# Locating short in underground conduit



## Jon Paul (Nov 25, 2013)

Hello all: I have a 12/3 run of about 60' partly indoors and partly in a PVC conduit. Problem: there is a short from ground to neutral. Question: How to locate the short: Most of the equipment to locate cables and shorts is very costly. Any way to deduct the distance from the end to the short? Kind Regards, Jon


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## jett95 (Sep 18, 2012)

Is there a gfi on that circuit


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## crazyboy (Nov 8, 2008)

Jon Paul said:


> Hello all: I have a 12/3 run of about 60' partly indoors and partly in a PVC conduit. Problem: there is a short from ground to neutral. Question: How to locate the short: Most of the equipment to locate cables and shorts is very costly. Any way to deduct the distance from the end to the short? Kind Regards, Jon


If its that short of a run in pipe just replace the wire.


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## wildleg (Apr 12, 2009)

what's the point of locating the fault ? pull it out and replace


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## McClary’s Electrical (Feb 21, 2009)

I agree with all of the above but to answer the mans question, a time domain refeclometer will tell you where it is.


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## 480sparky (Sep 20, 2007)

I've always wondered why anyone would spend thousands on test equipment when there's no need for it.


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## Joefixit2 (Nov 16, 2007)

Sounds like somebody put Romex underground. Did they use plumbing PVC fittings as well?


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## 480sparky (Sep 20, 2007)

Joefixit2 said:


> Sounds like somebody put Romex underground. Did they use plumbing PVC fittings as well?


Yeah, forget UF...... :laughing:


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## mertabird (Nov 14, 2013)

Right.... just replace the wire it probably much easier than renting equipement to locate the short, digging it up... then what... splicing .... that's not a good idea anyway.


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## rrolleston (Mar 6, 2012)

Connect some new wire to the old wire pull the old wire out and you won't have to locate a short in the wire. Scrap the old wire.


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## rrolleston (Mar 6, 2012)

I would also just pull THWN in the conduit because that is much easier than pulling UF into conduit.


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## Derek1 (Mar 27, 2013)

Jon Paul said:


> there is a short from ground to neutral.


get rid of the arc-fault breaker and call it a day.:thumbsup: lol

I would use a locator that our company has...but I have no idea what those things cost to buy or rent...

I agree with what others have said, get rid of it and run a new romex to the box that the PVC is connected to, and from there pull 12 awg thwn.


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## Jon Paul (Nov 25, 2013)

*more info, one solution*

Hello all: The conduit is PVC 3/4" SCH 40 electrical, a total run of 75' in several sections. There is no GFI and I am testing directly at the wire ends disconnected from the connectors and system. It was installed poorly, with many sharp bends and a U turn. No junction boxes or pull elbows to access it. It will be very hard to easily pull a new wire. If I know the fault location even approximately, I can localize the area and save time. One solution may be a milliohm meter, measure the loop resistance at each of the ends and calculate the resistance, assuming the fault is a dead short. I am open to your further ideas! With Kind Regards, Jon


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## 8V71 (Dec 23, 2011)

Jon Paul said:


> One solution may be a milliohm meter, measure the loop resistance at each of the ends and calculate the resistance, *assuming the fault is a dead short.*


Good thinking, but the chances of a zero ohm short is pushing it. Actually though, it wouldn't have to be a perfect short, but a consistent short that you could add to your calculations on each end. Don't move the wires around too much while you are doing this. :laughing:


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## sbrn33 (Mar 15, 2007)

Rent one from another electrical firm or just have them locate it for you. The $100 it cost will be well worth it to your customer. I am guessing you already have waaay to many hours in this already.


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## Jon Paul (Nov 25, 2013)

*2 solutions*

Hello all: Being an electrical engineer, I thought of 2 tests: #1 4 terminal resistance, #2 apply a powerful AC oscillator (audio or RF) and detect the field with an amplifier and headset like used to telephone lines. I found an old Fluke 8842A DVM in my pile of old equipment, it can read milliohms (4 terminal 4 lead measurement). I will check loop resistance from both near and far end and calculate, #12 ga has 1.588 Ohm/1000 ft. Just by comparing the near/far resistance I may get a clew, which section to replace and if the short is accessible in an elbow or junction. Cheers, Jon


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## CraigV (May 12, 2011)

"_Just by comparing the near/far resistance I may get a clew, which section to replace and if the short is accessible in an elbow or junction._ "

But you just wrote that there are no pull elbows and no junctions. 

Don't forget that there may be more than one short, or potential short, and fixing one damaged section may not be the end of it. Jobs that are done badly have a tendency to outwit all who try to apply logic. What if you locate the area, and find the insulation was stripped back for several feet? This is common in pulls with too many bends or where the conduit has sharp edges left in.

I think you'll best serve your customer by recommending a complete replacement of the conduit and wiring with a system that meets code.


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## rrolleston (Mar 6, 2012)

CraigV said:


> I think you'll best serve your customer by recommending a complete replacement of the conduit and wiring with a system that meets code.


Couldn't agree more. When I see an installation that is so bad I can't do a guaranteed a repair. I recommend replacement and give my price. Any splice to NM underground will not be code compliant and I would not be able to guarantee it so I would price replacing the whole thing.

Add a junction box in both buildings where the conduit exits the building. would allow you to replace the underground and splice it. But if even the inside install is really bad I would replace that too.

Any pictures of this install?


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## RIVETER (Sep 26, 2009)

Jon Paul said:


> Hello all: I have a 12/3 run of about 60' partly indoors and partly in a PVC conduit. Problem: there is a short from ground to neutral. Question: How to locate the short: Most of the equipment to locate cables and shorts is very costly. Any way to deduct the distance from the end to the short? Kind Regards, Jon


At that distance, pulling in three new wires would be quicker than posting on this forum.:thumbsup:


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## Shockdoc (Mar 4, 2010)

Start digging


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## 8V71 (Dec 23, 2011)

RIVETER said:


> At that distance, pulling in three new wires would be quicker than posting on this forum.:thumbsup:





Shockdoc said:


> Start digging


My take so far is.....

1) Home project
2) 12/3 Romex or UF
3) Conduit was installed by slipped over the wire.
4) It ain't gonna budge. :no:


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## McClary’s Electrical (Feb 21, 2009)

I hate a long cord!


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## nrp3 (Jan 24, 2009)

As much as I hate UF, it makes me money and has more than paid for said thousands of dollars in test equipment. Wise shopping on ebay netted me some mighty good deals on this stuff in great working order. I thought I was done for the season but picked up some good coin today chasing the fault the local guys couldn't find. $$$$$ to be had if you have the right gear, ie megger and fault locator. At least they had found the two poles it was between and marked them.


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## bobelectric (Feb 24, 2007)

Romex, in conduit outdoors doesn't fly .Wet location.


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## Next72969 (Dec 9, 2012)

bobelectric said:


> Romex, in conduit outdoors doesn't fly .Wet location.


thats why you use straps, to stop it from flying


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## Joefixit2 (Nov 16, 2007)

CraigV said:


> Jobs that are done badly have a tendency to outwit all who try to apply logic.


 :thumbsup::thumbsup::thumbsup:


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## bobelectric (Feb 24, 2007)

Next72969 said:


> thats why you use straps, to stop it from flying


 That's the reply we expect from a "Professional Contactors Forum".


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## wcord (Jan 23, 2011)

Jon Paul said:


> Hello all: *Being an electrical engineer*, I thought of 2 tests: #1 4 terminal resistance, #2 apply a powerful AC oscillator (audio or RF) and detect the field with an amplifier and headset like used to telephone lines. I found an old Fluke 8842A DVM in my pile of old equipment, it can read milliohms (4 terminal 4 lead measurement). I will check loop resistance from both near and far end and calculate, #12 ga has 1.588 Ohm/1000 ft. Just by comparing the near/far resistance I may get a clew, which section to replace and if the short is accessible in an elbow or junction. Cheers, Jon



Typical engineer:laughing:.
Make it so complicated, that it takes days and hundreds of dollars, and then end up doing as the tradesman suggested in the first place
Replace the wire and be done with it.


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