Sole-water heat pump with ground probe experiences?

Hello everyone,

we will be building a house soon ([Eckdaten sind unten]). A ground source heat pump is planned so far. However, the more I read about it, the more doubtful I become whether it is the right decision: lots of reports about broken air-to-water heat pumps at subzero temperatures (especially when you actually need them), malfunctioning defrosting processes of the outdoor unit, noise emissions from the outdoor unit, lifespan max. 15-20 years.
Therefore, I am considering a brine-to-water heat pump as an alternative. Our plot is rather small, so drilling is the only option. I am aware of the disadvantages regarding purchase/drilling costs and the requirement for approval, and these are acceptable. Ultimately, I need a system that works without problems, does not break down immediately at winter temperatures (and then the whole family waits a good week in a cold house until it is repaired), operates relatively quietly, and possibly lasts a long time. A passive cooling function in summer is also attractive.
These are the considerations; now the questions:
1. Does anyone have experience with brine-to-water heat pumps with probes? Especially whether they really function without problems?
2. The compressor is then located with the pump in the basement – how quiet is it?
3. Where is the drilling for the probe done – directly under the house or next to it? Regarding the time factor – should it be done before the construction of the house begins, or can it run parallel next to it?
4. How long does the approval process take approximately (possibly including water law permission)?

[Eckdaten des Hauses:]

[*]Semi-detached house, solid construction, not a KfW house (EnEV 2016)
[*]Two full floors + basement, ground floor + upper floor 68+68 sqm, plus approx. 30 sqm heated basement area
[*]Underfloor heating, controlled ventilation system ([Kontrollierte-Wohnraumlüftung]) with heat recovery and enthalpy heat exchanger
[*]No primary photovoltaic system

Thanks a lot!
Best regards
Nils

We are building with a brine-water heat pump. Moving in is not until the weekend after next, so I can't tell you much about the noise level, but brine-water heat pumps have a reputation for being rather quiet. The drilling was done at our place, right next to the house, after the shell construction was completed. The pipes then come through a core drilling into the house, and after that, you can build over it. The drilling company was given a power of attorney for the approval. It maybe took about 2 months and cost around €500.

Since you are building a semi-detached house ... the convoy is quite large and needs space. You might have to close the street

Experience only for about 5 months.

Nothing has happened yet.
According to the heating engineer, nothing major should happen either - in connection with the probe.
It is more likely that the heating system will cause problems. And like everywhere, you can also get a Monday model.

I hardly hear anything from the compressor. The controlled residential ventilation is louder. But only if you stand next to it.

Usually drilling is done next to the house.
The drilling device needs space to be set up. The drilling itself is unremarkable.

The time until approval depends on how deep you drill.
With us, up to 100m the district approval authority could issue the permit -> relatively quickly.
But since we needed 110m, Berlin had to approve it, as well as the radiation protection authority - due to potential final storage.
Duration about 8 weeks.
An alternative is, if you need to drill deeper because of the heat demand but don’t want to wait, to do two drillings.

The drilling itself was also done quite late with us: about 2-3 weeks before the heating delivery. And it only took 2 days.

We also had drilling done. The borehole must have a minimum distance of 3 meters from the boundary. The drilling company took care of the permit and drilling insurance themselves, everything cost around 500€ and was done fairly quickly, just a few weeks.

The drilling rig was quite small and occupied an area of perhaps not even 1.0x2.0 meters, plus a water container and compressor, so also manageable.

We went with one borehole to the full depth of 100 m. Drilling was done when the shell construction was complete.

It is worth mentioning that I sent out over 30 inquiries, also nationwide. Received 7 offers, the rest were booked out long-term. The offers ranged from 7,900€ to over 22k.

I cannot report anything about the noise level yet, but the heating technician assures that the pump is very quiet.

The heating technician described the difference between the brine-water heat pump and the air-water heat pump roughly as follows: operating an air-water heat pump is comparable to driving a car in city traffic: acceleration-braking, dependent on the outside air temperature. The ground source heat pump is more like highway driving, the pump hums evenly along – so somewhat gentler operation. Whether this is true – remains to be seen.

Our brine heat pump has been running for 2 months and hums, if anything, just a bit louder than a refrigerator from 2010 (but only when it really has to heat). 2x 80m boreholes in front of the house. If there is hardly any space, it would also be possible under the house in front of the concrete slab, but the borehole can also be built over in front of the house. We don’t regret our Novelan at all so far and currently have (measurable for only a short time) an annual performance factor of 6.17.
So the commissioning with the Alphainno. The manufacturer was amazed at the runtime of 24h/start/stop (good for a long service life). Air-water heat pumps are an ugly visible external unit.

The device for us is like a large refrigerator and takes up exactly that space in the utility room (plus the supply/return lines, etc.). The compressor is located at the bottom and above it the storage tank, all very compact.
The cooling function can only prove itself in the summer.
Timing-wise, we only had the boreholes drilled after moving in (frost/load/time). It is important when a late borehole drilling is done to have installed 2x KG DN100 with max. 15-degree bends beforehand (slab). Before building started, the advantage would have been that the device still had space on the property but you would never be able to access the wiring again if something was wrong.
My conclusion so far: absolutely PRO brine. :)

Borehole drilled in summer 2018 before the completion of the shell, 2 x 70 meters.
Permit from the district came lightning fast, € 353.13.
Commissioning of the heating system in autumn 2018. Since then, trouble-free and whisper-quiet.
6 kW heat pump heats 190 m² KFW 55.
Electric auxiliary heating rod was deactivated after the screed program.
Annual consumption without photovoltaic approx. 4200 kWh.
All in all: exactly the right decision. Anytime again.

P.S.: For future photovoltaic systems, be sure to have empty conduits installed!