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

Hi,
according to the website, the ALM 4-12 has a minimum output of 4kW, which seems oversized to me.
What does the heat load calculation say? The smaller one will surely be large enough. Is the tank a combined buffer or are the domestic hot water and heating sides separate?
Have them make an offer for a smaller ALM and recalculate. Apparently, you are not obliged to connect. How long are the prices guaranteed for the local heating?
Greetings from Hamburg

Hi,
thanks for your answer. To be honest, I’m not sure if the heat load calculation has already been done. As part of the KfW40 application, my energy consultant calculated some key figures, but the heat load calculation is probably done by the plumbing company, right?
What I have:
Annual heating demand = 8,559 kWh/a
Annual primary energy demand = [I]7.31 kWh/m2

I will contact our energy consultant and plumbing partner regarding this.
As far as I understand, the ALM has a combined tank integrated in the housing, but I really can’t find that clearly on the manufacturer’s site.

There is no obligation to connect. The supplier guarantees the prices for 3 years. After that, the 9.95 + possible market price fluctuations apply according to the following shares (45% wood chips + 15% electricity + 15% inflation + 25% wheat price)[/I]

Which senior specialist planned the 12 kW heat pump for you? "KfW40" houses, even with 200 sqm, have "difficulty" utilizing 5 kW heat pumps, and that only when they have to heat at NAT for weeks (in other words: never). To make a meaningful comparison, you should try to get an offer for a significantly smaller heat pump - ideally one that can modulate down to 1.5 kW. And please without a buffer - you don’t need it, it only causes additional costs and efficiency losses.

Do you also want to cool in summer? The option is obvious, especially if you have a photovoltaic system.

Cooling would be a nice side effect, but it is not a must right now.

Presumably, you were offered the iPump ALM series - there is a version with a 100l buffer tank and a 295l hot water tank integrated. I definitely wouldn't take that if I were you - at least have the iPump A 2-7 model offered to you as a comparison: it is much better dimensioned, has no buffer tank, only a 200l hot water tank (which in my opinion would also be sufficient for the size of Hamburg).

If your goal is to have R290 as refrigerant and a nominal COP over 4.5 (iPump A 2-7 does not meet these 2 criteria), then possibly as an alternative Aero ALM 2-8 + external hot water tank (200 to 300l), if space allows.

Presumably, you were offered the iPump ALM series – there is a version with a 100l buffer tank and a 295l hot water tank integrated. If I were you, I definitely wouldn't take this – at least have the iPump A 2-7 model offered as a comparison: it is much better sized, has no buffer tank, only a 200l hot water tank (which in my opinion would also be sufficient for the Hamburg size).

If your goal is to have R290 as the refrigerant and a nominal COP over 4.5 (iPump A 2-7 does not fulfill these 2 criteria), then possibly as an alternative Aero ALM 2-8 + external hot water tank (200 to 300l), if space permits.

Yes, exactly, the iPump ALM series was offered – what is the reason you would rather recommend an external hot water tank than the integrated combined tank (100l buffer and 295l hot water)?

Space might indeed become an issue, but presumably the Aero ALM series is also smaller than the iPump ALM series.

As mentioned, there is initially nothing against an integrated hot water storage tank. However, I would not spend extra money on a buffer storage tank on the heating side. It is basically only there to compensate for planning errors. Hence the recommendation for iPump A 2-7 as an alternative - only integrated hot water storage, without buffer storage, and much better suited to the heating load.

Hello,
as far as I can see on the IDM website, it is a combination storage tank installed as a hydraulic separator. The heat pump circuit and the heating circuit are separated. That is not good!
Such an installation makes sense with a high-temperature heat generator and a low-temperature heat sink, such as underfloor heating.
With a heat pump, the goal is solely to produce the required amount of heat, i.e., to adjust the flow temperature to the needed demand. With a system using a separating storage/combination storage, you would have to match the volume flow of the heating circuit (underfloor heating) as precisely as possible to the volume flow of the heat pump; only then is there a low energy loss due to the construction of the separating storage. However, the offered heat pump is a modulating heat pump, which is actually correct. The problem with separating storage, however, is the adjustment of the volume flows. The heat pump regulates not only the compressor output but also the volume flow to always have the optimal temperature difference in the heat pump circuit. The circulation pump of the heating circuit, however, operates at a fixed volume flow. Therefore, the volume flows cannot be optimally matched, and there is ALWAYS an efficiency loss!
Solution: the heat pump is connected directly to the underfloor heating; in doing so, to ensure the minimum volume flow, enough heating circuits must always be open ([ERR deactivate]). For hot water preparation, a three-way valve switches from the underfloor heating to the domestic hot water storage tank. A small storage tank (30-70l) can be planned in the return line of the heat pump to secure defrosting processes. This is not absolutely necessary, as the screed provides more heat for defrosting than a buffer tank, but at least the efficiency loss can then be neglected.

Summary:

1. Have a heating load calculation done.

2. Afterwards, have a SMALL heat pump offered accordingly, do not accept any safety margin in the heating output, as this already includes the heating load calculation. No separating storage/combination storage or similar constructs.

3. It is also important to calculate the room-specific heating load, then have the underfloor heating designed accordingly, including temperature specifications for the individual rooms. If necessary (mostly in bathrooms), consider additional wall heating. If towel radiators are planned, do not integrate them into the heating circuit but operate them electrically.

After moving in:
4. Thermally balance the rooms in the first winters (not via the [ERR]!), this is a personal task and not to be performed by the heating installer.

5. Regularly check operating behavior and cycle times.

Greetings from Hamburg