Heat pumps require a lot of energy and make noise

If I leave the thermostat at 15 degrees in unused rooms, then the room doesn’t heat up either, right?

You’re thinking too small. If you turn off the thermostat in the guest room and the bathroom is next door, then the bathroom heats the guest room through the walls. Interior walls are significantly worse insulated than exterior walls. However, this means that the calculated heating load for the bathroom is no longer correct and it won’t get warm. Modern heating systems are only slightly controlled by the thermostat, which is far too slow anyway. Modern heating systems are controlled by the flow temperature depending on the outside temperature, and the flow per room is adjusted to the expected heating load. If that isn’t correct because each room also has to heat another one, you can throw all the calculations in the trash. You still have the mindset of old buildings with radiators and high flow temperature. Back then, the thermostat actually controlled it. But that is no longer the case.

Hydraulic balancing has been done, the flow rate was adjusted again by the heating engineer yesterday.

Hydraulic balancing and flow rates for the whole house or have you set them all separately to heat the 80 sqm? I fear you have a hydraulic balancing for the whole house and you completely ruin it by closing off different rooms. Then you shouldn't be surprised by the result, because the 80 sqm are actually supposed to heat only 80 sqm and not the entire house (which they have to do in your case).

Am I supposed to open each valve to the full flow rate and let each room be flowed through with the full amount? Doesn’t that also increase consumption? I have to Google what the ERR caps are and possibly adjust them, also the bypass valve.

You should first open the ERR and let the heating do its intended job. That is what the technician planned and set it up for.

It’s just always the case that when I stand in front of the box and open various valves, it gets louder depending on how far and how much I open.

Why do you always mess around with that? I thought that

the flow rate was adjusted again by the heating engineer yesterday

and you’re ruining everything again? Addendum: explained it once again! Just believe us or Google and read up a bit. You now have a thermos flask or refrigerator as a house. Super insulated on the outside and so the heat has to distribute itself inside.

You are thinking too small. If you turn off the thermostat in the guest room and the bathroom is next to it, then the bathroom heats the guest room through the walls. Interior walls are significantly less insulated than exterior walls. However, this means that the calculated heating load for the bathroom no longer fits and it won’t get warm. Modern heating systems are only controlled slightly via the thermostat, which is anyway far too sluggish. Modern heating systems are controlled via the supply temperature depending on the outside temperature, and the flow per room is adjusted to the expected heating load. If this is incorrect because each room still has to heat another one, you can throw all the calculations in the trash. You are still thinking with the mentality of old buildings with radiators and high supply temperatures. Back then, the thermostat actually controlled it. But that is no longer the case.

That all sounds very clever. So should I set the office, guest room, and children’s room to 18 degrees, or should I open all thermostats completely? For example, we also turned off the valves completely upstairs and downstairs in the hallway with the heating technician because we thought that space was heated anyway. That was the boss personally, so he should know and must have done the calculations back then? He also told me, after we tested the actuators, that I could turn down the thermostat in the office again afterward. When the Bosch technician was here for installation, he also said I should set all thermostats to 30 and see if the supply temperature is sufficient. But I find that wasteful again, since the bedroom is set to 18 degrees, the living room to 21 degrees, and the children’s room recently again to 22 degrees according to the standard (when laying the underfloor heating regarding spacing). Then the unused children’s room would always get more heating than necessary?

Yes, I do believe you, I just wasn't aware of it. But I still think that the noise afterwards is not gone. Was it then really smart that the heating technician changed the pump inside from level 3 to 1 without being able to justify it? The technician must have had a reason for it back then? No, since he adjusted everything yesterday, I haven't done anything else, but it also didn't get quieter. Even at the beginning, when everything was on, it was still loud.

First read this for comparison, otherwise this will get lost in the details again.

Hydraulic balancing and flow rates for the whole house, or did you adjust them all separately for heating the 80 sqm?
I fear you have a hydraulic balancing for the whole house and you completely ruin it by closing off different rooms. Then you shouldn't be surprised by the result, because the 80 sqm are actually supposed to heat just 80 sqm and not the entire house (which they have to do in your case)

Hydraulic balancing for the whole house. But the boss from the heating company didn't set it according to any list or anything else. The meters on the pipe are noted for each circuit. Based on these meters, he then set between 0.8 and 2.0 L. 0.8 at 60 meters, 1.5 at 120 meters. So everything is very inaccurate in my opinion.