Air-to-water heat pump sizing in new construction

The 55 is included in the list of eligible items.
aroTHERM plus VWL 55/6 A 230V S2

Yes, I have seen that. But I have to operate it with a 30°C flow temperature so that I get the BAFA annual performance factor at -10°C NAT. Unfortunately, that is not possible with our building.

I see it this way: when our oversized heat pump finally wears out in >15 years (at least+hopefully), then I can install a properly sized one based on practical experience, without regard to BAFA, GU, the heating engineer, or warranty issues.

Just ask your office if they can calculate it when you lower the room temperature. With the same installation, that should reduce the calculated flow temperature, etc. then it fits. Otherwise, suggest to your wife to invest the money saved on the [Dailkkn] system in shoes, maybe then she'll accept the appearance.

I have a calculation for 30°C flow temperature. I would need a 10cm installation distance everywhere and 5cm in the bathrooms, and despite wall heating, I still have a undercoverage of 300W in both bathrooms. The basement rooms would each have -200W (20°C setpoint).

The engineering office strongly advised against this flow temperature. I would be very borderline on all sides and corners. There would be large undercoverages in the bathrooms/basement and I would then need >1300l/h volume flow of the heating circuit pump.

By the way, I definitely don’t get anywhere with the shoe argument. Then the discussion immediately shifts in the direction that they want the nice heat pump AND the shoes. I could save on bicycles or buy less computer stuff. The discussion then ends very quickly, very unpleasantly for me. ;)

The Bafa only wants a number on paper; it doesn't matter to them if you later have to set the flow temperature to 33 degrees because it gets too cold. That’s the crazy thing about the subsidy: if you have an old building and consume a lot of energy, you can quickly achieve a good annual performance factor, but if you have a super-insulated house and use little energy, it becomes increasingly difficult to achieve a good annual performance factor because the domestic hot water preparation worsens your values.

I agree. Adjust the calculation to fit the [BAFA - Förderung]. How you operate the system later? Nobody cares about that. It's the same with [ERR]. You have to install it, and you are allowed to dismantle it afterwards...

I have the feeling that my project is becoming increasingly complex here.

I fear that there is no optimum for me. Daikin has been forbidden by my wife and Vaillant only has heat pumps with weak heating circuit pumps. The 55 model only has an 860 flow rate. I cannot use it for my house, or I would have to make the temperature difference significantly larger.