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Old 09-09-2012, 17:51   #16
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Originally Posted by Andina Marie
GFIs on the dock only see half the problem. A hot boat leaking DC into the water or injecting DC current into the ground lead will not trip a GFI.

With years of experience I can say that running round and measuring the voltage in the water, even with the right equipment, will give you a mountain of data that defies analysis, even by experts.

If a particular boat is having problems thier first line of defense is an isolation transformer but since most can't afford the cost, space or weight a Galvanic Isolator is $100 of insurance well spent.

If the AC Voltage across the isolator is greater than about 0.75 volts then the methods suggested above for isolating the culprit can be used. I've measured as much as 5 volts AC on a marina ground. While the hot wires were 10 gauge or heavier the ground wire was only 16 gauge. It only takes one miswired boat returning current via the ground instead of the neutral to create havoc on the light gauge ground wire.

The most common cause of boats putting AC current on the ground is a combination of two things. First is a not uncommon wiring error (especially if the boat is using a domestic house breaker box) where the neutral and ground are connected together. This is WRONG. Then if that boat has a faulty shore power connection and loses the neutral the problem is compounded when the current flows back in the ground lead.
Dc leakage isn't a safety issue AC leakage is and RCBOs sort that out.

Dave
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Old 09-09-2012, 22:32   #17
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Re: A Marina in Need of Advice

No argument but the subject of this discussion was problems with rapid zinc deterioration which is an electrolysis subject not a safety subject.
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Old 10-09-2012, 13:07   #18
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Re: A Marina in Need of Advice

Here is a good summary from someone else with the same problem

The Marine Installer's Rant: The yacht club, rockets, and the electron police, The quest for the electrically perfect marina basin.
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