Inside the house 10° warmer than outside - how does that happen?

The 20 degrees room temperature display of the heating is not measured. This is an assumed value used for the heating curve. The bypass is normally supposed to ensure that cooler outside air is not heated via the WT. This should work automatically with a modern device.

Shading is the be-all and end-all. But the heating flow temperature must not be 30 degrees either. For what?? Something is wrong there.

Otherwise, 28 degrees is extreme. Without shading, we have a maximum of 25 degrees in spring, more like 23 degrees.

The HK recorded the soil temperature.

That helps massively and without it you will be cooked or have to cool against it

Okay, then we probably have to get used to it. I'm just surprised that it's so bad today. It has been pouring all day and outside it is a maximum of 20.

The bypass is supposed to normally ensure that cooler outside air is not heated by the heat exchanger.
That should work automatically with a modern device.

I would have the option to switch on "Bypass". Should I do that?
So currently it is set to "Exhaust". Otherwise, I could choose: "Off, Supply air, Bypass" or "Summer cassette" (but we don't have that).

The HK recorded the floor temperature.

I don't understand that, what does it mean?

You can change the summer cassette yourself. It is as difficult as changing a light bulb. With us, the setting [Sommerkassette] controls the system so that the ventilation is off as soon as the outside temperature is higher than the inside temperature.

You can change the summer cassette yourself. It's as difficult as changing a light bulb. In our system, the summer cassette setting regulates the system so that the ventilation is off as soon as the outside temperature is higher than the inside temperature.

I read something similar. A summer cassette would cost around €100 as far as I know. But how does your system know what the current indoor temperature is? Ours only has an outdoor sensor and consistently maintains 24°C inside for 20°C outside, so that doesn't match. Aren't you afraid that the heat exchanger will break if you have to store it outside the system for half a year every year? What would it cost as a replacement if it broke during the exchange?