18 G6RA, G6RK Service Manual
7. The furnace control must prove flame via the flame
sensor six seconds after the gas valve opens. If flame
is sensed, all burners are on and the ignitor cools off. If
no flame is sensed, the gas valve closes immediately
and the inducer continues to run. A second trial for
ignition (step 6) begins if no flame is sensed. On the fifth
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 satisfied, gas valve is de-
energized.
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 immediately 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 specified delay
(factory set at 120 seconds).
Furnace Fails to Operate
If the furnace does not operate check the following:
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 there any manual reset switches open?
7. Is the filter dirty or plugged?
8. Is the flame sensor coated? (Remove and clean with
steel wool.)
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 19.) If the furnace operates after
depressing the reset button, contact a qualified serviceman
to identify and repair the problem.
If the furnace continues to not operate, depress the red reset
button on the flame roll out switches. (See Figure 19.) If the
furnace operates after depressing the reset buttons, contact
a qualified serviceman to identify and repair the problem.
Twinning of Two Furnaces
The control board on a G6 series furnace is capable of being
twinned to another G6 furnace. The thermostat wires and the
3/16 inch quick-connect terminals marked "TWIN" on the
furnace controls must be connected together for twinning.
(See Figure 18.)
NOTE: Components are listed in order of sequence
of operation.
10. The inducer is de-energized after a 30 second post
purge.
11. The furnace control keeps the circulating air blower
energized for 120 second (factory set) or 60, 90, or 180
seconds (field adjustable). (See Figure 21.)
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 induced draft motor will run through post
purge. The circulating air blower continues to operate for
the specified 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 satisfied, the G and Y terminals
on the control board are de-energized opening the
compressor contactor.
4. The circulating air blower is de-energized after a 90
second delay.
CAUTION:
!
Label all wires prior to disconnection when
servicing controls. Wiring errors can cause
improper and dangerous operation.
Verify proper operation after servicing.
CAUTION:
!
Do not use matches, lighters, candles or other
sources of open flame to check for gas leaks.
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