Reznor 50418 Limit Switch

The Reznor 50418 Limit Switch is a critical OEM safety component engineered for Reznor HVAC equipment, specifically compatible with models like the UA100. This 125-145F auto limit switch functions as a high-limit safety cut-off, monitoring internal heat exchanger temperatures to prevent hazardous overheating. When the temperature exceeds the factory-calibrated 145°F threshold, the switch opens the electrical circuit to the gas valve, immediately halting combustion. Once the system cools to 125°F, the automatic reset limit switch closes the circuit, allowing for standard operation to resume.

For service contractors, the Reznor RZ050418 is an essential furnace replacement part for maintaining system integrity in industrial unit heaters and commercial furnaces. The bimetal disc design ensures precise temperature sensing and long-term durability under high-cycle conditions. Replacing a tripped or faulty L145-20F limit control is a standard procedure to resolve short-cycling issues and blower motor irregularities caused by restricted airflow or failing safety sensors.

Key Benefits

• Precise Thermal Protection: Factory-set 125-145°F range ensures the system operates within safe thermal parameters.
• OEM Compatibility: Genuine Reznor 50418 part ensures a perfect fit and reliable performance in UA100 and related series.
• Automatic Reset Functionality: Eliminates the need for manual intervention after a temporary overheat condition is cleared.
• Enhanced System Safety: Protects the heat exchanger from cracks and structural damage by preventing excessive heat buildup.

Common Questions

Why is my furnace blower running continuously but the burners won't ignite?
This is often a sign that the Reznor 50418 Limit Switch is stuck in the "open" position. When the limit switch fails or detects an overheat, it keeps the fan running to cool the heat exchanger while blocking the gas valve for safety.

Can I bypass the limit switch to test the furnace?
Bypassing a safety limit is not recommended. If the 50418 limit switch is tripping, you should first check for airflow obstructions, such as dirty filters or blocked return grilles, before replacing the component.

How do I verify if the 50418 switch is faulty?
Using a multimeter, check for continuity across the terminals when the switch is cool. A functioning automatic limit switch should show a "closed" circuit (0 ohms) at room temperature.

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.