Experiences with brine heat pump

So you can set the times when hot water is provided. For example, I have set it for morning and evening. You can calculate the time yourself. Google helps with that.

What do you think how much more such a system, like the one you have, costs?

We are currently still waiting for an offer with a fresh water station as an alternative to the currently planned hot water storage tank with heat exchanger. Since the current heat exchanger is supposed to come from Nibe and is quite expensive (1,400 euros gross), I estimate the additional costs of a fresh water station at about 1,000 euros excluding costs for extra effort in pipe installation and commissioning.

Case hot water storage tank: with which water does the heat exchanger load the hot water storage tank? The water heated by the brine-water heat pump to about 30 °C (flow temperature of the underfloor heating) is not sufficient for that, right? Is an electric heating element added or can the brine-water heat pump also manage this using the compressor?

Case stratified storage tank and fresh water station: did I understand correctly that in your stratified storage tank only water for domestic hot water is heated and your heating system is not connected to the stratified storage tank?

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

Even if I prefer to choose the storage tank a bit too large (270 or 300 liters), the water circulates constantly there, and then it’s not necessarily required to completely empty it daily, right? There is movement every time water is drawn.

How long does it actually take, if the 180l tank has been emptied halfway, until the heat pump has "refilled" the 90l? Does this depend on the settings of the heat pump / photovoltaic power etc., or does the heat pump generally always start immediately to heat new cold water and make it available again in the tank?

A heat pump with 6kW heating capacity will heat 90l of water from 10 degrees to 45 degrees in 40 minutes. If your heat pump is stronger, e.g. 10kW, it will be correspondingly faster. If the heat pump is allowed to additionally use a possibly existing heating element (e.g. 6kW), it will be even faster. However, the heating element is of course inefficient. Normally, this is not done.

The second question is when a heat pump (or generally a heating system) starts producing hot water. Usually, this depends on the hysteresis, i.e. falling below a preset temperature in the tank. If the temperature falls below the limit, hot water production begins until reaching an upper threshold. For example, if you set 45 degrees hot water temperature with a hysteresis of 2 degrees, hot water production starts below 43 degrees and works up to the 47 degrees target temperature. Additionally, other values for the start/end of hot water production can also be configured. Joedreck mentioned the option to set blocking times during which no hot water may be produced. I personally find this somewhat inflexible, but if it fits the lifestyle, it can certainly be done. With constant shower/bath behavior this might work, with a family with shift work maybe less so. You yourself also mention the influence of photovoltaics. That can also be done, e.g. via the "SG ready" function of the heat pump. If the inverter of the photovoltaic system has an output to indicate solar power production, this can be coupled with such a heat pump and e.g. overload the hot water tank. Instead of 43/45/47 degrees one can e.g. overload by +5K because cheaper photovoltaic power is available in the house at the moment.

In the case of hot water tanks: with what water does the heat exchanger charge the hot water tank? The water heated by the brine-water heat pump to about 30 °C (supply temperature of the underfloor heating) is not sufficient there, is it? Is there an additional heating element or can the brine-water heat pump also do this with the compressor?

Hot water is a separate circuit. This runs normally via the compressor, but is less efficient due to the higher target temperature. Therefore, it is also tried to keep the hot water temperature as low as possible. The heating technician will happily set you >50 degrees storage temperature. This is nice because the hot water supply then lasts correspondingly longer, but is inefficient. 45 degrees is a good starting value. If you then find that the storage volume is too small for your own hot water consumption, you can turn it up and thus "buy" yourself more comfort at the expense of efficiency.

many thanks for clarifying all the uncertainties. I will simply get a quote for a hot water tank and then simultaneously for a stratified storage tank with a fresh water station and then see what the costs say. The disadvantage of the fresh water station is that you always have to heat a few degrees more than you actually need later (about 5 Kelvin). And the additional cost of the fresh water station + stratified storage tank. And also higher maintenance costs / susceptibility compared to a simple hot water tank. We'll see.

What still puzzles me, however, is how you manage with a 180L hot water tank for four people? I would have chosen 270 or 300 liters for four people.

Today I measured my current shower head in the present apartment and 8 liters flow through per minute. I don't consider that particularly much and it is a standard shower head (far from a rain shower). If you now count 5-10 minutes per person, then in the 10-minute case you are at 80 liters for the first person. If you set your hot water tank as you suggested to 45 °C, then about 70 liters of the 80 liters for the first person might already be hot water from the tank, right? That doesn't add up, or do the dogs always bite the last one in the morning at your place? Or are you an ice-cold cold showerer?

So a man doesn’t need 8 minutes, I’d say. I need more like half that time. Also, no lady here starts the whole routine in the morning with washing hair, shaving, blow-drying. There’s simply no time for that. They do their washing routines in the evening. By the way, both of them hate the Rainshower because the cleaning effect is really not good on long hair. They use the extra handheld shower or just go straight into the tub (shaving legs, etc).