Troubleshooting: Heating Sequence of Operation (Continued)
HEATING SEQUENCE OF OPERATION
CONTINUED
THERMOSTAT CALLS FOR HEAT.
STATUS LED −− HEARTBEAT.
SEE BOX A.
FLAME SIGNAL ABOVE
(u1.40 microamps)
YES
YES
SINGLE−STAGE THERMOSTAT MODE (DIP SWITCH SET AT
YES 
START SECOND−STAGE RECOGNITION ON DELAY (10 OR 15 MINUTES).
STATUS LED −− HEARTBEAT
ROLLOUT SWITCHES CLOSED?
YES 
FIRST−STAGE (LOW FIRE)
PRESSURE SWITCH CLOSED?
NO
LOW FLAME SIGNAL
(Does not affect control operation) STATUS ERROR CODE 1 + 2.
TWO STAGE THERMOSTAT MODE (DIP SWITCH SET AT
YES
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| 45−SECOND INDOOR BLOWER ON DELAY BEGINS. |
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| STATUS LED −− HEARTBEAT. |
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| YES |
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YES |
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| NO | ||||
PRIMARY & SECONDARY LIMIT SWITCHES | ||||||||
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| CLOSED? |
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NO |
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| GAS VALVE OFF. COMBUSTION AIR INDUCER ON. |
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| INDOOR BLOWER ON. |
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| YES | STATUS ERROR CODE 5 + 1. SEQUENCE HOLDS |
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| UNTIL ROLLOUT SWITCH IS RESET AND MAIN |
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| POWER IS INTERRUPTED OR THERMOSTAT |
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| IS CYCLED OFF/ON FOR 3 SECOND MINIMUM. |
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YES
NO
NO
FIRST−STAGE HEAT DEMAND SATISFIED?
YES
GAS VALVE OFF, COMBUSTION AIR INDUCER
OFF FOLLOWING POST PURGE.
INDOOR BLOWER OFF WITH DELAY
STATUS LED −− PULSE
SECOND−STAGE HEAT DEMAND.
SECOND−STAGE HEAT DEMAND REQUIRED?
YES
SECOND STAGE PRESSURE SWITCH CLOSED?
ABNORMAL FLASH CODE.
NOTE − IF SECOND−STAGE PRESSURE SWITCH
WAS ORIGINALLY FOUND CLOSED,
ABNORMAL CODE WILL FLASH.
NO | YES |
SECOND−STAGE 30−SECOND DELAY ON BEGINS.
STATUS LED −− HEARTBEAT.
YES 
SECOND−STAGE COMBUSTION AIR INDUCER ON. SECOND−STAGE GAS VALVE ON. HIGH HEAT INDOOR BLOWER SPEED ON. STATUS LED −− HEARTBEAT.
YES 
SECOND−STAGE PRESSURE SWITCH CLOSED
IN LESS THAN TEN (10) SECONDS?
STATUS LED −− HEARTBEAT
YES
CONTINUED ON NEXT PAGE
GAS VALVE OFF, COMBUSTION AIR INDUCER OFF, |
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INDOOR BLOWER ON. |
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STATUS ERROR CODE 3 + 1. |
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HAS PRIMARY OR SECONDARY LIMIT | |||
SWITCH CLOSED WITHIN 3 MINUTES? |
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(Indoor blower on low speed during 3−minute period) |
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NO |
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LIMIT SWITCH WATCHGUARD MODE. |
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GAS VALVE OFF, COMBUSTION AIR INDUCER OFF, |
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INDOOR BLOWER OFF WITH DELAY. | YES | ||
STATUS ERROR CODE 4 + 5 | |||
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IS 60−MINUTE RESET PERIOD COMPLETE? |
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GAS VALVE OFF. COMBUSTION AIR INDUCER ON. INDOOR BLOWER OFF AFTER DELAY.
STATUS ERROR CODE 2 + 3. CONTROL RESTARTS YES IGNITION SEQUENCE IF PRESSURE SWITCH
CLOSES WITHIN 2−1/2 MINUTES.
| SECOND−STAGE PRESSURE SWITCH CLOSED | NO | |
| AT BEGINNING OF HEAT DEMAND? | ||
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| STATUS ERROR CODE 2 + 6. |
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| SECOND STAGE HEAT DEMAND |
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| STATUS LED −− HEARTBEAT. |
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| NO |
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| RETURNS TO FIRST−STAGE HEAT MODE WHICH |
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| CONTINUES UNTIL SECOND−STAGE PRESSURE |
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| SWITCH CAN BE PROVEN or HEAT DEMAND IS |
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| SATISFIED. FIVE (5) MINUTE WAIT PERIOD |
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NO | INITIATED BEFORE RETRY. WERE 5 ATTEMPTS |
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MADE FOR SECOND−STAGE HEAT? |
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| YES |
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| CONTINUES FIRST−STAGE HEATING DEMAND. |
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| WILL NOT REATTEMPT SECOND−STAGE |
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| HEATING DEMAND. |
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| STATUS ERROR CODE 2 + 5. |
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