Reznor 123974 Fan Switch

The Reznor 123974 Fan Switch is a precise thermal control engineered for gas-fired unit heaters and duct furnaces. Designed to manage blower cycles based on internal heat exchanger temperatures, this F135-30F fan control ensures the fan engages when the plenum reaches 135°F and terminates operation once it cools to 105°F (30°F differential). As a direct replacement for part 48706, it maintains the critical timing required to prevent heat exchanger stress while maximizing occupant comfort by avoiding cold drafts. This OEM-grade HVAC high-limit switch comes pre-mounted on a heavy-duty mounting bracket, facilitating a rapid drop-in installation during field service calls. For veteran contractors, the Reznor 123974 provides the mechanical reliability needed for commercial heater maintenance in high-demand environments. By regulating the F135-30F blower operation, this switch protects the system from thermal cycling issues often found in aging Reznor F, FE, and model 25/50 heating units.

• OEM Compatibility: Engineered as the direct replacement for discontinued part 48706, ensuring exact electrical and mounting specifications.
• Optimized Thermal Range: The F135-30F temperature setting provides a reliable 30-degree differential to prevent short-cycling of the blower motor.
• Rugged Installation: Includes an integrated mounting bracket for secure positioning within the heater cabinet, reducing mechanical vibration wear.
• System Efficiency: Accurate fan-on/fan-off control ensures maximum heat transfer from the exchanger before the cooling cycle ends.

Is the Reznor 123974 compatible with older model 48706 switches?
Yes, the 123974 is the official direct replacement for the legacy 48706 part number. It matches the original footprint and thermal profile required for safe furnace operation.

What are the specific temperature setpoints for this fan control?
This F135-30F switch is designed to close the circuit (fan on) at 135°F and open the circuit (fan off) at a temperature 30°F below that setpoint.

Does this part include the necessary mounting hardware?
The unit is supplied as a fan switch with bracket assembly, allowing for immediate attachment to the factory-drilled holes in the heater chassis.

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.