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A second trial for ignition (step 6) begins if no
fl ame is sensed. On the fi fth try for ignition,
the furnace control is locked out and the
red LED will blink 4 times repetitively. The
thermostat must be opened for at least ten
seconds to reset the furnace control after a
lock out. Otherwise, the furnace will attempt
another ignition sequence in 1 hour.
8. The furnace control energizes the circulating
air blower on the heating speed 30 seconds
after the gas valve circuit is energized .
9. When the thermostat has been satisfi ed,
gas valve is de-energized.
10. The inducer is de-energized after a 30
second postpurge.
11. The furnace control keeps the circulating air
blower energized for 120 seconds (factory
set) or 60, 90, or 180 seconds (fi eld adjust-
able). (See Figure 27.)
12. Abnormal conditions: If a limit opens during
operation, the inducer and circulating air
blower continue to operate. The gas valve
is de-energized immediately. The blowers
continue to operate until the limit closes.
When the limit closes the inducer blower is
de-energized immediately. The circulating
air blower continues to operate for the speci-
fi ed delay (factory set at 120 seconds).
Cooling Mode:
1. On a call for cooling the thermostat closes,
applying 24 VAC to the G and Y terminals
on the furnace control. This closes the
compressor contactor.
2. The furnace control energizes the circulating
blower (115 VAC) on the cooling speed.
3. When the thermostat is satisfi ed, the G and
Y terminals on the control board are de-ener-
gized opening the compressor contactor.
4. The circulating air blower is de-energized
after a 90 second delay.
Fan Mode:
1. On a call for fan operation, the thermostat
applies 24 VAC to the G terminal on the
furnace control board.
2. The circulating air blower is energized im-
mediately on the heating speed.
3. If the furnace is operated in the continuous
ON position at the thermostat and is then
switched to AUTO, the circulating blower will
operate for a specifi ed delay (factory set at
120 seconds).
Furnace Fails to Operate
If the furnace does not operate check the fol-
lowing:
1. Is the thermostat operating properly?
2. Are the blower compartment door(s) in
place?
3. Is the furnace disconnect closed?
4. Has the circuit breaker tripped or the control
board fuse burned open?
5. Is the gas turned on?
6. Are any manual reset switches open?
7. Is the fi lter dirty or plugged?
8. Is the fl ame sensor coated? (Remove and
clean with emery cloth.)
If the furnace locks out after 5 attempts for
ignition, it will try again every hour if a call for
heat remains. If the inducer and circulating air
blowers are operating, and items 1 through 8
have been checked, press the red reset button
on the vent safety switch. (See Figure 30.) If
the furnace operates after depressing the reset
button, contact a qualifi ed serviceman to identify
and repair the problem.
If the furnace continues to not operate, depress
the red reset buttons on the fl ame rollout switches.
(See Figure 30.) If the furnace operates after
depressing the reset buttons, contact a qualifi ed
servicemen to identify and repair the problem.
Twinning of Two Furnaces
The control board on these furnaces is capable
of being twinned to another furnace of the
same series, provided the circuit boards are
both UTEC type. If using UTEC control boards,
leave the fuses installed on each board. The
thermostat wires and the 1/4 inch quick-connect
terminals marked “TWIN” on the furnace controls
must be connected together for twinning. (See
Figure 31.)
W G Y R
Thermostat
A/C
Unit
Twin
Terminal
R
C
Y
G
W
R
C
Y
G
W
Twin
Terminal
Figure 31. Twinning