Lennox 20J98 Fan Limit

The Lennox 20J98 Fan Limit Control is a critical OEM replacement part designed for precision temperature regulation in residential heating systems and split-system HVAC units. Engineered to manage blower fan cycling and high-limit safety, this vertical-mount control ensures the furnace operates within safe thermal parameters. The Lennox 20J98 features a 7-inch insertion probe, making it a direct fit for many Lennox furnace limit switch applications. This fixed-setting fan limit switch is calibrated with an "In" (cut-in) temperature of 210°F and an "Out" (cut-out) temperature of 180°F. When the internal heat exchanger temperature hits the 210°F limit, the switch opens to break the burner circuit, preventing overheating. Once the temperature drops to the 180°F reset point, the circuit closes to resume normal operation. As a normally closed limit switch with an automatic reset, it provides the reliability required for professional-grade HVAC furnace repair and system maintenance.

• Direct OEM Compatibility: This genuine Lennox 20J98 ensures seamless integration with Lennox, Allied, Armstrong, and Ducane equipment, maintaining the original engineering specifications of the unit.
• Precise Thermal Response: Pre-calibrated at 210°F (Open) and 180°F (Close) to protect the heat exchanger from thermal stress and potential failure.
• Optimized Airflow Management: The 7-inch insertion length allows for accurate sensing of plenum air temperatures to ensure the blower fan activates and deactivates at the correct intervals.
• Automatic Reset Functionality: Features a bimetal disc designed to automatically reset after the system cools, reducing unnecessary service calls for manual resets.

What does the 210F In and 180F Out rating mean on a limit switch?
In the context of the 20J98, the "In" temperature of 210°F is the high-limit trip point where the switch opens to stop the heating cycle for safety. The "Out" temperature of 180°F is the reset point where the switch closes again to allow the furnace to fire after the plenum has cooled.

Can I use a 7-inch limit switch if my original part was shorter?
Insertion length is critical. A 7-inch fan limit control must be used only if the furnace plenum has sufficient clearance and the original specifications call for that depth. Using an incorrect length can result in inaccurate temperature readings or physical interference with internal components.

What are the signs that a Lennox 20J98 needs to be replaced?
If the furnace is "limit tripping" (shutting down before reaching the thermostat setpoint) or if the blower fan fails to engage or disengage correctly despite a functional motor, the limit switch may be out of calibration or have failed continuity tests.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.