Lennox EL280UHX Series Unit Information page 44

CONTINUED
FLAME SIGNAL ABOVE
( 1.40 microamps)
YES
SINGLE-STAGE THERMOSTAT MODE
(DIP SWITCH SET AT "ON")
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 "OFF")
YES
45-SECOND INDOOR BLOWER ON DELAY BEGINS.
YES
PRIMARY & SECONDARY LIMIT SWITCHES
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
STATUS ERROR CODE 5 + 1. SEQUENCE HOLDS
YES
UNTIL ROLLOUT SWITCH IS RESET AND MAIN
POWER IS INTERRUPTED OR THERMOSTAT
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,
IS 60-MINUTE RESET PERIOD COMPLETE?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
STATUS ERROR CODE 2 + 3. CONTROL RESTARTS
IGNITION SEQUENCE IF PRESSURE SWITCH
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
SATISFIED. FIVE (5) MINUTE WAIT PERIOD
INITIATED BEFORE RETRY. WERE 5 ATTEMPTS
NO
CONTINUES FIRST-STAGE HEATING DEMAND.
Page 44
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
CLOSED?
INDOOR BLOWER ON.
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
INDOOR BLOWER OFF AFTER DELAY.
CLOSES WITHIN 2-1/2 MINUTES.
AT BEGINNING OF HEAT DEMAND?
STATUS ERROR CODE 2 + 6.
SECOND STAGE HEAT DEMAND
STATUS LED -- HEARTBEAT.
NO
MADE FOR SECOND-STAGE HEAT?
YES
WILL NOT REATTEMPT SECOND-STAGE
HEATING DEMAND.
STATUS ERROR CODE 2 + 5.
NO
YES
YES
YES
NO