Air-to-water heat pump sizing in new construction

That is also my understanding so far. However, it would mean that everyone would then also get the buffer tank an

It might be attempted with some, but most (good) heating installers won’t sell you a buffer.

My concern is how far the modified heating circuits can be throttled and how that affects the head pressure or the flow rate under stress.

Since apparently not only narrower (and longer) but also more circuits have been installed, this should not be a problem. And you can throttle them down to zero if necessary.
If you can lower the supply temperature far enough, this is not even necessary. Then it regulates itself: the room is warm, heat transfer from the floor to the room no longer occurs because the delta T is too small. Flow rate does not matter. But this only works with small installation distances. So congrats. ;-)

5cm :) in the bathroom, 4 circles on 15 sqm. I want to see something like that :)

We already had a person including walls before, who was that? As a reference, we have about 250 sqm of heated area but Kfw 70 and an 8 kW heating system. A 6 kW one would have been more than enough.

I would also say that it is even a bit better with VA10 and 6 circles than VA15 with 4.

Since the bathroom is usually the "problem room," it would most likely not have been necessary, but you don't look a gift horse in the mouth, ...

So, I have received feedback from the engineering office regarding the smaller Vaillant. They increased the flow temperature from 33 to 33.5°C and the return temperature from 29 to 28.5°C, thus increasing the spread from 4 to 5 K.

Now the volume flows are lower and the small 75/6 A from Vaillant can deliver the volume flow.



Let's see how I can optimize this in the long term. It almost feels like an old building with 34°C flow temperature when I compare the benchmarks here with you. Our building structure with gables and bay windows plus many floor-to-ceiling windows really seems to make a big difference. But I hope for good solar gains in practice so that I can lower the flow temperature over the years.

The only downside is that I can't get the small 55/6, which would be perfect for our heating load, above an annual performance factor of 4.5...

So, I was able to solve the mystery. The installers on site are working according to old plans. As described above in the quote, the calculation was optimized last year because we were within the maximum volume flow range of the 75/6 with a spread of 4K and a flow temperature of 33°C. As a bonus, the balancing of the heating circuits in the WEK was also eliminated, as the number of heating circuits there could be reduced from 6 to 4.

The message therefore did not make it into the execution, although I had sent the plans again to both the site manager and the plumbers during the discussion about the wall heating.

Well, since that was the only change from the initial planning, my focus now is to pay attention to minimizing the heating loop distances upstairs in the bathroom. The rest should be fine; I will just have to throttle more in the WEK or else I will get grilled during the hydraulic balancing. I’d just have to send my wife on vacation for that time or something, because she will surely tear my head off during the hydraulic balancing since it won’t amuse her much to be constantly freezing and sweating alternately. :)

In the upstairs bathroom, the small area has been quite well utilized in my opinion. Unfortunately, the general contractor did not want to completely relocate the shower, even after long discussions, nor under the bathtub. Upstairs, the 5cm was still quite well achieved.



For the downstairs toilet, I roughly estimated about 7cm (should be 5cm). Except for the hallways and bathrooms, everything is now completely done with 10cm and looks really good in my eyes.