Mounting of the controlled residential ventilation ducts in the flat distributor

As I said, unfortunately I do not know the manufacturer and therefore I am fishing in murky waters whether this is actually absolutely unacceptable.

I would ask the installer to provide proof of correct fastening according to the manufacturer's instructions. Even if you now know that this is not the case.

I can't change the topic anyway at the moment, so I won't pour oil on the fire for now because I want the house to be finished someday. Once the manufacturer has (hopefully clearly) commented on this, I will take up the issue and insist on a "compensation proposal" from the general contractor during the final acceptance before settling the final invoice (the installer is not my direct contact). Because technically speaking, nothing more than cutting off the screws with a Dremel can probably be done. Whether I will then suffer any significant disadvantage regarding operation/hygiene/durability/etc. will be clarified by the expert. If that is not the case, at least I can claim to have maintained a stance. There are also a few other problem areas where the indicator clearly swings towards "botch," but I don't want to burden the atmosphere with presumably solvable problems all the time, even though I would have preferred it otherwise. What I wanted to achieve with the thread I have achieved: manufacturer and suggestions concerning my problem, thanks to everyone for this. I will keep you updated on what Fränkische says about the fastening using screws.

I just spoke with technical support on the phone.

According to the manufacturer, the pipes are secured by fully inserting them; they basically snap into place. Fixing them with screws is not necessary. It is not currently considered critical for the system in its current state because there is a filter in every air inlet that prevents dust from entering the system at all. It looks different when cleaning the system. Special tools are used here which no longer fit into the pipe because the screws are in the way. Additionally, the system is designed to be neutral (surfaces, odors, etc.). The galvanized steel screws simply do not fit into the concept. Not that you would smell them or anything like that, but they now represent a potential weak point in the system. As expected, it can only be somewhat concealed (cutting off the screws), but that does not undo the issue.

I need to sort this out for myself first and consider how and when I will bring this up. The goal should be to enable future cleaning (so cut off all the screws) and cover the slightly increased risk of another damage event (e.g., screw stubs beginning to corrode). The technician said that any form of chemicals has no place in the pipes, regarding the topic of "sealing screw stubs with resin."

Really annoying stuff :-/

Is cutting really that advantageous? Doesn’t it introduce metal shavings and could the screws rust because the galvanization is damaged?

Is cutting off really that advantageous? Doesn't that introduce metal shavings and could the screws rust because the galvanization is damaged?

One could also leave the screws as they are until the moment when the pipes need or should be cleaned. That could be in 5 years or only in 20 years. Cutting off is definitely not good, but if the pipes are ever to be cleaned, it is probably unavoidable. I also don't know what is better right now. Cut off now to see what happens in 4 years (keyword warranty) or leave them as is (never change a running system). The metal shavings could be vacuumed since the screws are about 5-7cm away from the outlet. You can actually see the screws from below with the naked eye. I just checked part of the ventilation pipes with my pipe camera and found that there is also a drilled hole damage at the level of the air distribution box. Things keep getting better :-D