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Old 02-03-2016, 21:02   #1
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GFI trips when charging on the hard

I recently stopped by my boat (on the hard in RI) to plug it into a GFI outlet at the marina to charge the batteries. The extension chord is plugged into a pigtail which is plugged into my normal shore power outlet on the boat. This has always worked fine and it gives me power to the boat so I can turn on lights etc... However, this time, as soon as I plugged the chord in, the GFI tripped. I made sure everything was turned off in the boat except the battery charger, but it still tripped. I finally plugged my battery charger directly into the extension chord and it worked fine.

What is the most likely cause? I do have a galvanic isolator in line, but it looked like the connections were all fine. Unfortunately, I am 1300 miles away from the boat now in Florida until late April, so I can't experiment. Just looking for thoughts.
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Old 03-03-2016, 03:35   #2
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Re: GFI trips when charging on the hard

Try plugging the pigtail into the GFI outlet by itself without connecting to the boat. If that trips then the pigtail is the problem.

If the GFI only trips when connected to the boat there is a problem with the boat wiring. Most likely there is corrosion at the shore power inlet connector. But it could be somewhere else.

The GFI trip is telling you that there is some current flow between the hot wire and the earth ground wire. So look for a place where there could be some way for that to happen. If you don't understand what this means hire a marine electrician to find it. This kind of issue can cause a boat to be seriously damaged when shore powered while in the water.
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Old 03-03-2016, 15:43   #3
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Re: GFI trips when charging on the hard

I had the same problem in the boat yard.
It was caused by the galvanic isolator.
The LED monitor for the GI was tripping the GFI.
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Old 03-03-2016, 17:10   #4
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Re: GFI trips when charging on the hard

Quote:
Originally Posted by Wainui View Post
I had the same problem in the boat yard.
It was caused by the galvanic isolator.
The LED monitor for the GI was tripping the GFI.
Regards
M
If the polarity indicator is designed and working correctly it should not cause a GFI trip. The fact that the GI caused a trip means it had failed in some way.
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Old 03-03-2016, 20:43   #5
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Re: GFI trips when charging on the hard

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Originally Posted by transmitterdan View Post
If the polarity indicator is designed and working correctly it should not cause a GFI trip. The fact that the GI caused a trip means it had failed in some way.
Correction: if the shore power outlet is miswired then a correctly functioning polarity indicator would likely cause a GFI trip.
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Old 03-03-2016, 21:00   #6
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Re: GFI trips when charging on the hard

Galvanic isolators fitted with alarms are known to trip elci/gfi devices


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Old 04-03-2016, 06:22   #7
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Re: GFI trips when charging on the hard

Folks, he said this setup used to work but now it doesn't. This eliminates several things. If it worked OK with the galvanic isolator before, that's probably not the problem.

Something is different now from the last time it worked. It may be as simple as using a different extension cord or a repaired one that has been miswired.

Other possibilities are that the wiring on the boat has been changed or the GFCI in the yard has been changed or miswired. I would suggest trying a different outlet in the boat yard before digging into the boat's wiring.

If it's not the cord or the adapter and nothing on the boat has changed, it's time to call in a pro.
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Old 04-03-2016, 06:51   #8
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Re: GFI trips when charging on the hard

A GFCI outlet monitors the current in the hot and neutral conductors and compares them. When no fault is present, the current is (obviously) the same. If the current is not the same, some is flowing somewhere else (ground) and the device trips.

Polarity indicators on boats predate GFCI protection. The "fault" light is connected between the neutral and ground. If everything is OK, there is no voltage difference and the light is unlit.

The "OK" light is connected between the hot conductor and ground (not neutral). Since there is 120 volts between the hot conductor and ground, the light is illuminated.

The problem with tis system is, it is actually a fault as far as the GFCI device is concerned because some current is flowing from the hot conductor to earth ground and there is an imbalance between the hot and neutral.

For this arrangement to not create a problem with a GFCI receptacle, the amount of current drawn by the polarity light must be less than the sensitivity of the GFCI device.

Fortunately, typical dock pedestal boat receptacles are not GFCI protected, we rely on the outlets on the boat for GFCI protection but there is a move to require them on dock pedestals and this will be a problem for many of us in the future.

If nothing has changed on the OP's boat and the receptacle in the yard has not been replaced with a more sensitive one, this is probably not what is causing his problem.
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