Goodman APG 13 Service Instructions Manual page 22

SYSTEM OPERATION
IGNITION CONTROL SEQUENCE OF OPERATION
A. Heating Operation: Low stage heat
1. Thermostat type is set to two-stage.
2. Thermostat "W1" input initiates low stage heating.
3. Induced draft blower is energized at high speed for the
pre-purge period. Pre-purge timer begins after control
recognizes pressure switch has closed.
4. Trial-for-ignition period begins after pre-purge period
expires. Low and high stage gas valves are energized
along with the igniter for trial-for-ignition period. Igniter
is de-energized when flame is detected.
5. Flame is achieved and detected during trial-for-ignition
period. Flame stabilization period begins when flame
is detected.
6. De-energize high stage gas valve and switch induced
draft blower to low speed within five seconds of flame
detection.
7. Air circulating blower is energized at low heat speed
after heat ON delay time expires. Heat ON delay timer
begins when flame is detected.
8. Control monitors thermostat, flame, limit, and pres-
sure switch inputs during low stage heating.
9. Thermostat "W1" input is removed.
10. Low stage gas valve is de-energized.
11. Induced draft blower remains energized at low speed
for post purge period.
12. Air circulating blower remains energized at low heat
speed for heat OFF delay. Heat OFF delay begins
when "W1" input is removed.
13. Control returns to Standby and awaits next thermostat
request.
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B. Heating Operation: High stage heat
1. Thermostat type is set to two-stage.
2. Thermostat "W1" and "W2" inputs initiate high stage
heating.
3. Induced draft blower is energized at high speed for the
pre-purge period. Pre-purge timer begins after control
recognizes pressure switch has closed.
4. Trial-for-ignition period begins after pre-purge period
expires. Low and high stage gas valves are energized
along with the igniter for trial-for-ignition period. Igniter
is de-energized when flame is detected.
5. Flame is achieved and detected during trial-for-ignition
period. Flame stabilization period begins when flame
is detected.
6. Gas valve and induced draft blower remain at high
stage and high speed.
7. Air circulating blower is energized at high heat speed
after heat ON delay time expires. Heat ON delay timer
begins when flame is detected.
8. Control monitors thermostat, flame, limit, and pres-
sure switch inputs during high stage heating.
9. Thermostat "W1" and "W2" inputs are removed.
10. High and low stage gas valves are de-energized.
11. Induced draft blower switches from high speed to low
speed and remains energized for post purge period.
12. Air circulating blower remains energized at high heat
speed for High Stage Heat OFF Delay period then
switches to low heat speed for the remainder of the
selected heat OFF delay. Heat OFF delay begins
when "W1" and "W2" inputs are removed.
13. Control returns to Standby and awaits next thermostat
request.
A/GPG15