# GFI Tripping



## noela (May 22, 2008)

I am having a problem, and not sure how to address it. I have a 20 amp GFI breaker for a 20 amp circuit to my shed. The line is 12-2 underground wire, I believe it to be one piece, but I'm not sure as I wasn't here when it was installed. The line is approximately 110' long. In the past, after a heavy rain, the GFI would trip, and after it stopped raining, I would re-set it. Didn't always do it, perhaps two or three times a year. I was always able to reset it. We had some very heavy rain this week, and I almost expected it to trip, and it didn't let me down. Went to run my trains today, and had no power, so, I went to the garage to re-set the GFI and it tripped as soon as I re-set it. Needless to say, I stopped trying to re-set it. Before, it was an inconvenience, because all that was in the shed was one outlet, and two CF light bulbs. I now have my power supply out there, and need it to run my non-battery powered locos. I am not really sure what is wrong, but I am thinking one of two things:
1. There is an open to ground, someplace along the route of the buried 20 amp line.
2. The GFI could be defective, and it should be replaced.
I am looking for some help in resolving this issue. I am thinking that the GFI probably isn't defective, and that I should pursue the possibility of a break in the line. Is there any way I can determine where a break in a line is, without digging up the line? Or, is there any way I can determine if the 
GFI is defective?
Needless to say any suggestions and/or direction is greatly appreciated.
Thank you.


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## Dean Whipple (Jan 2, 2008)

The GFI breakers are very sensitive and a lead pencil mark or a damp finger across the neutral wire to the ground wire will cause it to open the circuit, they are also because of this sensitivity prone to failure particularly after they have "blown" many times. 
If the ends of the wire are in an area that they might be exposed to moisture you might check there other then that I would guess that you have a pinhole somewhere in the underground wire, and I know of no way to detect where it might be. 
I would try replacing the GFI breaker and if that didn't work all you'd only be out the cost of a breaker and if it did work you might able to put off having to replace the underground wire for a while.....


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## Naptowneng (Jun 14, 2010)

I just had the same issue with my underground supply line. Rain = GFI trip. Odds are the GFI is doing its job, and you have a situation where moisture has accessed your underground supply wires. I ended digging mine up, and sure enough, there was a place underground where a plug was interted into a recepticle. I am sure that is where the problem was. I bought a "liquid electrical tape" product at the home store, and coated the area twice, and let dry. Problem stopped. Do you have any clear ideas where the wiires emerge from the ground, and if there are any splices or connections? The problem is likely at one of those. I realize you might not wish to dig wires up, and certainly could try a replacement breaker, but if that does not work, should be prepared to explore the most likely places where there may be moisture plus a break in the insulation or connection. Good luck.


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## barnmichael (Jan 2, 2008)

I agree with the probable weak GFI and would replace it. Also, I would try it with everything disconnected in the shed. For a run of 110' you're pushing it with #12 wire. I would use at least #10 but would prefer #8. If you have to dig it up. I would suggest putting in conduit. Makes it a lot safer for the wire. All kinds of little burrowing things like to chew on wire. 

If you stay with the existing wire, once it is working again, plug in and turn everything on you would normally have on in the shed. Then take a voltage reading in the shed. If it is below 110V your wire is too small. If it is below 100V you risk damaging your equipment. Running too small of wire long distances is one of the most common mistakes made with outdoor wiring.


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## Semper Vaporo (Jan 2, 2008)

GFCI measures the current flow "out of" the Hot wire and "back in" the Neutral wire. If the two measurements are different then the current out is going someplace other than back on the Neutral and the device will shut off the flow of current. You might have a spider web in the outlet box in the shed that is across the hot terminal to the box itself of some other place that allows a small amount of current to leak to the Earth. The spider might not even notice the web is electrified, but the difference in current Out and Back at the breaker will be enough to trip it. But I suspect it is a damaged wire underground. I also suggest you may need more than 12 gauge wire and it really should be all three wires, Hot, Neutral and Safety Ground (10-2 w/ground or 10-3)... and don't run Aluminium either!!!!


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## rhyman (Apr 19, 2009)

There is a handy on-line calculator at http://www.powerstream.com/Wire_Size.htm 
that will show you the results of using various gauge wire. You can plug in variables such as wire gauge, length of run, voltage, phases and current. 

For example, a 110 foot run of 120 volts, 20 Amp, single phase using AWG #12 wire will give you a voltage drop of 7.183 volts or 5.99%. By moving up to AWG #10 wire the voltage drop is 4.519 volts or 3.77%. And finally, if you move all the way up to AWG #8 wire, the voltage drop is 2.841 volts or 2.37%. Size does matter! 

The general "rule-of-thumb" for power transmission is AWG #10 for circuits up to 15 Amps and AWG #8 for circuits up to 24 Amps. Always consult your local or national electrical code or your electrician to decide what is legal!


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## noela (May 22, 2008)

Thank you so much. I am going to replace the breaker today, keeping my fingers crossed that the problem is in the breaker and not the wire. The wire is 12-2 w/ground, I checked it in the shed. I haven't gone into the panel in the garage, but will be doing so as soon as the sun come us and after breakfast. For my own edification, I will wire the white from the breaker to the buss, and the black to the hot lead to the shed. I am assuming that the ground wire for the shed is connected to the other ground wires in the panel. Does all that sound right? 
Again, thank you to everyone for your help. 

Noel


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## DKRickman (Mar 25, 2008)

A couple comments: 

First of all, is there a reason you're using a GFCI breaker instead of a regular breaker and a GFCI outlet in the circuit? The outlet would be a lot cheaper and more convenient for you to reset. Also, GFCI and lights (especially fluorescent lights) do not play nicely together for some reason, so if you have any lights in the shed, you might want to consider using a regular breaker. 

Second, even though your wire is underground rated, do you know how deeply it is buried, and are you sure that nothing has cut the insulation anywhere in that 110'? Around here (NC) the codes require that a bare cable like that be 18" deep - 12" if it's in conduit. I would second the suggestion to put the line in conduit if possible. Digging it up might be a good idea anyway - if Joe Homeowner was trying to save money, he might have spliced a couple shorter sections, rather than buying a 250' roll and only using a third of it. That splice could be a problem, especially if it was not done correctly.


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## noela (May 22, 2008)

I like the idea of using a GFCI outlet. I have two outlets in my shed, can I use one GFCI outlet to regulate both of them? 
Thank you. 

Noel


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## rhyman (Apr 19, 2009)

Just be careful how you connect the new GFI breaker. Installation of a GFI breaker is realtively simple. Flip the main breakers to the OFF position before opening the breaker panel. 


The GFI will install just like a standard breaker with one modification. In addition to the black (hot) wire, you must also connect the white (neutral) wire from the circuit to the GFI Breaker. Then connect the white wire pigtail from the GFI breaker to the neutral buss bar. When the GFI breaker trips and disconnects the power from the black wire, it will also disconnect the neutral wire. 


By disconnecting the hot and neutral wires when tripped, the outlets in the shed now have only 1 wire connected, the ground (copper with no jacket) wire. Since you cannot complete a circuit with only 1 wire, it makes it very difficult to have an electrical short.


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## rhyman (Apr 19, 2009)

If you decide to go with a GFI outlet rather than a GFI breaker, just make sure the GFI outlet is the first one in the shed and that all subsequent outlets are "downstream" from it. Then all of the outlets in the shed will be protected.


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## John J (Dec 29, 2007)

I vote for the Dig it up and start over idea. 

When it comes to sparky stuff you can't be too carful especially if you got kids around.


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## noela (May 22, 2008)

I have opted to do the shed based GFCI outlet, and put a 20 a. circuit breaker in the garage. Could not locate leak to ground using a borrowed megger, but this is a damp area. I will let you know how I make out. 
Thank you for all the help. 

Noel


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## Greg Elmassian (Jan 3, 2008)

Good luck Noel. 

Hint: If earthworms start popping out of the ground, you have found your "leak" ) 

Regards, Greg


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## noela (May 22, 2008)

Thanks Greg,
Everything is installed, and working fine. My hair didn't frizz or stand on edge. Can't test tracks until rain stops. I could, I guess, but why ask for trouble?
Thanks again for all the help.

Noel


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## krs (Feb 29, 2008)

Posted By Dean Whipple on 22 Jul 2010 04:21 PM 
I would try replacing the GFI breaker and if that didn't work all you'd only be out the cost of a breaker and if it did work you might able to put off having to replace the underground wire for a while.....


How much are GFI breakers in the US?
Here in Canada a 20 amp GFI breaker is over $100.- whereas a regular 20 amp regular breaker is less than $10.- and a GFI outlet around $15.-

Pretty expensive to just replace the GFI breaker on a whim.


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## Greg Elmassian (Jan 3, 2008)

They are sure expensive. I have a 220v 60 amp GFCI breakers. Don't even think about how expensive they are. 

Regards, Greg


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## Treeman (Jan 6, 2008)

You should move the Ground Fault protection close to the point of use. The underground cable does not need to be protected. A GFI is for personal protection only. By the way this is not a voltage drop issue.


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## pimanjc (Jan 2, 2008)

Ants and their larvae caused a GFI outlet to repeatedly trip. You might take a look.
JimC.


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## Dan Pierce (Jan 2, 2008)

In a damp area, make sure the electrical boxes for the outlets are the plastic ones with lots of room, not metal ones or small ones. Wires need room to breathe in a damp area or a GFCI will trip, even if it is at the end of a wire run near the load. 

Also, the voltage drop listed for a 20 amp circuit with all the specs mentioned are for a 20 amp draw. I always plan my loads for 1/2 the current on a line/breaker. Motors draw a lot on startup,then the run current is much lower!! 

With the newer type of regulated power supplies, the drop will not be noticed, and if you have a malibu type of light system, anu drop will give you longer bulb life. 

So, I think a voltage drop can sometimes be more help than harm!!!


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## noela (May 22, 2008)

The project is done, thanks to the contributors to this forum. I have installed a 20 amp breaker in the garage, and a 20 amp GFCI outlet (ganged to a second outlet) in the shed, all boxes are plastic, and allow for "breathing" room for the wires. The lights in the shed are no longer on the GFCI, but tapped directly off the feed to the shed. Still holding up after 24 hours. No earthworms, or heated breakers. Have had a large amount of rain recently. The only problem we now have in the area is that there is a Coyote roaming around. Saw one on Tuesday also at my local Golf Course. 
Again, thank you for all your help.


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## Greg Elmassian (Jan 3, 2008)

You need a special GFI for your new problem: 

GFI = Gun For Interlopers .... a pellet rifle will discourage him. 

Greg


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## John J (Dec 29, 2007)

Coyotes arnt too bad. I got one that comes about every afternoon for a drink of water. I left a train out one afternoon and he looke at it from end to end then contiuned on his wayl


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## Totalwrecker (Feb 26, 2009)

Coyotes and urban settings don't mix. Keep your pets inside and call animal control, usually they trap them and release out in the country. 

Other wise unless rabid pose no threat to humans. 

John


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## Road Foreman (Jan 2, 2008)

Noel, 

There are different depths for burial of wire outside with or without GFCI proction.. This depth is different for in conduct or direct burial.. I would contact an electrican there for his opinion.. Might solve a problem before it happens.. 

BulletBob


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