Carrier Gas Furnace Repair Manual

The Carrier Gas Furnace is a high-efficiency heating system designed for residential and light commercial applications. This manual covers installation, operation, maintenance, and troubleshooting procedures for various Carrier gas furnace models. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting Components 7. Operation Procedures 8. Safety Features 9. Maintenance & Cleaning 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Heat exchanger, blower assembly, gas valve, ignition system, control board, thermostat connection, pressure switches, flame sensor.

Feature	Description
Heat exchanger	Stainless steel primary and secondary heat exchangers
Blower assembly	Variable speed ECM motor for efficient operation
Gas valve	Modulating gas valve for precise temperature control
Ignition system	Hot surface igniter with flame sensor
Control board	Microprocessor-based control with diagnostic LEDs
Thermostat connection	Standard 24V thermostat terminals
Pressure switches	Safety switches for combustion air and venting
Flame sensor	Monitors burner flame during operation
Limit switches	High temperature safety cut-off
Drain system	Condensate removal for high-efficiency models

Installation

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

Position furnace: Place on stable, level surface with proper clearances.
Connect gas supply: Use approved gas piping with shut-off valve.
Install venting: Follow manufacturer specifications for vent pipe sizing and routing.
Electrical connections: Connect 120V power supply and thermostat wiring.
Drain connections: Install condensate drain line for high-efficiency models.

WARNING! Gas furnaces produce carbon monoxide; ensure proper venting. Only qualified technicians should perform installation.

First-Time Setup

Power on furnace; follow startup sequence.

Gas pressure check: Verify inlet and manifold gas pressures.
Combustion analysis: Check CO levels and combustion efficiency.
Blower settings: Adjust blower speeds for heating mode.
Thermostat configuration: Set up thermostat for proper furnace operation.
Safety checks: Verify all safety devices are functioning properly.

CAUTION! Always check for gas leaks using approved leak detection solution.

Specifications

Input Capacity: 40,000 to 120,000 BTU/h
Efficiency: 80% to 98% AFUE
Gas Type: Natural gas or propane (conversion kit required)
Electrical: 120V AC, 60Hz, 15A circuit
Blower Motor: ECM or PSC, variable speed
Control Voltage: 24V AC
Venting: Category I or IV depending on efficiency
Dimensions: Varies by model (typically 21"W x 21"D x 40"H)
Weight: 80 to 150 pounds

Controls and Settings

Access control board via front panel. Diagnostic LEDs indicate system status and error codes.

Control Board: POWER, STATUS LED, ERROR CODE display, DIP switches for configuration.

Temperature: Thermostat control, fan limits. Safety: Pressure switches, limit switches, rollout switches. Configuration: DIP switches for blower speeds, thermostat type, furnace capacity. Diagnostics: LED error codes for troubleshooting.

Connecting Components

Thermostat: Standard 24V connections. Gas supply: 1/2" to 3/4" black iron pipe. Electrical: 120V power, ground wire. Venting: PVC or metal vent pipe depending on category.

Turn off power and gas supply before making connections.
Match wire colors to terminal designations (R, W, Y, G, C).
Use proper pipe dope or Teflon tape on gas connections.
Ensure all electrical connections are tight and properly grounded.

Tip: Always use two wrenches when making gas connections to prevent twisting pipes.

Operation Procedures

Standard heating cycle sequence: thermostat call, inducer motor start, pressure switch verification, igniter warm-up, gas valve opening, flame sensing, blower activation.

Startup: Thermostat calls for heat, control board initiates sequence.
Pre-purge: Inducer motor runs to clear combustion chamber.
Ignition: Hot surface igniter heats up, gas valve opens.
Flame detection: Flame sensor confirms burner ignition.
Main operation: Blower activates, heat exchanger warms.
Shutdown: Thermostat satisfied, gas valve closes, blower continues for cool-down.
Safety monitoring: Continuous monitoring of all safety devices.

WARNING! Never bypass safety devices. Always follow proper shutdown procedures.

Safety Features

Flame rollout switches: Detect burner flame outside heat exchanger. Limit switches: Monitor heat exchanger temperature. Pressure switches: Verify proper venting operation. Flame sensor: Ensures gas valve only opens when flame is present.

Maintenance & Cleaning

Turn off power and gas before servicing. Regular maintenance includes filter replacement, burner cleaning, heat exchanger inspection, blower cleaning, and drain system clearing.

CAUTION! Use only approved cleaning materials. Never use compressed air on electronic components.

Regulatory Information

ANSI Z21.47: Certified for gas-fired central furnaces. UL 1995: Standard for heating and cooling equipment. All installations must comply with local building codes and NFPA 54. For technical support, contact Carrier Corporation at 1-800-CARRIER or visit www.carrier.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power, thermostat, door switch	Check circuit breaker, thermostat settings, door switch engagement.
No heat	Gas supply, igniter, flame sensor	Verify gas valve on, check igniter continuity, clean flame sensor.
Short cycling	Filter, limit switch, airflow	Replace filter, check limit switch, verify proper airflow.
Blower not working	Motor, capacitor, control board	Check motor windings, test capacitor, verify control board output.
Error codes flashing	Various system faults	Refer to error code chart in manual for specific diagnosis.

Reset: Power cycle furnace to clear temporary fault codes.

Service: 1-800-CARRIER; www.carrier.com