# Underground short on exterior lighting



## PaliBob (Jun 11, 2008)

Irish,Do you have a *Short?* or an *Open? *A Short means the C/B trips, an Open means no power. Either way the problem may not be easily solved. What does _"between post lights"_ mean? 10 ft? 100 ft?. Thanks for including the depth which is much deeper than code requirements. How do you know it's that deep? Is it direct burial or in conduit.

Is the problem on a 120V circuit or is it low voltage (12V)?

If you can see a cable going into the ground, what color is it. Do you have Gophers? 

Sorry for all the questions but these are all relevant because you didn't include much information with your question.
.


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## skymaster (Jun 6, 2007)

Is this new or old existing wiring? If OLD then may just be a whole bunch easier to just run new wire to the lights.


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## frustratedhalf (Sep 26, 2009)

*wiring*

Its new wiring, about 2 years old


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## Scuba_Dave (Jan 16, 2009)

Direct burial, or conduit?
Where are you located ?


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## frustratedhalf (Sep 26, 2009)

*exterior lighting short*

Hi Palibob
the light posts are about 150 feet apart, , the wire is approx. 2 feet deep (we dug the ditch ourselves because the electricians didn't want to do it) and we laid a gray cable directly into the ditch, had it inspected by the electrical inspector, filled it in and the rest the electrician did. (It's not in conduit), we just installed GFI's on each of the other two light posts just to find out which one was tripping the whole circuit and thats how we narrowed it down to the last light post. The wiring is about 2 years old and b4 now, everytime it rained thay would short out, but until recently we have been able to reset it and it would be fine for a while, now, it's just given up , propably fromthe wet summer we had. No we don't have gophers, just my husband ....:laughing: digging up the yard looking for the solution. It's 120V Thanks for your help


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## frustratedhalf (Sep 26, 2009)

Direct Burial...NJ


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## Yoyizit (Jul 11, 2008)

I guess if it's a wet insulation problem and it doesn't trip the CB [just the GFCI] you might be able to fix it by powering a hair dryer at the far end with the GFCI bypassed. The heavy current may dry out the wire.

Or, rent one of these
http://en.wikipedia.org/wiki/Time-domain_reflectometer


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## PaliBob (Jun 11, 2008)

frustratedhalf said:


> the light posts are about 150 feet apart,.........
> we just installed GFI's on each of the other two light posts .........
> 
> b4 now, everytime it rained thay would short out, but until recently we have been able to reset it and it would be fine for a while,......
> ...


 Frustrated, We're making progress. it appears that you have a GFI that trips due to a fault current leakage path that exceeds 5mA through all that buried cable

Now let me see if I understand the layout

1) Three Light Posts, each about 150' apart
2) There appears to be a problem between Post #2 and Post #3
3) Light Post #1 and #2 have a new GFI to isolate the problem

Question, Is there an original GFI that fed all three Posts and where is it located? 

If there is a buried cable to Post #1 ?
How long is it?
How long is the total length of buried cable?
.


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## Yoyizit (Jul 11, 2008)

"Normal" leakage current for 150' of Romex @ 60Hz is 0.8 mA with 450' using up half of your 5 mA "leakage budget".

With fixture capacitance your design might be marginal from the get-go.


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## J. V. (Jun 1, 2007)

Replace it. Even if you find it, you most likely will not have the ability to repair it. Use conduit this time, and in the future.


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## frustratedhalf (Sep 26, 2009)

There was an original GFI right at the house, the distance from there to the first light is about 40 feet and the total of buried cable would probably be about 400 feet.


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## Yoyizit (Jul 11, 2008)

frustratedhalf said:


> There was an original GFI right at the house, the distance from there to the first light is about 40 feet and the total of buried cable would probably be about 400 feet.


With 400' the GFCI should see about 2 mA of leakage. You can check this with a low wattage 120v incand. lamp and a voltmeter. At this low leakage the GFCI should take a while to trip, or not (see fig. 6.7, below)
http://books.google.com/books?id=NK...resnum=1#v=onepage&q="gfci trip time"&f=false


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## PaliBob (Jun 11, 2008)

Frustrated, Thanks for hanging in there and answering questions.
Correct me if I'm wrong, You have:
• About 400’ of UF buried cable >2’ deep, feeding 3 Light posts, now trips a GFCI

From your post’s, as I see it:

• You do* not *need a GFCI to feed the buried UF cable
• GFCI’s are *not* required for yard lights per se.
• GFCI’s are needed for people protection, not for lights.
• GFCI protection *is *required for all yard receptacles

I am no expert on the code, but if I’m wrong on this, we’ll hear soon as there are some real experts on this Forum that know tons more than me.
.


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## J. V. (Jun 1, 2007)

PaliBob said:


> Frustrated, Thanks for hanging in there and answering questions.
> Correct me if I'm wrong, You have:
> • About 400’ of UF buried cable >2’ deep, feeding 3 Light posts, now trips a GFCI
> 
> ...


Bob,
It is correct that you do not need GFCI protection for outside lights. GFCI protection is to protect you, not light fixtures. However, a combination of receptacles and lights on the same circuit would require GFCI protection.
I agree it does not seem right as you must change bulbs and touch fixtures too. If you wanted to put outside lights on GFCI, there is no reason why you could not do it. :thumbsup:


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## 220/221 (Oct 9, 2007)

> we laid a gray cable directly into the ditch


 


Sorry. Always install conduit......always.

Who came in behind you and did some digging. Landscapers perhaps? Did you come up short and have to make a splice underground?

My bet is landscapers/irrigation guys. Around here they dig thru stuff and make crappy splices all the time.


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