Air-to-water heat pump sizing in new construction

Hello everyone!

Our calculation was certainly "standard" and unfortunately based on 35° supply temperature.
I have not received more than the attached overview for BAFA (so far), but I do not really understand it.
Can someone comment on the information or tell me if I should receive further documentation?

Yes, we have a complete heating load calculation for each individual room. Beforehand, the thermal insulation calculation of the house was created. We received the sizing of the heat pump from Vaillant; the Arotherm Plus 35/6 (3.6 kW) will be installed.

How did Vaillant size your flow temperature? Can I get some information about that?

We are still waiting for 2 offers (monolithic construction with clinker), but the currently most interesting provider for double-shell masonry works with Vaillant devices, and for me it would be interesting how well Vaillant does its job?

Or whether it would be better to commission the IB with the individual room calculation (including the installation plan).

Vaillant will probably also only comply with the DIN standard and play it safe. That means room temperatures of 20°C (bathroom 24°C) and a flow temperature of 35°C. Individual calculations are always better, and with the mentioned IB quite affordable. Unfortunately, it cannot be predicted in advance whether the subcontractor from the main contractor/general contractor will accept something like that. I had alienated the subcontractor of my general contractor with this, who then diva-like completely terminated the collaboration. When I was looking for a replacement (the general contractor only had the subcontractor), another heating technician rejected the calculation and planning of the IB and thus the entire order. Another provider said nicely that they have something like that, but we definitely do our own calculation. And my current one basically also recalculated it himself, but since he came to the same result, it was okay for him to execute it that way. So in the end, it will practically only be really carried out accordingly if you do it yourself or if you have it written into the contract that it should be executed according to your planning documents. And even then it is not 100%.

I already find the room names great! Warning, ironic...

Hello everyone!

Our calculation certainly ran as "08/15" and unfortunately at 35° flow temperature.
I have not received more than the attached overview for BAFA (so far), but I don't really understand it.
Can someone comment on the information or tell me if I should receive further documentation?

Ask your installer to explain it. I am missing room names, heat demand/room, over-/undercoverage, design temperatures, heating circuit lengths, temperature spread, ..

How did Vaillant design your flow temperature? Can I get some information about that? Or whether it might be better to commission the individual room calculation (including the installation plan) with the IB.

Good morning, Vaillant does not design the flow temperature. We received a Vaillant document from the heating technician, where the correct heat pump was selected based on the heating load calculation. Our heating technician had the Arotherm Plus 55/6 in the offer, but it became the 35/6. An oversized heat pump can have disadvantages.

Hello everyone!

Our calculation certainly went "run-of-the-mill" and unfortunately at 35° flow temperature. I have not (yet) received more than the attached overview for the BAFA, but I do not make much sense of it. Can someone comment on the information or tell me if I should receive further documentation?

Your calculation is not yet a concrete heating load calculation. Our document has 35 pages. We only have a bungalow with 90m²; for a larger building, certainly more pages will be added. We are currently building a KFW Efficiency House 55. Before applying for KfW, we received the calculations from the energy consultant (thermal insulation calculation); otherwise, funding would have been impossible. Only at a later stage did the heating engineer come into the project (through the general contractor). The heating engineer commissioned the heating load calculation from his underfloor heating supplier. Due to this chain of general contractor, heating engineer, and underfloor heating manufacturer, there were often coordination problems. After 2 revisions, which always incurred costs, I accepted these. All wishes (e.g., flow temperature 30°) were not achieved. You could practically take a two-pronged approach. Solely commissioning external parties and the subsequent installation can lead to problems... here I mean, for example, irritation between the general contractor and heating engineer. You might also have a problem with warranty. If your house is not warm enough, what is the cause? With 2 calculations, you have good chances to identify differing results and their details.