We installed a Multiplus II about three years ago. We went back today to add a second MPII, while opening the inverter we found it full of dust and concrete pieces. Found out from the client that they did some renovations to the home after the install but we were not informed. The unit worked fine all this time, no alarms or any problems. All the dirt on the pictures came from inside the unit.
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Always in a hurry, never read, thats me 
Indeed. The better class inverters have an IP65 rating, the dust never gets inside 