Goodman Modulating Gas Furnace Installation Manual

The Goodman Modulating Gas Furnace is a high-efficiency heating system featuring variable-speed technology, modulating gas valve for precise temperature control, AFUE ratings up to 98%, compatibility with standard thermostat systems, built-in diagnostic controls, multi-speed blower motor, durable heat exchanger construction, and safety features including flame rollout and limit switches. Below are key sections for safety, installation, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Modulating gas valve, variable-speed blower motor, electronic ignition system, heat exchanger, pressure switches, diagnostic LED, filter compartment, gas valve, vent connections.

Safety Precautions

Follow all safety guidelines during installation and operation.

1. Gas leak check: Use soap solution to check all gas connections.
2. Ventilation: Ensure adequate combustion air and proper venting.
3. Clearances: Maintain required clearances to combustible materials.
4. Electrical safety: Disconnect power before servicing.

WARNING! Gas furnaces produce carbon monoxide; ensure proper venting and install CO detectors. Only qualified technicians should install and service this equipment.

Installation Requirements

Proper installation is critical for safe and efficient operation.

1. Location: Install in dry, well-ventilated area with service access.
2. Clearances: Minimum 1" sides, 6" front, 1" top, 0" bottom to combustibles.
3. Foundation: Level, solid foundation capable of supporting unit weight.
4. Ductwork: Properly sized and sealed duct system.
5. Gas supply: Adequate gas pressure and pipe sizing.

CAUTION! Unit is heavy; use proper lifting equipment and multiple personnel.

Specifications

• Input Capacity: 40,000-120,000 BTU/H modulating
• AFUE Rating: Up to 98%
• Gas Type: Natural Gas (convertible to LP)
• Gas Pressure: Natural: 3.5" WC, LP: 10" WC
• Electrical: 120V AC, 60Hz, 5-12 amps
• Blower Motor: Variable-speed ECM
• Vent Size: 2" PVC
• Drain Connection: 3/4" PVC
• Dimensions: Varies by model (typically 21"W x 21"D x 40"H)
• Weight: 90-150 lbs depending on model

Electrical Connections

Follow NEC and local electrical codes for all wiring.

1. Disconnect power before making electrical connections.
2. Connect 120V AC power to unit disconnect switch.
3. Connect thermostat wires to control board terminals (R, W, Y, G, C).
4. Ground unit according to local codes.
5. Verify proper voltage at unit (115-125V AC).

Tip: Use copper conductors only. Check polarity and ground continuity.

Gas Line Connections

Gas piping must comply with local codes and NFPA 54.

1. Install sediment trap upstream of gas valve.
2. Use pipe joint compound rated for natural/LP gas.
3. Pressure test entire system at 14" WC for 10 minutes.
4. Check for leaks with soap solution.
5. Verify manifold pressure: Natural gas 3.5" WC, LP gas 10" WC.

WARNING! Never use matches or open flames to check for gas leaks.

Venting System

Category IV venting system required for proper operation.

1. Use only PVC, CPVC, or ABS pipe approved for furnace venting.
2. Maintain minimum 1/4" per foot slope toward furnace.
3. Install condensate drain trap and route to approved drain.
4. Follow manufacturer's guidelines for vent length and elbows.
5. Terminate vents according to local codes (typically 12" above grade).

CAUTION! Improper venting can cause carbon monoxide poisoning.

Startup and Commissioning

Complete system checkout before placing in service.

1. Verify all connections are secure and proper.
2. Check gas pressure and adjust if necessary.
3. Test safety controls: limit switches, pressure switches, rollout switches.
4. Measure temperature rise (typically 30-60°F).
5. Check combustion analysis: CO2 8-10%, O2 5-9%, CO < 100 ppm.
6. Program thermostat for proper staging and fan control.

WARNING! Never bypass safety controls during testing.

Maintenance Procedures

Regular maintenance ensures optimal performance and safety.

1. Monthly: Check and replace air filter as needed.
2. Annual: Clean burners and heat exchanger.
3. Annual: Check and clean flame sensor.
4. Annual: Inspect vent system for obstructions.
5. Annual: Verify proper gas pressure and combustion.
6. Annual: Lubricate blower motor if required.

CAUTION! Disconnect power and gas before performing maintenance.

Regulatory Information

UL certified for safety. Complies with ANSI Z21.47 standards. CSA design certified. Installation must comply with National Fuel Gas Code NFPA 54, National Electrical Code NFPA 70, and local building codes. For technical support, contact Goodman Manufacturing at 1-877-466-8626 or visit www.goodmanmfg.com.

Troubleshooting

Reset: Power cycle unit to clear fault codes.

Service: 1-877-466-8626; www.goodmanmfg.com