Description
Lennox 18K80 AUTO Limit Switch Overview
The Lennox 18K80 is an OEM automatic (AUTO) limit switch engineered to protect furnaces and heating systems from dangerous overheating conditions. Designed as a direct factory replacement, this limit switch automatically resets once temperatures return to a safe operating range — eliminating the need for manual intervention and minimizing system downtime.
How It Works
The 18K80 limit switch continuously monitors heat exchanger or plenum temperatures. When the temperature exceeds the upper set point of 160°F, the switch opens the circuit and shuts down the burner to prevent equipment damage or fire hazard. Once the temperature drops back to the lower threshold of 130°F, the switch automatically resets and restores normal operation.
Key Features
- AUTO (automatic) reset operation — no manual reset required
- Opens at 160°F to protect against overheating
- Resets at 130°F for automatic restoration of normal operation
- OEM Lennox replacement part — ensures proper fit and function
- Direct drop-in replacement for compatible Lennox furnace models
- Reliable bimetal sensing element for accurate temperature response
Specifications
- Brand: Lennox
- Part Number / SKU: 18K80
- Switch Type: AUTO (Automatic Reset)
- Open Temperature: 160°F
- Reset Temperature: 130°F
- Application: Furnace / Heating System Limit Protection
Application
The Lennox 18K80 is intended for use in Lennox residential and light commercial furnaces as a high-limit safety control. Always verify compatibility with your specific furnace model before installation. Consult the equipment service manual or a qualified HVAC technician to confirm the correct replacement part.







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