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NOTE: Turning the screw clockwise increases the pressure
and turning the screw counter-clockwise decreases the
pressure. To prevent backing the screw all the way out from
the valve, turn the screw slowly.
4. Replace and tighten the regulator capscrew over the
adjustment screw.
Verifying Over-Temperature Limit Control
Operation
1. Verify the louvered control access panel is in place and that
there is power to the unit.
2. Block the return airflow to the unit by installing a close-off
plate in place of or upstream of the filter.
3. Set the thermostat above room temperature and verify the
units operating sequence on
NOTE: The over-temperature limit control should turn off
the gas valve within approximately four minutes (exact time
depends on the efficiency of the close-off when blocking the
return air). The circulating air and combustion blowers should
continue to run when the over-temperature limit control switch
opens.
4. Remove the close-off plate immediately after the over-
temperature limit control opens. If the unit operates for more
than four minutes with no return air, set the thermostat below
room temperature, shut off power to the unit, and replace
the over-temperature limit control.
Verifying Burner Operation
WARNING:
Uninsulated live components are exposed when
louvered control access panel is removed.
1. Remove the louvered control access panel and verify there
is power to the unit.
2. Set thermostat above room temperature and observe the
ignition sequence. NOTE: The burner flame should carry
over immediately between all burners without lifting off,
curling, or floating. The flames should be blue, without
yellow tips. Make sure the flame is drawn into the center
of the heat exchanger tube. In a properly adjusted burner
assembly, the flame bends down and to the right at the end
of the heat exchanger tube. The end of the flame will be
out of sight around the bend.
3. After validating flame characteristics, set the thermostat
below room temperature and verify the burner flame
extinguishes completely.
page
17.
OPERATING SEQUENCE
The operating sequences for the heating, cooling, and fan
modes are described below. Refer to the field and unit wiring
diagram. See
Figure 11 (page
Heating Mode
1. On a call for heat, the thermostat closes and applies 24
VAC to the W terminal of the control board.
2. The control board checks for continuity on the 24 VAC limit
control circuit through the over-temperature limit switch and
flame rollout switch in series. If an open limit is detected,
the control board will energize the inducer 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 (24 VAC) across
the pressure switch. If the pressure switch is closed, the
heat mode sequence will not continue. If it remains closed
for 10 seconds, the red LED will flash 3 times repetitively
until the fault condition clears.
4. The inducer energizes (if pressure switch is open).
5. The pressure switch will close. If the pressure switch does
not close after 10 seconds, the fault LED will flash 2 times
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 valves (24 VAC) will 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 reduced
by 3 seconds on each subsequent call for heat until
ignition failure occurs. Upon ignition failure, the warm-up
is increased 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 successful, it remains
there. Minimum and maximum warm-up time limits are set
at 6 and 54 seconds.
7. The furnace control must prove flame via the flame sensor
5 seconds after the gas valves open. If flame is sensed,
burners are on and the igniter 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 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. After the gas valve opens (30 seconds), the blower will
ramp to the selected airflow and continues to run.
9. When the thermostat has been satisfied, the W terminal on
the integrated control is de-energized.
10. The gas valve circuit is de-energized and the gas valve
closes.
11. The inducer motor will continue to run for the post purge
period of 25 seconds.
12. The main blower will continue to run for the BLOWER OFF
delay of 90 - 135 seconds.
26).
17
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