Is the heating oversized?

I have now read a bit more and found similar cases... as it seems, the boiler produces too much heat in a short time (which shows the rapid rise in the flow temperature)... this cannot be transported away quickly enough (since only a few heating circuits are open)... it quickly reaches the maximum set flow temperature of about 50 degrees and switches off... the flow then transports the heat away (which means the rapid drop in the flow temperature)... at about 25 degrees it switches on again and the cycle starts over.

The burner times are only a few minutes... which probably means about 150 to 200 burner starts per day... and that at already quite cold temperatures at the moment...

When the desired temperature in the room is reached, the controllers switch off automatically... and only switch on again when the temperature falls below... I have 11 heating circuits in the whole house... as mentioned, only 2-3 are open at any time... I cannot increase the temperature in the rooms on purpose to make the burner times longer...?

The heating installer will have to come again...

WPIC has said most of it.

I just checked the heating system online.
This is a very powerful system. In my opinion: way too oversized.
That can heat >>250 sqm of living space......Power to the People! 22kW heating for 140 sqm! Wow. Who did the calculations there? Unbelievable!

We have a usable area of 135 sqm, Kfw70 (Q_p and H_t tending to KFW-55). Our (very small) condensing boiler has 14 kW nominal power (11 for heating, 14 for hot water); and it is already way too big or not modulating low enough. Even at 23% (minimum modulating power = about 3kW) you usually are shooting sparrows with cannons. It took me many weeks to teach the device not to cycle with so many settings. <10 burner starts / operating hour.

In the documents for your heating, I didn’t see where the minimum modulating power is. I surely overlooked it and just estimate: 4-5 kW.
That is too much for a modern house of your property’s size.

The heating curve must also be turned down significantly. 45 degrees flow temperature for underfloor heating? With 40-45 degrees I run my flat radiators and feel comfortably warm; but definitely not underfloor heating.

That rings alarm bells for me. 28-32 degrees.... okay. But usually more is not necessary.

Your heating system really needs serious work again. As it is now, it definitely does not work properly! Since the heating system probably won’t be replaced now, an additional buffer storage must be added (one of the standard recipes to stop cycling).

Best regards
Thorsten

Was a heating load calculation ever done? I have a 5 kW wood stove on the upper floor (about 85 sqm), which overheats the entire floor. It also provides some heat downstairs; currently, we have no stove or other heating there (heating is installed but no underfloor heating, so the heating is not used). So 20 kW would be about twice what our house – an old building undergoing renovation but still losing plenty of heat unnecessarily, e.g. upward through the moderately insulated roof – would need. But we already had a heating technician here who back then wanted to sell us a 25 kW heating system, saying that’s how it’s done (rule of thumb instead of heating load calculation). The latter then showed something around 6 kW after renovation! If you can’t replace the gas boiler, how about installing a buffer tank? Then the boiler could heat the tank at full power and then stay off for the rest of the day – or longer. That way you could at least prevent short cycling.

We have 5.3 kW for 190 m² ... although I am still afraid that this is too little. 22 kW is in my opinion way too much... it's annoying, but the pure heating with gas is not that expensive (at least if it should ever fail...) Take a look in the pink forum - maybe you will get some suggestions for control optimization there.

How many sqm of heated area should be heated at minimum with a 20kw burner?

We have 5.3 kW for 190 m² ... although I am still afraid that this is too little.
22 kW is in my opinion way too much... it's annoying, but pure heating is not that expensive with gas (at least if it ever dies...)
Take a look in the pink forum - maybe you'll get some suggestions for optimizing the control.

I have calculated my heating load at 3.6 kW; 160 sqm above ground, 85 sqm in the ground (it doesn't get that cold there in winter, actually the ground stays just above 0 degrees except for the first few centimeters), but that only applies for the design temperature. Most of the time it is considerably warmer, i.e. at 0 degrees I have at most about 2 kW and so on.
I assume the 22 kW are supposed to ensure you can shower endlessly, or something like that. That's what the uninformed heating installer installs, because "as long as it's warm" (water).