White-Rodgers 5D51-35 Control

The White-Rodgers 5D51-35 is a heavy-duty fan and limit control engineered for high-static pressure applications and forced-air heating systems. This warm air control features a 5-inch insertion probe utilizing a bimetal sensing element to provide precise thermal response. As a universal furnace fan limit switch, it manages blower motor activation and provides critical high-limit safety cutouts to prevent heat exchanger damage. The unit includes adjustable fan on-off settings and a fixed or adjustable high limit, allowing technicians to fine-tune the furnace blower control sequence based on specific plenum temperatures. Built for durability in commercial and residential settings, the 5D51-35 replaces various HVAC safety limit switches and is compatible with 24V, 120V, and 240V circuits. Its rugged construction ensures reliable switching performance even in high-cycle environments, making it a standard inventory item for service contractors maintaining older atmospheric or power-vented furnaces.

• Flexible 5-inch Sensing Element: Designed for optimal placement within the plenum to ensure accurate temperature sensing and rapid response.
• Multi-Voltage Compatibility: Suitable for a wide range of electrical configurations, including 24V control circuits and line-voltage blower motors.
• Manual/Automatic Fan Switch: Features a summer fan switch for constant air circulation without engaging the heating cycle.
• High-Capacity Switch Design: Robust contacts built to handle the inductive load of fractional horsepower blower motors.
• Reliable Thermal Protection: Provides a mechanical high-limit safety break that operates independently of the primary thermostat logic.

What is the difference between the 5D51-35 and standard fan limit controls?
The 5D51-35 is specifically optimized for applications requiring a 5-inch insertion depth, ensuring the bimetal element is positioned correctly in the airflow path for accurate furnace high limit detection.

Can this control be used for cooling applications?
While primarily a heating control, the manual fan switch can be used to override the blower motor control for ventilation; however, it is not a dedicated A/C cooling relay.

How do you calibrate the fan-on and fan-off setpoints?
Adjust the internal dial pointers to the desired temperature markers. Ensure the "Fan-Off" setting is high enough to prevent cold drafts but low enough to maximize latent heat recovery from the heat exchanger.

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.