38
of a vacuum cleaner.
BE EXTREMELY CARE-
FUL NOT TO DAMAGE THE IGNITER
WHILE CLEANING THE BURNER.
17. Replace all the parts in reverse order from
which they were removed.
18. Follow the lighting instructions found on the
furnace door to return the furnace to operation.
Verify proper operation after servicing.
Cleaning of Burners
If the burners must be cleaned, follow the steps
below. See Figure 36 for component location and
identification.
1. Shut off the gas supply to the furnace either at
the meter or at a manual valve in the supply
piping.
2. Turn off all power to the furnace and set the
thermostat to the lowest temperature setting.
3. Remove the upper louvered door from the
furnace.
4. Turn the gas control lever to the OFF position.
5. Disconnect the wires from the gas valve,
igniter, and flame sensor.
6. Using wrenches, separate the ground-joint
union in the gas supply piping at the furnace.
7. Remove the piping between the gas valve and
the ground-joint union, if necessary.
8. Remove the screws that hold the burner as-
sembly in place and remove the burner assem-
bly.
BE EXTREMELY CAREFUL NOT TO
DAMAGE THE IGNITER WHILE REMOV-
ING THE BURNER ASSEMBLY.
9. Inspect the burners and clean them (if neces-
sary) with a soft wire brush and/or the nozzle
of a vacuum cleaner.
BE EXTREMELY CARE-
FUL NOT TO DAMAGE THE IGNITER
WHILE CLEANING THE BURNER.
10. Replace all the parts in reverse order from
which they were removed.
11. Follow the lighting instructions found on the
furnace door to return the furnace to operation.
Verify proper operation after servicing.
SYSTEM OPERATION INFORMATION
General
Proper maintenance is most important to achieve
the best performance from a furnace. Follow these
instructions for years of safe, trouble free operation.
1. Do not place combustible materials on or against
the furnace cabinet or within 6 inches of the vent
pipe.
2. Do not store gasoline or any other flammable
vapors and liquids in the vicinity of the furnace.
3. Change or replace the air filters monthly during
any period when the circulating blower is oper-
ating regularly.
4. Always replace the doors on the furnace after
servicing or cleaning/changing the filters. Do
not operate the furnace without all doors and
covers in place.
5. Avoid operating the furnace when windows and
doors are open.
6.
Be sure that the thermostat is properly
installed and is not being affected by drafts
or heat from lamps or other appliances.
Sequence of Operation
The operating sequences for the heating, cooling,
and fan modes are described below. Refer to the
field and furnace wiring diagrams; Figures 26, 27,
28, 29, 30, 31, 32, 33, 34 and 35.
Heating Mode:
1. On a call for heat the thermostat closes, apply-
ing 24 VAC to the W terminal on the control
board.
2. The control board checks for continuity on the
24 VAC limit control circuit (over-temperature
limit switch, flame rollout switches and blocked
vent switch in series). If an open limit is detected
the control board will energize the inducer and
the conditioned air blower. All other system
functions will be inoperable until the limit circuit
closes. While the limit is open, the red LED will
pulse at a rate of 1 blink per unit time.
3. The furnace control checks for continuity across
the pressure switch (24 VAC). If the pressure
switch is closed the heat mode sequence will
not continue. If it remains closed for 10 seconds
the red LED will blink 3 times repetitively until the
fault condition clears.
4. The inducer is energized.
5. The pressure switch will close. If the pressure
switch does not close after 10 seconds the fault
LED will blink 2 times repetitively and the inducer
will continue to run until the switch is closed.
6. The inducer will pre-purge for 30 seconds and
then the igniter will start its warm-up as follows:
Initial Power up: After 30 seconds of igniter
warm-up the gas valve (24 VAC) will then open.
The igniter circuit will stay energized for 3
seconds after the gas valve opens.
After Initial Power up: The control has a pro-
grammed adaptive ignition feature which varies
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