Lennox Whisper Heat Furnace Manual AFUE

The Lennox Whisper Heat Furnace is a high-efficiency gas furnace with AFUE ratings up to 98%, featuring variable-speed technology, quiet operation, durable heat exchanger, diagnostic controls, and compatibility with Lennox iComfort thermostats. Designed for residential heating with natural gas or propane, it includes safety features, easy maintenance access, and ENERGY STAR certification. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

Features at a Glance

Key components: Variable-speed blower motor, SilComfort noise reduction system, Duralok heat exchanger, Diagnostic LED, Gas valve, Ignition system, Air filter compartment.

Installation

Unpack and inspect contents. Ensure proper location with clearances.

1. Position furnace: Place on level surface in utility room or basement with required clearances.
2. Connect gas line: Use black iron pipe; apply pipe compound on threads; pressure test for leaks.
3. Connect venting: Use PVC for intake and exhaust; follow local codes for sizing and routing.
4. Electrical connections: Connect 120V power and thermostat wires; ensure proper grounding.
5. Ductwork: Attach supply and return ducts; seal joints with mastic or foil tape.

WARNING! Gas appliances can be hazardous; hire licensed professional for installation. Ensure adequate combustion air and proper venting.

First-Time Setup

Power on furnace; follow startup procedure.

1. Check gas supply: Ensure gas valve is open; verify pressure with manometer.
2. Set thermostat: Install compatible thermostat; set to heat mode and desired temperature.
3. Startup sequence: Switch power on; observe ignition sequence via diagnostic LED.
4. Adjust blower speed: Use dip switches for airflow matching to duct system.
5. Test operation: Run through heating cycle; check for proper airflow and temperature rise.

CAUTION! Never bypass safety controls. If furnace fails to start, check error codes and consult professional.

Specifications

• AFUE Rating: Up to 98%
• Fuel Type: Natural gas or propane
• Heating Capacity: 40,000 to 120,000 BTU/h
• Blower Motor: Variable-speed ECM
• Sound Level: As low as 65 dBA
• Venting: PVC pipe (2" standard)
• Electrical: 120V, 60Hz
• Dimensions: Varies by model (typical 21"W x 21"D x 40"H)
• Warranty: Limited lifetime on heat exchanger

Controls and Settings

Access controls via integrated control board or compatible thermostat.

Control Board: Diagnostic LED, DIP switches for blower speed, gas valve connector, thermostat terminals.

Thermostat Settings: Heat mode, fan control (auto/on), temperature setpoint, schedule programming. Blower Speed: Adjust via DIP switches for high/medium/low stages. Diagnostic Codes: LED flashes indicate specific error conditions (1 flash = pressure switch, 2 flashes = ignition failure, etc.). Safety: Limit switches, pressure switches, flame sensor, rollout switches.

Connecting Components

Gas line: Black iron pipe with sediment trap. Venting: PVC for intake and exhaust. Electrical: 120V power, thermostat wires.

1. Turn off gas and power before making connections.
2. Match pipe sizes (typically 1/2" to 3/4" for gas).
3. Use proper vent fittings and slope for condensation drainage.
4. Connect thermostat using standard color coding (R, W, G, Y, C).

Tip: Always pressure test gas lines and check for leaks with soap solution.

Operating Modes

Supports single-stage, two-stage, and variable-capacity operation.

1. Startup: Thermostat calls for heat; inducer motor starts; pressure switch proves draft.
2. Ignition: Hot surface igniter or direct spark ignites gas; flame sensor confirms.
3. Heating: Gas valve modulates; blower starts after heat exchanger warms.
4. Shutdown: Thermostat satisfied; gas valve closes; blower continues for cool-down.
5. Fan mode: Continuous or intermittent blower operation for air circulation.

WARNING! Never operate without proper venting or with blocked air filters. Monitor for unusual noises or odors.

Maintenance Features

Filter indicator: LED or reminder for filter changes. Self-diagnostics: Error codes for common issues. Easy access: Removable panels for filter replacement and component inspection.

Care & Cleaning

Turn off power before maintenance. Replace air filters monthly during heating season. Clean flame sensor annually with emery cloth. Inspect vent pipes for obstructions.

CAUTION! Do not use compressed air inside furnace; can damage components. Only qualified technicians should service gas and electrical systems.

Regulatory Information

ANSI Z21.47: Certified for gas-fired central furnaces. ENERGY STAR: Meets efficiency requirements. UL listed: Complies with safety standards. For support, visit www.lennox.com or contact 1-800-9-LENNOX. Manufactured by Lennox Industries Inc.; patents and trademarks apply.

Troubleshooting

Reset: Turn power off for 30 seconds then restart.

Service: 1-800-9-LENNOX; www.lennox.com