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Old 27-04-2008, 19:59   #1
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GFCI problem, maybe

Last weekend I fitted a couple of GFCI plugs. One in the first AC outlet (all our boat's ac sockets are in parallel on the same circuit) and one in the galley (isolating galley and engine room outlets seperate to the rest). This was pretty straightforward and all the outlets behind these were confirmed as working.

When returning to the boat this weekend I didn't retest the circuits and we went and had a pretty hard and enjoyable sail yesterday. As we were motoring back in we tried to use the galley outlets and found them to be inoperable and the GFCI circuit refused to reset. All prior outlets are functional. My guess was that something must have slipped and so I started digging this morning.

The socket's connections looked fine so I tried replacing it with a spare. This also refused to reset. I then removed the load hot and neutral connections (leaving the downstream ground still connected though) and it still won't reset.

Multimeter results at the socket are (approx):
  • Neutral to ground = ~108V
  • Hot to ground = ~118V
  • Neutral to Hot = ~14V
Any ideas?
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Old 27-04-2008, 21:43   #2
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And when I post in the wrong section how do I move the posting?
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Old 27-04-2008, 21:45   #3
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salt.

You'll find it.

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Old 27-04-2008, 22:12   #4
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When you say it will not reset do you mean you hear the pop of it turning itself off as if there were an actual ground fault?

For testing the circuit....
You should have zero voltage between ground and neutral and full voltage between hot and neutral. Your hot I believe is directly shorting to neutral...therefore it is shutting itself off. You have a direct short I believe or a faulty GFCI breaker. Go to the hardware store and get one of those 120 volt outlet testers. The light pattern on the tester will tell you what is happening. Remove the GFCI outlets from the circuit to confirm whether or not they are the problem or the circuit itself is the problem. You will obviously have to wire in a standard, non GFCI outlet in order to use the 120 volt tester. Make sure the circuit is on its own breaker at the source for safetys sake. Also, remove any loads from the circuit.

Senior mechanino is probably right...salt or something somewhere is causing a partial short between hot and neutral or hot and ground. Salt acts as high ohm resistor when it has crystalized and is still a little wet.

Also, dont use wire nuts...use crimp connectors. You probably already know that though.
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Old 28-04-2008, 08:35   #5
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As David said above, get a polarity tester from the local HW store - they are about $8 at HD. If you got salt into it, or it shorted, it's possible/likely that it's fried. Remove it, take it to a house, and try installing it there. Once you get it installed, then test it with the tester.
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Old 05-05-2008, 11:05   #6
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The polarity tester is a neat little device but didn't throw up anything. After checking the plugs I fitted I took my next best guess (the head outlet, which was also the last working outlet in the chain) and found it to be pretty corroded. Replacing this with another GFCI socket got everything working again.

There was no obvious leak. I'm guessing that the hull flexed somewhat, put some strain on one of the electrical cables (the boat is slightly over neatly wired - very little spare wire between sockets) and part of the corroded plug gave way. I really don't understand how the corroded plug continued to operate correctly while the downstream plug had incorrect inputs but am mainly happy to be operational again.
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