House construction with developer - electrical and warranty

Thank you for the clarification. Now "even I" ;) have understood it.

Somehow I can't edit right now. I actually intended to replace the standard room temperature controllers of the underfloor heating with digital ones (GIRA 3000). That would be the same problem.

Therefore the question: Would you do it yourself for cost reasons and take the above-mentioned risk? I'm not so sure anymore....

Therefore the question: Would you do it yourself for cost reasons and take the above-mentioned risk?

A clear yes to the question of a replacement. BUT: I would completely deactivate the controllers after moving in and make the "eyesore" disappear from the wall. It a) looks better and b) nobody needs the controllers with a functioning and well-adjusted heating system ;). And you also save money.

Yes, that's true as well. If you connect any kind of Chinese firecracker to a light outlet, the warranty is void.
He's just protecting himself.

I thought about it for a while, but no, that's not entirely true.
The electrician lays the cable and properly secures it according to the cross-section.

If there is a short circuit or a fire, it will be investigated whether the fuse failed (extremely unlikely), whether the loop resistance of the cable was not low enough (more likely), or whether the light bulb burned out (most likely).
But it is definitely NOT the case that the electrician is off the hook in every case as soon as I connect a lamp to his cable myself...

I don't really have any technical knowledge about that, but if the apartment is completely burned out, can that still be determined beyond doubt? Doesn't it rather end up with expert vs expert for years where eventually the financially weaker has to give up?

Well, the expert will definitely find the source of the fire. And if it’s in the [HAR] in the fuse box or at the light switch, then the electrician is definitely involved.