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

teh_M schrieb:

That actually fits quite well with my observations. We currently have a heat demand of 40-50 kWh. The district heating shows a power output between 1.5-2 kW when I check it.
Outdoor temperature averages around -12°C (10°F) over 24 hours.

Additionally, electricity consumption is 8-12 kWh.
With a COP of about 3.5, that seems to match the data from Zaba.

What kind of houses do you have??? A standard KFW55 building loses significantly more heat and would have a heat demand closer to 100 kWh at these temperatures (probably even more, according to calculations). That would translate into a COP of 7, which is impossible.

Bookstar schrieb:

A standard KFW55 model loses significantly more heat under those conditions and typically has a heating demand of around 100 kWh (theoretical value is actually higher).

How do you arrive at such a value?

Bookstar schrieb:

What kind of houses do you have??? A standard KFW55 building loses significantly more heat and at these temperatures usually has a heating demand of around 100 kWh (actually probably more). That would mean a COP of 7, which is impossible.

Here KFW40, window ventilation. About 150 sqm (1,615 sq ft) in Hamburg. Temperature between -1 and -7°C (30°F and 19°F). Indoor temperature 22.5–23°C (72.5–73.5°F). Domestic hot water at 49°C (120°F) with a 5 K (9°F) hysteresis, 300 l (79 gallons) hot water storage tank. Circulation during the day: 30 minutes in the morning and 60 minutes in the evening, pulsed. Hot water is produced once a day, rarely twice on weekends. Unfortunately, there is a 70 l (18 gallons) buffer in the heating circuit fixed in the return flow inside the heat pump (compact unit, only the domestic hot water buffer is separate). Of course, all thermostatic radiator valves are removed and without power, and the bypass valve is closed. Blower door test result slightly above passive house standard.
Total heat output for heating and hot water is 55–60 kWh per day. I am satisfied...

halmi schrieb:

How is that possible? Our heat pump is already at about 24.5 kWh, total consumption about 42 kWh.

The flow temperature is around 30 degrees Celsius (86°F), currently -8.2°C (17.2°F) outside temperature.

There hasn’t been a third heating cycle within 24 hours. That means there is another third heating cycle today, and since it’s getting even colder, the total house consumption will probably reach 35 kWh today. You just have to remember, I think you’re heating your entire 250 m² (2,690 sq ft). I only heat one-third of my 210 m² (2,260 sq ft) passively.

Yesterday it was actually 22.5 kWh. What I noticed, though, is that the hot water looks extremely power-hungry in the dat file (long cycle and slower rise than usual). @Bookstar, don’t you bathe every day? Would it be possible to narrow that down?

We have, similar to Daniel-Sp, a KfW40+ house with 150 m² (1,615 sq ft). The indoor temperature averages between 21-22°C (70-72°F), with hot water set to 47°C (117°F) stored in a 180 L (48 gal) tank.

From 8 PM last night until now, we have used 22 kWh of heating energy. The indoor temperature dropped by 0.5°C (0.9°F) due to nighttime setback and is currently 21.4°C (70.5°F). Outside, it is currently -22°C (-8°F), with a 24-hour average of -14.3°C (6°F).

Not everything is perfect yet, but I’m quite satisfied overall.

If you have more than 30% larger floor area or a different insulation standard(?), your results should be similar.

Daniel-Sp schrieb:

At AIT/Novelan, the manufacturer also provides a hydraulic diagram without buffer tanks and mixing assemblies, officially and with a warranty. I don’t understand why this is possible within that group but not with Brötje, since it’s the same technology.
Regarding the calculated COP of Brötje: how is it determined? Is the consumption of the circulation pumps measured as well? How is the heat output measured? There are many inaccurate methods usually installed by heat pump manufacturers. Some calculate it solely based on power consumption relative to flow rate and other parameters. I’m initially skeptical of the stated values. A COP of 5 at a supply temperature of almost 35°C (95°F) and an outdoor temperature of 1.3°C (34°F) would be an outstanding heat pump...

Yes, the consumption of the circulation pump is included in the total energy consumption. I don’t know exactly how Brötje measures the COP either.
For me, the most important factor, as mentioned, is the coordination of the flow rates between the circulation pump and the compressor.
My compressor also has a performance curve controlled by the outdoor temperature, so I have to coordinate a total of three "heating curves" together :p

I’m always surprised by how different the energy consumption values are here, and that it solely depends on the length of the pipes installed in the rooms.
It is quite surprising that the energy saving regulations require an energy-related renovation rate (ERR) but do not specify a maximum supply temperature!