Description
Lennox 56M66 AUTO Limit Switch Overview
The Lennox 56M66 is an OEM-grade automatic (AUTO) limit switch engineered to protect furnaces and heating systems from dangerous overtemperature conditions. With a trip range of 125–142°F, this limit switch continuously monitors heat exchanger temperatures and automatically interrupts the burner circuit when temperatures exceed the safe threshold — then resets automatically once temperatures return to normal operating range.
Key Features
- OEM Lennox replacement part — direct fit for compatible Lennox furnace models
- AUTO reset operation — automatically resets when temperature drops back within safe range
- Trip temperature range: 125–142°F for precise overheat protection
- Interrupts burner circuit to prevent heat exchanger damage and potential fire hazard
- Reliable bimetal or snap-disc sensing mechanism for consistent, repeatable performance
- Designed for residential and light commercial furnace applications
Why Limit Switches Matter
A properly functioning limit switch is a critical furnace safety component. It prevents the heat exchanger from overheating due to restricted airflow, dirty filters, or blower failures — conditions that can crack the heat exchanger and allow combustion gases to enter the living space. Replacing a failed limit switch with a genuine Lennox OEM part ensures your system operates within designed safety parameters.
Application
- Compatible with select Lennox furnace models — verify compatibility with your unit’s service manual or model number before ordering
- Ideal for HVAC technicians performing scheduled maintenance, safety inspections, or component replacement
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