Furnace Lennox Manual

The Lennox Furnace is a high-efficiency heating system designed for residential use, featuring advanced combustion technology, variable-speed blower motors, and smart thermostat compatibility. This manual covers installation, operation, maintenance, and troubleshooting for various Lennox furnace models. Below are key sections for safety, features, installation, setup, operation, and maintenance procedures.

Features at a Glance

Key components: High-efficiency heat exchanger, variable-speed blower motor, electronic ignition system, air filter compartment, combustion chamber, and control board.

Feature	Description
AFUE Rating	Up to 98.7% Annual Fuel Utilization Efficiency
Blower Motor	Variable-speed ECM motor for quiet operation
Ignition System	Hot surface ignition for reliable startup
Heat Exchanger	Stainless steel construction for durability
Filter System	Standard 1-inch or 4-inch media filter compatibility
Control Board	Microprocessor-based for precise temperature control
Safety Switches	Pressure switch, limit switch, rollout switch
Venting	PVC pipe compatible for direct venting
Thermostat Connection	Compatible with most 24V thermostats
Power Requirements	120V AC, 60Hz standard household current

Installation Requirements

Proper installation is critical for safe and efficient operation. Follow all local building codes and manufacturer guidelines.

1. Location: Install in dry, well-ventilated area with adequate clearance for service access.
2. Venting: Use approved PVC piping for combustion air and exhaust venting.
3. Gas Connection: Use approved gas pipe and fittings; pressure test before operation.
4. Electrical: Connect to dedicated 120V circuit with proper grounding.
5. Ductwork: Ensure proper sizing and sealing of supply and return ducts.

WARNING! Installation must be performed by qualified HVAC technician. Improper installation can cause fire, explosion, or carbon monoxide poisoning.

First-Time Setup

Initial setup and commissioning procedures for new installation.

1. Power up: Turn on electrical power and gas supply.
2. Thermostat setup: Program desired temperature settings and schedule.
3. System check: Verify proper ignition, flame sensing, and blower operation.
4. Airflow verification: Check supply air temperature and static pressure.
5. Combustion analysis: Verify proper gas pressure and combustion efficiency.

CAUTION! Never bypass safety controls or operate without proper venting. Ensure carbon monoxide detectors are installed and functioning.

Technical Specifications

• Models: Various models from 40,000 to 120,000 BTU/hr capacity
• AFUE Rating: 80% to 98.7% depending on model
• Gas Type: Natural gas or propane (conversion kit required)
• Electrical: 120V AC, 60Hz, 5-15 amp circuit
• Blower Motor: ECM variable speed, ½ to 1 HP
• Sound Rating: As low as 65 dBA operation
• Warranty: 20-year limited warranty on heat exchanger
• Dimensions: Varies by model (typically 21"W x 21"D x 40"H)
• Weight: 80-150 lbs depending on model

Controls and Settings

Access control board via front panel. LED status lights indicate system operation and error codes.

Control Board Features: Power switch, diagnostic LED, mode selection, blower speed adjustment, temperature limit settings.

Operating Modes: HEAT, COOL (with AC), FAN ONLY. Temperature Settings: Setpoint adjustment, differential settings, fan control. Advanced Settings: Blower delay, purge cycles, diagnostic mode. Safety Controls: High limit switch, pressure switch, flame sensor, rollout switch.

Thermostat Connection

Compatible with most 24V thermostats including programmable and smart thermostats.

1. Turn off power to furnace before connecting thermostat wires.
2. Connect R (24V), W (Heat), G (Fan), C (Common) terminals.
3. For advanced thermostats, additional Y (Cool) and O/B (Reversing valve) connections may be needed.
4. Program thermostat settings according to manufacturer instructions.

Tip: Use thermostat with adaptive recovery for optimal efficiency and comfort.

Operating Modes

Multiple operating modes for different comfort needs and efficiency requirements.

1. Heat Mode: Primary heating operation with variable blower speeds.
2. Fan Only: Continuous or intermittent blower operation for air circulation.
3. Emergency Heat: Backup heating mode for extreme conditions.
4. Smart Operation: Learns heating patterns for optimal efficiency.
5. Vacation Mode: Reduced operation during extended absences.

WARNING! Do not operate furnace if unusual odors, sounds, or performance issues are noticed. Shut off system and contact qualified service technician.

Maintenance Procedures

Regular maintenance ensures optimal performance and extends system life.

1. Monthly: Check and replace air filter as needed.
2. Seasonal: Inspect vent pipes for obstructions or damage.
3. Annual: Professional inspection and cleaning of burners, heat exchanger, and blower.
4. Biannual: Check gas pressure and combustion analysis.
5. As needed: Clean flame sensor and check safety controls.

CAUTION! Always turn off electrical power and gas supply before performing any maintenance. Use only manufacturer-approved replacement parts.

Safety Features

Multiple safety systems protect against hazardous conditions.

Safety Feature	Function
High Limit Switch	Shuts off burner if temperature exceeds safe limits
Pressure Switch	Ensures proper venting before ignition
Flame Sensor	Detects flame presence; shuts off gas if no flame
Rollout Switch	Prevents flame rollout from burner compartment
Ignition Control	Manages safe ignition sequence and lockout

Regulatory Information

UL listed and certified to ANSI Z21.47 standards. Complies with Department of Energy efficiency requirements. Manufactured to meet or exceed industry safety standards. For technical support or warranty service, contact Lennox International Inc. at 1-800-9-LENNOX or visit www.lennox.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power, thermostat, safety switch	Check circuit breaker, thermostat settings, safety switch status
No heat	Gas supply, ignition, filter	Verify gas valve on, check ignition sequence, replace dirty filter
Short cycling	Filter, limit switch, airflow	Clean/replace filter, check limit switch, verify proper airflow
Blower not working	Motor, capacitor, control board	Check motor operation, test capacitor, inspect control board
Unusual noises	Blower, bearings, ductwork	Inspect blower wheel, check motor bearings, examine duct connections

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

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