Troubleshooting Flowchart - A.O. Smith 12 40GPC T 100 Service Handbook

TROUBLESHOOTING FLOWCHART

APPLY POWER TO
APPLIANCE
NO
REQUEST
FOR HEAT
PRESENT?
YES
IS WAIT FOR PRESSURE
NO
SWITCH TO OPEN
PRESSURE SWITCH
DISPLAY ERROR
PROVEN OPEN WITHIN
5
NUMBER
SECONDS?
YES
COMBUSTION
FAN ON
IS
WAIT FOR PRESSURE
NO
PRESSURE SWITCH
SWITCH TO CLOSE
PROVEN CLOSED
DISPLAY ERROR
11
WITHIN
NUMBER
SECONDS?
YES
PREPURGE
COMBUSTION FAN
OFF
TURN OFF
NO
IS
COMBUSTION FAN,
IGNITOR
DISPLAY ERROR CODE
OKAY?
NUMBER
YES
IGNITOR ON FOR
WARM-UP TIME
GAS VALVE OPENS
COMBUSTION FAN
ON
MAIN
BURNER LIGHTS NO
AND IS SENSED
GAS VALVE CLOSES
DURING TRIAL
FOR
IGNITION
YES
IGNITOR TURNS OFF
YES
IS
FLAME SENSE GAS VALVE CLOSES
LOST?
NO
IS
NO WAIT FOR PRESSURE
PRESSURE SWITCH
SWITCH TO CLOSE
PROVEN CLOSED
DISPLAY ERROR
5
WITHIN
SECONDS?
YES
YES
IS
REQUEST FOR HEAT GAS VALVE OFF
NO
SATISFIED?
7
6
8
YES
LESS
3
THAN TRIES
FOR IGNITION?
NO
LOST
4
LESS THAN
TIMES?
NO
6
NUMBER
COMBUSTION FAN
OFF AFTER POST-
PURGE DELAY
23
IS NO WAIT FOR PRESSURE
PRESSURE SWITCH SWITCH TO OPEN
PROVEN OPEN WITHIN DISPLAY ERROR
5
SECONDS? NUMBER
YES
NO
WAIT FOR PRESSURE
SWITCH TO CLOSE
DISPLAY ERROR
6
NUMBER
INTERPURGE
YES
Please Note:
The control continually monitors
internal circuits and extern al sensors.
Error codes noted above, and those for
self-diagnostic faults can be found on
pages 20 through 22.
3 MINUTE
AUTOMATIC RESET
TIME DELAY
7
ONE HOUR
AUTOMATIC RESTART
TIME DELAY
TURN OFF
COMBUSTION FAN
AFTER POST-PURGE
COMBUSTION
FAN OFF
DISPLAY ERROR
YES
IS
PRESSURE SWITCH
PROVEN CLOSED
5
WITHIN
SECONDS?
3