Is HAR/technology sufficiently dimensioned? Any experiences?

Why are you worrying? Your architect or BU need to know what should go in there. That’s their job. Tell them you assume this and that goes in there. They have to check that.

The inverter is best placed in a as cool a location as possible.

Why are you worrying? Your architect or construction manager have to know what goes in there. That’s their job. Tell them you assume this and that will go in there. They have to check that.

Well, it’s our house and not the architect’s. Trust is good, but control is better. Personally, I’ve experienced that the heating engineer told a homeowner that the planned heating system wouldn’t work and they had to find another solution. Surely, the planner was to blame, but what can you do then? Besides getting annoyed, there’s not much left to do ;-)

Then you address your concerns and say, it is very important to me that everything can be realized without problems, I don’t want any weak compromises just because 1 sqm is missing now. Karsten

The inverter does not fit behind the door.

We have a Stiebel Eltron LWZ 604 Air or Tecalor TCO 2.5; the THZ 304 to 504 or LWZ 304 to 504 have similar requirements.
Space including room for maintenance about 3x1 m
Supply and exhaust air at the ceiling

You still need space for house connections. For us, it is over 2m of wall space for the multi-utility entry, house connection for electricity and water.

A user here also had this problem once, and the installer also had some hassle with where to place the connections.

Primarily, many wall meters are needed for hanging, etc.

A 1 m wide section of wall provides an additional 2 m of installation area.