Goodman Furnace Model GMSS960804CN Installation Manual

The Goodman GMSS960804CN is a high-efficiency gas furnace with 96% AFUE rating, 80,000 BTU input capacity, multi-speed ECM blower motor, two-stage gas valve, hot surface ignition system, corrosion-resistant heat exchanger, pressure switch safety controls, and compatibility with various thermostat systems. Below are key sections for safety, specifications, installation procedures, wiring, startup, and troubleshooting.

Features at a Glance

Key components: Two-stage gas valve, ECM blower motor, aluminized steel heat exchanger, hot surface igniter, pressure switches, flame sensor, condensate drain system.

Safety Precautions

Read all instructions before installation. Follow local codes and manufacturer guidelines.

1. Disconnect power before servicing: Turn off electrical power at circuit breaker.
2. Gas line safety: Check for leaks with soap solution; never use open flame.
3. Venting requirements: Ensure proper draft and clearances to combustible materials.
4. Carbon monoxide: Install CO detectors in living areas near bedrooms.

WARNING! Failure to follow safety procedures may result in fire, explosion, or carbon monoxide poisoning. Only qualified technicians should perform installation.

Specifications

• Model: GMSS960804CN
• AFUE: 96%
• Input BTU: 80,000
• Output BTU: 76,800
• Gas Type: Natural Gas
• Gas Pressure: 3.5" WC inlet, 3.2" WC manifold
• Electrical: 115V/60Hz, 5.2A
• Blower Speeds: Multi-speed ECM (Cooling: 1075 CFM, Heating: 800 CFM)
• Dimensions: 21"W x 21"D x 45"H
• Venting: 2" PVC recommended
• Weight: 125 lbs

Pre-Installation Requirements

Verify site conditions and gather necessary materials before beginning installation.

1. Location: Indoor installation only; minimum clearances: 0" sides, 1" front, 0" top, 0" back.
2. Combustion air: Ensure adequate fresh air supply per local codes.
3. Gas supply: 3/4" black iron pipe minimum; verify gas pressure available.
4. Electrical: Dedicated 15-amp circuit required.
5. Condensate drain: Route to floor drain or condensate pump.
6. Thermostat: Compatible with two-stage heating systems.

CAUTION! Check local building codes for specific requirements in your area.

Installation Procedures

Follow step-by-step installation sequence for proper operation.

1. Position furnace: Place on level surface; ensure proper clearances.
2. Install filter rack: Mount 16x25x1 filter rack in return air duct.
3. Connect ductwork: Seal all joints with approved duct sealant.
4. Set furnace: Level unit using shims if necessary.
5. Install vent pipes: Follow PVC venting instructions carefully.
6. Connect gas line: Use proper pipe dope and leak test.
7. Wire electrical: Follow wiring diagram exactly.
8. Connect thermostat: Use 18-gauge thermostat wire.

Electrical Wiring

Proper electrical connections are critical for safe operation.

1. Disconnect power at main breaker before wiring.
2. Connect line voltage: Black to L1, White to L2, Green to ground.
3. Connect low voltage: R to 24V hot, C to common, W1/W2 to heat stages.
4. Verify polarity: Ensure proper hot/neutral connections.
5. Secure connections: Use wire nuts and strain relief.

Tip: Use a multimeter to verify voltage before making connections.

Gas Line Connection

Gas piping must be properly sized and leak-tested.

1. Pipe sizing: Minimum 3/4" black iron pipe for runs under 30 feet.
2. Install sediment trap: Required within 3 feet of furnace connection.
3. Use proper sealant: Apply pipe dope to male threads only.
4. Leak test: Use soap solution; check all joints and valves.
5. Gas pressure test: Verify 3.5" WC inlet pressure with manometer.

WARNING! Never use an open flame to check for gas leaks.

Venting System

PVC vent pipes must be properly sized and supported.

1. Pipe size: 2" PVC Schedule 40 for most installations.
2. Maximum length: 60 feet equivalent with two 90° elbows.
3. Slope: 1/4" per foot back toward furnace for condensate drainage.
4. Clearances: Maintain 1" from combustible materials.
5. Termination: Follow local codes for exterior vent termination.

Startup & Commissioning

Complete system checkout before placing in service.

1. Restore power: Turn on circuit breaker.
2. Set thermostat: Call for heat to begin startup sequence.
3. Monitor ignition: Verify proper flame establishment.
4. Check gas pressure: Adjust manifold pressure to 3.2" WC if needed.
5. Verify airflow: Check temperature rise (35-65°F).
6. Test safety controls: Verify pressure switch, limit switch operation.
7. Measure combustion: Use analyzer for CO levels and efficiency.

CAUTION! Do not bypass safety controls during testing.

Maintenance

Regular maintenance ensures optimal performance and longevity.

• Monthly: Check and replace air filter as needed.
• Annual: Professional inspection and cleaning recommended.
• Seasonal: Verify condensate drain is clear and flowing.
• Biannual: Inspect heat exchanger for cracks or corrosion.

WARNING! Turn off power and gas before performing any maintenance.

Troubleshooting

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

Service: Contact qualified HVAC technician for complex issues.