Experiences with brine heat pump

What are your brine outlet temperatures at the end of the cycle currently? I am already at 0.2 °C – and I fear that this is not very good – I urgently need to ask the well driller again.

Not the slightest reason to worry. At 0.2 degrees brine outlet temperature, your inlet should be around 4 degrees. Where do you see a problem?

It has settled down a bit by now. At the moment, the brine inlet at the end of the cycle is about 2.6 °C and the brine outlet is about 1.2 °C. The temperature difference is rather small with us. I was just a bit shocked because I thought it would continue to decline, but the borehole apparently regenerates quite well on milder winter days. Saruss seems to be more of an exception with its 5 °C outlet cycles at the end of the winter.

It has settled somewhat by now. At the moment, the brine inlet at the end of the cycle is around 2.6 °C and the brine outlet is around 1.2 °C. The temperature difference is rather low in our case. I was just a bit shocked because I thought it would continue to drop, but the borehole apparently regenerates quite well on milder winter days. Saruss seems to be more of an exception with his 5 °C output cycles at the end of winter.

You have a temperature difference of 1.4 degrees? That is not optimal at all. What kind of house, size, insulation standard, which heat pump, details about the borehole....?

What does 5 degrees output at the end of winter mean anyway? If my borehole were 250 instead of 120 m, I would have that too. But at what cost? It always depends on the overall system/design in a heat pump setup, i.e. source, heat pump, and underfloor heating.

We have 2 times 70 meters drilling depth and 10 m supply line to the house.
The extraction capacity was, I believe, about 43 W/m (still in the box - was definitely better than the assumed 39 kW from the neighborhood according to LBeg).
It was grouted with Thermocem Basic (unfortunately - we didn’t know about that).
190 sqm, 5.3 kW Flexothem Exclusive, heating load is 5.5 kW (U-value, myself) - 6.3 kW (Vaillant); where I trust the U-value more than Vaillant, as Vaillant did not really consider the heat recovery of the ventilation (0.5 kW with U-value; 1.5 kW with Vaillant for the required heat output to compensate for the minimum air exchange rate).

I’m currently checking live again:
Energy integral at: -100 min (start -120 min)
Set flow temperature at: 27.5 °C
Flow temperature is at: 29.5 °C
Brine inlet: 3.4 °C
Brine outlet: 1.6 °C
Heating curve at 0.1 and desired temperature at 23 °C (it’s just the offset)

How cold is it with you that the supply temperature is already so high?

And you once said that you had a heating value calculation done - but I don't see a DIN calculation now. And please don't say that the U-value calculator is enough - you like to play around with it, but I would have had a professional do such an important thing.

The few euros you saved now...

Vaillant performed the HLB according to DIN EN 12831, German annex 07/2008 is indicated on it - I did write that after all. Well - it was -2 °C last night. We are still fiddling around a bit - we only moved in a week ago. It's possible that we will adjust the curve down a bit the day after tomorrow; you really only notice what you do 1-2 days later.