Experiences with brine heat pump

Yo I agree with bookstar...

The best protection against legionella is a properly sized tank, where in normal operation all the water volume is used up and thus renewed every 1 to max 2 days

Alternatively, just a hygiene tank or a fresh water station.

However, the fear is 100% justified.

Regards Nika

The total capacity of the probe is about 80% of the capacity of the selected heat pump.

Does that mean if I come to a heating load of 10 kW for a single-family house according to DIN 12831 (for easier calculation), then I only need a deep borehole that has a cooling/heating load of 8 kW? I would still take a 10 kW heat pump?

With the ring trench collector, however, a larger collector cannot hurt or does it also have to be exactly matched to the heating load of the house and is too much rather harmful?

I'm just a bit torn because there are also answers here that say that a modulating brine heat pump is not worth the extra money compared to the on/off heat pump. What is the current forum opinion in 2020? I have already talked to some geothermal companies and they always talked about a modulating heat pump.

Does that mean if I come to a heating load of 10 kW for a single-family house according to DIN 12831 (for simpler calculation), then I only need a deep borehole with a cooling/heating load of 8 kW? I would still take the heat pump at 10 kW?

With the trench collector, however, a larger collector cannot hurt, or does it also have to be exactly matched to the heating load of the house and too much is rather harmful?

I am just a bit torn because there are also answers here that say a modulating brine heat pump is not worth the extra money compared to the on/off heat pump. What is the current forum opinion in 2020? I have already talked to some geothermal companies and they always spoke of a modulating heat pump.

With the trench collector, it does not hurt to size it arbitrarily large, but the benefits gained from that are also manageable. Most people who oversize the trench collector do so out of pure fear. You can really trust the trench tool of the purple forum; even there buffers are already built in, and in practice smaller trenches are sufficient without problems (there are enough realized examples to be found in the forum).

Whether modulating or not is more of a matter of belief. More modern technology, advantages especially with photovoltaic systems on the roof, less cycling and thus theoretically longer service life, more efficient. But significantly more expensive and technology-heavy (something can also break). Nowadays, I would get a modulating one, but I still decided on a fixed one 3.5 years ago.

Does that mean that if, according to DIN 12831, I calculate a heating load of 10 kW for a single-family house (for simpler calculation), then I only need a deep borehole with a cooling/heating load of 8 kW? I would still choose the heat pump with 10 kW?

For the trench collector, however, a larger collector can't hurt, or does it also have to be exactly matched to the heating load of the house, and can too much be rather harmful?

I'm just a bit torn because there are also answers here saying that a modulating brine heat pump is not worth the extra money compared to an on/off heat pump. What is the current forum opinion in 2020? I have already spoken to some geothermal companies and they always talked about a modulating heat pump.

I can only speak from my personal experience regarding modulation – I have a heat pump without modulation. From my observations over the past years, I wouldn't know what advantages modulation would bring. Due to the very large thermal mass (the screed), the cycling of the heat pump is kept very limited with appropriate settings, i.e., in exceptional cases I have observed more than 4-5 cycles per day (depending on hot water usage, of course, if the whole family is bathing/showering one after another, this has to be balanced). Because it is otherwise a well-insulated solid construction, the indoor temperature still fluctuates less than 0.5°C, definitely not noticeable for us. If a heat pump operating with modulation, i.e., not at full power, does not have a worse efficiency than at full power, then I would not know why modulation should be detrimental. I also do not believe there is a noticeable difference in the average brine temperature. It remains relatively stable during the heating phases and overall in my system.

Regarding the above post: I would not know what the advantage of photovoltaic and a modulating heat pump is. The input power of the heat pump is relatively low compared to photovoltaic. When it is cold in winter – especially at night – the sun doesn't shine anyway, and if the sun shines during the day in winter, there is usually enough to operate the heat pump (mine needs perhaps 1.5 kW power even in the final phase of hot water, thanks to the high coefficients of performance). Otherwise, I use the photovoltaic system at this time of year to heat the hot water a bit more around noon, then it usually lasts until the next noon, and even with clouds the photovoltaic usually provides 1.5 kW.

Does that mean if I come to a heating load of 10 kW for the single-family house according to DIN 12831 (for easier calculation), then I only need a deep borehole with a cooling/heating load of 8 kW? I still take the heat pump with 10 kW?

Correct.
Plus the builder's anxiety meter (or that of the drilling company )

I can only speak from my personal experience regarding modulation – I have a heat pump without modulation. From my observations over the past years, I wouldn’t know what benefits modulation would bring. Due to the very large storage mass (the screed), the cycling of the heat pump is very limited with appropriate settings, i.e., I have so far only observed more than 4-5 cycles per day in exceptional cases.

I also have a brine-water heat pump without modulation and have had similar experiences. About 4-5 cycles per day in winter; without heating operation in summer, there are usually 2 cycles (domestic hot water, 180L integrated storage). This results in about 1250 cycles per year. In contrast, the durability is about 100,000 compressor starts. Expected service life of the compressor is therefore 80 years.
Wear is, in my opinion, not an argument in favor of a modulating brine-water heat pump. That’s why I didn’t choose such a model; it would have cost four digits more. I chose a maximally dumb brine-water heat pump.

Thank you for your answers. And yes, depending on the additional cost for the inverter compressor, you can really consider going back to a brine-water heat pump without modulation.

Because you say 180 L integrated storage (how many people?) What are the pros and cons of a hot water storage tank integrated directly into the heat pump? It should not be chosen too large, that’s clear. I once read max. 270 liters for 4 people.