Lennox ML180 Furnace Manuals

The Lennox ML180 is a high-efficiency gas furnace designed for residential heating applications. This 80% AFUE furnace features durable heat exchanger construction, multiple firing rates, and quiet operation. Below are key sections for safety, features, installation, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Installation Requirements 3. First-Time Setup 4. Technical Specifications 5. Controls and Settings 6. Venting and Combustion Air 7. Operation Procedures 8. Maintenance Schedule 9. Safety Information 10. Regulatory Compliance 11. Troubleshooting Guide

Features at a Glance

Key components: Duralok™ heat exchanger, multi-speed blower motor, hot surface ignition system, flame rollout switches, pressure switches, and integrated control board.

Feature	Description
Heat Exchanger	Duralok aluminized steel construction for durability
AFUE Rating	80% Annual Fuel Utilization Efficiency
Blower Motor	Multi-speed PSC motor for quiet operation
Ignition System	Hot surface ignition for reliable starts
Gas Valve	Multi-fire rate capability
Control Board	Integrated furnace control with diagnostic LED
Filter System	Standard 1-inch filter slot
Safety Controls	Flame rollout and limit switches
Venting	Category I venting compatible
Warranty	20-year heat exchanger limited warranty

Installation Requirements

Professional installation recommended. Ensure proper clearances and venting.

Location: Install in approved locations with proper clearances to combustibles.
Venting: Use approved Category I vent materials; maintain proper slope.
Gas Connection: Use black iron pipe with proper sizing; pressure test required.
Electrical: 120V AC power supply with proper grounding required.
Ductwork: Ensure proper sizing and sealing for optimal performance.

WARNING! Gas furnaces produce carbon monoxide; proper venting is critical. Only qualified technicians should install.

First-Time Setup

Initial startup must be performed by qualified technician.

Verify installation: Check all connections, clearances, and venting.
Gas pressure: Set manifold pressure per specifications on rating plate.
Electrical: Verify proper voltage and polarity.
Startup sequence: Follow manufacturer's startup procedure.
Combustion analysis: Verify proper combustion and venting performance.

CAUTION! Never operate furnace without proper venting and combustion air supply.

Technical Specifications

Model Series: ML180
AFUE Rating: 80%
Input BTU/H: 40,000 - 120,000 (varies by model)
Output BTU/H: 32,000 - 96,000 (varies by model)
Gas Type: Natural Gas (LP conversion kits available)
Electrical: 120V AC, 60Hz
Blower Motor: Multi-speed PSC
Static Pressure: 0.1" - 0.8" WC maximum
Venting: Category I, 4" - 7" diameter
Dimensions: Varies by model (check specific model data)

Controls and Settings

Integrated control board with diagnostic LED. Thermostat controls heating cycles.

Control Board: LED status light indicates operational mode and fault codes. Gas valve with multiple firing rates. Blower speed taps for different airflow requirements.

Thermostat Settings: Heat/Off/Auto fan modes. Temperature setpoints. Fan continuous or auto operation. Limit switches: High limit and flame rollout protection. Pressure switches: Verify proper venting operation.

Venting and Combustion Air

Category I venting required. Proper combustion air supply critical for safe operation.

Vent Materials: Use approved Category I vent pipe (Type B or L).
Vent Sizing: Follow manufacturer's specifications for proper diameter.
Combustion Air: Provide adequate fresh air supply per local codes.
Clearances: Maintain proper clearances to combustibles.

Tip: Regular inspection of vent system recommended annually.

Operation Procedures

Normal operation controlled by thermostat. Understand basic operating sequence.

Call for Heat: Thermostat signals furnace to start heating cycle.
Pre-purge: Blower operates to clear combustion chamber.
Ignition: Hot surface igniter glows, gas valve opens.
Flame Proving: Flame sensor confirms ignition.
Main Heat: Burners operate at selected firing rate.
Blower Operation: Indoor blower starts after heat exchanger warms.
Shutdown: Gas valve closes when thermostat satisfied.

WARNING! If furnace fails to ignite after several attempts, lockout occurs requiring reset.

Maintenance Schedule

Regular maintenance ensures safe and efficient operation.

Monthly: Check and replace air filter as needed
Annual: Professional inspection and cleaning
Seasonal: Check vent system for obstructions
As Needed: Clean flame sensor, check burners

CAUTION! Turn off power and gas supply before performing any maintenance.

Safety Information

Carbon monoxide detectors required in home with gas appliances.

WARNING! Gas furnaces produce carbon monoxide - ensure proper venting and combustion air. Install CO detectors near sleeping areas. Never block vents or combustion air openings. Professional service required for repairs.

Regulatory Compliance

UL listed and ANSI certified. Complies with applicable safety standards. Manufactured to meet efficiency standards. Local code compliance required for installation. For technical support, contact Lennox at 1-800-9-LENNOX or visit www.lennox.com.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power, thermostat, safety switch	Check power supply; verify thermostat setting; reset door switch.
No heat	Gas supply, ignition, filter	Verify gas valve on; check for ignition attempts; replace dirty filter.
Short cycling	Dirty filter, limit switch	Replace filter; check for restricted airflow; verify limit operation.
Blower won't stop	Thermostat fan setting	Check thermostat fan setting (Auto/On); verify control board.
Unusual noises	Motor, blower wheel, ducts	Inspect blower assembly; check for loose components; verify ductwork.

Reset: Turn power off for 30 seconds to reset control board.

Service: 1-800-9-LENNOX; www.lennox.com