Description
Lennox 20J99 AUTO Limit Switch Overview
The Lennox 20J99 is an automatic-reset high-limit switch designed to protect furnace heat exchangers and components from dangerous overtemperature conditions. With a sensing range of 130–160°F, this OEM replacement part monitors supply-air or plenum temperatures and interrupts the burner circuit when temperatures exceed the set point — then automatically resets once conditions return to a safe level.
Key Features
- Automatic (AUTO) reset operation — restores normal function once temperatures drop to a safe level
- Temperature range: 130–160°F
- Designed as a direct OEM replacement for compatible Lennox furnace models
- Protects heat exchangers and system components from thermal damage
- Interrupts burner operation on high-temperature fault for safe shutdown
- Reliable bimetal sensing element for accurate, repeatable performance
Application
The 20J99 limit switch is engineered for use in Lennox residential and light-commercial furnace applications. It is installed in the supply-air plenum or on the heat exchanger to monitor operating temperatures. When the sensed temperature rises above the 160°F trip point, the switch opens the burner control circuit, shutting down the heating system to prevent overheating damage. The auto-reset feature means the switch will close again automatically once temperatures fall back within the safe operating range, without requiring manual intervention.
Why Choose OEM Replacement Parts
Using genuine Lennox replacement components like the 20J99 ensures proper fit, calibration, and performance within your Lennox system. OEM parts maintain manufacturer specifications and help preserve equipment warranties and system efficiency.
Specifications
- Brand: Lennox
- Part Number: 20J99
- Switch Type: High-Limit, Auto-Reset
- Temperature Range: 130–160°F
- Application: Furnace high-limit protection
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