I have a separate inverter and charger, and use one outlet inside the boat to connect one or the other (but not both) to the AC wiring in the boat. (There are caution labels, and I ALWAYS check to make sure the inverter is unplugged prior to connecting shore power -- normally the boat is kept on a mooring so we almost never use shore power.) My shore-power breaker panel has GFCI protection and so does the 120VAC side of the inverter. When I power on the inverter it trips the GFCI on the inverter output plug, unless I power off the breaker on the shore-power panel. Is this normal or does it indicate a ground fault in my shore power wiring?