Lennox G60UH Service Manual page 42

CONTINUED
FLAME SIGNAL ABOVE
(u1.40 microamps)
YES
SINGLE−STAGE THERMOSTAT MODE
(DIP SWITCH SET AT SINGLE")
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?
YES
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
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
HEATING SEQUENCE OF OPERATION
NO
YES
TWO STAGE THERMOSTAT MODE
(DIP SWITCH SET AT TWO")
YES
45−SECOND INDOOR BLOWER ON DELAY BEGINS.
YES
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
STATUS ERROR CODE 5 + 1. SEQUENCE HOLDS
YES
UNTIL ROLLOUT SWITCH IS RESET AND MAIN
IS CYCLED OFF/ON FOR 3 SECOND MINIMUM.
NO
GAS VALVE OFF, COMBUSTION AIR INDUCER OFF,
(Indoor blower on low speed during 3−minute period)
GAS VALVE OFF, COMBUSTION AIR INDUCER OFF,
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
STATUS ERROR CODE 2 + 3. CONTROL RESTARTS
YES
SECOND−STAGE PRESSURE SWITCH CLOSED
RETURNS TO FIRST−STAGE HEAT MODE WHICH
CONTINUES UNTIL SECOND−STAGE PRESSURE
SWITCH CAN BE PROVEN or HEAT DEMAND IS
INITIATED BEFORE RETRY. WERE 5 ATTEMPTS
NO
CONTINUES FIRST−STAGE HEATING DEMAND.
Page 42
THERMOSTAT CALLS FOR HEAT.
STATUS LED −− HEARTBEAT.
SEE BOX A.
LOW FLAME SIGNAL
(Does not affect control operation)
STATUS ERROR CODE 1 + 2.
STATUS LED −− HEARTBEAT.
YES
PRIMARY & SECONDARY LIMIT SWITCHES
CLOSED?
INDOOR BLOWER ON.
POWER IS INTERRUPTED OR THERMOSTAT
INDOOR BLOWER ON.
STATUS ERROR CODE 3 + 1.
HAS PRIMARY OR SECONDARY LIMIT
SWITCH CLOSED WITHIN 3 MINUTES?
NO
LIMIT SWITCH WATCHGUARD MODE.
INDOOR BLOWER OFF WITH DELAY.
STATUS ERROR CODE 4 + 5
IS 60−MINUTE RESET PERIOD COMPLETE?
INDOOR BLOWER OFF AFTER DELAY.
IGNITION SEQUENCE IF PRESSURE SWITCH
CLOSES WITHIN 2−1/2 MINUTES.
AT BEGINNING OF HEAT DEMAND?
STATUS ERROR CODE 2 + 6.
SECOND STAGE HEAT DEMAND
STATUS LED −− HEARTBEAT.
NO
SATISFIED. FIVE (5) MINUTE WAIT PERIOD
MADE FOR SECOND−STAGE HEAT?
YES
WILL NOT REATTEMPT SECOND−STAGE
HEATING DEMAND.
STATUS ERROR CODE 2 + 5.
NO
YES
YES
YES
NO