Comment on my plan to make the underfloor heating

In our current flat we have a Danfoss CF-MC master controller for the underfloor heating. However I am never satisfied with the temperature in our rooms - either it’s too warm or too cold. Therefore I would add some shelly wifi relays to control the valves on my own. However I want still to be able to control them via the existing thermostats.
To do this I came out with the following plan.

This is the original wiring as it’s currently (Danfoss just switching the valve directly):

This is my planned wiring:

In order to be able to control via shelly as well as via the original thermostats, I came out with adding an additional relay to supply the SW input of the shelly with the output of the Danfoss.

What do you think - will this work without burning my house? :wink:
Any idea if I could save the additinal relay to connect the Danfoss output with the SW input of the Shelly?

Many thanks for your thoughts.

You need advice from a qualified electrician.

There is too much liability for people here to give advice if your house burns down because of it.

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Definitely so if you cannot answer that for yourself. For your own safety and anyone’s liability, please don’t ask or answer questions like this.
This is no forum on DIY, electrics or HVAC.

PS: red wires for neutral ??

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To be fair, it’s 24 Volt AC, with two transformers (i.e. there is no “neutral” potential at all) .

I think you meant to say DC it is and yes there’s no neutral in DC. But red for DC minus is still a wrong color code and to me that’s another (albeit small) hint that the OP is not familiar with planning this stuff and that he should leave that to an electrician.

The thermostats control the on off heating.

Adding more complexity in the system should be avoided until you fix the problem.

Where are the thermostats located?
Do they detect the temperature of floor or air?

As an Electrician I would attempt to fix the problem not overcome it with more control. It is likely you need a new thermostat.


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