41
perature limit switch, flame rollout switches
and blocked vent switch in series). If an
open limit is detected the control board will
energize the inducer blower. All other sys-
tem 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 pres-
sure switch does not close after 10 sec-
onds the fault LED will blink 2 times repeti-
tively 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
programmed adaptive ignition feature which
varies the warm-up period as follows: If
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 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 circulat-
ing air blower at a very low speed. After 30
seconds, the blower will ramp to the airflow
selected for heating.
9. When the thermostat has been satisfied,
gas valve is 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 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 circulat-
ing blower to 1/3 of the selected airflow for
approximately 30 seconds.
3. The circulating blower will then ramp to
approximately 3/4 of the selected airflow for
another 30 seconds before adjusting to full
airflow until the thermostat is satisfied.
4. When the thermostat is satisfied, the G and
Y terminals on the control board are de-
energized opening the compressor
contactor.
5. The circulating air blower will operate at
1/2 of the selected speed for 60 seconds,
and de-energize.
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 ramps to 1/2 of the
selected airflow.
Summary of Contents for TC060
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