Upgrading wet UFH REHAU analogue thermostats with Heatmiser neoStat V2

1 Oct 2020
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United Kingdom

I've searched this forum but not found anything matching my current issue, so please kindly help me.

I have a property with wet underfloor heating, a REHAU system with 4 zones each with their own REHAU Star 20 thermostat. These are basic analogue dial thermostats. My intention is to upgrade these to digital thermostats with remote control, hence buying Heatmiser neoStat V2 controls. I have the hub also, but first things first.

I'm reluctant to get an electrician out to help me just yet because of the whole COVID sitch, so I was hoping to the wiring of the upgrade myself.

However, I am having trouble matching the wiring from the Star 20 to the neoStat V2. Please see these images for what I mean.

REHAU STAR 20 wiring:

Terminal explanation - this image is for Star 30 but it is the same for Star 20 also.

The neoStat v2 that I am trying to upgrade to:

The wiring centre:

Please help!

Adding, desired state is:
  1. The neoStat should work in a thermostatic mode (not time clock)
  2. I want to be able to set the target temperature on the neoStat to control this zone specifically. When the neoStat is calling for heat, I should see the corresponding actuator valve in the closet (wiring centre image) open up.
  3. Optionally connect the neoStat to the neoHub (yet to buy)
Last edited:
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Have you actually opened the instructions included with the Neostat yet? It's all explained in there. L to L, N to N, A1 is input, A2 is output
Thanks muggles, I must admit I was confused by the 4 different wiring options included in their instructions. I’m also not totally confident interpreting the wiring diagrams.

L to L, and N to N is fairly obvious admittedly.

But, I’m still unsure how I map from the Star 20 to the neoStat the arrow terminal (switching output to valve) and the clock terminal (temperature setback). Which one of these goes to A1 and A2?

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