Reznor 86979 Limit Switch

The Reznor 86979 Limit Switch is a critical safety component designed for precise thermal monitoring in Reznor unit heaters and commercial HVAC systems. This 115-135F AUTO limit switch functions as a high-limit safety control, automatically interrupting the burner circuit if internal heat exchanger temperatures exceed the maximum set point of 135°F. Engineered for durability, it features an automatic reset mechanism that restores operation once the temperature drops to the 115°F differential threshold. This specific HVAC high limit control is compatible with various Reznor gas-fired units, ensuring the system operates within safe thermal parameters to prevent heat exchanger fatigue and potential safety hazards. As a direct OEM replacement part, it ensures proper fitment and electrical calibration for contractors performing maintenance or emergency repairs. Its snap-action bimetal disk construction provides reliable switching logic, maintaining the structural integrity of the furnace while preventing nuisance tripping in high-demand environments.

• Precise Thermal Calibration: Calibrated for 115°F to 135°F range to ensure exact safety cut-off points.
• Automatic Reset Functionality: Simplifies troubleshooting by restoring the circuit once safe temperatures are reached.
• Rugged OEM Construction: Built to withstand the high-temperature cycles typical of Reznor gas-fired heaters.
• Simplified Installation: Standard footprint for quick field replacement, reducing labor time on the job site.

What causes this limit switch to trip frequently?
Frequent tripping usually indicates restricted airflow, often due to a clogged air filter, a failing blower motor, or an undersized ducting system causing the heat exchanger to overheat.

Is the Reznor 86979 a manual or automatic reset?
This is an automatic reset limit switch. It will close the circuit automatically once the temperature cools to the 115°F lower limit.

Can I bypass this switch for testing purposes?
Bypassing a safety limit is never recommended for permanent operation. It should only be done briefly by a qualified technician to diagnose a faulty sensor versus an actual overtemp condition.

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.