Rheem Classic 90 Plus Furnace Manual

The Rheem Classic 90 Plus is a high-efficiency gas furnace featuring AFUE ratings up to 90%, two-stage gas valve operation, variable-speed blower motor, durable aluminized steel heat exchanger, electronic ignition system, diagnostic LED lights, multi-speed direct drive blower, and compatibility with various thermostat systems. Designed for residential forced-air heating applications with natural gas or propane capability. Below are key sections for safety, features, installation, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Two-stage gas valve, variable-speed blower motor, aluminized steel heat exchanger, electronic ignition, diagnostic LED, pressure switches, flame sensor, limit switches.

Installation Requirements

Professional installation required. Verify local codes and obtain permits.

1. Location: Install in approved areas with proper clearances and combustion air.
2. Venting: Use approved PVC or CPVC for direct vent systems.
3. Gas connection: Use black iron pipe with proper sizing and leak testing.
4. Electrical: 120V AC power with proper grounding and disconnect.
5. Ductwork: Properly sized and sealed return and supply ducts.

WARNING! Gas furnaces produce carbon monoxide; improper installation can be lethal. Hire qualified HVAC technician.

First-Time Setup

Professional startup and commissioning required.

1. Verify installation: Check all connections, clearances, and venting.
2. Gas pressure: Adjust manifold pressure per specifications.
3. Blower speed: Set appropriate CFM for heating application.
4. Thermostat: Connect compatible two-stage thermostat.
5. Test operation: Verify proper ignition, heating, and safety functions.

CAUTION! Never bypass safety controls. Test carbon monoxide detectors.

Technical Specifications

• AFUE Rating: Up to 90%
• Input BTU/h: 40,000 to 120,000 (model dependent)
• Stages: Two-stage heating operation
• Blower Type: Variable-speed, multi-speed direct drive
• Heat Exchanger: Aluminized steel primary and secondary
• Ignition: Hot surface electronic ignition
• Voltage: 120V AC, 60Hz
• Gas Type: Natural gas or propane (conversion kit required)
• Venting: PVC/CPVC direct vent or conventional
• Warranty: Limited lifetime heat exchanger, 5-year parts

Controls and Operation

Integrated control board manages all furnace functions with diagnostic capabilities.

Thermostat: Compatible with most 24VAC thermostats; two-stage recommended for optimal performance.

Operation: Control board monitors safety devices, manages ignition sequence, controls blower operation, and provides diagnostic codes via LED. Normal sequence: thermostat call for heat, pressure switch verification, inducer motor start, igniter warm-up, gas valve opening, flame detection, blower activation after heat exchanger warm-up.

Venting and Combustion Air

Direct vent (PVC) or conventional venting options available.

1. Direct vent: Use 2" or 3" PVC/CPVC pipe for intake and exhaust.
2. Conventional: B-vent required with proper clearances.
3. Combustion air: Ensure adequate fresh air supply per local codes.
4. Vent termination: Follow manufacturer clearances from windows, doors, and openings.

Tip: Keep vent pipes clear of debris and snow accumulation.

Maintenance Procedures

Annual professional maintenance recommended.

1. Filter replacement: Change every 1-3 months depending on usage.
2. Heat exchanger inspection: Check for cracks or corrosion annually.
3. Blower cleaning: Vacuum blower wheel and housing annually.
4. Flame sensor: Clean with emery cloth annually.
5. Drain system: Clear condensate drain lines and trap monthly.
6. Vent inspection: Check for obstructions and proper slope.

WARNING! Turn off power and gas before servicing. Only qualified technicians should perform internal maintenance.

Safety Features

Multiple safety systems: Flame rollout switches, high limit switches, pressure switches, flame sensor, igniter safety timing, blower door safety switch.

Care & Cleaning

Regular maintenance ensures optimal performance and safety.

CAUTION! Never operate without filter. Keep area around furnace clear of combustible materials. Test carbon monoxide detectors monthly.

Regulatory Information

UL listed and ANSI certified. Complies with applicable ASHRAE standards. Manufactured to meet North American safety and performance requirements. For technical support, contact Rheem at 1-800-432-8373 or visit www.rheem.com. Serial number and model number located on unit rating plate.

Troubleshooting

Diagnostic LED: Refer to control board LED flash patterns for specific error codes.

Service: 1-800-432-8373; www.rheem.com