20
18-CD21D1-12
Installer’s Guide
When the thermostat is satisfied, R and W thermostat
contacts open, the gas valve will close, the flames will
extinguish, and the induced draft blower will be de-en-
ergized. The indoor blower motor will continue to run
for the fan off period (fixed at 100 seconds), then will
be de-energized by the control module.
▲
WARNING
!
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could re-
sult in serious injury, death or property damage. Never
test for gas leaks with an open flame. Use a commer-
cially available soap solution made specifically for the
detection of leaks to check all connections. A fire or ex-
plosion may result causing property damage, personal
injury, or loss of life.
START-UP AND ADJUSTMENT
PRELIMINARY INSPECTIONS
With gas and electrical power “OFF”
1. Duct connections are properly sealed
2. Filters are in place
3. Venting is properly assembled
4. Blower door is in place
Turn knob on main gas valve within the unit to the
“
OFF
” position. Turn the external gas valve to “ON”.
Purge the air from the gas lines. After purging, check
all gas connections for leaks with a soapy solution –
DO NOT CHECK WITH AN OPEN FLAME.
Allow
5 minutes for any gas that might have escaped to dis-
sipate. LP Gas, being heavier than air, may require
forced ventilation. Turn the knob on the gas valve in
the unit to the “ON” position.
COMBUSTION AND INPUT CHECK
1. Make sure all gas appliances are off except the fur-
nace.
2. Clock the gas meter with the furnace operating
(determine the dial rating of the meter) for one
revolution.
3. Match the “Sec” column in the gas flow (in cfh) Ta-
ble 13 with the time clocked.
4. Read the “Flow” column opposite the number of
seconds clocked.
5. Use the following factors if necessary:
For 1 Cu. Ft. Dial Gas Flow CFH =
Chart Flow Reading ÷ 2
For 1/2 Cu. Ft. Dial Gas Flow CFH =
Chart Flow Reading ÷ 4
For 5 Cu. Ft. Dial Gas Flow CFH =
10X Chart Flow Reading ÷ 4
6. Multiply the final figure by the heating value of
the gas obtained from the utility company and
compare to the nameplate rating. This must not
exceed the nameplate rating.
Gas Valve Adjustment
Changes can be made by adjusting the manifold pres-
sure (See Table 12), or changing orifices (orifice
change may not always be required). To adjust the
manifold pressure:
1. Turn off all electrical power to the system.
2. Attach a manifold pressure gauge with flexible
tubing to the outlet pressure boss marked “OUT
P” on White-Rodgers gas valve model 36G or 36J.
See Figure 26 for White-Rodgers gas valve model
36J. See Figure 25 for White-Rodgers gas valve
model 36G.
3. Loosen (Do Not remove) the pressure tap test set
screw one turn with 3/32" hex wrench.
a. The pressure tap adjustment kit (KIT07611)
contains a 3/32" hex wrence, a 5/16" hose and
a connector and can be ordered through Global
Parts.
4. Turn on system power and energize valve.
5. Adjust gas heat by removing the adjustment regu-
lator cover screw.
a. To increase outlet pressure, turn the regulator
adjust screw clockwise.
b. To decrease outlet pressure, turn the regulator
adjust screw counterclockwise.
c. Adjust regulator until pressure shown on mano-
meter matches the pressure specified in Table
12.
1. The input of no more than nameplate rating
and no less than 93% of the nameplate rating,
unless the unit is derated for high altitude.
d. Replace and tighten the regulator cover screw
securely.
6. Cycle the valve several times to verify regulator
setting.
a. Repeat steps 5-6 if needed.
7. Turn off all electrical power to the system.
8. Remove the manometer and flexible tubing and
tighten the pressure tap screw.
As the induced draft blower comes up to speed, the
pressure switch contacts will close and the ignitor
warm up period will begin. The ignitor will heat for
approx. 20 seconds, then the gas valve is energized to
permit gas flow to the burners. The flame sensor con-
firms that ignition has been achieved within the 6 sec-
ond ignition trial period.
After the flame sensor confirms that ignition has been
achieved, the delay fan ON period (fixed at 45 seconds)
begins timing. After the delay of 45 seconds, the in-
door blower motor will be energized and will continue
to run during the heating cycle.
