Description
The Lennox 78W99 is an OEM replacement L235-30F high-limit switch engineered to protect Lennox furnaces from dangerous overheating conditions. When supply-air temperatures exceed the rated setpoint, the limit switch opens the control circuit, shutting down the burner and preventing heat exchanger damage, equipment failure, or potential fire hazards. Once temperatures fall back within the safe operating range, the switch automatically resets, restoring normal furnace operation.
How It Works
The L235-30F designation identifies this as a limit switch with an open setpoint of 235°F and a 30°F differential, meaning the switch resets at approximately 205°F. This automatic reset action eliminates the need for manual intervention after a nuisance trip, making it ideal for residential and light-commercial Lennox furnace applications.
Key Features
- OEM Lennox replacement part — ensures proper fit and function
- Opens at 235°F to interrupt the burner circuit during overtemperature events
- 30°F differential for automatic reset at approximately 205°F
- Protects heat exchangers, burners, and downstream components from thermal damage
- Automatic reset design minimizes service call frequency
- Direct OEM replacement for compatible Lennox furnace models
Application
- Designed for use in Lennox gas furnaces requiring an L235-30F limit switch
- Suitable for residential and light-commercial heating systems
- Replaces worn, failed, or nuisance-tripping original limit switches
Why Replace Your Limit Switch?
A faulty or aging limit switch can cause repeated furnace shutdowns, inconsistent heating, or — in the worst case — allow the furnace to operate at unsafe temperatures. Installing a genuine Lennox OEM replacement like the 78W99 restores proper safety operation and extends the life of your heating system.
Ordering Information
- SKU: 78W99
- Model: L235-30F
- Brand: Lennox
- Type: High-Limit Switch
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