Heat pump underdimensioned for a 6-family house?

Thank you first of all for these hints. As for the recommended heating load calculation, I am wondering, however, a) whether it HAD to be done during the 2012 construction planning? b) whom I can contact, the developer or the heating engineer? c) whether those mentioned even have to provide this calculation to me as the apartment buyer? I rather assume - if my suspicion of an underdimensioned system is correct - that all parties will stonewall. And then? Involve an expert, just on suspicion, and how much does that cost? And will the owners' association cooperate? As was correctly pointed out here, the heating costs for the four landlords in the building are just a pass-through item.

I would rather discuss the usage behavior with the other owners!

A heat pump must be set up in a disciplined way, etc.

Just a small question, how warm is your hot water?

What is the flow temperature at the underfloor heating directly at the heat pump?

How high are the thermostats in the apartments?

Absolutely nothing will happen if four out of six owners have rented out their properties and the costs are thus willingly borne by the tenants.
Take it or leave it.

I would rather discuss the usage behavior with the other owners!

Well, it seems rather unlikely to me that all six apartment owners - four of whom are tenants - do not care at all about energy costs and always run their heating at full power. In addition, the heat in the apartments can only be set via the thermostat; all other settings are probably only adjustable directly on the system. And according to the heating engineer, these are correct.

At the latest, when the first tenants terminate their leases due to high additional costs, there will be discussions.

Yes, of course, those at the system are correct. It is getting warm after all. He is not interested in the rest. And that is the terrible thing about it. A heat load calculation does NOT have to be done at first. You can also estimate. It’s just dumb then. Heat pumps are extremely sensitive to too high flow temperatures and also the required volume flow. I personally suspect a complete planning failure and the resulting high running costs. On top of that, incorrect heating behavior and you have the misery.