Hello! We are currently building a single-family house to KfW40 standard and are supposed to have a Bosch air-to-water heat pump installed. Our heat pump was ordered back in December 2022, but it has not been delivered yet, and there is no clear indication of when it will arrive. Our construction company now says they can install the same model (Compress CS7400iAW ORMB-S) within two weeks, but with lower capacity, specifically 5 kW instead of 7 kW. According to our heating load calculation, our house requires 2.8 kW without hot water and a total of 3.4 kW including hot water. So, it seems that 5 kW should be sufficient. The question is – is this really the case, or am I misunderstanding something? Or should we wait for the 7 kW unit, even though delivery is completely uncertain? We are a family of five living in Schleswig-Holstein. I also asked about alternatives, for example, an air-to-water heat pump from Vaillant. I was told that this is an option, but it would have to be ordered new, with a delivery time of about three months, which should be more certain. Could someone recommend: take the 5 kW unit, wait for the 7 kW, or go with the Vaillant?
H
Häuschenbauer431 Jan 2025 19:56I would like to bring this thread back up from the depths.
Brief details about the house:
- 160 m² (1,722 sq ft) on 2 full floors
- 42.5 Poroton blocks (filled)
- Ventilation system with heat recovery
- Primary energy demand: just under 22 kWh/m² per year
- Transmission heat loss: 0.21 W/(m²·K)
Now the question, and I only want to ask for experience-based opinions and suggestions.
So far, the plan is to use the Vaillant Arotherm plus VWL 75/6 a. This won’t be excessively oversized, but the question is whether I should rather go for the 55/6 model?
Or would both heat pumps likely work well?
I would appreciate any assessments you can share!
Have a great weekend!
Brief details about the house:
- 160 m² (1,722 sq ft) on 2 full floors
- 42.5 Poroton blocks (filled)
- Ventilation system with heat recovery
- Primary energy demand: just under 22 kWh/m² per year
- Transmission heat loss: 0.21 W/(m²·K)
Now the question, and I only want to ask for experience-based opinions and suggestions.
So far, the plan is to use the Vaillant Arotherm plus VWL 75/6 a. This won’t be excessively oversized, but the question is whether I should rather go for the 55/6 model?
Or would both heat pumps likely work well?
I would appreciate any assessments you can share!
Have a great weekend!
H
Häuschenbauer431 Jan 2025 22:55I tend to agree with that as well. Thanks in advance.
Häuschenbauer4 schrieb:
I want to bring this thread back up from the depths.
Brief details about the house:
- 160 sqm (1,722 sq ft) over 2 full floors
- 42.5 Poroton (filled)
- Ventilation system with heat recovery
- Primary energy demand: just under 22 kWh/m² per year
- Transmission heat loss: 0.21 W/(m²·K)
Now the question, and I only want to ask about experiences and suggestions.
So far, the plan is for the Vaillant Arotherm plus VWL 75/6 a. It won’t be excessively oversized, but the question is whether I should possibly choose the 55/6 instead?
Or will both heat pumps likely work well?
I would appreciate some of your assessments!
Have a nice weekend! What does the heating load calculation say?
I have 120 sqm (1,292 sq ft) and a primary energy demand of 34, Ytong 42.5, and a heating load of 4 kW.
I have the 55 model and it is fine, sometimes even a bit oversized.
H
Häuschenbauer42 Feb 2025 10:14@Yasper81
I still need to have a heating load calculation explained to me. For now, I was mainly looking for a rough estimate.
But looking at your figures, the 55 model should probably be sufficient for me as well?
Various online calculators give results between 4-6 kW. Presumably, the 75 model will cycle more frequently, and the 55 will activate the electric heating element sooner? The 75 might also have the advantage of heating the domestic hot water tank faster if it gets emptied quickly.
I still need to have a heating load calculation explained to me. For now, I was mainly looking for a rough estimate.
But looking at your figures, the 55 model should probably be sufficient for me as well?
Various online calculators give results between 4-6 kW. Presumably, the 75 model will cycle more frequently, and the 55 will activate the electric heating element sooner? The 75 might also have the advantage of heating the domestic hot water tank faster if it gets emptied quickly.
Häuschenbauer4 schrieb:
Turn on the heating element a bit earlier at 55°C (131°F)?When do you need it? At -15°C (5°F). How often do you have those temperatures? In 90% of Germany, the heating element is never needed because the heat pump mainly operates at partial load anyway.Similar topics