Integral device Stibel Eltron LWZ 504 with central supply air

Still doesn't explain the volume

It could, if the system increases power when more effort is needed due to the filter.

It could, if the system increases the power due to more effort caused by the filter.

It has not been noticeable for us. We don't have 504, but 604. The filters are the same and it's worth a try.

According to the SE technician, the filters are correctly installed; he also removed them, vacuumed them, and explained to me that I should never turn them over, but always reinstall them with the same side facing up after cleaning - we also put markers on the system indicating which side must be on top. I have now slightly lowered the hot water temperature to 45 degrees. However, this does not affect the ventilation. I still need to look more closely at the temperatures (base temperature, slope, etc.) ... it always takes 2-3 days to really notice a change. Overall, I currently consider the entire system to be a complete design failure - the nightmare of one’s own four walls. The only option for us at the moment is to run the heating and ventilation only when we are out of the house, but that cannot be a long-term solution. I will get back to you when I have a statement from the installing plumbing company. Best regards A. Rösner

They are set up with us as follows (all supply air values, the exhaust air is each 20-30m³ higher):
Level 1: 120m³/h (intended for night operation)
Level 2: 220m³/h (intended for day operation)
Level 3: 250m³/h (party level)

How large is the living area, how high are the ceilings?

Assuming that the required air flow was calculated correctly, the system is in my opinion unsuitable.
According to the datasheet, the nominal volume flow is for 240m2 and maximum for 300m2. The rule of thumb is actually to run at a maximum of 50% load, because beyond that it becomes excessively loud and requires electricity. Unfortunately, no corresponding graph can be found that shows this ratio as other manufacturers publish.
Based on these values, the integrated ventilation is in my opinion suitable for up to a maximum of 150sqm ventilated area, assuming normal ceiling heights and an air exchange rate of 0.4/h (nominal ventilation).

But I can't imagine that the ventilation can make such loud noises as it sounds to me from the TE's description. The humming rather comes from the compressor!?

Yes, then it is not properly decoupled.