Lennox Furnace Manual 80MGF

The Lennox 80MGF is a high-efficiency gas furnace with 80% AFUE rating, featuring single-stage operation, durable heat exchanger, multi-speed blower motor, electronic ignition system, built-in diagnostic controls, safety shut-off features, and compatibility with various thermostat systems. Designed for residential heating applications with natural gas or propane capability. Below are key sections for safety, features, installation, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Durable aluminized steel heat exchanger, induced draft combustion system, hot surface igniter, multi-speed direct drive blower, integrated control board, pressure switches, flame sensor, and filter compartment.

Installation

Unpack and inspect all components. Ensure proper clearances and venting requirements.

1. Position furnace: Place on stable, level surface with proper clearances (1-inch minimum sides, 6-inch front).
2. Connect gas line: Use black iron pipe with proper thread sealant; pressure test for leaks.
3. Install venting: Use approved PVC or metal vent pipe per local codes.
4. Electrical connections: Connect 120V power supply and thermostat wiring.
5. Install condensate drain: Route to suitable drain location.

WARNING! Gas appliances can be dangerous; only qualified technicians should perform installation. Ensure proper ventilation and gas line integrity.

First-Time Setup

Complete installation checks before initial startup.

1. Verify gas connections: Check for leaks with soap solution.
2. Confirm electrical: Ensure proper voltage and grounding.
3. Check venting: Verify proper slope and termination.
4. Install air filter: Insert clean 1-inch filter.
5. Startup sequence: Turn on gas supply, then electrical power.
6. Test operation: Set thermostat to heat mode and verify proper ignition.

CAUTION! Never operate without proper venting. Ensure combustion air supply is adequate.

Specifications

• Model: 80MGF Series
• AFUE Rating: 80%
• Input BTU/H: 40,000 - 120,000 (varies by model)
• Gas Type: Natural gas or propane (conversion kit required)
• Electrical: 120V AC, 60Hz
• Blower Speeds: Multi-speed for heating and continuous fan
• Venting: PVC or metal Category I venting
• Dimensions: Varies by model (typical 21"W x 21"D x 40"H)
• Warranty: 20-year heat exchanger limited warranty

Controls and Settings

Integrated control board manages all furnace operations with LED status indicators.

Control Board Features: Self-diagnostic capability, status LED, safety lockout, automatic reset, blower control, gas valve control.

Thermostat Connections: R (24V power), W (Heat), G (Fan), C (Common). Status LED Codes: Steady green (normal operation), flashing codes indicate specific faults. Blower Speeds: Adjustable for heating and continuous fan operation via dip switches.

Connecting Thermostat

Compatible with most 24V thermostat systems. Basic 4-wire connection recommended.

1. Turn off power to furnace at electrical disconnect.
2. Remove furnace access panel to access control board.
3. Connect thermostat wires: R to R, W to W, G to G, C to C.
4. Secure connections and replace access panel.
5. Restore power and test thermostat operation.

Tip: Use thermostat with appropriate heating system compatibility. Programmable thermostats recommended for energy savings.

Operating Procedures

Normal operation controlled through thermostat settings.

1. Set thermostat to desired temperature in HEAT mode.
2. Furnace will initiate startup sequence: inducer motor starts, pressure switch verifies, igniter heats, gas valve opens.
3. Burners ignite; flame sensor confirms ignition.
4. Blower motor starts after warm-up period.
5. Shutdown sequence reverses process when thermostat satisfied.
6. Continuous fan operation available through thermostat FAN setting.

WARNING! Never adjust gas pressure or limit settings without proper training and equipment.

Maintenance Schedule

Regular maintenance ensures optimal performance and safety.

Care & Cleaning

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

CAUTION! Never use water or liquid cleaners on electrical components. Keep combustion area clear of debris.

Regulatory Information

ANSI Z21.47/CSA 2.3: Certified for safety standards. UL listed. Must be installed in accordance with National Fuel Gas Code and local building codes. For natural gas installations, minimum gas supply pressure 5" w.c., maximum 14" w.c. Copyright © Lennox Industries Inc. For technical support, contact 1-800-9-LENNOX or visit www.lennox.com.

Troubleshooting

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

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