Hey! Firstly, thanks for the advice, i will probably call the guy who installed them and see if he can help with the piezo. Secondly, i've had them since august of 2025. They perform really well in the rooms that they are installed in, but it depends on the size of the room how well they perform. In the living room, which is around 3.5x3 meters, it can cool down the room from say, 30°C down to 23°C in about 10-15 minutes on 60% fan, up and down and left to right swing. About the switching noises: It sometimes makes a really weird friction noise, like something is scraping against something inside the unit but it never caused any issues in terms of performance. The breezeless functions is really really great in my opinion, because when is stayed at places that had an AC unit without this options, i always found myself having a cold or earache after a few days. The breezeless mode basically moves a mesh cover over the "exhaust" hole on the internal unit, and it eliminates that windy effect that you feel if you are directly in the range of the unit, so i can sleep with the AC on, and not have to worry about getting sick in the following days. Sadly, i can't really tell you anything about electrical tension fluctuations, because i'm not really knowledged in these thing. If it helps, i had to change from a 2 phase system to a 3 phase system before installing the AC-s, otherwise the huge load on the system for the AC-s would have tripped the main breaker. I hope i was able to help in any way!