When power at the dock lets you down
6/1/2020

Several months ago we heard about boat owners complaining of electrical problems at some marinas on the west coast of Florida. Leakage of electrical current at shoreside facilities is nothing new—and it can be deadly in some instances. Updated rules governing electrical installations at marinas were put in place years ago but apparently they didn’t solve the problem. We asked electrical expert Ed Sherman to explain what was going on. The following report is excerpted from an article he wrote for Marine Electronics Journal.


By Ed Sherman

So, your customer is ecstatic over their new boat and the $40,000 worth of electronic equipment you just installed. That is, all except for one minor detail that seems unexplainable: every time the boat plugs into shore power the main ground fault protection device at their newly rewired marina trips, shutting off the power to their boat and all their neighbors on the dock. What could possibly be wrong? After all they just spent $600,000 on their new dream cruiser. Further complicating the issue is that your customer says that when they took their first cruise down the bay and plugged in at a transient dock at a quaint and much older marina down the bay, there were no problems with the shore power. What’s up here?

To answer this question requires a look back at some interesting history relative to both dock wiring as well as boat wiring. Let me begin by identifying the root cause of the dilemma that has emerged. In-water electric shock death, more commonly known today in the marina world as ESD, is what got this ball rolling. Believe me, this ball has been winding down a long and winding road over the last decade, in part due to a general lack of understanding of the problem and its causes as well as changes in the choice of equipment used on new boats.
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