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 shown on this page.
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
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
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
NOTE: For gas to gas conversion, consult your dealer for
O PREVENT UNRELIABLE OPERATION OR EQUIPMENT DAMAGE
INLET GAS SUPPLY PRESSURE MUST BE AS SPECIFIED ON THE UNIT
RATING PLATE WITH ALL OTHER HOUSEHOLD GAS FIRED APPLIANCES
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
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. 3600 / 46 = 78.
This tells us that in one hour, the furnace would consume
78 cu. ft. of gas.
The typical value range for 1 cu. ft. of natural gas is around
1000 BTU. Check with your gas utility, if possible. In this
example, the furnace is consuming 78,000 BTUH.
NOTE: The final manifold pressure cannot vary by
more than ± 0.3" w.c. for Natural and + 0.5" for
LP from the specified setting. Consult your local
gas supplier if additional input rate adjustment is
4. Turn ON gas to and relight all other appliances turned off
in step 1. Be certain that all appliances are functioning
properly and that all pilot burners are operating.
Temperature rise must be within the range specified on the
unit rating plate. An incorrect temperature rise may result in
condensing in or overheating of the heat exchanger. An airflow
and temperature rise table is provided in the Specification Sheet
applicable to your model. Determine and adjust temperature
rise as follows:
1. Operate furnace with burners firing for approximately
ten minutes. Ensure all registers are open and all
duct dampers are in their final (fully or partially open)
2. Place thermometers in the return and supply ducts
as close to the furnace as possible. Thermometers
must not be influenced by radiant heat by being able
to "see" the heat exchanger.
3. Subtract the return air temperature from the supply
air temperature to determine the air temperature
rise. Allow adequate time for thermometer readings to
4. Adjust temperature rise by adjusting the circulator blower
speed. Increase blower speed to reduce temperature
rise. Decrease blower speed to increase temperature
rise. Refer to Startup Procedure and Adjustment
-Circulator Blower Speeds for speed changing details.
Temperature Rise Measurement