Lennox EL280UHE Series Unit Information page 44

Troubleshooting: Heating Sequence of Operation (Continued)
CONTINUED
SECOND-STAGE (HIGH FIRE) HEAT
PRESSURE SWITCH CLOSED?
YES
HEAT DEMAND SATISFIED?
STATUS LED -- HEARTBEAT.
YES
SINGLE-STAGE THERMOSTAT MODE
(DIP SWITCH SET AT "SINGLE")
YES
GAS VALVE OFF, COMBUSTION AIR
INDUCER OFF AFTER 5-SECOND
LOW SPEED POST PURGE PERIOD,
INDOOR BLOWER OFF DELAY
INITIATED ON LOW HEAT SPEED.
STATUS LED -- HEARTBEAT.
DEMAND FOR HEAT SATISFIED.
POWER ON STAND BY.
STATUS LED -- PULSE.
HEATING SEQUENCE OF OPERATION
NO
YES
TWO STAGE THERMOSTAT MODE?
(DIP SWITCH SET AT "TWO")
YES
FIRST AND SECOND STAGE HEAT
YES
DEMAND SATISFIED SIMULTANEOUSLY.
STATUS LED -- HEARTBEAT.
Page 44
SEE BOX A
NORMAL OPERATION.
SEE BOX B
THERMOSTAT CALLS FOR HEAT.
RETURN TO FIRST-STAGE HEAT MODE.
FIRST-STAGE CONTINUES UNTIL SECOND-
STAGE PRESSURE SWITCH CAN BE PROVEN
or HEAT DEMAND IS SATISFIED. A FIVE (5)
MINUTE WAIT PERIOD IS INITIATED BEFORE
RETRY. WERE 5 ATTEMPTS MADE FOR
SECOND-STAGE HEAT?
NO
SEE BOX C
FIRST-STAGE HEAT DEMAND SATISFIED?
NO
STATUS LED -- HEARTBEAT.
GAS VALVE, COMBUSTION AIR INDUCER
AND INDOOR BLOWER RETURN TO FIRST-
STAGE OPERATION.
STATUS LED -- HEARTBEAT.
FIRST STAGE HEAT DEMAND SATISFIED?
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER
OFF AFTER 5-SECOND LOW SPEED POST-
PURGE PERIOD. INDOOR BLOWER OFF.
DELAY INITIATED ON LOW HEAT SPEED.
STATUS LED -- PULSE.
YES
SECOND STAGE HEAT
DEMAND SATISFIED?
YES