Is the heating oversized?

Heat pump? That's a gas heating system!

Sorry, misread. But it should be the same.

then adjust the heating curve on the heat pump (set the flow temperature lower) until only your desired temperature is reached. Then it fits and your heat pump will only consume the energy it really needs.
Although, according to my layman’s estimate, the heat pump is also oversized.

But if the flow rate in all rooms is set to max. and thus all 11 heating circuits are open, doesn't the heating system then pump itself "to death"??? It has to supply all heating circuits with water...??? This means 11 x 2 liters/min flow rate, i.e., 22 liters/min in total... and that 24 hours a day...???

Besides, then the whole point of my temperature-controlled room sensors is lost... because the heating is always on...??? I thought I set the temperature in the room and the controller takes care of it....

So like I have it set to 20 degrees right now:

> too cold > controller opens flow until 20 degrees is reached again
> too warm > controller stops flow until the 20 degrees is undershot again...

As a result, when the target temperature in the house is reached, only a few rooms have the flow open > the boiler cannot modulate down to this small heat demand (because about 7 KW minimum).... therefore the heat exchanger heats up too quickly and the boiler switches off (reaching the max. set flow temperature)... and then switches on again (it cycles) i.e. only pulsating / slow heating of the rooms.

The system behavior with this design is, as mentioned, predictable.

I was honestly shocked by the 7 kW minimum output you mentioned. The heating system is definitely oversized / too powerful for a 140 sqm house with modern construction/insulation. Last year, even at -12 degrees, I never needed 7 kW. At most, 4.5 - 5 kW briefly, then back to 3.3.

With correct sizing and flow, your controllers would intervene very gently, if at all necessary. Such a drastic on/off control only occurs because too much power is going into the flow + the flow temperature is too high.

In my personal opinion, the solution consists of three options:
a) Let the system keep cycling (--> significantly shortens the lifespan)
b) Replace the system with a smaller one (unlikely, but you can try it, warranty as already explained here in the thread)
c) Install a buffer tank for the heating flow (of course also under warranty).

Best regards
Thorsten

Besides, doesn't that defeat the purpose of my temperature-controlled room sensors... because the heating is always on...??? I thought I set the temperature in the room and the controller takes care of it....

So, as in my case currently set to 20 degrees:

> too cold > controller opens flow until 20 degrees is reached again
> too warm > controller stops flow until the temperature falls below 20 degrees again...

As a result, once the set temperature is reached in the house, the flow is only open in a few rooms > the boiler cannot modulate down on this small heat demand (because approx. 7 kW minimum).... therefore the heat exchanger heats up too quickly and the boiler switches off (reaching the maximum set supply temperature)... and then switches back on again (it cycles) i.e. only pulse-type / slow heating of the rooms.

Example description of how I understood it as a layman:

Your variant:
You have now reached 20 degrees in your rooms. The valve closes. However, the heating doesn’t know about this (probably controlled by outside temperature and return temperature) and runs at 45 degrees against the closed valve.
No heating energy reaches the room anymore, but the 45 degrees warm water in your floor first heats the room further. After some time, the floor starts to lose heat over a few hours, then the room slowly cools down and then your temperature controller eventually recognizes that it’s below 20 degrees again. So valve opens again.
In the meantime, your heating system has noticed through the warm return flow that the energy isn’t leaving and stops heating further. Eventually, the significantly colder return flow from the previously shut-off circuits comes, and your heating switches on again. Then it has to heat the estimated 20 degrees return water back up to 45 degrees supply and pumps it back into your circuit. The floor heats up again first, then slowly the room and at some point your controller notices that it is again above 20 degrees. Then it closes. But you still have 45 degrees warm water in the floor that continues heating the room…. And the cycle starts all over again.

My variant:
The heating runs around the clock and pumps the warm water according to the supply temperature along the heating curve into the rooms (currently with -4 degrees outside temperature approx. 30 degrees supply). The water returns at about 27 degrees, the heating heats the three degrees back up and lets it circulate again.

You can calculate for yourself which variant causes the heating to cycle more, has a higher electricity consumption, or makes the rooms more evenly warm etc.

According to the Energy Saving Ordinance, I have an ht of 0.285. What is it for you?
That also explains why everyone says, do a heating load calculation and don’t come to me with Energy Saving Ordinance papers.
No, but apart from that, there are so many assumptions in the calculation that actually aren’t correct; starting with generic thermal bridge values, it says "windows with Uw<1.00 (we are realistically well below that), perimeter/basement is 0.035 insulation instead of 0.038 insulation.
I calculated with the actual materials, dimensions, etc. from the planning for the construction site, according to the tenders, so of course it was more accurate.

0.30 - is not the best. However, we also changed a few details - better insulated roof, much better basement windows and one completely removed, floor insulation removed, instead more insulation calculated on the floor, better front door...

Estimated at the end then 0.28... but that wouldn’t make 3 kW difference either, so I’m sticking with the 8 kW heater because we also need a lot of hot water.

Maybe I’ll have the calculation adjusted again with new values.