range from
0 to 12 inches of water to the tapped opening in the gas
valve. See “Outlet (Manifold) Pressure Tap” in Figure 33.
Check your measurements. For natural gas, the manifold
pressure must between 3.0 and 3.6 inches water column
(3.5 nominal). The low stage manifold pressure must be
between 1.6 and 2.2 inches water column (1.9 nominal).
For propane gas, it must be between 9.7 and 10.3 inches
water column (10.0 nominal).
The low stage manifold
pressure must be between 5.7 and 6.3 inches water column
(6.0 nominal). Any major changes in flow should be made
by changing the size of the burner orifice.
If pressure adjustments are necessary, make them in small
variations. To adjust, use the pressure regulator. Remove
the adjustment screw or cover on the gas valve. Using a
3/32” Allen wrench, turn out (counterclockwise) to de-
crease pressure, turn in (clockwise) to increase pressure.
Page 22