Type R3F: Piston flow switches, reed switch contact, 1/2" BSPP male thread

Main applications: Product developed for electrical or gas instantaneous water heaters. Water inlet is done directly by the ½ ” BSPP male thread. Mandatory vertical mounting, with water inlet from the bottom. Connection to internal copper piping DN10 with quick coupling.

Built-in overpressure valve

Functional principle: Magnetic piston mounted in line with the flow and activating a reed switch through the wall. The return of the piston is by made by spring. No seal or liquid can pass between the piping system

and the electrical contact. Suitable for potable water. Must not be used for water containing magnetic particles or high viscosity liquids, which block the movement of the piston.

Adjustment: Can be factory set by adjusting the spring force and/ or changing the piston diameter

Body material: PPO compatible with drinking water.

Piston: PPO

Spring: 304 stainless steel

Electrical rating: Max 1A, Max 70W, Max 250V, resistive load. Use on inductive circuits reduces electrical rating. We recommend to protect the reed switch with contact protection device when used in inductive loads

Electric contact type: Normally open, closes by flow rise

Liquids compatibility: For use with clean water and liquids without magnetic particles and without chemical incompatibility with  PPO and stainless steel

Nominal pressure at 20°C: 1MPa (PN10)

Flow detection set point factory setting limits:

Close by flow rise: 4 to 12 L/min

Open by flow decrease:  About 0.4 to 0.5 L/min lower than close value

Nominal diameter: DN10

Mandatory mounting position: on vertical pipes, upstream flow

Water pipe connection:

– Water inlet: on male ½” fitting with gasket with 2 anti-rotation lugs. recommended torque 5N.m

– Water outlet:  fast-on connection with O-ring and clips on DN10 beaded copper tubes. OD 12 to 12.7 mm

Liquids temperature range: 5 to 80°C

Ambient temperature range: 5 to 50°C

Overpressure valve calibration value: 1.5 MPa +0.5, -0

Ingress protection: IP65

Electrical connection: 2 x AWG24 wires (0.2mm²), PVC insulation, T80°, standard length 300 mm.

Accessories: brass terminations for brazing or soldering on other pipes diameters : see last section of this catalogue

Options (MOQ apply): cable with connector or terminals, other cable length, other calibration values. On request it is possible to produce  these models with upside water inlet

Important note: Standard copper tubes diameter for building applications (Water and gas) are given by the EN1057 standard, which defines the nominal diameter (DN) as the inside diameter. Copper tubes for applications in air conditioning and refrigeration are described in EN 12735-1 and those for vacuum and medical gases and vacuum are described in EN 13348. The EN127357 standard defines the copper tubes for refrigeration with diameters in inches.

Copper tubes are often described in France by the outside diameter followed by the thickness in mm.


Main references  (with 300 mm wires)



Close on flow rise (L/min) Open on flow decrease (L/min)
R3FA670400150330 4 ±0.2



6±0.25 2±0.25
R3FA670800150330 8±0.3



2D&3D Drawing