For your Information. 

This is the answer from Mastervolt concerning the Installation of charger/inverter on Amel 54

"The AC is not connected to the DC terminals inside, the DC is floating to the housing.
however, the AC input is not galphanic isolated from the shore, for this you need a isolation transformer, and create your own ships ground in your boat.
the combi Ultra has an option to switch on a ground relay, this means the neutral in AC output will be connected to the ground in inverter mode automatically. in charger mode (this means there is a AC input like a shore connection, then this relay will be deactivated, because theoretical, the hot and neutral line can be swapped, and you don't want the hot line to be connected to the ground.
our high frequency isolation transformer is 88000355 mass GI 3,5
http://www.mastervolt.com/products/mass-gi/mass-gi-35-kva-16a-lightweight/

hope this helps,

best regards, 
Edwin van der Kroon"

 

Any comment ?  Wolfgang Weber SY ELISE  Amel 54 # 162