American Standard 90 Furnace Manual

The American Standard 90 Furnace is a high-efficiency gas furnace with AFUE ratings up to 90%, featuring variable-speed blower technology, durable heat exchanger construction, quiet operation, and compatibility with various thermostat systems. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: High-efficiency heat exchanger, variable-speed blower motor, electronic ignition system, multi-speed inducer motor, integrated control board.

Installation Requirements

Unpack and inspect all components. Ensure proper clearances and ventilation.

1. Location: Install in dry, clean area with proper combustion air supply.
2. Clearances: Maintain minimum 1-inch clearance from combustible materials.
3. Venting: Use approved PVC or CPVC pipe for intake and exhaust.
4. Gas connection: Use black iron pipe with proper thread sealant.
5. Electrical: Connect to 120V AC power with proper grounding.

WARNING! Installation must be performed by qualified HVAC technician. Gas furnaces can produce carbon monoxide - ensure proper venting.

First-Time Setup

Power on furnace; follow startup sequence.

1. Thermostat setup: Connect compatible thermostat and set to heating mode.
2. Gas pressure: Verify proper manifold pressure per specifications.
3. Airflow: Set blower speed for proper CFM delivery.
4. Combustion: Verify proper combustion analysis readings.
5. Safety check: Test all limit switches and safety controls.

CAUTION! Only qualified technicians should perform initial setup and testing.

Specifications

• AFUE Rating: Up to 90% efficiency
• Input Capacity: 40,000 to 120,000 BTU/h models available
• Gas Type: Natural gas (LP conversion kit available)
• Electrical: 120V AC, 60Hz, 15 amp circuit
• Blower Type: Variable-speed ECM
• Airflow: 600-2000 CFM depending on model
• Venting: 2-inch PVC intake and exhaust
• Sound Rating: As low as 65 dBA
• Warranty: 20-year heat exchanger, 5-year parts

Controls and Settings

Access control board via front panel. LED status light for diagnostics.

Thermostat Controls: HEAT/COOL/OFF mode, FAN AUTO/ON, temperature setpoint, system switch.

Blower Settings: Multiple speed taps for heating and cooling operation. Gas Pressure: Adjustable manifold pressure for optimal combustion. Limit Controls: Auto-reset high limit switches. Diagnostic Codes: LED flash patterns indicate system status and fault conditions.

Connecting Thermostat

Compatible with most 24V thermostat systems. Standard 5-wire connection.

1. Turn off power to furnace before wiring.
2. Connect thermostat wires to control board: R (24V), W (Heat), G (Fan), C (Common), Y (Cool).
3. Use proper wire nuts and secure connections.
4. Restore power and test operation.

Tip: Use thermostat with compatible features for optimal performance.

Operation Modes

Multiple operating modes for efficient heating.

1. Heating Cycle: Thermostat calls for heat, inducer starts, igniter heats, gas valve opens.
2. Blower Operation: Blower starts after heat exchanger warms up, continues during heat call.
3. Post-purge: Blower continues after heat cycle to remove residual heat.
4. Fan Only: Circulates air without heating for improved air distribution.
5. Standby: System waits for next heat call with minimal power consumption.

WARNING! Do not attempt to override safety controls. If furnace locks out, call qualified technician.

Maintenance Procedures

Regular maintenance ensures optimal performance and safety.

1. Monthly: Check and replace air filter as needed.
2. Seasonal: Inspect vent pipes for obstructions.
3. Annual: Professional inspection and cleaning.
4. Burner inspection: Clean burners and verify proper flame pattern.
5. Heat exchanger: Visual inspection for cracks or damage.
6. Blower: Clean blower wheel and housing.

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

Safety Features

Multiple safety systems protect against hazardous conditions.

• Flame Rollout Switches: Detect improper burner flames
• High Limit Switches: Prevent overheating
• Pressure Switches: Verify proper venting operation
• Flame Sensor: Confirms burner ignition
• Gas Valve: Automatic shutoff if ignition fails
• Control Board Diagnostics: Monitors system operation

Regulatory Information

UL listed and ANSI certified. Complies with ASHRAE standards for residential gas furnaces. Manufactured to meet or exceed industry safety standards. For technical support, contact American Standard at 1-800-4-AMERICAN or visit www.americanstandardair.com.

Troubleshooting

Reset: Turn power off for 30 seconds then restore. If problem persists, call technician.

Service: 1-800-4-AMERICAN; www.americanstandardair.com