The Dwyer P2 series is a compact, economical piston-type flow switch designed for both air and pure water applications. Its innovative piston design incorporates a hermetically sealed SPST magnetic reed switch, ensuring reliable and repeatable flow detection without the need for external power. The switch is preset at the factory, eliminating field calibration requirements and simplifying installation.

Principle of Operation

The P2 flow switch operates on a simple magnetic piston principle. As fluid flows through the device, it displaces a spring-loaded piston containing a permanent magnet. When the piston reaches a predetermined position, the magnetic field actuates a hermetically sealed reed switch, completing or interrupting an electrical circuit. The switch is factory-set to specific actuation points, ensuring consistent performance from unit to unit. When flow ceases or drops below the set point, the spring returns the piston to its resting position and the switch deactivates.

Technical Specifications

• Media: Compatible liquids or gases (air and pure water).
• Wetted Materials: Housing and piston: PPE & PS (Noryl®); Spring and stop pin: 316 Stainless Steel.
• Temperature Limits: 0 to 212°F (-18 to 100°C).
• Pressure Limits: 150 psig (10.3 bar) at 70°F; 50 psig (3.4 bar) at 212°F.
• Switch Type: SPST, Normally Open (N.O.).
• Electrical Rating: 0.17A @ 120 VAC, 0.08A @ 240 VAC, 0.13A @ 120 VDC, 0.06A @ 240 VDC.
• Electrical Connection: 22 AWG, 18" (45.7 cm) PVC lead wires.
• Process Connection: 1/4" male NPT.
• Mounting Orientation: Any position (set points based on vertical, inlet down orientation).
• Required Filtration: 50 microns or better.
• Weight: 2 oz (0.06 kg).
• Agency Approval: CE.

Preset Actuation Points

The P2 series offers multiple factory-set models for both liquid and gas applications:

• For Water: Models P2-11 (0.05 GPM), P2-12 (0.25 GPM), P2-13 (0.5 GPM), P2-14 (1.0 GPM).
• For Air at 5 psi: Models P2-15 (0.42 CFM / 11.9 LPM), P2-16 (1.0 CFM / 28.3 LPM), P2-17 (2.5 CFM / 70.8 LPM), P2-18 (5.0 CFM / 141.6 LPM).

Applications

The P2 series is widely used in pure water equipment (reverse osmosis, deionized water systems), filter life monitoring, heat exchangers, cooling applications, laser cooling systems, semiconductor manufacturing equipment, and analytical instrumentation.