Geothermal heat pump single-family house 200m² underfloor heating kfw55 - setting/optimization

Hello. We moved into the new single-family house in March. I didn’t make any optimizations to the heating after that. Now, as the temperatures are rising, I have started to deal with it.

Facts about the house:

[*
Single-family house (residential) basement + 2.5 floors (gable roof habitable/also underfloor heating) -> 4 floor heating circuits
[*]about 200 sqm underfloor heating
[*]2 bathrooms WITHOUT additional heating
[*]kfw55
[*]ventilation system with heat recovery
[*]currently 2 rooms in the basement are unoccupied/unused + the technical room
[*]in the attic there are also 2 children's rooms unoccupied/unused


Facts about the heating system (the descriptions are from the invoice):


[*]High-efficiency brine/water heat pump Dimplex SI 8TU
[*]High-efficiency brine package SZB 140E for brine/water heat pump with electronically controlled brine circulation pump Yonos Para 25/1-10
[*]Multifunctional storage tank Geysir MTL-WP650 Efficiency class B (150mm insulation thickness) with connection possibility for several heat generators, with stratification plate for large volume flows, content 850l, hot water preparation in flow-counterflow principle via stainless steel heat exchanger, incl. differential temperature controller and flow sensor for hot water tapping system
[*]Hydraulic connection of the heat pump to the multifunctional storage tank with precision steel pipe 28x1.5 incl. insulation, 1 piece zone charging pump Dimplex UPH 75-25P with shut-off set switchable for heating and for hot water charging
[*]Integration of the heating system with heating circuit sets Easyflow DN 25 R1" with EPP insulation type 2 with 3-way mixer, with mixer motor and circulation pump Grundfos UPM3 Auto
[*](ERR in 3/4 of the rooms) - currently switched off
[*]Cooling station Dimplex PKS 14 Econ for passive cooling via geothermal probes, consisting of heat exchanger, brine circulation pump, cooling modules for network operation with heat pump manager and temperature sensor
[*]Room temperature controller Dimplex Smart RTC, for optimizing weather-dependent control via a reference room


My previous attempts:


[*]Hot water:
[LIST]
[*]First, I took care of the hot water preparation. It was initially set to 50°C with a 2° hysteresis. At Dimplex, this means for hot water that when it drops to 48°, it heats up again to 50°. That was basically fine but led to heating water 2-3 times a day even without hot water use. However, since the pump only ran very shortly, we had about 0.7 kWh/day on average in summer.
[*]Then I experimented with lowering the temperature, blocking times, and increasing the hysteresis. As the "consumption optimum," 50° and 7° hysteresis with blocking times from 8 pm to 5 pm turned out best for us. This meant that the pump sometimes did not run for a whole day. But that was still 0.5 kWh/day. This means hardly any consumption reduction with partly noticeable comfort losses. Currently, I am at 48° and 4° hysteresis and blocking time from 10 pm to 5 pm. Since we use hot water almost exclusively in the evening, this works well for us throughout the day. For bathing/more demand, the water is reheated if necessary. I am currently experimenting with 5 or 6 degrees hysteresis as the heat loss seems to be lower during heating operation and we might be able to skip a day occasionally. Let’s see...


[*]Now to the heating, my attempts:


[*]All ERR "off", the heating circuits turned up by feel and tried to readjust. It was controlled via fixed-value return temperature, which I tested by increasing from 23 to 26 degrees. Consumption and COP were very satisfactory. Unfortunately, I could not achieve more than 22° in the bathroom without it becoming too warm in the other rooms (where it quickly reached 22°, which is too much for me).
[*]Then I turned the ERR back on in the kids' rooms.
[*]After a one-week vacation where I completely switched off the heating, I started again from scratch. I tried to proceed as recommended by turning the warmest room (bathroom) fully on (about 2.2 l/min) and then increasing the temperature until satisfied. But of course, the heating is totally oversized for that?! The heating started 20 times for 10-15 minutes each, the supply was then nicely at 30-33 degrees, but the temperature did not seem to come from the heat pump. I’m attaching a picture of the behavior.
[*]Because I suspected that this was due to insufficient flow and I did not dare to change the heating pump setting, I slowly turned other rooms slightly up.
[*]I also started to increase the fixed temperature to 27 or 28 degrees and ensured via hysteresis that the pump ran less often but longer. Now I am quite satisfied with the temperatures in the house. The values still look strange to me, though. I believe I now have many rooms/area/buffer mass that only have so little flow that the whole "cooled mass" continuously circulates and always reaches the return flow again. It doesn’t bother me per se, but I don’t want to provoke any damage. I am attaching a picture as well.
[*]Finally, I ensured via lowering the temperature at night and in the morning that the heating starts at favorable times. Currently 2 starts of about 2-3 hours each are enough.

Questions:

[*]Have I completely lost my way? Or are the approaches suitable? Unfortunately, I can’t really rely on the heating technician. He is certainly competent but firstly hardly reachable and secondly surely overwhelmed with such optimization ideas.
[*]What about rooms that are unused? Use the screed as a buffer and still have them slightly turned up (<0.5 l/min)?
[*]I increasingly believe that we cannot properly control this large spread between 23° in the bathroom and 20.5° in the rooms - does it really require additional heating? We actually only need the bathroom heated to 23° for about 2 hours and 4 hours in the evening. Otherwise, 21-22 degrees would surely be sufficient there.
[*]Tips for settings

Personal "preferences"

[*]The underfloor heating is off in the bedroom - still, it quickly reaches 19-20 degrees, which is almost too warm.
[*]In the 3 kids’ rooms the ERR closes from 5 pm to 3 am (for sleeping - with time delay)
[*]Other rooms 20-21 degrees
[*]Living kitchen 21-22 degrees
[*]Bathrooms 23 degrees

Phew. Unfortunately, another huge combination storage tank that is supposed to tame the heat pump oversized with an 8kW nominal capacity. A problem creator and efficiency killer. Now it is here. What are the heating curves in the heating circuit and mixing circuit? For best efficiency, the mixing circuit should always be fully open. I don't have a good feeling about the bathroom. Demand-based reheating is usually cheaper than raising the heating curve and throttling the underfloor heating, at least gentler on the heat pump. I am not familiar with dimplex, can only give general tips for support. Do you have a well understandable sketch of the system hydraulics?

1. Obtain documents for heating design including hydraulic balancing
2. Perform hydraulic balancing according to the documents
3. Run the heating system as calculated (50 degrees hot water is already okay, for example, I manage well with a 7-degree hysteresis, so the system runs once a day or twice a day when three girls use the rain shower intensively. I see blocking times as unnecessary – at most sensible in connection with [Photovoltaik Anlage])
4. Return with the results and fine-tune the system

First of all, forget about achieving differences of more than three degrees within the thermal envelope!

So sleeping at 18 and bathroom at 23 is simply not possible.
Trying to achieve something like that only leads to frustration.
Interior doors and walls are simply not insulated.

Phew. Unfortunately another huge combination storage tank that is supposed to tame the heat pump, which is oversized with a nominal capacity of 8 kW. A problem causer and efficiency killer.
Now it’s there.
What are the heating curves in the heating circuit and the mixing circuit? For best efficiency, the mixing circuit should always be fully open.
I don’t have a good feeling about the bathroom. Demand-oriented reheating is usually cheaper than raising the heating curve and throttling the underfloor heating, at least gentler on the heat pump.
I’m not familiar with dimplex, I can only give general tips for support.
Do you have a well-understandable sketch of the system hydraulics?

Whereas the Zeeh storage tank is also recommended by some efficiency junkies. But yes, if I had had more time, I probably would have decided differently. The idea was to eventually charge the storage tank with photovoltaics when the sun is shining.
I don’t have a sketch. Unfortunately, the heating engineer is not the type to explain such things well. I would consider myself technically savvy, but every time he was here he was busy tinkering with lots of things (there were also some stupid issues - e.g., the auxiliary heating pump exploded during the screed program) and he is very time constrained, so I haven’t fully figured out the system 100% yet.

1. Obtain documents for heating design including hydraulic balancing
2. Perform hydraulic balancing according to documents
3. Let the heating run as calculated (50 degrees for hot water is okay, for example I manage well with 7 degrees hysteresis, so the system runs once a day or if three girls heavily use the rain shower, twice a day. Blocking times I see as unnecessary – at most useful in conjunction with a photovoltaic system)
4. Come back with the results and fine-tune the system

The hydraulic balancing was requested by the energy consultant for the subsidy anyway. It is also available. Some things seem very suspicious to me (basement at 18° still over 2 l/min flow and bathroom at targeted 24° only 0.9 l/min – can that be right? The values are surely for having ERR then?)
It will be carried out soon. Or rather, in the rooms with ERR (but there are only 3) I have already set that myself. In all other rooms I have significantly reduced it, and in the bathrooms fully open?!
Regarding 3.: practically that will be correct. However, since we only used the shower once early in the morning within half a year and 40° is still sufficient there, and because we decided against circulation, we only draw warm water from the faucet in the evenings and thus only need warm water for showering and dishwashing in the evenings. I would still find it annoying if the water were heated at 11 p.m. instead of preferably cooling down to 41 degrees by 5 p.m.

First of all, forget about achieving differences of more than three degrees within the thermal envelope!

So sleeping at 18 and bathroom at 23 is simply not feasible.
Trying to achieve something like that just frustrates.
Interior doors and walls are simply not insulated.

Well, three degrees would already be sufficient. And currently it really looks quite good.
In the bedroom it is 19.5 (even 18.5/19 for a while when airing in the evening) and in the adjacent bathroom 23, sometimes even 23.5.
So even if the heating curve looks strange and apparently is not mixed particularly well?! I am currently very satisfied. But it has only been running like this for three days and I hoped that after complete heating up in the rooms the consumption would stabilize.

You should also heat the unused rooms. Otherwise, you unnecessarily transfer heat from the heated to the unheated rooms. Which rooms adjoin the bathroom? These must be heated as well, even if they are not used. You ask about optimizing the settings. What are the current heating curves for the heating circuit and mixing circuit?