Many boat owners are unaware of the importance that a galvanic isolator plays in the shore power circuit of their vessel. In the simplest terms, a GI protects your vessel from harmful shifts in hull potential from interaction with other vessels which are plugged into the same shore power circuit. There should be a GI for each shore power cord and they will be typically located close to the point where the shore power cable enters the boat. The GI is connected in series with the shore power ground conductor. HERE IS THE IMPORTANT PART. Because of it’s postition in the ground circuit, the GI should be tested by a professional yearly to ensure ground continuity. A failure of the GI could leave a vessel ungrounded resulting in a potentially lethal scenario for both those onboard and those in the water. There are on the market, newer types of galvanic isolators which are “fail safe”, meaning that should they fail they fail with the ground still connected. The fail safe GI offers security in the form of a guaranteed ground, but they still should be periodically checked to ensure isolation. The ABYC (American Boat & Yacht Council) http://abyc.com/ has recently changed their regulations to require compliant vessels to use fail safe galvanic isolators. Vessels built in the past year should be compliant, if your boat is older than that the isolator(s) should be checked for proper operation and possibly upgraded to fail safe type.
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