McDonnell & Miller FS8-W Switch

As a seasoned technician, you know the McDonnell & Miller FS8-W Flow Switch is the industry standard for rugged, reliable liquid flow monitoring in high-stakes environments. This unit, part number 120601, is the direct replacement for the legacy FS8-WG flow switch and is designed specifically for general-purpose applications that demand a NEMA 4X rated enclosure. Whether you are dealing with indoor moisture or or outdoor exposure, the water-tight and dust-tight housing ensures the internal SPDT snap switch remains protected. Built with a 1-inch NPT connection and a sealed Monel bellows, it handles operating pressures up to 160 PSI and fluid temperatures ranging from 32°F to 225°F. Every 120601 flow switch includes a versatile kit of four stainless steel paddles (1", 2", 3", and 6"), allowing you to field-configure the device for various pipe sizes without needing additional parts. The sensitivity adjusting screw makes fine-tuning the setpoint straightforward for precise pump or boiler control.

• Field Versatility: Includes four interchangeable stainless steel paddles to accommodate pipe diameters from 1" to 6" and beyond.
• Environmental Protection: The NEMA 4X enclosure provides superior resistance against corrosion, moisture, and dust for demanding mechanical rooms.
• Interchangeable Design: Ideal drop-in replacement for NEMA 4X style switches from Potter, Taco, Watts, and Penn.
• High-Pressure Capability: Engineered with a Monel bellows to reliably manage system pressures up to 160 PSI (11.3 kg/cm²).
• Simplified Wiring: Features a single pole, double throw (SPDT) snap action switch for flexible normally open or normally closed wiring configurations.

Common Questions

What is the difference between the FS8-W and the FS8-WG?
The FS8-W (120601) is the standard NEMA 4X model. The "G" in the legacy FS8-WG designated gold-plated contacts for low-voltage/low-current applications. The modern FS8-W serves as a high-reliability replacement for these units in most general-purpose mechanical systems.

Can the paddles be modified?
Yes, the 6-inch stainless steel paddle can be trimmed to fit specific pipe diameters between the standard sizes to meet exact flow requirements on-site.

Is this switch suitable for potable water?
While the McDonnell & Miller FS8-W is excellent for closed-loop HVACR, boiler, and industrial process systems, it is generally not intended for potable water applications where specific lead-free certifications are required by local codes.

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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.