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LDAP-IOM (01-22) 207733-A
12 . If flame is extinguished during main burner operation, integrated control system closes main valve and must be
reset by interrupting power to control circuit (refer to lighting instructions provided with heater) .
13 . TO TURN OFF GAS TO APPLIANCE:
a . Set thermostat to lowest setting .
b . If service is to be performed, turn OFF all electric power to appliance .
c . Open the access door .
d . Turn gas control knob(s) clockwise to OFF (do not force) .
e . Close access door .
Operating Sequences
describes the heater’s normal operating sequence .
describes the heater’s abnormal heat cycle
functions .
describes the heater’s fault modes . Refer to
for circuit board LED indications .
Table 14. Operating Sequence (Normal Heat Cycle)
Step
Condition
Action
1 . Call for
heat
Terminal W is energized
Thermostat calls for heat by energizing terminal W
Control determines whether limit switch is open or closed and if heat section and flue
collection box section (unit sizes 800 and 1200) pressure switches are open
Auto-reset or manual-reset high
temperature limit switch is open
Control proceeds as specified in
: abnormal function
Limit Switch Operation
Heat section or flue collection box
section pressure switch is closed
Green LED on circuit board flashes four times
Control waits indefinitely for pressure switches to open
Pressure switches are open
Control proceeds to step 2
2 . Prepurge
Heat section and main venter
motors are energized
Control waits for heat section and flue collection box section (unit sizes 800 and 1200)
pressure switches to close
Either pressure switch not closed
within 30 seconds of venter motors
energizing
Green LED on circuit board flashes two times
Control maintains venter motor(s) energized indefinitely as long as call for heat remains
and either pressure switch is open
Pressure switch(s) proven closed
Control begins prepurge
Flame is present at any time during
prepurge
Prepurge is restarted
Flame is present long enough to
cause lockout
If flame is sensed longer than 20 seconds while gas valve is de-energized, control
energizes heat section venter motor, main venter motor, and fan motor on heat speed
When flame is no longer sensed, venter motors run through post-purge and fan motor
runs through selected delay OFF time
Control proceeds to soft lockout but still responds to open limit and flame
Yellow LED on circuit board flashes rapidly when lockout is due to undesired flame
Venter motors runs for 20-second
prepurge time
Control proceeds to step 3
3 . Ignition
trial period
Spark and main gas valve are
energized
The venter remains energized
Flame is sensed during first 16
seconds
Control de-energizes spark and proceeds to heat fan ON delay
Flame is not sensed during first 16
seconds
Control de-energizes spark and maintains gas valve energized for additional 1-second
flame-proving period
Flame is not present after flame-
proving period
Control de-energizes gas valve and proceeds with ignition retries as specified in
: abnormal function
Ignition Retry
Flame is present after flame-proving
period
Control proceeds to step 4
4 . Fan ON
delay
30 seconds after gas valve has
opened
Control energizes fan motor
Gas valve and venter motors remain
energized
Control proceeds to step 5
5 . Steady
heat
High temperature limit switches are
closed
Control continuously monitors inputs
Pressure switches are closed
Flame is established
Thermostat call for heat remains
Thermostat call for heat is removed
Control de-energizes gas valve and proceeds to steps 6 and 7
6 . Post-purge
Thermostat is satisfied
Venter motor remains on for 45-second post-purge period
7 . Fan OFF
delay
Fan motor is de-energized after selected fan OFF delay
