Amana GUD115C50A Furnace Service Manual

The Amana GUD115C50A is a high-efficiency gas furnace with 115,000 BTU input capacity, 80% AFUE rating, single-stage operation, natural gas compatibility, multi-speed blower motor, hot surface ignition system, aluminized steel heat exchanger, and integrated diagnostic controls. Below are key sections for safety, technical specifications, installation, operation, maintenance, troubleshooting, and warranty information.

1. Safety Precautions 2. Technical Specifications 3. Installation Requirements 4. Electrical Connections 5. Gas Supply Connections 6. Venting Requirements 7. Startup and Operation 8. Maintenance Procedures 9. Diagnostic Codes 10. Troubleshooting Guide 11. Parts List

Safety Precautions

Critical safety information for proper installation and service.

Hazard	Precaution
Gas Leaks	Check all connections with leak detection solution; no open flames
Electrical Shock	Disconnect power before servicing; use lockout/tagout procedures
Carbon Monoxide	Ensure proper venting; install CO detectors in living spaces
High Temperatures	Allow furnace to cool before servicing internal components
Combustible Materials	Maintain clearance per installation instructions

Technical Specifications

Model: GUD115C50A
Input Capacity: 115,000 BTU/h
AFUE Rating: 80%
Gas Type: Natural Gas
Manifold Pressure: 3.5" W.C.
Electrical: 120V, 60Hz, 1PH
Blower Motor: Multi-speed, direct drive
Ignition System: Hot surface ignition
Heat Exchanger: Aluminized steel tubular
Dimensions: 21" W x 21" D x 45" H

Installation Requirements

Proper installation guidelines for safe and efficient operation.

Location: Install in dry, clean area with adequate combustion air
Clearances: Maintain 1" sides, 1" rear, 6" front, 24" top
Combustion Air: Ensure adequate fresh air supply per local codes
Drain Line: Install condensate drain with proper slope
Leveling: Ensure furnace is level for proper condensate drainage

WARNING! Installation must comply with local codes and regulations. Professional installation recommended.

Electrical Connections

Wiring and electrical connection procedures.

Disconnect power at main service panel
Connect 120V supply to furnace junction box
Connect thermostat wires to control board terminals
Verify proper grounding of all electrical components
Check blower motor rotation and speed settings

CAUTION! All electrical work must be performed by qualified personnel.

Gas Supply Connections

Natural gas connection and pressure verification.

Use approved gas pipe and fittings
Install sediment trap before gas valve
Check for leaks with approved leak detection solution
Verify manifold pressure: 3.5" W.C. ± 0.3"
Check incoming gas pressure: 7" W.C. minimum

DANGER! Gas leaks can cause explosion or fire. Test all connections thoroughly.

Venting Requirements

Proper vent system installation for safe operation.

Vent Material: PVC Schedule 40 or equivalent
Vent Size: 2" minimum diameter
Vent Slope: 1/4" per foot toward furnace
Clearances: Maintain 1" from combustible materials
Termination: Follow local code requirements for vent termination

Startup and Operation

Initial startup procedure and normal operation sequence.

Verify all connections are secure and proper
Restore electrical power and gas supply
Set thermostat to heating mode and raise temperature
Observe ignition sequence: inducer motor, pressure switch, igniter, gas valve
Verify proper flame and blower operation
Check temperature rise: 35-65°F

Maintenance Procedures

Routine maintenance for optimal performance and longevity.

Component	Maintenance Interval	Procedure
Air Filter	Monthly	Clean or replace 1" filter
Blower Assembly	Annually	Clean blower wheel and housing
Heat Exchanger	Annually	Inspect for cracks or corrosion
Burners	Annually	Clean and inspect for proper flame
Vent System	Annually	Inspect for obstructions or damage

Diagnostic Codes

LED flash codes for troubleshooting control board issues.

Flash Pattern	Description	Action
1 Flash	Ignition lockout	Check gas supply, igniter, flame sensor
2 Flashes	Pressure switch fault	Check inducer, venting, pressure switch
3 Flashes	Rollout switch open	Check for restricted airflow, heat exchanger
4 Flashes	Limit switch open	Check airflow, filter, blower operation
5 Flashes	Flame sensed with gas valve off	Check gas valve, control board

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No heat	Thermostat, power, gas valve	Check thermostat setting, circuit breaker, gas supply
Furnace won't start	Door switch, limit switch	Ensure door properly closed, check limit switches
Short cycling	Dirty filter, airflow restriction	Replace filter, check vents and registers
Blower runs continuously	Thermostat fan setting	Check thermostat fan setting (auto/on)
Unusual noises	Blower, inducer motor	Inspect blower wheel, motor bearings, inducer assembly

Parts List

Common replacement parts for Amana GUD115C50A furnace.

Control Board: Part # 1108-221
Igniter: Part # 1108-145
Gas Valve: Part # 1108-189
Blower Motor: Part # 1108-167
Pressure Switch: Part # 1108-203
Flame Sensor: Part # 1108-156
Air Filter: 16x25x1 (standard)

Service Support: 1-888-492-6762; www.amana.com