McDonnell & Miller FS4-3 General Purpose Liquid Flow Switch

McDonnell & Miller FS4-3 General Purpose Liquid Flow Switch is a rugged paddle-type flow switch designed for reliable liquid flow monitoring in a wide range of systems. This 1 inch nominal size unit features a threaded end connection and a SPDT snap switch to deliver precise on/off signals as flow is detected.

Built for durability, the FS4-3 operates from 32 to 300°F and withstands up to 160 PSI. Electrical ratings include 7.4 A at 120 VAC and 3.7 A at 240 VAC, with a 125 VA input at 120/240 VAC, 50/60 Hz. The paddle-type flow switch employs a hardened stainless steel bearing and a sealed Monel bellows, delivering long life in challenging liquids while maintaining accurate switching.

• Sensitivity adjustable screw for precise setpoint
• Includes two electrical knock-outs for easy wiring
• Hardened stainless steel bearing for durability
• Sealed Monel bellows for reliable operation in fluids
• 1" nominal size with threaded end connection
• SPDT snap switch provides simple control wiring
• UL (Canada and US) and CSA certified for safety
• Flow ranges: 6–10.2 GPM (flow) and 3.6–9.2 GPM (no flow)
• Current rating: 7.4 A at 120 VAC / 3.7 A at 240 VAC
• Input rating: 125 VA at 120/240 VAC, 50/60 Hz

Ideal for general purpose flow sensing in boiler, HVAC, water treatment, and pump systems where dependable liquid monitoring is essential.