Underfloor heating air-water heat pump. House too warm when the sun shines

You have first of all also heated up the previously unheated screed, which costs energy.

Especially in order to be able to close the bypass valve, you should dismantle the actuators.
Please take another look at the graphic I posted. There you can see the effect of the ERR. Some heat pump species also call it the "efficiency reduction controller."

When the underfloor heating is balanced and the heating curve is adjusted, the consumption will decrease, but mainly when the produced heat flows into the underfloor heating and does not bypass it via the bypass valve.

Efficiency reduction controller

Like!

It's a matter of resistance (pipe length, diameter, bending radius-laying distance). Heating water also takes the path of least resistance. As I said, more went through when I closed the bypass valve.

So, my adjustment of the volume was 8 hours ago and nothing has changed in the bathroom so far, still 20.9°.
Oh man, hopefully it helps ..

8h is too short, wait about 24h

Hey, SOS, why is there no volume at all in the main bathroom now?!
:-/

Hm, is it stuck? You had 2l/min earlier, right?
Did the heating stop at some point?
Is the heating running now? Turn it and see if anything moves. Do you already have the thermometer?