White-Rodgers 3L09-9 Limit Switch

The White-Rodgers 3L09-9 Limit Switch is a high-reliability, board-mounted 1/2" bimetal disc limit control designed for precise thermal oversight in forced-air heating systems and industrial furnace applications. This snap-action safety device utilizes an open-on-rise switch action to interrupt the electrical circuit when the ambient temperature reaches a fixed open temperature of 190 degrees F. Integrated auto-reset functionality ensures the circuit closes once the temperature drops to the fixed close temperature of 170 degrees F, maintaining equipment uptime without manual intervention.

Engineered with a 3.12" insertion length, this 3L series temperature control provides optimal sensing positioning within the air stream for rapid response. Its high-speed contact separation minimizes arcing and extends service intervals. This switch is rated for pilot duty at 278 VA and handles resistive loads up to 15.0A at 120 VAC, making it a versatile HVAC replacement limit switch for various OEM configurations. For technicians, the slotted mounting holes and standard 1/2" disc design facilitate drop-in installation on circuit boards or plenums.

• Precise Thermal Safety: Fixed 190°F cutout prevents heat exchanger overheating by cutting power to the gas valve or heating element.
• Automatic System Recovery: Closes at 170°F for seamless auto-reset operation once cooling is achieved.
• Robust Contact Performance: The snap-action bimetal disc ensures clean contact breaks, reducing electrical wear.
• Standardized Fit: 3.12-inch sensing probe and board-mount design accommodate a wide range of furnace and heater models.

Is the 3L09-9 compatible with millivolt or line voltage systems?
This switch is rated for 24V, 120V, 240V, and 277V applications, supporting both electrical and gas-fired equipment. Always verify your specific circuit’s amperage draw against the technical ratings.

What causes a limit switch to "trip" if there isn't a fire?
Tripping usually indicates restricted airflow, such as a clogged filter or a failing blower motor, causing heat to build up beyond the 190°F threshold.

Can I manually adjust the temperature setpoints?
No, this model features factory-fixed settings. Attempting to recalibrate or modify the bimetal disc will damage the internal mechanism and compromise safety.

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.