Lennox Furnace User Manual

The Lennox Furnace is a high-efficiency heating system designed for residential use, featuring advanced combustion technology, variable-speed blower motors, durable heat exchangers, quiet operation, and smart thermostat compatibility. Available in various models with AFUE ratings up to 98.7%. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: High-efficiency heat exchanger, Variable-speed blower motor, Ignition control module, Air filter compartment, Gas valve, Pressure switches, Flue vent connection.

Installation

Unpack and inspect all components. Ensure proper location with adequate clearance.

1. Position furnace: Place on level surface in well-ventilated area with proper clearances.
2. Connect gas supply: Use approved gas piping with shutoff valve near unit.
3. Connect electrical: 120V AC power supply with dedicated circuit.
4. Connect venting: Install PVC vent pipes according to local codes.
5. Connect thermostat: Run low-voltage wiring to thermostat location.
6. Connect ductwork: Secure supply and return air ducts properly.

WARNING! Installation must be performed by qualified HVAC technician. Gas connections require leak testing.

First-Time Setup

Power on furnace; follow startup sequence.

1. Verify gas supply: Ensure gas valve is open and connections are secure.
2. Check electrical: Confirm power is available at unit and thermostat.
3. Set thermostat: Program desired temperature settings and schedules.
4. Test operation: Initiate heating cycle to verify proper function.
5. Check airflow: Verify adequate airflow through all registers.
6. Monitor operation: Observe for proper ignition and flame stability.

CAUTION! Never bypass safety controls. Keep combustible materials away from furnace.

Specifications

• Heating Capacity: 40,000 to 120,000 BTU/h depending on model
• AFUE Rating: Up to 98.7% efficiency
• Motor Type: Variable-speed ECM blower motor
• Gas Type: Natural gas or LP/propane (conversion kit required)
• Electrical: 120V AC, 60Hz, 15 amp circuit
• Venting: PVC pipe (2-inch or 3-inch diameter)
• Sound Level: As low as 65 dBA in operation
• Warranty: Limited lifetime warranty on heat exchanger
• Dimensions: Varies by model (typical: 21"W x 21"D x 48"H)

Controls and Settings

Access control board via front panel. Status lights indicate system operation.

Thermostat Controls: Temperature setting, Fan mode (Auto/On), System mode (Heat/Off), Program schedules.

Control Board: Power switch, Status LED lights, Diagnostic codes, Blower speed adjustments, Gas valve control. Settings: Temperature differential, Fan delay, Blower speeds, Lockout timers. Diagnostics: Error code display, System status indicators, Reset procedures.

Connecting Thermostat

Compatible with conventional 24V thermostats and smart thermostats.

1. Turn off power to furnace before wiring.
2. Identify thermostat wires: R (power), W (heat), G (fan), C (common).
3. Connect wires to control board terminals matching thermostat connections.
4. Secure thermostat to wall and restore power.
5. Program thermostat settings as desired.

Tip: Use compatible thermostat for optimal efficiency and features.

Operation Modes

Heating modes: Single-stage, Two-stage, Modulating operation.

1. Heat Mode: Furnace responds to thermostat heat calls.
2. Fan Mode: Continuous fan operation for air circulation.
3. Standby Mode: System ready but not actively heating.
4. Lockout Mode: Safety shutdown requiring reset.
5. Diagnostic Mode: Service mode for troubleshooting.

WARNING! Do not attempt to override safety controls. Contact professional service if system locks out repeatedly.

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

CAUTION! Always turn off power before performing any maintenance.

Safety Features

Multiple safety systems protect against hazardous conditions.

• Flame rollout switches
• High limit switches
• Pressure switches
• Ignition safety lockout
• Gas valve safety shutoff
• Blower door safety switch

EMERGENCY: If you smell gas, evacuate immediately and call gas company from outside.

Regulatory Information

UL listed and ANSI certified. Complies with ASHRAE standards. Meets DOE efficiency requirements. Manufactured to ISO 9001 quality standards. For technical support, contact Lennox at 1-800-9-LENNOX or visit www.lennox.com. Copyright © 2025 Lennox Industries Inc. All rights reserved.

Troubleshooting

Reset: Turn power off for 30 seconds, then restore. Check error codes on control board.

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