Xylem FS-1 High Sensitivity Liquid Flow Switch 1/2" NPT SPDT

The Xylem McDonnell & Miller FS-1 is a high-sensitivity liquid flow switch designed for general purpose applications in HVAC, hydronic heating, and air conditioning systems. This compact in-line flow switch monitors liquid flow and activates electrical equipment when flow is detected or interrupted, providing essential protection against low or no-flow conditions.

Key Features:

• 1/2" NPT threaded connection for easy in-line installation without requiring a pipe tee
• Single pole, double throw (SPDT) snap-action switch for reliable circuit control
• Adjustable sensitivity screw allows precise flow rate adjustment for various applications
• Completely sealed switch compartment protects internal components from liquid exposure
• Paddle mechanism senses flow and activates electrical switch to control connected equipment
• High flow capacity despite compact size

Specifications:

• Maximum operating pressure: 100 PSI (7 kg/cm²)
• Temperature range: 32°F to 225°F (0°C to 107°C) for both fluid and ambient
• Suitable for water, fuel oil, and some viscous liquids and oils

Ideal for preventing damage to pumps, boilers, chillers, and other HVAC equipment by automatically controlling operation based on flow conditions. The FS-1's compact design makes it perfect for installations in confined spaces where reliable flow monitoring is essential.