ᐅ Ground Source Heat Pump for a 200 m² Single-Family Home with Underfloor Heating, KfW55 Standard – Settings and Optimization

Then something is wrong here...
Hot water 4.2??

Hangman schrieb:

I find that hard to believe: our heating system is probably not super highly optimized because, with such a ridiculously low consumption, I lack the motivation to fine-tune it. Still, since commissioning, we have a COP of 4.2 for domestic hot water, 5.9 for heating, and 5.6 combined.

Including electricity for the heating pump and heat pump controls? Your values are similar to mine. But I just read that the distribution system for heating must be taken into account. In my case, that’s roughly 35W just for the heating pump (which runs continuously below freezing), 25W standby for the heat pump, ERR+-valves, and the other pumps, plus the heating pump running while heating consumes up to 255W. That means I have at least 25W running constantly, the heating pump at 35W runs about 15% of the time when the ambient temperature is above 5°C (41°F), 100% below 5°C (41°F), and for about 6 hours a day, another 255W load is added. Roughly, that’s around 2kWh on heating days (probably more), 0.7kWh on summer days, and about 1 to 1.5kWh in passive cooling mode. Of course, that significantly lowers the COP, especially for domestic hot water.

I have now roughly estimated the consumption values for the components that run on household electricity. This reduces the COP for domestic hot water from 3.8 to 1.9 and for heating from 6.1 to 4.1 — quite disappointing. For five months of hot water and one month of heating, this currently results in a COP of about 3.3 — with an upward trend. It looks like I’ll have to be happy if I reach a COP of 4 after one year. That was the expected absolute minimum. But we’ll see, there is certainly some potential for improvements. However, I never expected the heat pump to draw so much power from the household electricity in standby mode and for the operating pumps. That amounts to around 500 kWh per year.

grericht schrieb:

But I never expected the heat pump to draw so much electricity from the house supply while on standby and during pump operation. That’s about 500 kWh per year.

You don’t have to look at it that way. The consumption for this "auxiliary equipment" only seems high because the building’s energy demand is low and the heat generation is efficient.

In the end, only the electricity bill counts, not the intermediate values along the way. Of course, I understand the desire to optimize, but you don’t have to push it to the extreme. I pay €40 in heating costs per month (195 m² (2,100 ft²), 4 people) – how much time should I invest to achieve a 5% improvement?

guckuck2 schrieb:

In the end, only the electricity bill matters, not the intermediate values. Of course, I understand the desire to optimize, but you don’t have to take it to the extreme. I have heating costs of 40€ per month (195m² (2100 sq ft), 4 people) – how much time should I invest in a 5% potential savings?

Basically, that’s absolutely correct. For me, it will probably also come down to around 40€. It’s less about the money for me. I always hope that besides the goal of eliminating major consumers, everyone also looks for easy savings potential among the smaller consumers. For example, the heating mostly runs in winter, when there is little yield from photovoltaics. From a climate perspective, it definitely makes sense to focus precisely on what else can be done there. – But yes, ideally, one would simply have built a 150m² (1600 sq ft) house instead of a 200m² (2150 sq ft) one. That would be more sustainable.

I find it hard to understand how such values are reached inside the house. Yesterday, by mistake, both floor-to-ceiling windows in the bedroom were tilted open, and we still had "only" 19°C (66°F) in the bedroom. Just two adults lying in bed produce about 400 watts, which should noticeably raise the temperature in any new build after 6-8 hours.

The ventilation system alone should already regulate the temperature fairly evenly throughout the house, or do you not have one?