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ignition is successful the warm-up is
re-
duced by 3-seconds on each subsequent
call for heat until ignition failure occurs.
Upon ignition failure, the warm-up is
in-
creased by 3-seconds on the next try. If
successful, the timing remains fixed at this
level. In general, whenever ignition failure
occurs the warm-up interval is increased
by 3-seconds on the next try. And if suc-
cessful, it remains there. Minimum and
maximum warm-up time limits are set at 6
and 54 seconds, respectively.
7. The furnace control must prove flame via
the flame sensor 5 seconds after the gas
valve opens. If flame is sensed, all burners
are on and the igniter cools off. If no flame
is sensed, the gas valve closes immedi-
ately 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 and the red LED
will blink 4 times repetitively. The thermostat
must be off for at least ten seconds to reset
the furnace control after a lock out. Other-
wise, the furnace will attempt another igni-
tion sequence in 1 hour.
8. The thermostat sends a signal to the inter-
face control to operate the blower at se-
lected speed.
9. When the thermostat controller has been
satisfied, high fire of the gas valve is de-
energized and then operates back at low
fire. Main blower stages to lower speed.
Low fire is satisfied, the low fire will be de-
energized.
10. The inducer is de-energized after a 30
second postpurge.
11. The circulating air blower remains on for
120 seconds.
12. Abnormal conditions: If a limit opens during
operation, the inducer blower continues to
operate. The gas valve is de-energized
immediately. The inducer blower continues
to operate until the limit closes, then is de-
energized.
Cooling Mode:
1. On a call for cooling the thermostat sends
a signal to the interface control to operate
the blower and outdoor unit.
2. The circulation blower will then ramp to the
selected airflow.
3. The system will modulate capacity and
airflow rate to match the load requirements.
If the temperature falls below the set point,
the control will shut the system off.
Fan Mode:
1. On a call for fan operation, the thermostat
sends a continuous on signal to the blower.
2. The circulating air blower ramps to the
programmed airflow rate for the FAN ON
mode.
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 con-
trol board fuse burned open?
5. Is the gas turned on?
6. Are any manual reset switches open?
7. Is the filter dirty or plugged?
8. Is the flame 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.
