Old Lennox Gas Furnace Manual

The Old Lennox Gas Furnace is a reliable heating system designed for residential use, featuring natural gas operation, electronic ignition, variable-speed blower motor, thermal efficiency ratings, safety shut-off controls, and compatibility with standard thermostat systems. Below are key sections for safety precautions, technical specifications, installation guidelines, operation instructions, maintenance procedures, and troubleshooting.

1. Safety Precautions 2. Technical Specifications 3. Installation Guidelines 4. Operation Instructions 5. Maintenance Procedures 6. Control Settings 7. Venting Requirements 8. Gas Connections 9. Electrical Wiring 10. Troubleshooting Guide

Safety Precautions

Critical safety information for proper furnace operation and user protection.

Hazard Type	Precaution
Gas Leaks	Install carbon monoxide detectors; check connections regularly
Fire Hazard	Keep combustible materials 3 feet from furnace
Electrical Shock	Disconnect power before servicing
Burn Risk	Allow furnace to cool before maintenance
Venting Issues	Ensure proper ventilation to prevent CO buildup

Technical Specifications

Fuel Type: Natural Gas
Input BTU/H: 80,000 - 120,000 (model dependent)
Thermal Efficiency: 80% AFUE
Blower Motor: Variable-speed ECM
Ignition System: Electronic hot surface
Voltage: 120V AC, 60Hz
Gas Pressure: 3.5" WC natural gas
Vent Size: 4" PVC or metal
Dimensions: Varies by model (typically 21"W x 26"D x 40"H)

Installation Guidelines

Proper installation ensures safe and efficient furnace operation.

Location: Install in well-ventilated area with clearance for service access
Venting: Follow local codes for proper vent pipe installation
Gas Connection: Use approved pipe compound on male threads only
Electrical: Connect to dedicated 15-amp circuit
Ductwork: Ensure proper sizing and sealing
Thermostat: Install compatible 24V thermostat

WARNING! Installation must comply with local building codes and be performed by qualified technician.

Operation Instructions

Standard operating procedures for daily use.

Thermostat Setting: Set desired temperature on thermostat
System Switch: Set to HEAT mode
Fan Control: AUTO for automatic operation, ON for continuous
Pilot Light: Electronic ignition - no manual lighting required
Seasonal Startup: Verify proper venting and gas pressure

CAUTION! If furnace fails to ignite after three attempts, wait 5 minutes before retrying.

Maintenance Procedures

Regular maintenance ensures optimal performance and longevity.

Maintenance Task	Frequency	Procedure
Filter Replacement	Monthly	Replace disposable filter or clean permanent filter
Blower Cleaning	Annually	Vacuum blower assembly and motor
Heat Exchanger Inspection	Annually	Check for cracks or corrosion
Burner Cleaning	Annually	Clean burner orifices and surfaces
Vent Inspection	Seasonally	Check for blockages or damage

Control Settings

Understanding furnace control board settings and adjustments.

Control Board: LED status lights indicate system operation and error codes.

Fan Speed Settings: Adjust blower speeds for heating mode. Limit Switch: High-temperature safety cutoff. Gas Valve: Regulates gas flow to burners. Ignition Control: Manages spark sequence and flame detection.

Venting Requirements

Proper venting is critical for safe operation.

Vent Material: Use approved PVC or metal vent pipe
Clearances: Maintain required clearances from combustible materials
Termination: Install vent termination according to manufacturer specifications
Slope: Ensure proper slope for condensation drainage
Supports: Secure vent pipes at recommended intervals

Tip: Always check local building codes for specific venting requirements.

Gas Connections

Proper gas line installation and connection procedures.

Pipe Sizing: Use adequate pipe size for BTU load and length
Shut-off Valve: Install approved gas shut-off valve within 6 feet
Pressure Test: Test for leaks with soap solution - never with open flame
Drip Leg: Install sediment trap before gas valve
Connection: Use approved pipe compound or tape on male threads only

WARNING! Gas connections must be performed by licensed professional.

Electrical Wiring

Electrical connection requirements and safety.

Power Supply: 120V AC, 15 amp dedicated circuit
Grounding: Proper equipment grounding required
Thermostat Wiring: Standard 5-wire or 2-wire system compatible
Low Voltage: 24V control circuit for thermostat operation
Disconnect: Install service disconnect within sight of furnace

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No Heat	Thermostat setting, power, gas supply	Check thermostat, circuit breaker, gas valve
Furnace Short Cycling	Dirty filter, blocked vent, limit switch	Replace filter, clear vent obstructions
Blower Not Running	Motor capacitor, control board	Check capacitor, verify control voltage
Gas Odor	Gas leak, improper combustion	Shut off gas immediately, call professional
Pilot Won't Stay Lit	Thermocouple, gas pressure	Replace thermocouple, check gas pressure

Reset Procedure: Turn thermostat off, wait 30 seconds, turn back on.

Service: Contact qualified HVAC technician for complex issues.