ᐅ Air-to-Water Heat Pump: Current Consumption and Data

That’s what I meant earlier about the strange hot water behavior at low ambient temperatures. The hot water production usually looks like the one on the far left.

Zaba12 schrieb:

This is what I meant earlier about the unusual hot water behavior at low outdoor temperatures. Normally, the hot water preparation looks like the example on the far left.

Unfortunately, there is no time scale shown here. But just the ratio between the heat pump’s operating time and idle time is quite impressive. Practically no heat is lost from the house. In my case, the heat pump runs almost continuously at -5 degrees Celsius (23°F). Sometimes it stops for about 3 hours, but then the return temperature drops by 3 degrees Celsius (5°F) and it starts running again...

Daniel-Sp schrieb:

The design is obviously nonsense for a heat pump...

Yeah, I thought so too. But I’m afraid it’s a standard approach since these are planning firms, and the calculations clearly use standard values. For example, an air-to-water heat pump is checked off, and so on...

Bookstar schrieb:

Unfortunately, there is no timeline here. But just the ratio of runtime to standstill time for the heat pump is very impressive. In fact, almost no heat is lost from the house. For me, the heat pump runs almost continuously at -5 degrees Celsius (23°F). Sometimes it stops for 3 hours, but then the return temperature drops by 3 degrees Celsius (5°F) and it starts again...

I think now it’s easier to understand, including why yesterday’s 22.5 kWh was pure coincidence and why today will be higher.

Daniel-Sp schrieb:

The data from the energy performance certificate are basically useless; they do not accurately reflect the actual consumption. For example, the energy certificate does not evaluate the quality of the design of the underfloor heating at all.

We only moved in at the end of November, and I’m currently trying to reconcile the energy performance certificate and the actual consumption 🙂 It’s not a long-term consumption figure yet, but what I find quite fitting is the transmission loss of the building envelope compared to the current heat pump consumption. We have a total transmission loss of about 100 W/K (56 BTU/h·°F), which at a temperature difference of around 35 K (35 °C) results in a heating demand of 3.5 kW (12,000 BTU/h), or 84 kWh (84 kWh) per day. With a heating coefficient of performance of around 5.9, this corresponds to about 14 kWh (14 kWh) of electricity demand per day... and that currently matches quite well.

I am ignoring the internal gains estimated in the energy performance certificate, as these are roughly compensated by the ventilation losses.

This calculation is straightforward with a large temperature difference, especially since I have a modulating heat pump. Once the heating demand falls below the lowest modulation stage, the heat pump will cycle on and off... I assume then that the above method no longer applies. We’ll see.

Bookstar schrieb:

That doesn’t add up, or am I missing something...

I don’t fully understand the question, but for the bathroom there is a heat loss of 912 watts, meaning that out of the required 1,612 watts, only 700 come from the underfloor heating. The rest must be provided from elsewhere ==> you need to tell us what electric heaters are installed on the walls.
It’s completely unclear how such a design can be made when different pipe spacing options are possible. You have 100mm (4 inches) everywhere. In the bathroom, 75mm (3 inches) or even better 50mm (2 inches) would have been feasible.
Also unclear is the use of a 35/28°C (95/82°F) design temperature. Why such a high flow temperature with such a large temperature difference?