How Galvanic Isolators Work
Remember that the galvanic isolator needs to be able to fulfill multiple roles in your boat's AC shore power system. Eliminating one of the components that make up a galvanic cell is one of its functions. But because it is installed in series with the green grounding conductor in your boat's AC shore power system, it must also ensure that electrical continuity is always maintained in that wire.
For that reason, the American Boat & Yacht Council (ABYC) has some strict guidelines in its standard addressing galvanic isolators. The isolators must be rated for system amperage, usually 30 or 50 amps. They must be hard wired into the system without the use of any friction type connections and meet a series of design specifications to ensure that they can never inadvertently open circuit, effectively eliminating the all-important safety ground for your boat. The newest designs incorporate technology that can identify these units as "fail safe." Simply put, this designation ensures that even after something as significant as a lightning strike, the galvanic isolator will maintain continuity of the safety ground on board your boat. It may not continue to protect your underwater metals, but the safety ground will be intact, one reason why a galvanic isolator should be regularly checked for proper function.