ᐅ Ground Source Heat Pump for a 200 m² Single-Family Home with Underfloor Heating, KfW55 Standard – Settings and Optimization

How do you come to the conclusion that I cool down the thermal envelope by ventilating crosswise for 5 minutes? This only causes an air exchange that blows out all the dirt that accumulates in the room overnight.

A short while ago, it was still 10 minutes.

Just briefly again:
The bedroom is heated by adjacent rooms.
The bedroom is still cold. Possible cause: poorly insulated exterior wall, or ventilation losses.

Basic physics.

Basically, I would plan for the bedroom to have heating just like the living room, especially if people are regularly using the room. This is particularly important in the bedroom! For us, two people sleep there every day. It doesn’t help me to know what temperature the room has after a two-week vacation – it might well be too cold then. In my planning, I factor in the presence of 2 people * 8 hours/day. From this, it seems almost impossible to maintain a temperature difference of more than 2 degrees compared to the hallway and the bathroom as adjacent rooms UNLESS I regularly open the thermal envelope and ventilate. In that case, I seem to be able to achieve an average temperature of around 19–20°C (66–68°F) during use (2 people * 8 hours/day), instead of 20–20.5°C (68–69°F), when the hallway is at 21.5°C (71°F) and the bathroom at 23°C (73°F). At least, I have not heard any counterexamples from Alessandro.

I would like to raise my questions again:

• Are the specified heat output values for heat pumps usually standardized and calibrated? Can these values be trusted, or are they (possibly even intentionally) optimistic? Are these values calculated and/or measured?
• Does it make sense to provide some heating to rooms that are supposed to be kept as cold as possible but border warmer rooms? For example, the bedroom? It doesn’t make sense to me, since the heat from 2 people * 8 hours/day plus heat transfer from neighboring rooms is already significant.
• Does it make sense to heat unused rooms that could serve as thermal buffers (e.g., cellar rooms), and if so, what temperature or heat input is recommended? With the door open, it’s almost impossible to keep them below 20°C (68°F) since other rooms in the cellar are occupied. They already benefit from the heat of those rooms without direct heating. With the door closed, they provide less thermal storage benefit?! Here, I would assume it could be useful to heat these rooms slightly, while lowering the temperature in adjacent rooms to maintain a uniform temperature throughout and thus increase the thermal storage volume.
• According to the hydraulic balancing calculation, my bathrooms should only have a flow rate of 0.9 and 0.7 liters/min (0.24 and 0.18 gallons/min). However, I have both valves fully open (>2 liters/min (0.53 gallons/min)). The house connection room, on the other hand, is specified at 15°C (59°F) with 2.2 liters/min (0.58 gallons/min) full flow (I was not consulted). In the house connection room, I set 0.5 liters/min (0.13 gallons/min), yet it still has 21°C (70°F) (the entire technical equipment is there). The bathroom has 23°C (73°F) when fully open, although 24°C (75°F) was "agreed on." The flow rates for the bathroom and the house connection room aren’t very different. This doesn’t make sense to me unless it is assumed that thermostatic radiator valves are installed. But isn’t the goal of the heating load calculation and hydraulic balancing exactly to avoid relying on these? I should mention that the heating load calculation and hydraulic balancing were done only afterwards, as we switched to a KfW 55 standard during construction. The construction company and their heating installer used this program for the first time and thus "forgot" these steps initially. We had to hire an external company to do the calculations, and soon the heating installer will come to adjust the hydraulic balancing. I am skeptical whether these values make any practical sense.

1. At least with Stiebel Eltron, this is not very precise / tends to be optimistic. I assume it is similar with others.

4. You are ignoring the installation distances. 2 liters per minute through 10 meters (33 feet) of pipe compared to 1 liter per minute through 100 meters (328 feet) of pipe. Where is more thermal energy transferred? (With the same delta T)

grericht schrieb:

Are the specifications for the heat output of heat pumps usually standardized and calibrated? Can these be trusted, or are the values (possibly even deliberately) exaggerated? Are these figures calculated and/or measured?

The "heat quantity" or output can be calculated based on the flow rate and the temperature difference between the supply and return temperatures.
Deviations can occur depending on the water properties, so if additives are present, the value would need to be adjusted, but I believe no one does this.
Whether anything extra is added on top of that, I obviously can’t answer!

grericht schrieb:

Does it make sense to heat rooms that should be kept as cool as possible but are adjacent to warm rooms, for example the bedroom? For me, it doesn’t make sense because the heat input from 2 people * 8h/day plus heat exchange from the neighboring rooms is already too high.

What do you mean by "make sense"? Consumption or comfort?
Overall, the heat pump will probably consume less energy if all rooms are heated.
As always, turn off the bypass valve (ERR), ensure flow everywhere → lower supply temperature, lower consumption.
However, the temperature differences will be smaller there, which some people find uncomfortable (for example, in the bedroom).

grericht schrieb:

Does it make sense to heat rooms that are not used but could serve as heat storage (e.g. cellar rooms), and if so, what temperature/heat input? With the door open, it’s hardly possible to keep these below 20°C (68°F) since other rooms in the cellar are occupied. They already benefit from the neighboring rooms without their own heat input. And with the door closed, they have less storage benefit?! Here I would suspect that it might make sense to heat these rooms slightly, while lowering heat in adjacent rooms to keep the same temperature everywhere and thus increase the storage volume?

Why consider them as storage? The answer is basically the same as above.
Of course, this only makes sense if the cellar is well insulated!

grericht schrieb:

But isn’t this exactly the goal of a heating load calculation or a hydraulic balancing, so that you could dispense with this approach?

Yes.
At first, the calculation sounds a bit odd, but you would need to look at it in more detail to assess it more precisely.