McDonnell & Miller FS7-4J Switch

The McDonnell & Miller FS7-4J (Part Number 120060) is a heavy-duty industrial liquid flow switch designed for high-demand applications including secondary filtration, hydronic heating, and process cooling. This model features a 1 1/4" BSPT connection and is equipped with a single pole, double throw (SPDT) snap switch, allowing for simultaneous make-and-break circuit control. Built for durability, it utilizes brass construction and a magnetic switching mechanism that eliminates the need for failure-prone bellows. The trimmable stainless steel paddles offer versatility for various pipe diameters, while the integrated sensitivity screw allows for precise field adjustments. Engineered to handle a maximum pressure of 300 PSI and fluid temperatures up to 300°F (149°C), the FS7-4J flow switch ensures reliable flow detection in large-scale HVACR systems. This unit is professionally rated for horizontal installations and provides a critical failsafe for pumps and boilers by monitoring consistent velocity within the line.

• High-Pressure Performance: Rated for up to 300 PSI, making it suitable for rigorous industrial and commercial liquid lines.
• Bellows-Free Design: The magnetic switching mechanism prevents common leak points associated with traditional bellows-style switches.
• Universal Compatibility: Includes trimmable stainless steel paddles to accommodate diverse pipe sizes and flow requirements.
• Rugged Build: Features a corrosion-resistant brass body and sealed tube construction for long-term service in industrial liquid flow applications.
• Field Adjustable: Outfitted with a sensitivity adjustment screw to fine-tune the set point for specific flow velocities.

Is the FS7-4J compatible with NPT piping?
The FS7-4J specifically utilizes 1 1/4" BSPT (British Standard Pipe Taper) threads. If your system uses NPT, ensure you have the correct adapters or select the standard FS7-4 model to maintain a leak-free seal.

Can this switch be installed on a vertical pipe?
No, for accurate flow switch operation, this unit must be mounted on the top side of a horizontal pipe run. Vertical installation can cause the paddle to hang incorrectly, leading to a false "flow" or "no-flow" signal.

Is this model suitable for potable water?
The FS7-4J is intended for industrial heating, cooling, and process water. It is not rated for use in potable water systems. For those applications, a lead-free certified model is required.

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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.