Lennox Furnace G23Q3 4-100-2 Manual

The Lennox G23Q3 4-100-2 is a high-efficiency gas furnace designed for residential heating applications. This two-stage furnace features variable-speed blower technology, electronic ignition, and advanced diagnostic controls. With AFUE ratings up to 95%, it provides reliable and efficient heating performance. Below are key sections covering 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 Instructions 8. Maintenance Procedures 9. Safety Information 10. Regulatory Compliance 11. Troubleshooting Guide

Features at a Glance

Key components: Two-stage gas valve, variable-speed ECM blower motor, hot surface ignitor, flame sensor, pressure switches, and diagnostic control board.

Feature	Description
Two-stage operation	Provides efficient heating at low and high stages
Variable-speed blower	Quiet operation and improved comfort
Electronic ignition	Reliable startup with hot surface ignitor
Diagnostic controls	LED status lights for troubleshooting
Dual-port burners	Efficient combustion with low emissions
Multi-speed blower	Adjustable airflow for optimal performance
Pressure switches	Safety verification of venting system
Flame sensor	Monitors burner operation
Gas valve	Precise fuel control
Heat exchanger	Durable aluminized steel construction

Installation Requirements

Professional installation required. Verify local codes and obtain necessary permits.

Location: Install in approved area with proper clearances and combustion air.
Venting: Use approved PVC or CPVC for direct vent installation.
Gas supply: Connect to proper gas line with shutoff valve.
Electrical: Connect to 120V AC power with proper grounding.
Ductwork: Ensure proper sizing and sealing.

WARNING! Gas furnaces produce carbon monoxide. Proper installation and venting are critical for safety.

First-Time Setup

Initial startup must be performed by qualified technician.

Verify installation: Check all connections, clearances, and venting.
Gas pressure: Adjust manifold pressure per specifications.
Blower speed: Set appropriate speeds for heating operation.
System check: Test ignition sequence and safety controls.
Commissioning: Verify proper operation and document settings.

CAUTION! Only qualified personnel should perform initial startup and adjustment.

Technical Specifications

Model: G23Q3 4-100-2
Input Capacity: 100,000 BTU/h
Output Capacity: 95,000 BTU/h
AFUE Rating: Up to 95%
Stages: Two-stage heating
Blower Type: Variable-speed ECM
Gas Type: Natural gas
Electrical: 120V, 60Hz
Venting: Direct vent or conventional
Dimensions: Consult installation manual

Controls and Settings

Integrated furnace control board with diagnostic LED. Thermostat connections for single or two-stage operation.

Control Board: LED status lights, dip switch settings, terminal connections.

Operating Modes: Single-stage or two-stage operation selectable via dip switches. Blower Speeds: Adjustable for heating operation. Safety Controls: Limit switches, pressure switches, flame sensor, rollout switches. Diagnostics: LED flash codes for troubleshooting.

Venting and Combustion Air

Direct vent system using PVC pipe. Ensure proper sizing and slope.

Vent pipe: Use approved PVC or CPVC material.
Termination: Follow clearance requirements for vent termination.
Combustion air: Provide adequate fresh air supply.
Vent length: Follow manufacturer's maximum length specifications.

Tip: Regular inspection of vent system is essential for safe operation.

Operation Instructions

Normal operation controlled by thermostat. Two-stage operation provides efficient heating.

Thermostat call: Set thermostat to desired temperature.
Ignition sequence: Control board initiates pre-purge, ignitor warm-up, gas valve opening.
Flame verification: Flame sensor confirms ignition.
Blower operation: Blower starts after heat exchanger warm-up period.
Stage operation: First stage operates for moderate heating needs; second stage for high demand.
Shutdown: Thermostat satisfied, gas valve closes, blower continues for cool-down.

WARNING! Never operate furnace without proper venting and combustion air.

Maintenance Procedures

Annual maintenance by qualified technician recommended.

Air filter: Replace or clean monthly during heating season.
Burners: Inspect and clean annually.
Heat exchanger: Visual inspection for cracks or damage.
Vent system: Check for obstructions or damage.
Blower assembly: Clean and lubricate as needed.
Safety controls: Test operation of all safety devices.

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

Safety Information

Carbon monoxide detectors required in living spaces. Regular professional inspection essential.

WARNING! Gas furnaces can produce carbon monoxide - a deadly, odorless gas. Install CO detectors and ensure proper venting.

Regulatory Compliance

UL listed and ANSI certified. Complies with applicable safety standards. Installation must meet local building codes and utility requirements. 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 lockout	Check power supply; verify thermostat settings; reset if locked out.
No heat	Gas supply, ignition failure	Verify gas valve open; check for ignition attempts; inspect flame sensor.
Short cycling	Dirty filter, airflow restriction	Replace air filter; check for blocked vents or registers.
Blower not running	Motor, capacitor, control board	Check blower motor operation; verify control signals.
Lockout condition	Safety device activation	Check LED error codes; reset power; identify and correct fault.

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

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