The McDonnell & Miller FS251 Snap Switch (Part Number 120611) is an industrial-grade liquid flow switch engineered for heavy-duty HVACR and process piping applications

are usually sufficient

It is verified for HI-B

provides exceptional durability and corrosion resistance for chilled or hot water applications up to 250°F (120°C) and glycol solutions up to 60%

The raised seat design ensures that sediment and water cannot be trapped

Nordyne 921378 Control Board 320788-704 The McDonnell & Miller FS251The Nordyne 921378 Control Board is a critical OEM replacement designed to manage the ignition sequence and blower timing for specific Nordyne furnace and air handler models. As a veteran grade HVAC control board, it serves as the central hub for system logic, regulating the inducer motor, gas valve, and indoor blower to ensure precise HVAC system operation. This board replaces legacy part number 624786 and is engineered for high performance furnace