McDonnell & Miller FS6-3/4 Switch

The McDonnell & Miller FS6-3/4 (Part Number 115400) is a high-sensitivity, 3/4" NPT in-line liquid flow switch engineered for heavy-duty industrial and commercial applications. Designed for systems requiring precise actuation at extremely low flow rates, this snap-acting SPDT switch provides reliable signaling for water treatment, cooling loops, and booster pumps. Unlike standard paddle switches, the FS6 series features an in-line configuration that eliminates the need for a pipe tee, reducing pressure drop and simplifying installation in tight mechanical runs. The switch compartment is completely sealed from the process fluid, ensuring long-term performance in demanding environments. Technicians can easily fine-tune the set point using the external sensitivity adjusting screw to match specific flow requirements. With a NEMA 1 enclosure and peak operating pressure of 100 psi, this McDonnell & Miller flow switch is the standard for protecting expensive components like compressors and bearings from low-flow conditions.

• High Sensitivity: Actuates at flow rates as low as 0.12 GPM, making it ideal for precision metering and electronic circuit cooling.
• In-Line Design: Streamlined 3/4" NPT connection type integrates directly into the piping without additional fittings.
• Sealed Construction: The switch mechanism is isolated from the liquid, preventing corrosion and debris interference.
• Field Adjustable: Features an external screw for rapid sensitivity calibration without system teardown.
• Versatile Electrical: SPDT snap-acting switch supports various wiring configurations for alarms or motor starters.

• Can this switch be used in horizontal or vertical piping? While optimized for horizontal runs, it can function in vertical lines with upward flow; however, the sensitivity settings must be adjusted to account for the paddle weight.
• What is the maximum fluid temperature rating? This unit is rated for fluid temperatures ranging from 32°F to 225°F.
• Is the FS6-3/4 suitable for high-pressure systems? This model is designed for a maximum operating pressure of 100 psi. For higher pressure requirements, consult the technical data for the FS1 or FS7 series.

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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.