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?
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stjoob_at5 Mar 2025 14:37Häuschenbauer4 schrieb:
It’s me again. Today, I looked at the performance charts for the 55/6 and 75/6 models and marked the bivalence point for the electric heating element as well as the temperature at which the system starts cycling, based on my primary energy demand (4.1 kW heating + 1.5 kW domestic hot water = 5.6 kW).
According to this, everything clearly favors the 55/6. Do you have any other comments? Definitely the 55/6. When sizing, the domestic hot water is not considered together with heating (the system either heats or produces hot water). So even with the 55/6, the unit still has some capacity margin. Then there is the electric heating element, which basically acts as a backup safety net.
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Häuschenbauer45 Mar 2025 19:51@stjoob_at
Thank you also for your opinion on this.
Thank you also for your opinion on this.