ᐅ Which air-to-water heat pump is best for a new build?

Deliverer schrieb:

Beforehand, neither you nor the heating installer should worry about the model. It can basically only go wrong. Determine the heating load, then select the appropriate model. Not bigger, even if it modulates aggressively.

A 9 kW heat pump is definitely too large for a new build. That’s the capacity my uninsulated older building of 260 sq m (2,800 sq ft) requires. I estimate you will need about 3.5 to 4 kW. Unlike oil or gas systems, an oversized heat pump is really problematic. It’s much less efficient and will break down much earlier than necessary. Plus, it requires expensive additional hardware like buffers, hydraulic separators, and overflow valves, which you could avoid by choosing the right heat pump size. Oh, and of course, a 4 kW heat pump is much cheaper than a 9 kW one. So this sizing difference can actually mean thousands of dollars (or euros)!

I don’t know exactly where these are required. I have both a new build from 2016 and an older building from 2020, and neither has these units installed. But apparently, they might be mandatory somewhere. Those who calculate the heating load can also apply for an exemption.

In any case, you should definitely leave them out. They cost a lot of money. Just the electrician has to install many more meters of wiring. Then they consume electricity continuously, and ON TOP OF THAT, they mess up the precise control of the underfloor heating. All that WITHOUT any added benefit at all. So do your research and get rid of these devices; this is technology from 40 years ago, before heat pumps existed.

We are building a detached single-family house with brick construction and external thermal insulation composite system (ETICS). We comply with the energy saving regulation, but do not have a specific KfW standard. With 170 sq m (1,830 sq ft) total (152 sq m (1,635 sq ft) heated), is 3.5 to 4 kW really sufficient? I would have expected more.

Then it seems that the LWDV from Alpha Innotec is really oversized. What do you think about the LWAV (also by Alpha Innotec) as an alternative? It comes in two versions. The smaller one has 6 kW.

Actually, it doesn’t make much sense to install a hydronic heating system anymore. But unfortunately, not everyone can build to Passive House standards...

If that’s not possible, the insulation should at least be good enough to manage with around four kW. And if it’s five… well, it’s still better than a newly built old building.

At these heat loads, you can genuinely cover a significant part of your own energy needs with your roof, since heating during the day will be sufficient. Buying energy externally is something no one will want to do much in the future.

So: a large, simple roof (not a complex shape!), fully covered with photovoltaic panels, good quality windows, proper insulation, a ventilation system with heat recovery—and the future will be bright. ;-)

Alpha Innotec also offers a non-inverter controlled system with the LWD. However, an inverter is recommended. What are your thoughts?

The reported performance figures in the heat pump consumption database clearly show an efficiency advantage of inverter models. However, this only applies with proper operation and correct design of the underfloor heating system. Oversizing remains a disadvantage, even with inverter units.

Oetzberger schrieb:

The reported performance figures in the heat pump consumption database clearly show an efficiency advantage for inverter models. However, this only applies with proper operation and correct design of the underfloor heating system. Oversizing is still a disadvantage, even with an inverter.

Thank you. Until now, I didn’t realize how easy it is to make mistakes with underfloor heating. What should I pay attention to so I can properly oversee my builder or general contractor in this regard?

Pipe spacing 7.5 cm (3 inches), 5 cm (2 inches) in the bathroom. In the bathroom, at least one more wall as well. All loops between 80 and 100 meters (260 and 330 feet).