The LEFOO FS51/52 series is a robust paddle-type flow switch designed to monitor and control the flow of water, ethylene glycol, and other non-hazardous liquids in industrial systems. Operating on a mechanical vane principle, the switch features a stainless steel paddle that is displaced by fluid flow. When the flow rate exceeds or falls below the user-adjustable setpoint, the built-in single-pole double-throw (SPDT) microswitch changes state, allowing it to open or close an electrical circuit.

Key Features

• Adjustable Flow Setpoint: The switching point can be easily adjusted on-site by trimming the stainless steel paddles or selecting the appropriate paddle configuration, providing flexibility for various pipe sizes and flow requirements.
• Wide Pipe Size Compatibility: Standard configuration with 3 paddles covers pipe diameters from 25mm to 75mm. With the optional 6-inch paddle, the switch can be used in pipes from 100mm to 150mm.
• High Electrical Rating: Features a 10A @ 250V AC SPDT contact, capable of directly controlling pumps, valves, or alarms without external relays.
• Durable Construction: Available with brass or stainless steel bodies (with optional stainless steel connection for ammonia and other aggressive media). The FS52 model features a fully enclosed housing with IP53 protection, effective against dust and water ingress (a little condensation is allowed).
• Long Service Life: The bellows are rated for 500,000 cycles, ensuring reliable long-term operation.
• Easy Installation: The FS52 model provides ample wiring space for user convenience. The switch is designed for horizontal pipe installation; vertical installation is allowed only with upward flow direction.

Technical Specifications

• Flow Adjustment Range (m³/h): See detailed table for specific pipe diameters. For example, for DN25 pipe (3 paddles): Min adjustment flow increase 0.95, decrease 0.57; Max adjustment flow increase 2.0, decrease 1.93. For DN150 pipe (4 paddles): Min adjustment flow increase 46.6, decrease 38.6; Max adjustment flow increase 94.26, decrease 90.85.
• Electrical Connection: 1 SPDT (Form C) contacts.
• Electrical Endurance: 500,000 cycles.
• Ambient Temperature: 0°C to 60°C.
• Ingress Protection: IP53 (FS52 model).
• Process Connections: 1", 1/2", 3/4" NPT female threads.
• Approvals: CE certified.

Applications

The FS51/52 series is ideal for a wide range of industrial flow monitoring applications, including chiller protection (shutting off compressor when cooling water flow fails), HVAC systems, pump dry-run protection, chemical dosing monitoring, and general flow/no-flow detection in water and compatible liquid lines.