White-Rodgers 5D51-90 Control

The White-Rodgers 5D51-90 Control is a versatile fan and limit control designed for precise regulation of blower operation and high-limit safety protection in forced-air furnaces. Field-tested for reliability, this unit features an 8-inch insertion bimetal element, making it an ideal universal replacement part for plenum installations where space is at a premium. The fan switch operates on a "close on rise" logic with an adjustable range of 50°F to 265°F, allowing technicians to fine-tune the adjustable differential for optimal airflow cycles. Meanwhile, the limit switch provides a "open on rise" safety function with a fixed 25°F differential across a 100°F to 300°F range.

Built for the professional contractor, the 5D51-90 includes slotted mounting holes and a removable solid copper jumper to accommodate both line voltage and low voltage circuits. The inclusion of long terminal screws and a built-in summer fan switch ensures streamlined HVAC installation and manual ventilation control without disturbing your meticulously set temperature cut-in and cut-out pointers.

• Universal Compatibility: Engineered as a heavy-duty bimetal furnace control that replaces multiple OEM HVAC controls across various brands.
• Precision Control: Features individual pointers for independent fan cut-in and cut-out adjustments, ensuring cabinet heat is managed effectively.
• Space-Saver Design: The single 8-inch element probe is specifically designed for narrow plenums where dual-element controls won't clear internal components.
• Manual Summer Switch: Integrated lever allows for manual fan activation for seasonal air circulation without changing the primary heating settings.
• Electrical Versatility: Suitable for 120V, 240V, or 24V/millivolt circuits when the factory-installed jumper is removed, making it a "truck stock" essential.

How do I set the fan cut-in and cut-out on this control?
Hold the dial securely and move the individual pointers. The "Fan On" pointer sets the start temperature for the blower, while the "Fan Off" pointer sets the stop temperature. Do not force the pointers past the internal mechanical stops.

Can I use the 5D51-90 for low-voltage burner circuits?
Yes. While it comes with a factory-installed line voltage jumper for simplified wiring, you can remove the solid copper jumper to isolate the limit switch for use in 24V or millivolt safety loops.

What is the purpose of the 8-inch insertion element?
The 8-inch probe length ensures the bimetal coil reaches deep enough into the warm air stream for an accurate reading, which is critical for preventing high-limit trips or premature fan cycling in larger furnace cabinets.

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.