The Lennox G8 Gas Furnace is a high-efficiency residential heating system featuring advanced combustion technology, electronic ignition, variable-speed blower motor, durable heat exchanger construction, multiple heating stages, integrated diagnostic controls, safety shut-off systems, and compatibility with various thermostat configurations. Designed for reliable performance with natural gas or propane operation. Below are key sections for safety, features, installation, operation, maintenance, and troubleshooting.
Key components: Durable aluminized steel heat exchanger, electronic ignition system, variable-speed blower motor, integrated control board, gas valve assembly, pressure switches, flame sensor, and limit controls.
| Feature | Description |
|---|---|
| Heat Exchanger | Aluminized steel clamshell design for efficient heat transfer |
| Ignition System | Hot surface electronic ignition for reliable startup |
| Blower Motor | Variable-speed ECM for quiet operation and efficiency |
| Control Board | Integrated microprocessor with diagnostic LED |
| Gas Valve | Multi-port design for precise fuel control |
| Pressure Switches | Safety verification of draft inducer operation |
| Flame Sensor | Rod-type sensor for flame detection |
| Limit Controls | High-temperature safety shut-off protection |
| Venting | PVC pipe compatible for sidewall or roof termination |
| Thermostat Compatibility | Works with standard and programmable thermostats |
Professional installation required. Verify local codes and obtain permits.
WARNING! Gas appliances can produce carbon monoxide. Proper installation and venting are critical for safety. Use qualified HVAC technician.
Professional startup procedure required for warranty validation.
CAUTION! Never bypass safety controls. Document all measurements for service records.
Integrated control board manages all furnace functions with LED status indicator.
Control Board LED Codes: Steady green = normal operation, Slow flash = pressure switch error, Rapid flash = flame sensor error, Continuous flash = limit circuit lockout.
Thermostat Operation: Set heat mode and desired temperature. Furnace will cycle automatically based on demand. Blower operation includes heating cycle delay and post-purge timing.
Direct vent or conventional venting options available.
Tip: Check vent pipes annually for obstructions or damage.
Annual professional maintenance recommended for optimal performance.
WARNING! Turn off gas and electrical power before servicing. Use qualified technician.
Multiple safety features protect against hazardous conditions.
| Safety Feature | Function |
|---|---|
| Flame Rollout Switch | Detects improper burner combustion |
| High Limit Switch | Prevents overheating of heat exchanger |
| Pressure Switches | Verify proper venting operation |
| Flame Sensor | Confirms burner ignition |
| Gas Valve | Automatic shut-off if flame not detected |
| Ignition Control | Limited trial for ignition attempts |
Regular inspection ensures safe and efficient operation.
Monthly: Check and replace air filter. Verify furnace area is clear of combustible materials. Listen for unusual noises during operation.
Annual: Professional inspection of heat exchanger, burners, venting, and safety controls. Test carbon monoxide detectors in living spaces.
CAUTION! Never store chemicals or flammable materials near furnace. Keep combustion air openings clear.
UL listed and ANSI Z21.47 certified. Complies with U.S. Department of Energy efficiency standards. Installation must meet National Fuel Gas Code (NFPA 54) and local building codes. For Canadian installations, complies with CSA standards. Copyright © Lennox Industries Inc. All rights reserved. For technical support, contact authorized Lennox dealer or 1-800-9-LENNOX.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Furnace won't start | Power, thermostat, door switch | Check circuit breaker, thermostat setting, ensure door properly closed |
| No heat | Gas supply, ignition | Verify gas valve on, check for ignition attempts, review LED codes |
| Short cycling | Filter, limit switch | Replace dirty filter, check for restricted airflow, verify limit operation |
| Blower won't stop | Thermostat, control board | Check thermostat fan setting, test control board fan relay |
| Unusual noises | Blower, inducer motor | Inspect blower wheel balance, check inducer motor bearings |
| Lockout condition | Safety control | Reset power, diagnose LED code, check affected safety device |
Reset Procedure: Turn thermostat to off, turn off power for 30 seconds, restore power, set thermostat to heat.
Service: Contact authorized Lennox dealer for professional service. 1-800-9-LENNOX