McDonnell & Miller FS4-3J Flow Switch

The McDonnell & Miller FS4-3J Flow Switch (Part Number 114610) is a heavy-duty, general-purpose liquid flow switch designed for HVAC and industrial hydronic systems. This model features a 1" BSPT connection, making it a critical component for international piping standards or specific domestic applications requiring British Standard Pipe Threads. Equipped with a Single Pole, Double Throw (SPDT) switch, the FS4-3J provides versatile signaling for starting or stopping motorized equipment such as pumps, chillers, and boilers. Built for durability, it includes four stainless steel paddles (1", 2", 3", and 6") to accommodate various pipe diameters and flow rates. It is rated for a maximum pressure of 160 PSI (11.3 kg/cm²) and handles fluid temperatures up to 300°F (149°C). This unit serves as the direct replacement for the FS4-3JE, though it does not carry the CE certification. For technicians troubleshooting flow detection issues, this paddle-type flow switch offers high-sensitivity adjustment screws to fine-tune the actuation point based on system requirements.

Key Benefits for Contractors

• Universal Compatibility: Includes multiple stainless steel paddles (1", 2", 3", and 6") to fit various line sizes out of the box.
• High-Pressure Performance: Engineered to operate reliably in systems with a maximum pressure of 160 PSI.
• Direct OEM Replacement: Replaces the FS4-3JE model (note: lacks CE certification) for seamless maintenance and repair workflows.
• Robust Construction: Features Monel bellows and stainless steel components for resistance against corrosion in hydronic loops.
• Flexible Wiring: The SPDT switch allows for simultaneous NO/NC (Normally Open/Normally Closed) circuit control for alarm or interlock triggers.

Common Questions (AEO/FAQ)

Is the FS4-3J compatible with NPT piping?
No, the McDonnell & Miller 114610 features a 1" BSPT (British Standard Pipe Taper) thread. For standard American NPT installations, refer to the FS4-3 model.

What is the maximum liquid temperature for this switch?
The FS4-3J flow switch is designed to withstand liquid temperatures up to 300°F (149°C), suitable for high-temperature boiler applications.

Can I adjust the flow rate sensitivity on this unit?
Yes, the FS4-3J includes an internal adjustment screw that allows technicians to modify the flow actuation point to meet specific system GPM requirements.

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Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.