White-Rodgers 3L09-5 Limit Switch

The White-Rodgers 3L09-5 is a professional-grade board mount limit control engineered for precision temperature monitoring in forced-air heating applications. This 1/2" bimetal disc limit switch features a 3.12" insertion length, making it a critical safety component for high-limit sensing within the heat exchanger airflow. As an open on rise switch action device, it is factory-calibrated to break the electrical circuit at a fixed 160°F and automatically reset at 140°F, ensuring the HVAC high limit reset cycle maintains safe internal operating temperatures.

Designed for seamless integration, this unit serves as the direct replacement for R40154B002 and is compatible with various OEM furnace configurations. The snap-action bimetal element provides high-speed contact separation, which minimizes arcing and extends the life of the internal SPST contacts while maintaining a consistent 160 degree fixed open temperature. For contractors performing field service, this auto-reset limit switch offers the reliability required for high-cycle residential and light commercial equipment.

• Precise Thermal Response: Features a 1/2" snap-action bimetal disc for rapid and reliable circuit interruption at 160°F.
• Broad Compatibility: Serves as a primary service solution for White-Rodgers 3L09-5 specifications and specialized OEM part numbers.
• Durable Construction: Engineered with a 3.12" probe for optimal positioning within the plenum or heat exchanger cabinet.
• Automatic Reset: Simplifies system recovery by closing the circuit once temperatures drop to the 140°F setpoint.
• Compact Board Mount Design: Facilitates easy installation on integrated furnace control boards or dedicated mounting brackets.

What is the correct 3L09-5 mounting orientation for vertical airflow?
This board-mounted control should be installed so the 3.12-inch sensing element is positioned directly in the warmest discharge air stream, following the original manufacturer’s bracket alignment.

Can the 160°F setpoint be adjusted for high-altitude applications?
No, the White-Rodgers 3L09-5 is a fixed-temperature device. Calibrations are set at the factory to ensure safety integrity; any attempt to alter the setpoints will compromise the component.

Is this switch compatible with 24V or 120V control circuits?
Yes, it is rated for both low-voltage and line-voltage applications, typically handling up to 15A at 120VAC, making it versatile for various furnace control schemes.

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.