McDonnell & Miller FS254 Snap Switch R-410A Mechanical Leverage: The 12-inch length

Mechanical Leverage: The 12-inch length provides the buoyancy-to-pressure ratio required for high-capacity float valve level control

Enhanced System Safety: Employs close on fall logic to verify proper draft before allowing the gas valve to energize

ensuring that system diagnostic data remains accessible and accurate

ensure the sensing bulb is securely strapped at the 10 or 2 o’clock position on the suction line and properly insulated to prevent false readings from ambient air

High Close-off Pressure: Designed to maintain 100% bubble-tight shut-off

McDonnell & Miller FS254 Snap Switch R-410A Mechanical Leverage: The 12-inch lengthThe McDonnell & Miller FS254 Snap Switch (Part Number 120610) is a heavy duty, general purpose liquid flow switch engineered for high reliability monitoring in HVACR and industrial hydronic systems. This unit is the direct replacement for the legacy FS 254 and offers a field proven solution for starting or stopping electrically operated equipment including automatic burners, circulator pumps, and system alarms. Built with a NEMA 4 enclosure, the FS254