GFCI / Galvanic Isolator Problem - SailNet Community

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  #1  
Old 01-07-2008
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GFCI / Galvanic Isolator Problem

OK, troubleshooters, see if you can point me in the right direction.

A customer came into the yard with a severely (and I do mean SEVERELY) eroded sail drive unit...It's a J-1o9 / Yanmar...fairly new, maybe 6-9 mos...even smells new. He had brought the boat to SF from Santa Barbara several months ago and docked her at a local marina. Divers had never noticed anything amiss during routine cleaning either in Santa Barbara or here, and his zinc(s) were always reported to be in reasonable condition, and were replaced when necessary. However, he, for some reason moved his boat to another private marina, or dock, and that's when the fun began.
I immediately suspected he had a Galvanic Isolator problem...that is, no Isolator; but in fact he does, a good one too, though I forget the brand at the moment...don't know about capacitors, they're usually fairly large, and I 'm reasonably sure this unit doesn't have one, but it does have a rather elaborate monitoring system. All well and good, except...
Whenever I plug into the yard's power, I trip the GFCI. Not the AC breaker, but the GFCI. I know this should point me squarely at a leakage between the neutral and ground. There are only three AC branch circuits: Water heater, Battery charger, and Outlets. So I dutifully removed each of the neutrals in turn from their buss until I could get the power to stay on long enough to think I had it (water heater) licked. Disconnected the heater, re connected the others, but no cigar...stays on long enough for me to turn on the charger on but that's it
Anyway, this can't be that difficult...I'm probably not seeing the forest for the trees. Any and all suggestions welcome.

BTW, I measure >5m between neut and gnd with main AC ON; >40M when off.

Howard Keiper
Sea Quest
Berkeley
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Old 01-07-2008
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Re:

Is it possible that the shore power unit (on the pier) is not properly grounded? Considering it is a private marina - and problem has not existed before (assuming) - it could be faulty at the pier and not an issue at all with his set-up (and in which case you would get that behavior on the boat as that is what GFI is designed to do...)...

One thing to check for is there a reverse polarity condition?

kascomarine com /flowchart-gfcitrip . pdf

Has a very good troubleshooting guide...
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Old 01-07-2008
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Might be worth getting a pigtail that lets you use a 110 AC polarity/wiring check plug on it.



Until you eliminate the shorepower circuit itself as a possible problem, you won't get anywhere with the troubleshooting.
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Don't ignore the hot lines in your search. Keep in mind during your troubleshooting that a GFCI circuit looks for a difference in current between the hot line and the neutral line. The current flowing to the device in the hot line must return through the designated neutral. You could have a slight current leakage (corroded connections, etc.) in the hot line that isn't enough to trip the CB but more than enough to activate the GFCI circuitry. While a proper ground is mandatroy for saftey, it is not required for the GFCI to operate.

Good Luck!
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Old 01-08-2008
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Quote:
Originally Posted by sailingdog View Post
Might be worth getting a pigtail that lets you use a 110 AC polarity/wiring check plug on it.



Until you eliminate the shorepower circuit itself as a possible problem, you won't get anywhere with the troubleshooting.
Ooh, I want one of those. What I'm reading in my "Metal Corrosion in Boats" books is giving me nightmares.
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They're about $8 at the Home Depot or so. Well worth having in your tool kit. BTW, they do make one for testing GFCI outlets that has a button on it that connects hot to neutral IIRC... Much better than the tweezers in the outlet method of checking one.
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Ooh, I want one of those. What I'm reading in my "Metal Corrosion in Boats" books is giving me nightmares.
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Thanks for the tip, SD. Yes, poking metal into sockets is questionable fun at best.
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Depends on who is holding the metal involved.
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Thanks for the tip, SD. Yes, poking metal into sockets is questionable fun at best.
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Depends on who is holding the metal involved.
..........and how wet their feet are!
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Cool

Where are the inverters grounded? Has this boat had it's electrical system upgraded from the original configuration?

Based on my experience if the engine is used as a ground for electrical systems other than it's own (alternator, generator, whatever) as opposed to the battery banks, the engine's drive line components hanging out in the water will become the anode for the electrical system.

What a bummer!
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