White-Rodgers 3L09-1 Limit Switch

The White-Rodgers 3L09-1 Limit Switch is a high-performance 1/2" bimetal disc limit control designed for precise thermal regulation in HVAC furnaces and commercial heating equipment. Engineered for board-mounted configurations, this snap disc thermostat operates with an open on rise switch action, effectively breaking the circuit at a fixed open temperature of 140°F. As a critical safety component, it prevents heat exchanger overheating by monitoring the air stream via its 1.87" insertion length. The 36T style limit switch features auto reset functionality, allowing the circuit to re-close automatically once the temperature drops to the fixed close temperature of 100°F. This specific HVAC high-limit switch is essential for maintaining equipment safety standards and ensuring consistent cycling. Its robust construction provides high-speed contact separation, making it a reliable direct replacement limit switch for technicians servicing units that require board-level terminal connections and a 40°F fixed differential.

• Precise Calibration: Factory-set at 140°F open and 100°F close for consistent high-limit protection without the need for field adjustments.
• Automatic Reset: Facilitates seamless system recovery after temporary thermal excursions, reducing unnecessary manual intervention.
• Optimized Insertion: The 1.87-inch depth ensures the bimetal sensing element is properly positioned within the air stream for rapid response times.
• Board-Mount Design: Specifically engineered for direct mounting on control boards with standard 1/4-inch terminals for a secure electrical connection.

What is the difference between an auto-reset and manual-reset limit switch?
The 3L09-1 is an auto-reset limit switch, meaning it will automatically restore the electrical circuit once the temperature cools to 100°F. Manual-reset models require a technician to physically press a button to resume operation, a safety feature typically reserved for rollout switches rather than primary limit controls.

Can this switch be used as a fan control?
No, this unit is configured as a limit control (open on rise). While fan controls often share similar bimetal disc technology, they typically operate with a "close on rise" action to engage the blower as the system heats up.

Is the 1.87-inch insertion length compatible with my existing bracket?
This 1.87" insertion limit switch is designed for standard board-mounted applications. Verify that your specific furnace model allows for this probe depth to ensure the 1/2-inch disc has adequate clearance and proper exposure to the heat exchanger’s airflow.

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.