Lenox Lennox Merit Series ML180UHE Gas Furnace Heating Operations and Troubleshooting
Page 39

Troubleshooting: Heating Sequence of Operation

NO

HEATING SEQUENCE OF OPERATION

NORMAL HEATING MODE

 

 

ABNORMAL HEATING MODE

 

 

 

 

 

 

 

 

 

 

 

 

POWER ON

 

 

 

 

 

 

 

NO

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INDOOR BLOWER DELAY OFF.

CONTROL SELF−CHECK OKAY?

 

 

LED SLOW FLASH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(RESET CONTROL BY TURNING MAIN POWER OFF.)

 

 

YES

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IS POLARITY CORRECT?

 

 

LED FLASHES CODE 1 − POLARITY REVERSED.

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

IS THERE A PROPER GROUND?

 

 

LED FLASHES CODE 2 − IMPROPER GROUND.

 

 

YES

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LED FLASHES CODE 13 − LOW LINE VOLTAGE.

 

 

IS VOLTAGE

 

 

 

 

 

CONTROL WILL NOT RESPOND TO A CALL FOR

 

 

ABOVE 70 VOLTS?

 

 

 

 

HEATING UNTIL VOLTAGE RISES ABOVE 75 VOLTS.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

 

NO

LED FLASHES CODE 8 − ROLLOUT SWITCH OPEN.

 

 

 

 

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

ROLLOUT SWITCH CLOSED?

 

 

INDOOR BLOWER ON.

 

 

 

 

 

 

 

 

 

 

 

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES

 

 

YES

 

 

 

 

 

 

AND POWER IS RESET OR T’STAT IS INTERRUPTED

 

 

 

 

 

 

 

FOR MINIMUM OF 1 SECOND.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

LED FLASHES CODE 12 − FLAME SENSED

 

 

BURNER OFF?

 

WITHOUT GAS VALVE ENERGIZED.

 

 

 

 

(Flame sensed without gas valve energized)

 

 

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

 

 

 

 

YES

 

 

 

 

 

 

INDOOR BLOWER ON HEATING SPEED.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NORMAL OPERATION:

 

 

 

 

 

LED SLOW FLASH

 

 

 

YES

 

THERMOSTAT CALLS FOR HEAT:

LED FLASHES CODE 7 − PRIMARY LMIT

OPEN. COMBUSTION AIR INDUCER

LED SLOW FLASH

OFF.INDOOR BLOWER ON

 

YES

NO

 

PRIMARY LIMIT SWITCH. CLOSED?

 

 

 

 

 

 

 

 

LED FLASHES CODE 11 − PRESSURE

 

 

 

YES

 

 

 

 

 

 

SWITCH CLOSED.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GAS VALVE OFF COMBUSTION AIR

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IS COMBUSTION AIR

 

 

 

INDUCER OFF. INDOOR BLOWER

 

 

 

 

 

 

 

 

 

 

PRESSURE SWITCH OPEN?

 

 

 

 

OFF WITH DELAY.

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

 

(Sequence holds until pressure switch

 

 

 

 

 

 

 

 

opens or thermostat resets control.)

 

 

 

 

 

 

 

 

 

 

 

 

 

IS COMBUSTION AIR INDUCER

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ENERGIZED?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

 

 

 

 

 

 

NO

LED FLASHES CODE 9 − PRESSURE SWITCH FAILED

 

 

YES

 

 

 

 

 

HAS COMBUSTION AIR PRESSURE

TO CLOSE OR OPENED DURING HEAT DEMAND.

 

 

 

SWITCH CLOSED IN 2.5 MINUTES?

 

PRESSURE SWITCH IS IN WATCHGUARD MODE. GAS

 

 

 

 

 

 

 

YES

 

 

 

VALVE OFF. COMBUSTION AIR INDUCER OFF.

 

 

 

 

 

 

INDOOR BLOWER OFF WITH DELAY. IS 5-MINUTE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESET PERIOD COMPLETE?

 

 

 

CONTINUED NEXT PAGE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Page 39

Page 38 Page 40
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Page 38 Page 40
Contents Table of Contents Installation Instructions ML180UHETOP View Unit Dimensions − inches mmGas Valve Parts ArrangementMake−Up Box Heat Exchanger Combustion Air Inducer Burner BoxSafety Information ML180UHE Gas FurnaceShipping and Packing List General Use of Furnace as Construction HeaterCombustion, Dilution & Ventilation Air Equipment in Confined Space ALL AIR from Inside Equipment in Confined Space Setting Equipment Return Air Typical Horizontal Application Horizontal Application Installation Clearances Top LeftRight End BottomDuct System FiltersLeft Side Vent Discharge VentingUpflow Position Top Vent DischargeSide Vent Discharge − no modifications necessary Horizontal Left Position Horizontal Right PositionHorizontal Left Position Side Vent DischargeVent Connection Upflow and Horizontal Position Common Venting Using Metal−Lined Masonry Chimney −1/2 18 − The common vent diameter must always be at least as Cated or common venting system, you must inspectFeet FAN + FAN FAN + NAT 130 Carbon Monoxide Poisoning Hazard Gas supply piping should not allow more than 0.5W.C. drop Ers or straps. Install a drip leg in vertical pipe runs to− In some localities, codes may require the installation Gas PipingHorizontal Application Left−Side Air DischargeRight−Side Air Discharge Interior MAKE−UP BOX Installation ElectricalElectrostatic Discharge ESD Thermostat Designations ML180UHE Schematic Wiring Diagram and Sequence of Operation Integrated Control Typical ML180UHE Field Wiring DiagramUnit Start−Up For Your Safety Read Before LightingHigh Altitude Gas Pressure AdjustmentGAS Meter Clocking Chart Proper CombustionManifold Pressure Settings at all Altitudes Other Unit AdjustmentsNo Jumper Heat FAN-OFF Time in Seconds1345 1380995 975 115 945230 Single Side Return Air − Air volumes in bold require fieldOrder to maintain proper air velocity 640 1940 420 1750 310Electrical SHOCK, Fire Or Explosion Hazard Service −045 and −070 units ML180UHE BURNER, Combustion AIR Inducer Assembly Heat Exchanger Removal −090, −110 −135 unitsRepair Parts List Planned ServiceRED LED Integrated Control Diagnostic CodesHeating Sequence of Operation Normal Heating Mode Abnormal Heating ModeHeating Sequence Cooling Sequence of Operation Normal Cooling Mode Abnormal Cooling ModeContinuous FAN Sequence of Operation Start−Up & Performance Check List Drain Line Cooling ModeTemperature Rise Unit Operation
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