Recommendation air-water heat pump vs. local near heating network KFW40 new building

Yes, the limitation to IDM is not really optimal in this case - there are some other providers (unfortunately mainly from Japan/South Korea) that have 4 to 5 kW heat pumps, also modulating down to just over 1 kW. These would fit much better and bring significant savings, especially during the transitional season. Some of them are also designed as monoblocks, meaning you lose just as little space indoors as with an all-in-one device. And they are also significantly cheaper...

Now I have to turn to you again because my heating engineer still recommends the ALM 4-12 for me, with a heating load of 5.05 kW (without hot water). Furthermore, he writes that a value of 7 kW is assumed for hot water production. I cannot reconcile this value at all with the common recommendations of 0.25 kW per person per day. Perhaps he means a total demand of 7 kW for heating and hot water combined, but even then I wouldn’t choose the 4-12 variant, right?

For illustration, I have plotted the heating demand (5 kW heating + 1.25 kW hot water) into the performance curves of the iPump ALM 2-8 and 4-12. You can actually see quite clearly that the 4-12 will be constantly cycling at temperatures above -5 degrees because the minimum power is 4 kW. Even the 2-8 variant does not run really efficiently at temperatures above 5 degrees, or do I have a mistake in my thinking? In any case, the bivalence point is outside the corridor recommended by iDM from -3 to -10 degrees in both cases.

It would be great if you could let me know whether I have made a mistake somewhere :)

Hi
the heat pump either produces hot water or heats, but never both at the same time. So you don’t need to add anything there. During the domestic hot water preparation period (depending on the performance of the heat pump 30-60min) the screed cools down measurably but not noticeably. The heat pump may then heat briefly at a higher modulation stage, but you don’t need a more powerful heat pump because of that!
How free are you then in your choice?

Creating the drawings was a great idea and clearly shows how both devices are oversized. One is just significantly more oversized than the other.

Or what was your NAT again? ;-)

Hi
The heat pump either produces hot water or heats, but never both at the same time. So you don't need to add anything there. During the domestic hot water preparation time (depending on the performance of the heat pump 30-60min), the screed cools down measurably but not noticeably. The heat pump may then briefly heat at a higher modulation level, but that doesn’t mean you need a more powerful heat pump!
How free are you then in your choice?

Thanks for your explanation!
Well, we are building with a developer who in turn has a heating technician who sells iDM and Viessmann. So theoretically we are somewhat limited unless I insist strongly on another manufacturer. But I have heard basically little bad about iDM, so I would generally stick with it.

Making the drawings was a great idea and nicely shows how both devices are oversized.
One is even significantly more oversized than the other.

Or what was your NAT again? ;-)

Our NAT is -13.5 degrees. In the drawing, however, I even assumed the worse case of -16 degrees.
But there are few heat pumps that have even less capacity. Is cycling of the heat pump at demands below 2kW really that detrimental, or is that only a minor disadvantage so that I might still switch to district heating?