While the wall-mount version is a contained assembly

The McDonnell & Miller 302900 Cam

It handles a working pressure up to 650 PSIG

Normally open (NO) configuration for reliable circuit interruption and safety

McDonnell & Miller FS254 Snap Switch Refrigerant While the wall-mount version isThe 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