Goodman Furnace Model GMSS Installation Manual

The Goodman GMSS series is a high-efficiency gas furnace designed for residential installation. This multi-speed furnace features AFUE ratings up to 96%, electronic ignition, induced draft combustion, and compatibility with various thermostat systems. Below are key sections covering safety precautions, installation procedures, electrical connections, startup procedures, maintenance, and troubleshooting guidelines.

Features at a Glance

Key components: Multi-speed blower motor, hot surface ignitor, induced draft motor, stainless steel heat exchanger, integrated control board, pressure switches, and flame sensor.

Safety Precautions

Read all instructions before beginning installation. Ensure proper clearances and ventilation.

1. Gas line installation: Only qualified technicians should handle gas connections.
2. Electrical connections: Disconnect power before servicing; follow local electrical codes.
3. Combustion air: Ensure adequate combustion and ventilation air supply.
4. Clearances: Maintain minimum clearances to combustible materials.

WARNING! Failure to follow safety precautions may result in fire, explosion, carbon monoxide poisoning, or electrical shock. Installation must comply with all local codes and ordinances.

Pre-Installation Requirements

Verify site conditions and gather necessary tools and materials before installation.

1. Location selection: Choose area with proper clearances and access for service.
2. Combustion air: Calculate required combustion air based on installation type.
3. Gas supply: Verify adequate gas pressure and pipe sizing.
4. Electrical: Ensure proper voltage (120V) and dedicated circuit.
5. Venting: Plan vent pipe routing and termination location.

CAUTION! Installation in garages requires 18-inch elevation above floor. Never install in sleeping rooms or bathrooms.

Technical Specifications

• Model Series: GMSS96
• Input BTU/H: 40,000 - 120,000 (varies by model)
• Output BTU/H: 38,400 - 115,200 (varies by model)
• AFUE: Up to 96%
• Electrical: 120V, 60Hz, 15A circuit
• Gas Type: Natural gas or propane (conversion kit required)
• Gas Pressure: Natural: 3.5" WC; Propane: 10" WC
• Blower Speeds: Multi-speed for heating and cooling
• Sound Rating: Ultra-quiet operation
• Warranty: Limited lifetime heat exchanger, 10-year parts

Installation Procedures

Follow step-by-step installation sequence for proper furnace setup.

Positioning: Place furnace on level surface, ensure proper clearances (typically 1" sides, 1" rear, 6" front, 24" above).

Ductwork: Connect supply and return ducts securely. Use flexible connectors if needed. Filter installation: Install appropriate air filter in filter rack. Condensate drain: Connect PVC drain line to condensate trap and route to drain.

Electrical Connections

Connect power supply and thermostat wiring according to wiring diagram.

1. Disconnect power at service panel before making connections.
2. Connect 120V power supply to furnace junction box.
3. Connect thermostat wires to control board terminals (R, W, Y, G, C).
4. Connect humidifier or electronic air cleaner if applicable.
5. Verify proper grounding of all electrical components.

Tip: Use wire nuts and electrical tape for secure connections. Follow local electrical codes.

Gas Line Connections

Gas piping must be properly sized and tested for leaks.

1. Install sediment trap upstream of gas valve.
2. Use pipe joint compound rated for natural gas.
3. Connect gas supply line to furnace gas valve.
4. Test for leaks with soap solution or electronic detector.
5. Verify manifold pressure with manometer.

WARNING! Never use matches or open flame to check for gas leaks. Always perform leak test before placing furnace in operation.

Venting System

PVC vent pipe installation for direct vent systems.

1. Plan vent route with minimum elbows and proper slope.
2. Use PVC primer and cement for secure joints.
3. Maintain minimum clearances to combustible materials.
4. Install termination kit with proper clearance from windows and doors.
5. Verify vent pipe is supported every 4 feet.

CAUTION! Do not use CPVC or ABS pipe. Vent must terminate at least 12 inches above ground level and 3 feet from any opening into building.

Startup and Commissioning

Complete system checkout and performance verification.

1. Restore power and gas supply to furnace.
2. Set thermostat to heat mode above room temperature.
3. Observe ignition sequence and flame establishment.
4. Verify proper vent operation and temperature rise.
5. Check gas pressure and adjust if necessary.
6. Test safety controls and limit switches.

WARNING! Never bypass safety controls. If furnace fails to operate properly, shut off power and gas until problem is corrected.

Maintenance Procedures

Regular maintenance ensures optimal performance and longevity.

Monthly: Check and replace air filter as needed. Annual: Professional inspection and cleaning of burners, heat exchanger, and vent system. Blower maintenance: Clean blower wheel and housing annually. Condensate system: Flush condensate trap and drain line each season.

Troubleshooting

Reset: Power cycle furnace to clear temporary lockouts.

Service: Contact qualified HVAC technician for complex issues. Goodman Manufacturing: 1-713-861-2500; www.goodmanmfg.com