Rheem Imperial 90 Plus Furnace Manual

The Rheem Imperial 90 Plus is a high-efficiency gas furnace with AFUE ratings up to 90%, featuring a durable heat exchanger, multi-speed blower motor, electronic ignition system, built-in diagnostic controls, safety shut-off devices, and compatibility with various thermostat systems. Designed for residential heating applications with natural gas or propane capability. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Stainless steel heat exchanger, induced draft blower, electronic ignition, multi-speed ECM blower motor, integrated control board, pressure switches, flame sensor, and diagnostic LED.

Installation Requirements

Professional installation required. Ensure proper location and clearances.

1. Location: Install in well-ventilated area with adequate combustion air.
2. Clearances: Maintain minimum clearances per local codes (typically 1-inch sides, 6-inch front).
3. Venting: Install PVC vent pipes according to manufacturer specifications.
4. Gas Connection: Use approved gas piping materials; pressure test before operation.
5. Electrical: Connect to dedicated 120V circuit with proper grounding.
6. Drain Line: Install condensate drain line with proper trap and routing.

WARNING! Installation must be performed by qualified HVAC technician. Improper installation can cause fire, explosion, or carbon monoxide poisoning.

First-Time Setup

Initial startup must be performed by qualified technician.

1. Verify installation: Check all connections, clearances, and venting.
2. Gas pressure: Set manifold pressure to specifications (3.5" WC natural gas).
3. Electrical: Verify proper voltage and grounding.
4. Startup sequence: Follow manufacturer's startup procedure step-by-step.
5. System check: Verify proper ignition, flame, and blower operation.
6. Temperature rise: Measure and adjust to specified range.

CAUTION! Never attempt startup without proper training and equipment. Carbon monoxide detectors required in living spaces.

Technical Specifications

• Model Series: Imperial 90 Plus
• AFUE: Up to 90%
• Input BTU/h: 40,000 - 120,000 (varies by model)
• Gas Type: Natural gas or propane (conversion kit required)
• Electrical: 120V, 60Hz, 1.5-3.0 amps
• Blower Motor: ECM multi-speed
• Venting: 2" PVC schedule 40
• Sound Level: < 65 dBA
• Warranty: 20-year heat exchanger, 5-year parts
• Dimensions: Varies by model (typically 21"W x 26"D x 40"H)

Controls and Settings

Integrated control board with diagnostic LED. Access door switch for safety.

Control Board: LED status light indicates system operation and fault codes.

Thermostat Connections: R (24V), W (Heat), G (Fan), C (Common). Blower Speed Settings: Cooling, heating, and continuous fan speeds adjustable via control board dip switches. Gas Valve: Pressure adjustment for proper flame characteristics. Limit Switches: Auto-reset high temperature protection.

Venting and Combustion Air

Direct vent system using PVC pipe. Separate combustion air required for confined spaces.

1. Vent Pipe: Use PVC schedule 40, minimum 2-inch diameter.
2. Termination: Maintain proper clearances from windows, doors, and air intakes.
3. Slope: Vent pipes must slope back to furnace for condensate drainage.
4. Combustion Air: Provide adequate fresh air per local codes.
5. Concentric Kits: Available for sidewall venting applications.

Tip: Always verify vent system integrity with combustion analyzer during startup.

Operating Instructions

Normal operation controlled by thermostat.

1. Set thermostat to desired temperature and HEAT mode.
2. Furnace will initiate startup sequence: inducer motor, pressure switch verification, ignition, flame proving.
3. Once flame established, blower will start after predetermined delay.
4. At thermostat satisfaction, gas valve closes, inducer continues for post-purge.
5. Blower continues for heat dissipation then shuts off.
6. For continuous fan operation, set thermostat to FAN ON position.

WARNING! Never operate furnace with access panels removed. Keep combustible materials away from furnace.

Maintenance Procedures

Annual maintenance by qualified technician recommended.

1. Filter Replacement: Change every 1-3 months depending on usage.
2. Heat Exchanger: Inspect annually for cracks or corrosion.
3. Burners: Clean and verify proper flame pattern.
4. Flame Sensor: Clean with emery cloth annually.
5. Vent System: Inspect for obstructions or damage.
6. Drain System: Clean condensate trap and drain line.
7. Blower: Clean wheel and housing as needed.

CAUTION! Turn off power and gas supply before performing any maintenance.

Safety Features

Multiple safety devices protect against hazardous conditions.

Regulatory Information

UL listed and ANSI certified. Complies with U.S. Department of Energy efficiency standards. Manufactured to meet or exceed ASHRAE 90.1 requirements. For natural gas operation: ANSI Z21.47; For propane operation: ANSI Z21.47. All installations must comply with National Fuel Gas Code NFPA 54 and local codes. Copyright © Rheem Manufacturing Company. For support, visit www.rheem.com or contact 1-800-432-8373.

Troubleshooting

Reset Procedure: Turn thermostat off, turn furnace power off for 30 seconds, restore power, then thermostat.

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