Lennox International Inc Merit Series Gas Furnace Troubleshooting Cooling Sequence of Operation

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Troubleshooting: Cooling Sequence of Operation

COOLING SEQUENCE OF OPERATION

NORMAL COOLING MODE

 

 

ABNORMAL COOLING MODE

 

 

 

 

 

 

 

 

 

 

 

 

POWER ON

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IGNITION CONTROL MAIN POWER ON.

 

 

 

 

 

 

 

 

 

 

NO

 

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

 

CONTROL SELF DIAGNOSTIC CHECK.

 

INDOOR BLOWER OFF WITH NORMAL DELAY.

 

IS CONTROL OPERATING NORMALLY?

 

 

SIGNAL CIRCUIT BOARD FAILURE AT LED.

 

 

 

YES

 

 

 

 

INTERRUPT MAIN POWER TO RESET CONTROL.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SIGNAL IMPROPER GROUND AT LED.

 

IS THERE A PROPER GROUND?

 

 

CONTROL WILL CONTINUE TO CALL FOR COOLING

 

 

 

YES

 

 

 

 

IN THIS CONDITION.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

SIGNAL POLARITY REVERSED AT LED. CONTROL

 

 

 

 

 

 

 

 

 

IS POLARITY CORRECT?

 

 

WILL CONTINUE TO CALL FOR COOLING IN THIS

 

 

 

 

 

 

 

 

CONDITION.

 

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

IS VOLTAGE

 

 

 

LED SIGNALS LOW VOLTAGE. CONTROL WILL

 

 

 

 

 

 

 

 

 

ABOVE 90 VOLTS?

 

 

 

CONTINUE TO CALL FOR COOLING

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

IN THIS CONDITION.

 

 

 

 

 

 

 

 

 

 

 

 

 

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

INDOOR BLOWER ON.

ROLLOUT SWITCH MONITORED CONTINUOUSLY.

 

 

SIGNAL ROLL-OUT SWITCH OPEN AT LED.

IS ROLLOUT SWITCH CLOSED?

 

 

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES

 

 

 

 

 

 

 

AND MAIN POWER IS INTERRUPTED OR THERMOSTAT

 

 

YES

 

 

 

 

IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LED: SLOW FLASH RATE REMAINS UNCHANGED

THROUGHOUT COOLING CYCLE.

THERMOSTAT CALLS FOR COOLING.

COMPRESSOR CONTACTOR AND SYSTEM FAN

ENERGIZED WITH 2-SECOND DELAY

(COOLING SPEED). EAC TERM. ENERGIZED.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN AND EAC TERM. OFF

WITH 45-SECOND DELAY.

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Contents Installation Instructions ML180UH Table of ContentsUnit Dimensions − inches mm TOP ViewParts Arrangement Safety Information ML180UH Gas FurnaceShipping and Packing List Use of Furnace as Construction Heater GeneralCombustion, Dilution & Ventilation Air Equipment in Confined Space ALL AIR from Inside Equipment in Confined Space Setting Equipment Return Air Plenum Horizontal Application Installation Clearances Top Left RightEnd Bottom Filters Duct SystemTop Vent Discharge VentingUpflow Position Left Side Vent DischargeHorizontal Left Position Horizontal Right PositionSide Vent Discharge Vent Connection Upflow and Horizontal Position Common Venting Using Metal−Lined Masonry Chimney −1/2 Cated or common venting system, you must inspect 18 − The common vent diameter must always be at least asFeet FAN + FAN FAN + NAT 112 175 169 278 Carbon Monoxide Poisoning Hazard Gas Piping Ers or straps. Install a drip leg in vertical pipe runs to− In some localities, codes may require the installation Every 8 to 10 feet 2.44 to 3.01 m with suitable hangHorizontal Application Left−Side Air DischargeRight−Side Air Discharge Interior MAKE−UP BOX Installation ElectricalElectrostatic Discharge ESD Thermostat Designations ML180UH Schematic Wiring Diagram and Sequence of Operation Typical ML180UH Field Wiring Diagram Integrated ControlFor Your Safety Read Before Lighting Unit Start−UpGas Pressure Adjustment Proper CombustionHigh Altitude Other Unit Adjustments Manifold Pressure Settings at all AltitudesHeat FAN-OFF Time in Seconds No Jumper680 453 900750 885860 Single Side Return Air − Air volumes in bold require field1391 653Service Electrical SHOCK, Fire Or Explosion Hazard−090, −110 −135 units ML180UH BURNER, Combustion AIR Inducer AssemblyHeat Exchanger Removal −045 and −070 unitsPage Planned Service Repair Parts ListIntegrated Control Diagnostic Codes DescriptionTroubleshooting Heating Sequence of Operation Normal Heating Mode Abnormal Heating ModeHeating Sequence Troubleshooting Cooling Sequence of Operation Normal Cooling Mode Abnormal Cooling ModeTroubleshooting Continuous Fan Sequence of Operation Continuous Heat Speed FAN Sequence of Operation

Merit Series Gas Furnace specifications

Lennox International Inc. is a leading name in the heating and cooling industry, and their Merit Series Gas Furnace embodies the commitment to quality and efficiency that the company is known for. The Merit Series is designed to provide reliable heating in a sustainable manner, making it an excellent choice for homeowners seeking comfort without excessive energy bills.

One of the standout features of the Merit Series Gas Furnace is its efficiency ratings. The units in this series typically boast Annual Fuel Utilization Efficiency (AFUE) ratings of up to 95%. This level of efficiency means that the furnace converts a significant portion of the fuel it uses into heat, ultimately lowering operating costs. Such energy-efficient performance is not only beneficial for the wallet but also promotes environmental sustainability.

The Merit Series also incorporates advanced technologies that enhance its operation. The inclusion of a multi-speed blower motor is a notable feature that provides thoughtful airflow management throughout the home. By adjusting the speed according to the heating needs, the furnace optimizes comfort levels while minimizing noise and energy consumption. Homeowners can enjoy a warm environment without the disruptive sounds often associated with traditional furnaces.

Moreover, the Merit Series comes equipped with durable construction materials designed to withstand the test of time. From the robust heat exchanger to the heavy-gauge cabinet, Lennox focuses on longevity and reliability. This ensures that homeowners can trust their furnace to operate effectively even in the harshest winter conditions.

Safety features are also integral to the design of the Merit Series Gas Furnace. With an integrated Flame Sensor and a built-in safety shut-off system, the furnace ensures that any irregularities in operation are promptly detected and addressed. Such measures provide peace of mind for families using the heating system throughout the cold months.

Installation and maintenance are further simplified with the Merit Series. Its design facilitates easier access for HVAC professionals, allowing for quicker installations and routine service, ensuring that homeowners spend less time and money on upkeep.

In conclusion, Lennox International Inc.'s Merit Series Gas Furnace combines efficiency, advanced technology, and robust construction, making it a top choice for families looking to enhance their home's heating system. With its energy-saving innovations and commitment to reliability, the Merit Series stands as an exemplary option in today’s market.