Experiences with brine heat pump

that was not meant as an attack / criticism

Sorry, I didn’t see your reply at all. Don’t worry, I didn’t take it as an attack. I wasn’t referring to a buffer tank for the heating circuit, but a storage tank for the domestic hot water. Somehow the warm domestic water needs to be stored. There are different types, e.g. hygienic storage tanks, domestic hot water tanks with heat exchangers, or layered storage tanks. The latter is great for a fresh water station, since you always have the warmest water at the top and the cold water is layered at the bottom.

I wouldn’t install a buffer tank in the heating circuit anymore either.

Thanks, but I still don't quite understand something. In a stratified storage tank, isn't the temperature in the upper warm layer significantly higher than in a "normal hot water storage tank" (over 60 °C and thus no legionella problem, right)? And that is much more demanding for the heat pump than heating a 180L hot water storage tank to 45 °C, for example, right? So I thought that stratified storage tanks are primarily used with gas heating systems or solar systems and not with heat pumps.

But it sounds interesting. How much would you estimate that a stratified storage tank + fresh water station costs more in investment than a "normal" hot water storage tank with 180 or 270 liters?

Is there a special model at Nibe that is particularly suitable for a stratified storage tank or generally all NIBE ground source heat pumps? How many liters does your stratified storage tank hold in total and how many °C and liters does it have per layer?

To meet water hygiene requirements, there are different solutions.
Keep hot water at a high temperature. This means higher losses and higher consumption, especially with a heat pump.

Keep hot water at a low temperature, but then choose the storage tank small enough so that the water is safely used up daily.

Storage with fresh water: the hot water is always freshly generated. The water in the storage tank needs to be about +5 degrees C above the desired hot water temperature.
Personally, I find this solution the best, but it costs the most.

The temperature in the stratified tank depends on your settings. Here too, the target temperature can be set to, for example, 45 °C.

A stratified tank usually also has baffle plates, stratification charging pipes, or calm return flows to optimize the temperature-dependent stratification in the tank. When charging, it is therefore important that the hot water does not flow in with a high volume flow rate, but with a low volume flow rate, so that the water can layer without swirling. This can be done quite well, for example, with a Nibe S1155 (or 1255), as the volume flow rate is very low (290 l/h). With this model, the stratification would probably work quite well even with an empty hot water tank. With a fresh water station, however, the return flow should be calmed, for example, using baffle plates. Otherwise, the stratification could be worsened (since it partly returns to the tank at 25 l/min or 1,500 l/h when multiple consumers are open).

In terms of temperature, due to losses in the heat exchanger of the fresh water station, the hot water must be stored approximately 3-5 K warmer so that you have your desired temperature. But this ensures very hygienic conditions and virtually no chance for Legionella.

Okay, thank you both, understood.

What do you think, how much more does a system like the one you have cost?

Of course, you can half-empty 180 liters with a hot bathtub bath. If the Rainshower shower is supposed to start immediately afterwards, it could get tight. However, in everyday life, we have not experienced any restrictions yet. The advantage is hygiene; you have a lot of water changes in the tank. In addition, it benefits the efficiency of the heat pump.

How long does it actually take, if the 180-liter storage tank has been half emptied, until the heat pump has "refilled" the 90 liters? Does it depend on the settings of the heat pump / photovoltaic power, etc., or does the heat pump usually start immediately to heat new cold water and make it available again in the storage tank?

An FWS sounds good, but of course, it's additional costs and possibly higher maintenance costs?

Therefore, the question is, how fast does it work with a half-empty 180-liter tank or however large it may be. Thank you