Dear all, a Multi 3k PMP122300001 @ v552 we have installed in a campervan is making very strange noises when inverting, like a very fast clickering relais or similar. This ONLY happens when a coffee machine (Nespresso DeLonghi Lattissima One) is brewing coffee. All other devices run perfectly smooth with no noise from the Multi (except for the fan of course), like induction cooker, Truma Combi 6E, aircondition, charging E-Bikes etc.
Coffee machine itself was also checked without any issues. The sound is reproducable and not dependant to any thermal or humidity situation, battery level, time or similar. Sound only occurs when coffee is brewed, not during heating phase.
Wiring (~3m) is done with FLY copper 50mm² wire, two for each positive and negative, case ground terminal is grounded to car body, all lugs checked for good connections and proper pressing, fuses are good. AC wiring is 3x2,5mm² to AC distribution and 3x1,5mm² to outlets, all tested and fine.
As I cannot really describe the sound, I recorded it and placed it on Youtube (video is gray, please only pay attention to sound). Can be found here: https://youtube.com/shorts/S8dvaW7hLrk (you can hear the coffee machine in the background). The noise level can be compared to the clickering of a ballpoint pen.
System also contains a Cerbo GX if this could help in diagnosis.
We’ve never had this before. What might cause this sound, what does it mean and how could we fix this? Any ideas? Help is highly appreciated! Thank you!