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Old 18-06-2014, 05:28   #1
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Stray Current / GFCI Problem

So lately, every now and then, but not everyday, when we get home from work, we find the power off and the single GFCI, through which all the others are downstream, has been tripped.

It has become frequent enough to make replacing the GFCI with a new one appear on my to-do list, thought being "oh well maybe it's a bad one and I'll just replace it to see if that solves the problem"

I replaced all of them with new two years ago. I think they are all fifteen amp, our shore power is thirty, we don't really use that much power.

The thing is, in spite of being a frequent occurrence, it is not so frequent as to be routine and in fact has seemed completely random.

Then, last night, the thing wouldn't stay set for more than five minutes for about a half hour period, the rest of the night no problems.

Any thoughts on how to identify the source of the problem would be most appreciated. Presumably there is some stray current somewhere but I don't know if it is a my boat problem or if it's someone else.

They have been doing a bunch of arc welding at the marina lately, not sure that is a relevant issue.

Thanks!
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Old 18-06-2014, 06:11   #2
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Re: Stray Current / GFCI Problem

If what is tripping is a true ground fault (GF) breaker thrn what you have is current leaking INSIDE YOUR BOAT DOWNSTREAM OF THE BREAKER from the hot/live wire (or the neutral wire if far enough from ground potential) back to the generator through means other than hot and neutral wires. This has nothing to do with what is usually called "stray currents".

You have not stated the miliamp rating of your main GF breaker. If it is a usual IEC 30mA GF breaker then it will only trip when there is something wrong. (Another story are the cheap American GF breakers built into outlets that are rated at less than that but they are not built well.)

Whenever the main GF breaker trips disconnect all the circuits downstream (ideally not just hot but also neutral if you know that neutral is more than a couple volts from the green earth wire; a first world electrical system will have two pole breakers that do that for you in each circuit). Then reset the GF breaker and connect back one circuit at a time. The problem will be in the circuits that makes the GF breaker trip when connected. You should do this troubleshooting quickly because the trip maybe due to something that got wet and if you let that dry you will not find the fault.

Always be suspicious about electric water heaters when you have a fault like this.

Please report how it goes. It will help to know what boat you have because Euro and US AC installations are quite different.

Cheers

C


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Old 18-06-2014, 06:16   #3
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Re: Stray Current / GFCI Problem

I was afraid of something like that, I will have to do some poking around, obviously there is a problem but I have no idea where it would be as it's only outlets on that leg. American built boat, older. No water heater installed.
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Old 19-06-2014, 00:48   #4
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Re: Stray Current / GFCI Problem

if it's tripping and nothing is plugged into any of the outlets I'd start by replacing it.

are all the outlets GFCI or just the first one? "I replaced all of them 2 years ago" makes it sound like they are all GFCI. if so this is wrong. only the first one should be. having GFCI's behind GFCI's will cause false triping.
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Old 19-06-2014, 01:05   #5
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Re: Stray Current / GFCI Problem

Start with the understanding on what trips a GFI.

Current "out" of the GFI != to current "In" the gfi. i.e. some current going somewhere other than "back" to the source. Typically a path to ground. (hence the name ground fault)..

Nothing plugged into a gfi and it trips? Replace it. UNLESS, there's something wired downstream -- make sure that's not the case.

They do really go bad. Replace and see if it solves the problem. Easy $12 troubleshooting path.
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Old 19-06-2014, 04:28   #6
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Re: Stray Current / GFCI Problem

Thanks again. I replaced all the outlets with new GFCI's when I bought the boat about two years ago. The only thing on that circuit are outlets and the only things plugged into the outlet are basically a small dorm-type refrigerator, a fan, and sometimes a laptop.

Knowing that the outlets were newish made wonder if the problem was outside of the boat somehow. I guess I should have just trusted my gut and replaced it earlier.
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Old 19-06-2014, 11:02   #7
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Re: Stray Current / GFCI Problem

So when it start's tripping again, start unplugging things and see if the tripping goes away. I'm thinking the dorm fridge or laptop power supply might be a problem. I actually am leaning toward the laptop power supply perhaps having a leaky capacitor. That or a intermittent short to ground at the fridge compressor,which would be odd.
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Old 19-06-2014, 16:06   #8
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Re: Stray Current / GFCI Problem

Quote:
Originally Posted by smac999 View Post
are all the outlets GFCI or just the first one? "I replaced all of them 2 years ago" makes it sound like they are all GFCI. if so this is wrong. only the first one should be. having GFCI's behind GFCI's will cause false triping.
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Originally Posted by Delancey View Post
Thanks again. I replaced all the outlets with new GFCI's when I bought the boat about two years ago.

So you're saying every outlet on that circuit is a GFCI outlet?


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Originally Posted by jeepbluetj View Post
They do really go bad. Replace and see if it solves the problem. Easy $12 troubleshooting path.

Yes, they really do go bad sometimes.

And sometimes they get wet, and work as expected.

-Chris
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Old 19-06-2014, 16:21   #9
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Re: Stray Current / GFCI Problem

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Originally Posted by smac999 View Post
are all the outlets GFCI or just the first one? "I replaced all of them 2 years ago" makes it sound like they are all GFCI. if so this is wrong.only the first one should be.
+1 so far.

Quote:
Originally Posted by smac999 View Post
having GFCI's behind GFCI's will cause false triping.
Now I lost you. I know the US has a very quirky approach for GF breakers, which starts from believing you need go go down to 5mA (vs 30mA elsewhere, which has proven safe) and goes on to use outlet-mounted GF breakers that cost less than a pack of cigarettes (instead of a more expensive and reliable whole-house device as in other places), hence they end up with a very unreliable solution, but...

..can you please explain why "having GFCI's behind GFCI's will cause false triping"?

I am curious about this because in some places in the rest of the world we use nested GF breakers (say 5mA for a jacuzzi under a 30mA for the whole house) in certain cases and I have never seen or heard problems. After all, a GF breaker does not CAUSE a leak to ground, does it?
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Old 19-06-2014, 16:50   #10
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Re: Stray Current / GFCI Problem

All GFCI's, two downstream from the problem one at the panel. All of them two years old. Seemingly random tripping I can't correlate to any activity.
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Old 19-06-2014, 17:57   #11
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Re: Stray Current / GFCI Problem

Are there things downstream of the breakers which are not plugged in, like battery chargers and water heaters??

If you have connected the AC ground to the DC ground, break that connection and see if the problem goes away.

Another source of trips is a reverse polarity light.
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Old 19-06-2014, 21:14   #12
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Re: Stray Current / GFCI Problem

replace the first gfci with a new one and replace the downstream ones with normal outlets. make sure you have the input and output of the first one in the correct place as they have a input and load side to them.
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Old 19-06-2014, 21:15   #13
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Re: Stray Current / GFCI Problem

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Originally Posted by donradcliffe View Post
Are there things downstream of the breakers which are not plugged in, like battery chargers and water heaters??

If you have connected the AC ground to the DC ground, break that connection and see if the problem goes away.

Another source of trips is a reverse polarity light.
none of this has anything to do with a gfci outlet tripping on and outlet circuit with nothing plugged into them. we are downstream of the panel and breakers.
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Old 19-06-2014, 21:19   #14
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Re: Stray Current / GFCI Problem

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+1 so far.



Now I lost you. I know the US has a very quirky approach for GF breakers, which starts from believing you need go go down to 5mA (vs 30mA elsewhere, which has proven safe) and goes on to use outlet-mounted GF breakers that cost less than a pack of cigarettes (instead of a more expensive and reliable whole-house device as in other places), hence they end up with a very unreliable solution, but...

..can you please explain why "having GFCI's behind GFCI's will cause false triping"?

I am curious about this because in some places in the rest of the world we use nested GF breakers (say 5mA for a jacuzzi under a 30mA for the whole house) in certain cases and I have never seen or heard problems. After all, a GF breaker does not CAUSE a leak to ground, does it?
30ma would kill you in a heart beat. the deadly number is a lot closer to 5 then 30.

daisy chaining 5ma gcfi outlets is just not done. putting a 5ma after a 30 would likely cause less or no problems as the 30 would be a lot harder to false trip then a 5ma.
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Old 20-06-2014, 11:00   #15
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Re: Stray Current / GFCI Problem

An argument can be made for using multiple GFCIs in one circuit. The simple fact that if you trip the up line GFCI from the down line outlet then you must remove yourself to reset the up line. Lets say your in the engine room working and its down line.

Now if you want to string multiple GFCI's in one circuit, all down line GFCI's are connected to the line side or parallel. Do not connect to the load side of the up line, protected side.

Now a fault in one location won't take out the whole circuit. It will render the faulted portion of the circuit safe.

Lloyd



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replace the first gfci with a new one and replace the downstream ones with normal outlets. make sure you have the input and output of the first one in the correct place as they have a input and load side to them.
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