McDonnell & Miller FS251 General Purpose Liquid Flow Switch

McDonnell & Miller FS251 General Purpose Liquid Flow Switch is a paddle-type flow switch designed for reliable liquid monitoring in industrial applications. This 1 inch nominal size unit features threaded end connections, a SPDT snap switch, and a rugged NEMA 1 enclosure, making it suitable for a wide range of liquids and installation environments.

Engineered for precise response, the FS251 supports a wide flow band—from 5.8 to 17.6 GPM when flowing and 5.1 to 6.53 GPM in no-flow conditions—with a temperature rating of 32 to 225°F and a pressure rating up to 160 PSI. The adjustable sensitivity screw lets you tailor activation to your system, while the EPDM O-ring ensures a reliable seal. This UL- and CSA-listed device supports 120/240 VAC service with current ratings of 7.4 A at 120 VAC and 3.7 A at 240 VAC, and up to 125 VA input supply.

• Paddle-type sensing for dependable liquid flow detection
• Nominal size 1 inch with threaded end connections
• SPDT snap switch for simple circuit interfacing
• NEMA 1 enclosure protects electronics in indoor environments
• Wide flow ranges 5.8–17.6 GPM (flow) / 5.1–6.53 GPM (no flow)
• Operating range 32–225°F and 160 PSI
• Reliability features including EPDM O-ring and adjustable sensitivity
• Certifications UL and CSA listed for US/Canada