A quick look at shore-power devices and wiring guidance available to protect you, your crew and your boat while plugged in at the dock.
Galvanic isolators are designed to prevent your boat from suffering from, or contributing to, galvanic corrosion while plugged into shore power by blocking low-level DC current caused by galvanic action. A “fail-safe” galvanic isolator is by far the best choice because ABYC requires that, if a fail-safe isolator malfunctions, it must fail in the closed position — that way the green safety wire is still available to protect the boat from AC short circuits.
Reverse Polarity Indicator
If the neutral wire becomes hot, you lose protection from circuit breakers that are installed in the hot wire. Also, reverse polarity can electrify a boat’s underwater metals. A shore-power plug’s shape prevents it from being plugged in the wrong way but doesn’t prevent improper wiring. ABYC requires a reverse polarity indicator on boats that don’t have an isolation transformer and that place circuit breakers only in the hot wire of branch circuits.
An isolation transformer transfers electricity from the shore to the boat without the shore wires physically touching the boat’s wires, turning your boat into its own power source. If there is a fault, the current no longer seeks a path through the water back to shore. ABYC allows isolation transformers installed within 10 feet of a shore-power inlet in lieu of the equipment leakage circuit interrupter (ELCI) devices now required by ABYC.