Is the heating oversized?

I’ve done that now too... I’m now at 17 liters flow....unfortunately, I can only observe in the evening how long the heating times will be now...

What exactly does the boiler modulate on? In other words, which parameter tells it to run at lower output? Is it sensible in my case to throttle the max heat output... according to the default setting it was like this:

Min. heat output: 36%
Max. heat output: 84% (now I have 50%)

Would it therefore make sense to say Min (36%) = Max heat output (36)? That would still be 7.3 kW..

Usually nowadays, the output is mainly controlled via the heating curve. Other parameters can (in fact do) also come into play (setpoint vs actual at flow temperature, return temperature, temperature drops, and much more).

With your heating system, as already mentioned, the minimum heat output is the problem anyway, as it is simply too high for the house. Therefore, in my opinion, you don’t need to worry too much about whether the maximum should be limited. You probably also can’t set Min = Max (but, as said, that is just a guess).

With the 7 kW minimum output, the system will continue to cycle cheerfully without technical changes. The problem of cycling is often and gladly encountered even with heating systems with significantly less capacity; with the size you have in your house, as said, it is always inherently built in. Something has to be changed there.

Best regards Thorsten

Despite the open flow and 17 liters/min, the device heats for max. 10-15 minutes at a time and then turns off again... it is now heating from 23 to about 34 degrees...

Problem now: Somehow I only reach about 19 degrees in the living area and the consumption has risen to about 9-10 m³ (with cycles it was 22 degrees and about 6-7 m³)... so I have now turned the ERR down again and increased the design temperature... because it became too cold for my partner... I spoke with the heating technician by phone, he says everything is correct and functioning....

Would installing a buffer tank (300 or 500 liters) help me???... then the boiler could fire fully into it and I would always have immediate heat when I need it... and the boiler would only turn on 2-3 times to heat the buffer...???

Your heating engineer wants to charmingly talk his way out. What he installed simply does *not* work optimally.

Please Google once Wikibooks/Optimization of Small Heating Systems/Measures Against Heat Loss

You should slowly stop wasting time complaining with the people (so, with your heating engineer of course) and establish clear facts.

Why is it too cold now?
Because the flow does not occur continuously. The supply temperature rises. But the heat does not leave the floor that quickly. The burner shuts off again. And waits (often it has a hysteresis of 5-15 minutes before it turns on again).

If the oversized heating system remains, in my opinion the buffer tank is the only option. I don't think the buffer needs to be 300 liters right away (that is a huge container). Off the cuff I would say (an expert has to give the exact number): 70-120 liters.

You are currently consuming 7 to 10 cubic meters of gas per day?
Good God. That's way too much. We have a similarly sized house. I only need about 2.7/day. If it is -10 degrees outside, I need just under 4.

Best regards Thorsten