Troubleshooting: Heating Sequence of Operation (Continued)

HEATING SEQUENCE OF OPERATION

CONTINUED

THERMOSTAT CALLS FOR HEAT

STATUS LED − HEARTBEAT.

(Refer to box A on previous page)

1FIRST−STAGE (LOW FIRE) PRESSURE SWITCH CLOSED WITHIN 2.0 MINUTES?

YES

 

 

15−SECOND COMBUSTION AIR INDUCER

 

PRE−PURGE INITIATED BY CLOSED FIRST−STAGE

 

 

PRESSURE SWITCH (or 15 SECOND

1

INTER−PURGE PERIOD.)

STATUS LED −− HEARTBEAT.

 

 

 

 

 

 

 

 

 

 

 

IGNITOR WARM−UP (20 SECONDS)

 

 

STATUS LED −− HEARTBEAT.

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

 

IS IGNITOR INTACT AND CONNECTED?

 

 

YES

 

 

 

 

 

NO

NO

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER OFF. UNIT WILL RETRY AFTER 5−MINUTE WAIT PERIOD.

STATUS ERROR CODE 2 + 3.

COMBUSTION AIR INDUCER

 

LOW AND HIGH

NO

 

PRESSURE SWITCH

 

 

ENERGIZED ON HIGH SPEED

 

 

 

 

CLOSED WITHIN 30

 

 

 

 

YES

 

 

SECONDS

 

 

 

 

 

 

 

 

 

COMBUSTION AIR INDUCER OFF, IGNITOR OFF. SIGNAL HOLDS UNTIL IGNITOR IS REPLACED OR RECONNECTED.

STATUS ERROR CODE 4 + 7.

2AT END OF IGNITOR 20 SECOND WARM UP PERIOD, 4−SECOND TRIAL FOR IGNITION.

GAS VALVE OPENS, IGNITOR ENERGIZED DURING

4−SECOND TRIAL UNTIL FLAME SENSED.

YES

4−SECOND FLAME STABILIZATION PERIOD.

NO

YES

IS VOLTAGE ABOVE 90 VOLTS?

NO

COMBUSTION AIR INDUCER OFF, IGNITOR OFF. SIGNAL HOLDS UNTIL VOLTAGE RISES ABOVE 95 VOLTS. STATUS ERROR CODE 4 + 8.

FLAME RECTIFICATION CURRENT CHECK

CAN FLAME BE PROVEN WITHIN 4

SECONDS AFTER GAS VALVE OPENS?

(u0.20 microamps)

GAS VALVE OFF. COMBUSTION AIR INDUCER ON. INDOOR BLOWER OFF.

STATUS LED −− HEARTBEAT.

HAS CONTROL FAILED TO SENSE

FLAME FOR FIVE CONSECUTIVE TRIES

DURING A SINGLE HEAT DEMAND?

YES

NO

FLAME PRESENT?

YES

CONTINUED ON NEXT PAGE

NO

WATCHGUARD MODE. GAS VALVE OFF,

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF.

STATUS ERROR CODE 4 + 1.

IS 60−MINUTE RESET PERIOD COMPLETE?

YES

HAS CONTROL RESET IGNITION SEQUENCE

FOUR (4) TIMES?

WATCHGUARD MODE.

STATUS ERROR CODE 4 + 3.

YES

NO

1If the furnace is operating on continuous fan mode (terminals

air inducer will energize on high speed, the gas valve will energize on second−stage heat and the furnace

will operate on high fire. Furnace will stay on high fire 60 seconds then switch to low fire.

2If combustion air inducer is operating on high speed and gas valve is energized on second− stage heat, 20 seconds after flame is sensed furnace will switch to low fire.

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Lennox International Inc Elite Series Gas Furnace Upflow/Horizontal Air Discharge, EL280UH Heating Sequence of Operation

Elite Series Gas Furnace Upflow/Horizontal Air Discharge, EL280UH specifications

Lennox International Inc. has established itself as a leader in the heating and cooling industry, providing innovative solutions for both residential and commercial environments. One of their notable products is the EL280UH, a high-efficiency gas furnace designed to offer optimal comfort while minimizing energy consumption.

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