Inverters and AC Transfer switch
If you have another source of AC (in addition to the Inverter), such as Shore Power or/and a Generator, you need a Transfer Switch - either Internal or External to the Inverter. This could be as simple as:
(2) 2-Pole main Breakers with a Lockout Slide, which requires that (1) Breaker be Off prior to turning the other on.
(Ie: Blue Sea Systems #4125 on Pacer page 4 - http://www.pacermarine.com/catalogparts/magneticbreakers.pdf )
ABYC A-188.8.131.52 (Inverters):
If an inverter, and any other source(s) of AC can supply a branch circuit or receptacle, then the transfer from one power source circuit to another shall be made by a means that opens one source circuit before closing the alternate source circuit, preventing arc-over or feedback between sources.
Email me, if you need FAXED diagrams.