White-Rodgers 3F05-2 Fan Switch

The White-Rodgers 3F05-2 is a heavy-duty adjustable snap disc fan control engineered for high-reliability air management in HVAC systems and industrial heating units. As a high-performance 3/4-inch fan switch, this 74T12-310709 model features a single pole single throw (SPST) configuration with a close on rise switch action. It provides a field-adjustable temperature range from 140°F to 180°F and a fixed 20°F differential, ensuring precise fan cycling and preventing short-cycling in high-demand environments. This auto reset fan switch is designed to reduce truck stock by replacing multiple fixed-temperature discs including the 3F05-4 and various Therm-O-Disc equivalents. Built with 1/4-inch quick connect terminals and a flanged airstream mount, it supports 120V/240V AC applications with a motor rating of up to 14.0A FL at 120V. Technical professionals utilize the 3F05-2 to optimize blower operation in residential furnaces and commercial unit heaters where accurate thermal response and durable mechanical switching are non-negotiable.

• Universal Compatibility: Replaces a wide array of fixed-temperature snap discs, simplifying inventory for field technicians.
• Precision Thermal Response: The close on rise mechanism ensures the fan initiates immediately upon reaching the set point between 140°F and 180°F.
• Industrial Build Quality: Features SPST contacts rated for heavy motor loads, providing long-term switching stability.
• Flexible Mounting: The 3/4-inch flanged design allows for a secure airstream mount in standard furnace and heater openings.

How do you adjust the set point on the 3F05-2?
The set point is adjusted using the visible dial on the face of the control. Turn the dial to the desired cut-in temperature within the 140°F to 180°F range; the fan will then turn off at 20°F below that selected temperature.

What does the "close on rise" action signify?
In fan control applications, "close on rise" means the electrical contacts complete the circuit when the temperature increases to the set point, which energizes the blower motor to distribute air.

Can this replace a Therm-O-Disc 74T12 style switch?
Yes, the White-Rodgers 3F05-2 is a direct replacement for the 74T12-310709 and is designed to fit the standard mounting footprint of 3/4-inch snap disc thermostats.

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.