Viessmann Combi Boiler Water Flow Sensor – Grundfos VFS 1-20 E (96577493), Vitopend 100-W / Vitodens 100-W

The Viessmann combi boiler water flow sensor is an electronic sensor that detects that water is passing, and its flow rate, in the combi boiler's hot water circuit when a tap is opened. It is the Grundfos-manufactured VFS 1-20 E type (Grundfos part no 96577493). With the vortex principle, which has no rotating part inside, it measures the flow rate in the 1–20 l/min range and also senses the water temperature in the same body. The combi boiler PCB switches to hot water mode according to this signal.

Compatibility

• According to the package label, Viessmann combi boilers with type codes WH1D, B1KC, VB1C and VB1B.
• The WH1D type is in the Viessmann Vitopend 100-W series, the B1KC type in the Vitodens 100-W series.

The appliance type code is written on the combi boiler's type label. Before ordering, compare the "VFS 1-20" marking on the label of the removed sensor and the socket structure.

Fault Symptoms

• The combi boiler does not ignite or ignites late when the hot water tap is opened.
• The hot water temperature fluctuates; the combi boiler goes out at low flow rates.

Limescale and sediment accumulating on the wetted surface of the sensor can also cause similar symptoms.

Package Contents

• Water flow sensor (O-ring fitted)
• Metal retaining clip

Technical Specifications

• Manufacturer / type: Grundfos VFS 1-20 E
• Part no: 96577493
• Measuring principle: Vortex, no moving parts
• Flow range: 1–20 l/min
• Additional measurement: Water temperature
• Connection: Push-fit type, O-ring sealed, secured with metal clip
• Place of use: Combi boiler domestic hot water circuit

Frequently Asked Questions

Is this part a pressure sensor?

No. The sensor measures the water flow (flow rate) and temperature in the combi boiler's hot water circuit; it does not measure the system pressure. If you are looking for a system pressure sensor, see the Switches and Pressure Sensors category.

How does it differ from a turbine flow sensor?

There is no rotating turbine inside; it measures the flow rate from the vortices created by the water. For this reason, the turbine jamming seen in turbine sensors does not occur.

Which combi boiler does it fit?

According to the package label, it fits Viessmann combi boilers with type codes WH1D, B1KC, VB1C and VB1B (Vitopend 100-W, Vitodens 100-W). Order after comparing with the removed sensor.