Heat pump is not compatible with a water-bearing fireplace

Oh wow, you could still scroll further in the datasheet and there actually is an A16, which you apparently have.
With that device, you could wonderfully heat a multi-family house!
It probably consumes not only a lot of electricity but also cycles frequently, but that would then be the next task after you have the power consumption somewhat under control.
How do you measure the power consumption anyway?
So where does the 65 kWh consumption figure come from?

And yes, 28 degrees would also be expensive with my wood chip or gas heating.
That has nothing to do with the heat pump.

But as I said, first do the basics if you can't find a heating technician:
Only turn on the heating rod at below zero temperatures. Both for heating and hot water.
Set the heating curve reasonably, according to the instructions.
All room thermostats to sensible values, maybe 2 for the bedroom, the rest 3 or 4 depending on desired temperature.
Turn up the bathroom fully.

And then adjust the flow rates at the distribution boxes, but maybe later.

I'm confused by everything too, so that fits!

So I just saw these data on the heating system
RT target 19 degrees, reduced 17
Heating curve
Slope 0.8
Level 0 K
Flow temperature 27 degrees

Our heating engineer comes about once a week and "tries" things out... changes the connections, etc. All without success.
The thermostats are therefore turned down because it is "overheated" 20 degrees in these rooms and that is enough. The doors are always open. Only in the bathroom do I want it warmer, so it is turned up there.

Bold! And every time I struggle with my 0.4 and think that is too much.

----------------------------------------------------------------------------------------------

Forget the idea that the heat pump heats individual rooms.

Imagine your whole house with the rooms as one big water circuit.

Each room has an access point that can be regulated and determines how much water flows through in what time.

The entire circuit is heated to one temperature.

To bring a room to the desired temperature, you have to allow a certain amount of water in depending on the room size.

If all rooms are the same size, that is no problem, you simply let the same amount of water in everywhere.

But rooms are always different sizes, so you have to allow the amount that fits the room in each case.

You regulate this via the access (manifold box of the underfloor heating, here you can adjust the flow rate).

Unfortunately, it is the case that some rooms do not get enough water to heat them to the desired temperature (usually bathrooms since they are small and higher temperatures are desired).

Now you can either create space for more water (smaller pipe spacing or wall heating) or you increase the temperature of the water.

Increasing the temperature (this is the known flow temperature) does bring the desired heat into the bathroom, but the other rooms also become warmer.

So you have to reduce the amount of water there until you reach your desired temperature.

This whole thing is called thermal balancing.

Now there is the problem that at low outside temperatures the heat is no longer sufficient.

You could increase the amount coming into each room now, but then you would have the problem that you have to precisely adjust everything again to make it fit and you are also limited by the smaller rooms where no more water can flow in.

But our heating system knows from the outdoor sensor that the outside temperature is dropping.

So it increases the flow temperature to compensate.

Since previously all rooms were adjusted to their correct temperature during the thermal balancing, this works.

This is the heating curve of the heating system; it contains how much the flow temperature must be changed when the outside temperature changes.

This is now a simplified representation, but it depicts the basic function.

Because we have the photovoltaic system, we have an app that "monitors" the power. The consumption data comes from there and I can clearly see when the heating switches on...

Because we have the photovoltaic system, we have an app that "monitors" the electricity. The consumption data comes from there and I can clearly see when the heating turns on…

:oops: :oops: :oops:
We had a curve like that yesterday, the plasterers had taped our outdoor unit with foil and forgot to remove it.

Edit: The question is what your heating system is doing when it shuts off every 2 hours like crazy.
Our system only shows such high values when it is producing hot water. But not every 2 hours.
I don’t think it’s the underfloor heating, that’s probably your domestic water?