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

@Bookstar The energy performance certificate is a tricky topic; I also had long discussions with the energy consultant and eventually gave up.
In my case, the final energy demand is listed as 47 kWh/m² (square meter) including auxiliary energy (so with hot water). But that refers to the amount of heat I need since district heating is my energy source. For you, according to the energy consultant, it shows electricity consumption... That’s completely misleading in terms of comparability.

If your value says 25 kWh/m², you have to consider the COP (coefficient of performance)... so 25 kWh * 4 COP = 100 kWh heat per m², with 200 m² you end up at 20,000 kWh.

For me, it’s 47 kWh heat * 150 m² = 7,000 kWh heat per year. That matches up.

I think Zaba had something like 10 kWh/m²? With a COP of 4.x, that also comes close to my heating demand, and the consumption data fits pretty well.

Zaba12 schrieb:

Have you ever tried leaving all the ERRs fully open and lowering the heating curve?

Maybe I’m thinking about this wrong because my heat pump is controlled by the return flow. The supply temperature is reached relatively quickly. In terms of energy consumption, the jump from a supply temperature of 30°C (86°F) to, for example, 33°C (91°F) only makes a difference for about 15 minutes. That’s negligible at 2 kWh. What takes longer, of course, is reaching the target return temperature.

But this only happens once because the temperature level then adjusts with respect to the return temperature.

Of course, I have done that. The house simply requires the energy it needs.
If I kept all the ERRs permanently open, I would constantly have a temperature difference of 2-3 K (3.6-5.4°F) between the heat pump’s supply temperature and the underfloor heating supply temperature due to the buffer.
Only when some circuits are closed by the ERRs do the flow rates adjust so that the supply temperatures match, allowing me to give more flow to the bathroom and thus reach just over 23°C (73°F).

My heat pump is also controlled by the return flow and calculates the supply temperature as return temperature plus ΔT (5 K).
So, if the return temperature is 28°C (82°F), the supply temperature is 33°C (91°F).
As the return temperature rises, the supply temperature rises in parallel.
The compressor modulates the flow so that the ΔT of 5 K (9°F) remains constant, which is why I never exceed 1000 liters per hour (264 gallons per hour) flow through the heat pump. It operates around 5 kW output even at outside temperatures of -12°C (10°F) 🙄
That’s also why I’m concerned about the low ΔT in the heating circuits and whether it might be better to keep that at 5 K (9°F) as well, so the heat pump can run at its nominal flow rate...

I just dug up some old documents. There are indeed calculations for everything.

Heat load calculation: 8.3 kW
Design flow temperature: 35 degrees Celsius (95°F)
Return temperature: 28 degrees Celsius (82°F)
Flow rate: 1000 liters per hour (264 US gallons per hour)
Standard outdoor temperature: -16 degrees Celsius (3°F)
Average temperature: 7 degrees Celsius (45°F)

I just set the pump to test with a design temperature of -16 degrees Celsius (3°F), and the target return temperature comes out to 29 degrees Celsius (84°F). That would almost fit perfectly.

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

Zaba12 schrieb:

Fix

Then it always operates at full compressor capacity, so the electrical power consumption remains constant; only the heat output varies depending on the outside temperature. The daily consumption is determined solely by the operating time.

Daniel-Sp schrieb:

Then it always runs at full compressor capacity, so the electrical power consumption is always the same, only the heat output varies according to the outside temperature. The daily consumption is determined solely by the operating time.

I didn’t say anything different. So, roughly speaking, with my system the operating time = consumption depends only on the outside temperature.

Leaving aside the topic of insulation.