Lennox 56M66 Limit Switch

The Lennox 56M66 Limit Switch (Part # 56M6601) is a critical OEM HVAC component designed for high-limit protection in residential and commercial heating systems. Engineered specifically as a draft inducer limit switch, this NCO-56M66 disc-style control features a normally closed circuit that opens on temperature rise to prevent heat exchanger damage and unsafe operating conditions. The switch is calibrated with an open temperature of 142°F and a 15°F differential, allowing for an automatic reset at 127°F once the system has cooled sufficiently. This L142-15F limit control is built for long-term reliability in demanding environments, commonly used in Lennox furnace repair and compatible with Allied, Armstrong, and Ducane equipment. Its compact 0.05 lb design ensures a precise fit in tight draft inducer housings where accurate thermal sensing is paramount. By maintaining a strict 125-142°F operating range, this auto-reset thermal switch serves as a primary safety safeguard, cutting power to the burner or inducer motor if exhaust temperatures exceed safe thresholds.

Key Benefits for Technicians:

• Precise Thermal Safety: Precisely calibrated to open at 142°F, protecting the draft inducer motor assembly and heat exchanger from overheating.
• Automatic Reset Functionality: Features a 15°F differential that resets the circuit at 127°F, eliminating the need for manual intervention after temporary temperature spikes.
• OEM Compatibility: Genuine Lennox 56M6601 part ensures exact electrical ratings and mounting alignment for Lennox HVAC systems.
• Durable Disc Style: Robust construction designed to withstand rapid cycling and high thermal stress in exhaust paths.
• Wide Application: Versatile cross-compatibility with various 80M52 draft inducer setups and furnace models across the Lennox brand family.

Common Questions:

What causes a Lennox 56M66 limit switch to trip frequently?
Frequent tripping usually indicates restricted airflow, a failing draft inducer motor, or a cracked heat exchanger. Ensure the venting is clear and the inducer is pulling the correct RPM before replacing the switch.

Can I use a manual reset switch in place of the 56M6601?
No. The Lennox 56M66 is an auto-reset limit switch. Replacing it with a manual reset or a switch with a different temperature rating can lead to system lockouts or unsafe operating conditions.

Is this switch compatible with other brands?
Yes, besides Lennox, the 56M66 limit switch is a standard replacement for many Allied Air, Armstrong, and Ducane furnaces that utilize the same 142-15F specification.

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.