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GALVANIC ISOLATORS

Sep 23, 2019


Often overlooked, this piece of equipment is critical in the fight against corrosion.

Although not as capable as an isolation transformer, the galvanic isolator can go a long way toward extending sacrificial anode service life and mitigating corrosion, at much lower cost and nearly insignificant weight compared to the transformer. If your boat is plugged into shore power on a regular basis, you need a galvanic isolator installed in your shore power system.

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.

Where And How To Install A Galvanic Isolator

The galvanic isolator is installed in the green grounding conductor in your shore power system. It works by introducing a low DC voltage in that conductor. Because galvanic voltages and currents run below that level, the net effect is that galvanic current flow is stopped, effectively isolating your boat from your neighbors on the dock, at least galvanically. Because the green wire's primary role is to act as a fault-carrying conductor in the event of a shore power equipment fault, the electronics used to block the galvanic current have no impact on AC current flow when there may be a fault.

If your boat is plugged into a dock regularly, you need a galvanic isolator (or an isolation transformer). If you have an older boat with an isolator installed, you should have a marine electrician test it to ensure that it is functioning properly and that it meets current standards that apply. Early isolators had inherent shortcomings that can make them unsafe. The problem is that you won’t have any idea whether it is functioning without testing the unit properly. If in doubt, get a qualified marine technician to test it or consider replacing with a new fail-safe unit.