33
10.0
Measuring Inlet Gas Pressure (Alt. Method)
Figure 50
Gas Manifold Pressure Measurement and
Adjustment
Only small variations in gas pressure should be made by
adjusting the gas valve pressure regulator. The manifold
pressure must be measured with the burners operating.
To measure and adjust the manifold pressure, use the
following procedure.
1.
Turn OFF gas to furnace at the manual gas shutoff
valve external to the furnace.
2.
Turn off all electrical power to the system.
3.
Outlet pressure tap connections: White-Rodgers
36J22 valve: Back outlet pressure test screw (outlet
pressure tap) out one turn (counterclockwise, not
more than one turn).
4. Connect calibrated manometer (or appropriate
pressure gauge) at the gas valve outlet pressure tap.
See White-Rodgers 36J22Y-204 gas valve Figure 49
for location of outlet pressure tap.
5. Turn ON the gas supply.
6. Turn on power and close thermostat “R” and “W”
contacts to provide a call for heat.
7. Measure the gas manifold pressure with burners
firing. Adjust manifold pressure using the Manifold
Gas Pressure table 10 shown below.
Gas
Range
Nominal
Natural
2.8 - 3.2" w.c.
3.0" w.c.
Manifold Gas Pressure
Table 10
8. Remove regulator cover screw from the outlet
pressure regulator adjust tower and turn screw
clockwise to increase pressure or counterclockwise to
decrease pressure. Replace regulator cover screw.
9.
Turn off all electrical power and gas supply to the
system.
10. Remove the manometer hose from the hose barb
fitting or outlet pressure tap.
11.
Replace outlet pressure tap: White-Rodgers 36J22
valve: Turn outlet pressure test screw in to seal
pressure port (clockwise, 7 in-lb minimum).
12. Turn on electrical power and gas supply to the
system.
13. Close thermostat contacts “R” and “W” to energize the
valve.
Using a leak detection solution or soap suds, check for
leaks at outlet or screw (White-Rodgers valve). Bubbles
forming indicate a leak. SHUT OFF GAS AND REPAIR ALL
LEAKS IMMEDIATELY!
CAUTION
To prevent unreliable operation or equipment damage, the
inlet gas supply pressure must be as specified on the unit
rating plate with all other household gas fired appliances
operating.
Gas Input Rate Measurement (Natural Gas Only)
The actual gas input rate to the furnace must never be
greater than that specified on the unit rating plate. To
measure natural gas input using the gas meter, use the
following procedure.
1. Turn OFF the gas supply to all other gas-burning
appliances except the furnace.
2.
While the furnace is operating at high fire rate, time
and record one complete revolution of the gas meter
dial, measuring the smallest quantity, usually the dial
that indicates 1/2 cu. ft. per revolution. You will use this
number to calculate the quantity of gas in cubic ft. if
the furnace would consume if it ran steadily for one
hour (3600 seconds).
3.
If the 1/2 cu. ft. dial was used, multiply your number x
2.
EXAMPLE:
If it took 23 seconds to complete one
revolution of the 1/2 ft. dial (23 x 2 = 46).
This tells us that at this rate, it would take 46 seconds to
consume one cu. ft. of gas.
