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Lennox MERIT ML180UH

Lennox MERIT ML180UH
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Page 1
06/11
*2P0611*
506816−01
*P506816-01*
2011 Lennox Industries Inc.
Dallas, Texas, USA
AIR FLOW
UPFLOW
AIR FLOW
AIR FLOW
HORIZONTAL RIGHT
HORIZONTAL LEFT
INSTALLATION
INSTRUCTIONS
ML180UH
MERIT
®
SERIES GAS FURNACE
UPFLOW / HORIZONTAL AIR DISCHARGE
506816−01
06/2011
Supersedes 506778−01
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This is a safety alert symbol and should never be ignored.
When you see this symbol on labels or in manuals, be alert
to the potential for personal injury or death.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a licensed professional installer (or
equivalent), service agency or the gas supplier.
CAUTION
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
Table of Contents
Unit Dimensions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Arrangement 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ML180UH Gas Furnace 4. . . . . . . . . . . . . . . . . . . . . . . . . .
Shipping and Packing List 4. . . . . . . . . . . . . . . . . . . . . . . .
Safety Information 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Use of Furnace as a Construction Heater 5. . . . . . . . . . .
General 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Combustion, Dilution & Ventilation Air 6. . . . . . . . . . . . . .
Setting Equipment 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filters 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Duct System 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Venting 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Piping 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Integrated Control 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unit Start−Up 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Pressure Adjustment 30. . . . . . . . . . . . . . . . . . . . . . .
High Altitude 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Proper Combustion 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other Unit Adjustments 31. . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Performance Data 33. . . . . . . . . . . . . . . . . . . . . . .
Service 35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Planned Service 38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repair Parts List 38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Integrated Control Diagnostic Codes 39. . . . . . . . . . . . . .
Troubleshooting 40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Litho U.S.A.
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Lennox MERIT ML180UH Specifications

General IconGeneral
AFUE80%
Blower MotorPSC
Gas ValveSingle-stage
Ignition SystemHot surface ignition
Fuel TypeNatural gas or Propane
Heating Capacity44, 000-132, 000 BTU/h
Warranty5-Year Limited Warranty on covered components

Summary

General Information and Safety

Safety Alerts

Safety warnings for installation and handling of the furnace.

Unit Dimensions

Parts Arrangement

ML180 UH Gas Furnace Details

Shipping and Packing List

Contents of the furnace shipment and items that may be ordered separately.

Safety Information and Certifications

Crucial safety warnings, certifications, and installation codes.

Installation Clearances and Locations

Required clearances and suitable installation locations for the furnace.

Installation Considerations

Installation with Cooling Coils

Guidelines for installing the furnace in conjunction with cooling units.

Use as Construction Heater

Conditions and precautions for using the furnace during construction.

General Installation Guidelines

General recommendations for furnace placement and installation.

Combustion, Dilution & Ventilation Air

Air Requirements for Installation Spaces

Unconfined Space Air Requirements

Guidelines for air supply in unconfined installation spaces.

Confined Space Air Requirements

Guidelines for air supply in confined installation spaces.

Air Intake Methods

Methods for supplying combustion and ventilation air from inside or outside.

Equipment Setup and Clearances

Setting Equipment

Proper positioning and leveling of the furnace unit.

Upflow Application Clearances

Minimum clearances required for upflow installations.

Return Air Connections

Upflow Return Air

Connecting return air for upflow installations and filter requirements.

Optional Return Air Base

Details on using an optional return air base for upflow configurations.

Horizontal Installation

Removing the Bottom Panel

Procedure for removing the bottom panel for horizontal mounting.

Horizontal Application Clearances

Minimum clearances for horizontal furnace installations.

Horizontal Return Air

Connecting return air for furnaces installed in horizontal positions.

Ducting and Filtration

Horizontal Platform Installation

Guidelines for installing the furnace on a platform in a horizontal orientation.

Filters

Filter requirements and recommendations for the unit.

Duct System Sizing

Standards for sizing and installing supply and return air duct systems.

Supply and Return Air Plenums

Requirements for supply and return air plenums, including access panels.

Venting Requirements

General Venting Information

General guidelines and factory-installed components for venting.

Venting with Masonry Chimney

Additional requirements for venting the furnace using a masonry chimney.

General Venting Standards

Common Venting with Metal-Lined Masonry Chimney

Procedures and requirements for common venting with lined masonry chimneys.

Common Venting Procedures

Removal from Common Vent

Steps for safely removing the furnace from a shared venting system.

Gas Piping and Supply

Gas Piping Requirements

Guidelines and precautions for gas supply piping installation.

Gas Supply and Sizing

Connecting gas supply and recommended pipe sizes for capacity.

Electrical and Leak Checks

Leak Check Procedures

Steps for performing a gas piping leak check.

Electrical Precautions and ESD

Safety measures for electrical connections and electrostatic discharge.

Control System and Accessories

Thermostat and Generator Requirements

Thermostat wiring and generator voltage specifications for operation.

Accessory Terminals and Blower Speeds

Connections for accessories and adjustment of blower speeds.

Wiring Diagram and Sequence of Operation

Schematic Wiring Diagram

Detailed wiring diagram for the furnace's integrated control system.

Heating Sequence of Operation

Step-by-step process for furnace operation during heating cycles.

Unit Start-Up and Gas Valve Operation

Safety Before Lighting

Critical safety warnings and checks before lighting the furnace.

Gas Valve and Unit Operation

Procedures for operating the gas valve and starting the furnace.

Failure to Operate Troubleshooting

Common issues and checks when the furnace fails to start.

Performance Adjustments and Checks

Heating Sequence and Gas Pressure

Steps for checking heating sequence and adjusting gas pressure.

Combustion and High Altitude Settings

Procedures for checking proper combustion and high altitude adjustments.

Unit Adjustments and Settings

Manifold Pressure and Altitude Settings

Recommended manifold pressure settings for various altitudes.

Other Unit Adjustments and Controls

Adjustments for limits, switches, temperature rise, and fan control.

Blower, Electrical, and Ignition Settings

Blower Speed and Fan-Off Delay

Adjusting blower speeds and fan-off delay settings.

Electrical Checks and Electronic Ignition

Performing electrical checks and understanding electronic ignition features.

Blower Performance Data

Service and Maintenance

General Service Precautions

Essential safety warnings and procedures before performing service.

Component Checks

Routine checks for filters, flue system, and electrical connections.

Cleaning Heat Exchanger and Burners

Service and Parts Information

Planned Service Items

Annual inspection checklist for furnace components.

Repair Parts List

List of available replacement parts for the furnace.

Integrated Control Diagnostic Codes

Troubleshooting Heating Sequence

Heating Sequence of Operation

Flowchart for diagnosing heating operation problems.

Troubleshooting Cooling Sequence

Cooling Sequence of Operation

Flowchart for diagnosing cooling operation problems.

Troubleshooting Fan Operation

Continuous Fan Sequence of Operation

Flowchart for diagnosing issues with the continuous fan mode.

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