GE 21LG Furnace Manual

The GE 21LG Furnace is a high-efficiency gas furnace designed for residential heating applications. This model features advanced combustion technology, multiple heating stages, variable-speed blower motor, electronic ignition system, built-in diagnostic controls, safety shut-off features, and energy-efficient operation. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Heat exchanger, burners, blower assembly, gas valve, ignition system, control board, filter compartment, flue outlet.

Feature	Description
Heat exchanger	Stainless steel construction for efficient heat transfer
Burner assembly	Multi-port burners for clean combustion
Blower motor	Variable-speed ECM motor for quiet operation
Gas valve	Precise gas flow control with safety shut-off
Ignition system	Electronic hot surface ignition
Control board	Microprocessor-based with diagnostic LEDs
Filter compartment	Standard 1-inch filter access
Flue outlet	PVC compatible for sidewall or roof venting
Pressure switches	Safety verification of proper venting
Limit switches	Over-temperature protection

Installation

Unpack and inspect contents. Ensure proper location with adequate clearance.

1. Position furnace: Place on stable, level surface with minimum clearances as specified.
2. Connect gas supply: Use approved gas piping and fittings; pressure test for leaks.
3. Connect electrical: 120V AC power supply with proper grounding.
4. Connect thermostat: Use 18-gauge thermostat wire.
5. Connect venting: Install PVC vent pipes according to local codes.
6. Connect ductwork: Secure supply and return air ducts.

WARNING! Gas furnaces produce carbon monoxide; proper venting is critical. Installation must comply with local codes and be performed by qualified technician.

First-Time Setup

Power on furnace; follow startup sequence.

1. Verify gas supply: Ensure gas valve is open and pressure is correct.
2. Check electrical: Confirm proper voltage at unit.
3. Set thermostat: Program desired temperature settings.
4. Test operation: Initiate heating cycle and verify proper ignition.
5. Check airflow: Verify proper air delivery through registers.
6. Monitor operation: Observe complete heating cycle for normal operation.

CAUTION! Never bypass safety devices. If furnace fails to start properly, shut off power and gas, then consult troubleshooting section.

Specifications

• Heating Capacity: 60,000-100,000 BTU/h (model dependent)
• Efficiency: Up to 96% AFUE
• Gas Type: Natural gas (convertible to LP with kit)
• Electrical: 120V AC, 60Hz, 15A circuit
• Blower Motor: Variable-speed ECM
• Stages: Single or two-stage heating (model dependent)
• Venting: PVC pipe (2-inch minimum)
• Filter Size: Standard 16x25x1 inch
• Sound Level: Less than 70 dB
• Warranty: Limited lifetime heat exchanger, 10 years parts

Controls and Settings

Access control board via front panel. LED status lights indicate operating mode and fault codes.

Control Board: POWER switch, Diagnostic LEDs, DIP switch settings, Reset button.

Operating Modes: HEAT, OFF, FAN ON. Blower Settings: Auto, Continuous. Temperature Control: Via thermostat. Diagnostic Codes: Flash patterns indicate specific faults (refer to service manual). DIP Switches: Configure heating stages, blower speeds, accessory options.

Connecting Thermostat

Standard thermostat connections: R (power), W (heat), G (fan), Y (cool), C (common).

1. Turn off power to furnace before wiring.
2. Strip thermostat wires 1/4 inch.
3. Connect wires to corresponding terminals on control board.
4. Secure connections and replace access panel.
5. Restore power and test operation.

Tip: Use programmable thermostat for optimal energy efficiency and comfort.

Operating Modes

Supports heating and fan-only operation.

1. Heating Mode: Thermostat calls for heat, ignition sequence begins, burners light, blower activates after heat exchanger warms.
2. Fan Mode: Continuous fan operation for air circulation.
3. Standby Mode: System ready but not actively heating.
4. Safety Shutdown: Automatic shutdown if fault detected.
5. Lockout Mode: System locks out after multiple failed ignition attempts.

WARNING! Never operate furnace without proper venting and air filters. Ensure combustion air supply is adequate.

Maintenance Procedures

Regular maintenance ensures optimal performance and safety.

1. Monthly: Check and replace air filter as needed.
2. Seasonal: Inspect vent system for obstructions.
3. Annual: Professional inspection and cleaning of burners, heat exchanger, blower assembly.
4. As needed: Clean flame sensor, check gas pressure, verify safety controls.

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

Care & Cleaning

Turn off power before cleaning. Use soft brush and vacuum for dust removal.

CAUTION! Do not use water or liquid cleaners. Keep electrical components dry. Never operate with wet filters.

Regulatory Information

UL certified for safety. ANSI Z21.47 compliant. Meets DOE energy efficiency standards. Installation must comply with National Fuel Gas Code (NFPA 54) and local building codes. For technical support, contact GE Appliances at 1-800-432-2737 or visit www.geappliances.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power, thermostat, gas supply	Check circuit breaker, thermostat setting, gas valve position
No heat	Ignition failure, gas supply	Check for spark at igniter, verify gas pressure
Blower not running	Motor, capacitor, control board	Check voltage to motor, test capacitor, inspect control board
Short cycling	Dirty filter, airflow restriction	Replace filter, check for blocked vents/registers
Unusual noises	Loose components, airflow issues	Tighten access panels, check ductwork, inspect blower wheel
Lockout mode	Repeated ignition failure	Reset power, check flame sensor, verify gas valve operation

Reset: Turn power off for 30 seconds, then restore.

Service: 1-800-432-2737; www.geappliances.com