34
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!
NOTE:
For gas to gas conversion, consult your dealer for appropriate conversion.
G
AS
I
NPUT
R
ATE
M
EASUREMENT
(N
ATURAL
G
AS
O
NLY
)
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. 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 required.
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.
T
EMPERATURE
R
ISE
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) position.
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 stabilize.
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.
SUPPLY
AIR
RETURN
AIR
Temperature Rise Measurement
Figure 40
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