Goodman Gas Furnace Service Manual

The Goodman Gas Furnace is a high-efficiency heating system designed for residential use, featuring advanced combustion technology, multiple safety controls, and energy-efficient operation. This manual covers installation, operation, maintenance, troubleshooting, and safety procedures for certified HVAC technicians. Below are key sections for safety protocols, technical specifications, installation procedures, maintenance schedules, and troubleshooting guidelines.

1. Safety Information 2. Technical Specifications 3. Installation Procedures 4. System Components 5. Operation Instructions 6. Maintenance Schedule 7. Electrical Wiring 8. Gas Connections 9. Venting Requirements 10. Error Codes 11. Troubleshooting Guide

Safety Information

Critical safety protocols for handling and servicing Goodman gas furnaces.

Hazard Type	Safety Precautions
Gas Leaks	Use leak detection solution; never use open flame to check for leaks
Electrical Shock	Disconnect power before servicing; use lockout/tagout procedures
Carbon Monoxide	Ensure proper venting; install CO detectors in living areas
High Temperatures	Allow system to cool before handling combustion components
Moving Parts	Keep hands clear of blower wheel and inducer motor during operation

Technical Specifications

Detailed technical data for Goodman gas furnace models.

Input Capacity: 40,000 - 120,000 BTU/H
Efficiency Rating: 80% - 96% AFUE
Gas Type: Natural Gas or LP (with conversion kit)
Electrical Requirements: 120V AC, 60Hz, 15A circuit
Static Pressure: 0.1 - 0.9 inches WC maximum
Vent Size: 2" - 6" PVC depending on model
Operating Temp Range: -30°F to 150°F ambient
Warranty: Limited lifetime heat exchanger, 10-year parts

Installation Procedures

Step-by-step installation guidelines for certified technicians.

Location Selection: Install in dry, clean area with adequate combustion air and service clearance
Combustion Air: Ensure proper fresh air intake according to local codes
Venting: Install PVC vent pipes with proper slope and termination clearances
Gas Connection: Use approved pipe compound; pressure test at 14" WC for 10 minutes
Electrical: Connect to dedicated 15A circuit; install disconnect switch within sight
Ductwork: Seal all connections; ensure proper airflow and static pressure
Startup: Perform complete startup sequence and combustion analysis

WARNING! Installation must comply with all local codes and manufacturer specifications. Only qualified technicians should perform installation.

System Components

Major components and their functions in Goodman gas furnace systems.

Component	Function
Heat Exchanger	Transfers heat from combustion gases to air stream
Gas Valve	Regulates gas flow to burners; includes safety shutoff
Inducer Motor	Creates draft for combustion and venting
Blower Motor	Circulates air through heat exchanger and ductwork
Ignition System	Hot surface igniter or intermittent pilot ignition
Control Board	Monitors safety devices and controls system operation
Flame Sensor	Detects burner flame; shuts off gas if no flame
Pressure Switches	Verify proper venting and inducer operation

Operation Instructions

Proper operation procedures and control settings.

Thermostat Settings: Set to HEAT mode with desired temperature
System Sequence: Inducer motor starts, pressure switch closes, igniter heats, gas valve opens
Blower Operation: Blower starts after heat exchanger warm-up delay
Cycle Completion: Gas valve closes when thermostat satisfied, blower runs for post-purge
Continuous Fan: Use FAN ON setting for continuous air circulation

Note: System includes built-in delays to ensure proper operation and safety.

Maintenance Schedule

Recommended maintenance intervals and procedures.

Maintenance Task	Frequency	Procedure
Air Filter Replacement	Monthly during heating season	Install clean filter with arrow pointing toward blower
Blower Cleaning	Annually	Vacuum blower assembly and motor
Heat Exchanger Inspection	Annually	Visual inspection for cracks or corrosion
Burner Cleaning	Annually	Clean burners and inspect flame pattern
Vent System Inspection	Annually	Check for obstructions and proper slope
Gas Pressure Check	Annually	Verify manifold pressure and adjust if needed

Electrical Wiring

Electrical connections and control circuit diagrams.

Power Supply: 120V AC connection to control board L1 and L2 terminals
Thermostat Wiring: Connect R, W, G, C terminals per wiring diagram
Safety Devices: Series connection of limit switches, rollout switches, pressure switches
Motor Speeds: Blower motor has multiple speed taps for heating/cooling/continuous fan
Diagnostic LED: Control board LED flashes error codes for troubleshooting

CAUTION! Always disconnect power before servicing electrical components.

Gas Connections

Gas line installation and pressure adjustment procedures.

Pipe Sizing: Use adequate pipe size based on length and BTU input
Shutoff Valve: Install manual gas shutoff valve within 6 feet of unit
Drip Leg: Install sediment trap before gas connection
Pressure Test: Test gas lines at 14" WC for 10 minutes with no pressure drop
Manifold Pressure: Adjust gas valve to specified manifold pressure (typically 3.5" WC natural gas)
Combustion Analysis: Verify CO2 levels and temperature rise within specifications

Venting Requirements

PVC vent pipe installation guidelines and clearances.

Pipe Material: Schedule 40 PVC or CPVC for combustion venting
Vent Sizing: 2" minimum diameter; larger for longer runs
Termination Clearances: 12" from grade, 3' from operable windows
Slope: 1/4" per foot back toward furnace for condensation drainage
Support: Support pipes every 4 feet; use proper hangers
Sealing: Use PVC cement on all joints; ensure watertight seals

Error Codes

Control board LED flash codes for diagnostic purposes.

Flash Pattern	Error Description	Possible Causes
1 Flash	Pressure Switch Error	Blocked vent, inducer failure, switch malfunction
2 Flashes	Ignition Failure	Gas supply, igniter, flame sensor, gas valve
3 Flashes	Limit Switch Lockout	Restricted airflow, dirty filter, blower issues
4 Flashes	Flame Loss Error	Flame sensor, gas pressure, grounding issues
5 Flashes	Rollout Switch Trip	Blocked heat exchanger, improper combustion
Continuous	Normal Operation	System operating properly

Troubleshooting Guide

Common service issues and corrective actions.

Symptom	Possible Cause	Corrective Action
No Heat	Thermostat, power, gas supply	Check thermostat setting, circuit breaker, gas valve
Short Cycling	Dirty filter, airflow restriction	Replace filter, check ductwork, verify static pressure
Blower Not Running	Motor, capacitor, control board	Check voltage to motor, test capacitor, verify control signals
Unusual Noises	Loose components, airflow issues	Tighten mounting hardware, check for obstructions
Pilot/Igniter Failure	Igniter, flame sensor, gas valve	Test igniter continuity, clean flame sensor, check gas pressure
High CO Readings	Combustion issues, heat exchanger	Adjust air shutter, check for cracks in heat exchanger

Reset Procedure: Power cycle unit to clear lockout conditions.

Technical Support: 1-877-254-4729; www.goodmanmfg.com