White-Rodgers 3L09-25 Limit Switch

The White-Rodgers 3L09-25 is a high-performance board mount limit control designed for precise thermal regulation in forced-air heating systems. This 1/2" bimetal disc switch features a fixed setpoint that opens at 200°F and automatically closes at 180°F, effectively managing high-limit safety protocols. Engineering-grade Therm-O-Disc Type 36T technology ensures high-speed contact separation, providing exceptional life cycle characteristics even under heavy electrical loads. With a 3.12" extension strap, this Style 612717 sensor reaches deep into the airstream to deliver rapid thermal response times. This SPST (Single Pole, Single Throw) limit is a professional-grade replacement for many gas and electric furnace configurations, offering 15A resistive capacity at 120VAC. The robust construction of the White-Rodgers 3L09-25 limit switch is built for consistent performance in demanding HVACR environments where rapid temperature monitoring is critical for equipment protection and operational uptime.

Key Benefits

• Reliable Safety Protection: Features a 20°F fixed differential to prevent short-cycling while ensuring your equipment remains within safe operating temperatures.
• Rapid Thermal Response: The 1/2" bimetal disc design offers nearly instantaneous contact separation upon reaching the 200°F threshold.
• Optimized Airflow Sensing: The 3.12-inch board mount extension allows the sensor to be positioned accurately within the plenum for the most representative temperature reading.
• High Compatibility: Direct replacement for Therm-O-Disc Style 612717 and Type 36T controls commonly found in major furnace brands.
• Industrial-Grade Ratings: Capable of handling up to 15 Amps at 120VAC, making it suitable for a wide range of resistive and inductive heating loads.

Common Questions

A board mount limit like the White-Rodgers 3L09-25 uses an extension strap to place the sensing element directly into the moving air stream, whereas surface mounts detect the temperature of the heat exchanger or plenum wall. This allows for a more accurate reading of the actual internal air temperature.

No, this model is an automatic reset control. Once the temperature drops to the 180°F closing point, the internal bimetal disc will snap back to the closed position, restoring the electrical circuit without technician intervention.

While the switch is robust, it should be mounted firmly to the control board to ensure the 3.12" strap is positioned in the specified airflow path. Proper alignment prevents "dead spots" in temperature sensing and ensures the 200°F open limit is hit accurately.

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.