3 heating loops in the bathroom, 1 not working, what to do?

Unfortunately, I can't answer that for you either, as I am not an expert in this matter. On the ground floor, we also have two heating loops for a 6m² guest bathroom. The bathroom upstairs, which is the one in question here, has a pipe area of 11.2m². The total area of the bathroom is 14.8m².

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Purely based on the planned lengths, someone participated there. Everything between 60 and 100m. Not too short and not too long, that keeps the pressure loss within limits without hydraulic short-circuit. That is why 3 circuits were created in the bathroom.

But that was the only thing he really thought through... I find the VA of 200 in the rooms too large for a new building, but the 50 in the bathroom too small. I can't remember ever encountering a 50 installation spacing. You can also overdo it. With a 100 spacing, he could have easily filled the bathroom with one loop. Of course, the bathroom loop would then be longer than the ones in the rooms, but that's what the hydraulic balancing is for. Completely regardless of the sensibility of the individual loops, I would simply call the heating engineer and explain the problem to him. Regardless of the distance, he has to stand by his work (and even wants flow rate) for his work.

We have deliberately chosen the 50 cm spacing in order to achieve a pleasant and higher temperature in the bathroom without additional heating than in the other rooms.

As mentioned, I cannot call in the heating engineer because:

a) he is not my contractual partner but the [GÜ]
b) he did not install the underfloor heating but another company that also did the screed etc. (also via the [GÜ])
c) the heating itself is running

Then you have to go through your contract partner so that they send you someone with competence in the matter - apparently the screed company from your point b).

The problem is that with the crystal ball-like remote diagnosis, a blockage in the heating loop cannot be ruled out. Full water level is indicated behind the valve, the loop still does not get warm, and it obviously is not due to the actuators either. A specialist company has to handle this, in my opinion.

By the way, does anyone of you have a good guide for a self hydraulic balancing of underfloor heating ready? Any link or something like that?