# Energized EMT in garage - I'm stumped!



## 480sparky (Sep 20, 2007)

Took these at the original install:

First box in garage, pipe under box has 12/3 UF (red wire not used):











Up overhead above entry door, then box for splitting pipes to switches and lights:




















Pipe then through a keyless, 











then over to door opener (GFCI protected):


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## 3xdad (Jan 25, 2011)

Ken, the EMT coming up into first box. Does it go into the ground or is the whole raceway floating?

Obviously you are reading voltage with the UF energized. Maybe an open N underground?

edit: wait...i think i see a bushed EMT connector on that bottom tube.
Well, just keep dividing and conquering.


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## BuzzKill (Oct 27, 2008)

I'm amazed 480 is having a problem!


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## chicken steve (Mar 22, 2011)

3xdad said:


> Ken, the EMT coming up into first box. Does it go into the ground or is the whole raceway floating?
> 
> Obviously you are reading voltage with the UF energized. Maybe an open N underground?


Or the whole place IS a noodle Dad.

If this structure is between the house and serving Xformer, try using your Vtick in the same emt pipe location, and shutting the house down 480....

~CS~


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## 480sparky (Sep 20, 2007)

It's EMT down to some flex that stops at the floor. The flex was original. I just extended it with EMT.


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## 3xdad (Jan 25, 2011)

i'm just throwing stuff out there.

IMO, a pen light will light up against EMT with the circuit energized anyway under normal conditions.

i see it's metal flex into a coupling or something.

If he's getting shocked, there is a bad N somewhere.


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## 480sparky (Sep 20, 2007)

3xdad said:


> i'm just throwing stuff out there.
> 
> IMO, a pen light will light up against EMT with the circuit energized anyway under normal conditions.
> 
> ...



Good noodle.... everything works as it should (lights, door operator, etc.)

My thinking is the UF is damaged under the slab and is starting to get a high-resistance short to whatever the sleeve is. I know there's a raceway through the slab, but it's probably just EMT or rigid to sleeve the UF and stops with the bottom of the slab.

But it's too sloppy of a mess to deal with today, plus the HO kinda kicked me out since he had to go to work and wouldn't let me investigate further. I'll hopefully be back next week.


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## Kaffeene (Feb 11, 2014)

Have you tested continuity of the ground and neutral back to the house?


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## 480sparky (Sep 20, 2007)

Kaffeene said:


> Have you tested continuity of the ground and neutral back to the house?


I can't find where the UF gets power from in the house. I took apart all the switches and receps near where it comes it (it disappears between the original siding and the ledgerboard of the deck. My guess is there's a buried splice in the ceiling of the (finished ) basement.

If I had the time I would have tried to tone it out. But I couldn't spend as much time as I'd like to trace this all down.

I'm posting this in hopes someone has come across a similar situation and may have come across a similar off-the-beaten-path problem.


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## backstay (Feb 3, 2011)

I didn't see a voltage check from H to EMT, G to EMT or N to EMT. And with a low resistance meter(Wiggy). You say the red isn't used at the garage. Is it possible that it's connected on the house end and that's what has started to go to ground?


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## Roger123 (Sep 23, 2007)

backstay said:


> I didn't see a voltage check from H to EMT, G to EMT or N to EMT. And with a low resistance meter(Wiggy). You say the red isn't used at the garage. Is it possible that it's connected on the house end and that's what has started to go to ground?


This is my though also.


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## 480sparky (Sep 20, 2007)

backstay said:


> I didn't see a voltage check from H to EMT, G to EMT or N to EMT. And with a low resistance meter(Wiggy). You say the red isn't used at the garage. Is it possible that it's connected on the house end and that's what has started to go to ground?



EMT is attached to the incoming ground of the UF. So H-G and H-EMT would be identical. I also used a lamp pigtail to see if anything unusual showed up. It lit up on H-N and H-G but nothing at N-G.

No voltage from anything to red.


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## backstay (Feb 3, 2011)

480sparky said:


> EMT is attached to the incoming ground of the UF. So H-G and H-EMT would be identical. I also used a lamp pigtail to see if anything unusual showed up. It lit up on H-N and H-G but nothing at N-G.
> 
> No voltage from anything to red.


So your ground at the house is open also. But you said there is no voltage between G and N? I would also check the current flow. What wire(s) is the return going through.


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## 3xdad (Jan 25, 2011)

480sparky said:


> Good noodle.... everything works as it should (lights, door operator, etc.)
> 
> My thinking is the UF is damaged under the slab and is starting to get a high-resistance short to whatever the sleeve is. I know there's a raceway through the slab, but it's probably just EMT or rigid to sleeve the UF and stops with the bottom of the slab.
> 
> But it's too sloppy of a mess to deal with today, plus the HO kinda kicked me out since he had to go to work and wouldn't let me investigate further. I'll hopefully be back next week


That's the thing. You really can't verify the N is good until you have time to really isolate that circuit. Good readings without a load have thrown me many times. (you have more skills than i, i'm just really curious as to what it is.)

Until you can get in there and see if the red on the MWBC is causing the problem or the EMT and whatever else ferrous pipe is the return, it's moot.

Let us know what it was.


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## Kaffeene (Feb 11, 2014)

What light up volt tester are you using? Is it the super senstiive low voltage kind? 
And what was the homeowner touching when the received the shock? EMT and other grounded object? 
Could it be stray voltage?


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## 480sparky (Sep 20, 2007)

backstay said:


> So your ground at the house is open also. But you said there is no voltage between G and N? I would also check the current flow. What wire(s) is the return going through.



If both the noodle and ground are open,then nothing would work.

Ground and neutral are not open. Power is flowing back through neutral.


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## Kaffeene (Feb 11, 2014)

Also did you do any readings between the ground rod and EG?


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## 480sparky (Sep 20, 2007)

Kaffeene said:


> What light up volt tester are you using? Is it the super senstiive low voltage kind?
> And what was the homeowner touching when the received the shock? EMT and other grounded object?
> Could it be stray voltage?



Couldn't tell you the brand off-hand, but it's a common one in this trade (but not Fluke).

HO is touching the 2-g switch box (between the entry door and garage door) and the track of the overhead door.

Stray voltage was my first thought, but a ground rod doesn't solve it. It just makes a nice pretty spark when hooked up.


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## chicken steve (Mar 22, 2011)

You need more time to poke around with this 480....

~CS~


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## Roger123 (Sep 23, 2007)

Well than, I agree with high resistance short. It sounds like the pipe is solidly grounded and there is still some amount of voltage on it, enough to cause it to spark, but not enough to open the OCPD. Put a heavy load on the system and see if your voltage collapses.


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## chicken steve (Mar 22, 2011)

I carry a bag of meters in the proletariat chariot , when i'm stumped like this i drag them all out because it makes me think _'oh yeah, i didn't check that.....'_:001_huh:~CS~:whistling2:


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## jarhead0531 (Jun 1, 2010)

I have a possible idea of what you are seeing, but first I will explain the situation I experienced.

I have the panel cover off in my own house doing something, and I decided to check current on line side conductors. One leg was 2, other leg was 4, neutral was 12. WTF?!?! 

I know my area of town still has full metal water pipes out to the street, I have an ufer, my cold water, and 2 ground rods (all in place before I moved in, guy was a welder). So I start walking around looking at other people services. The house next door that is rental has the oldest looking service, it is a rental, but my friend lives there so I knock on his door. Ask him if I can check something out in the basement. I put my amp clamp on the cold water pipe ground and find my stray 10 amps of current.

They call poco, they fix the problem at the bugs. Rental, and I don't like the owners or I would have fixed it myself.

You said the feed is in emt or ridgid through the slab, which is grounded to your emt. It is possible your problem relates to that emt being the "noodle" for a messed up service near by.

Try shutting off the main breaker, if you still have anything on that pipe, you are the noodle for someone else. Good luck finding that crap, god knows I got lucky.


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## aftershockews (Dec 22, 2012)

I have a feeling that your issue is not that circuit but upstream either at the house panels or the POCO.


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## Dennis Alwon (May 9, 2009)

Disconnect the equipment grounding conductor in the UF and see if you are still energized. If so and the emt is connected to metal pipe in the ground then you may have transient voltage that is in the earth from the power company or from the UF as you suggested


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## pete87 (Oct 22, 2012)

480 , break at 12/3 wire connection and work back towards house .

In think 12/3 feed originally fed a light at garage , switched also at the house . Everything compounded from there with hack wiring .



Pete


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## MTW (Aug 28, 2013)

Open MGN's are the primary cause of stray voltage, so that's my vote.


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## Breakfasteatre (Sep 8, 2009)

what is an mgn? sometimes the excessive use of acronyms is frustrating


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## aftershockews (Dec 22, 2012)

Breakfasteatre said:


> what is an mgn? sometimes the excessive use of acronyms is frustrating


*M*y *G*randmother's *N*aked?


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## Breakfasteatre (Sep 8, 2009)

multi-grounded neutral. Google actually pulled through with an acronym!


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## Black Dog (Oct 16, 2011)

aftershockews said:


> *M*y *G*randmother's *N*aked?


:laughing::laughing:


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## Black Dog (Oct 16, 2011)

480sparky said:


> Couldn't tell you the brand off-hand, but it's a common one in this trade (but not Fluke).
> 
> HO is touching the 2-g switch box (between the entry door and garage door) and the track of the overhead door.
> 
> Stray voltage was my first thought, but a ground rod doesn't solve it. It just makes a nice pretty spark when hooked up.



Sounds like the garage door track is not grounded to the system and the equipment ground conductor is not connected or continuous to the main service.

Like you said the circuit is not a home-run to the main service, so I'm sure it's on the largest circuit in the house with 50 splice boxes, receptacles, switches, light fixtures.......


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## Breakfasteatre (Sep 8, 2009)

Im going to use this thread to help _my_ understanding, hopefully 480 doesnt mind.

I was reading that:

"The National Electrical Code (NEC) requires the neutral in the service disconnect and over current panel board to be connected to the earth also. Now the secondary neutral is connected to earth a second time. A parallel connection of the neutral to earth now exists permitting hazardous electric current to flow continuously uncontrolled over the earth."

Im not understanding why this would lead to an energized earth and in turn a safety hazard. Why is it choosing to travel to earth and not back to the transformer? Or is the referencing to the parallel path through the earth the path it is taking back to the transformer?


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## 480sparky (Sep 20, 2007)

Breakfasteatre said:


> Im going to use this thread to help _my_ understanding, hopefully 480 doesnt mind.
> 
> I was reading that:
> 
> ...



How is the (secondary, whatever that is) neutral connected to earth?


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## chicken steve (Mar 22, 2011)

Kirchoff's Laws are often misinterpreted in the _suggestion_ that current returns in the path of _least _resistance, where it is in reality taking_ any _path _relative _to it's resistance BreakfastDude.

Ergo, much of the physical world is a _conductor_ , very little of which is a true dielectric. The plot thickens when MGN , or MEN(multiple earthed noodles) enter Kirchoffs equation. The more proximal they are, or less R value they have (due to wet earth or PH) the more they conduct.

~CS~


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## wendon (Sep 27, 2010)

I take it you did pull in a grounding conductor and didn't rely on the EMT for grounding purposes? If the underground wire is going bad, you could be getting voltage on the grounding conductor. Any buried boxes????:whistling2:


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## 480sparky (Sep 20, 2007)

wendon said:


> I take it you did pull in a grounding conductor and didn't rely on the EMT for grounding purposes? If the underground wire is going bad, you could be getting voltage on the grounding conductor. Any buried boxes????:whistling2:


EMT is the ground from the first box on.


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## RIVETER (Sep 26, 2009)

If you read a voltage from emt to ground then look for a "pinched" neutral.


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## glen1971 (Oct 10, 2012)

What is the voltage from your new rod to each conductor in your 12/3 coming in, including the ground? Then between each conductor.. Maybe that will help pinpoint which leg is giving you the grief.. Is it possible to reach the main panel with a wire from your new ground rod? Verify voltages at the main panel too, see if you can see if the issue is upstream of your work... Is the HO ok with you determining which breaker(s) it is that feeds the garage? Just throwing some ideas out there..


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## CADPoint (Jul 5, 2007)

> Fast-forward to this morning. New owner calls and says he's getting shocked. But only when it rains.


If I missed it forgive me. You need to megger the line from the house to
garage. (I realize you didn't find the circuit)((old school it came of kitchen or bedroom))

The water or weather events is the key. It's a hot short to ground that is;
the hot is faulting on the race way that's into the earth at the garage with a weather event. You didn't discover what was feeding the out structure meaning what is exactly under or between the house and garage!

A fox and hound or some sort of circuit tracer that makes noise on circuit should be tried to isolate the feed to garage. Nothing short of isolation
of this circuit or a new circuit will stop this mess.

Seems there was nothing wrong with the refit it's what's between a shovel
and a new circuit is the only cure.


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## Kaffeene (Feb 11, 2014)

I was wondering about readings from the ground rod as well.


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## wendon (Sep 27, 2010)

480sparky said:


> EMT is the ground from the first box on.


Do you have a short somewhere down the line and a loose fitting, locknut, etc? Bootlegged neutral? Interesting problem but shouldn't be too hard to find if you can get back in the building.


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## Aegis (Mar 18, 2011)

I'm confused a little, did you kill the breaker feeding the garage and then check the EMT? Did you turn off the whole main panel in the house and check the EMT? 

I had a similar problem once, it was commercial and it was coming from another building.


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## Spunk#7 (Nov 30, 2012)

I have had sub-panels with remote ground rods that were very high resistance,causing all the metal to be energized,but would not trip a breaker. Solution was to run a new ground wire from the main panel to the sub panel. Have you checked all your EMT straps/boxes/screws/nails possibly coming into contact with a hot wire? Good Luck!


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## pete87 (Oct 22, 2012)

pete87 said:


> 480 , break at 12/3 wire connection and work back towards house .
> 
> I think 12/3 feed originally fed a light at garage only , switched also at the house . Everything compounded from there with hack wiring .
> 
> Pete



My bets are still with this . "Hacked Out 12/3 Lighting Feed ".



Pete


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## RIVETER (Sep 26, 2009)

Did you get the answer you needed?


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## 480sparky (Sep 20, 2007)

Haven't been back yet.


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## boots 211 (Aug 21, 2009)

You did this work years ago, I would wonder if anything was done in the house, lately. Does house have k/t wiring, maybe someone mixing wires and catching a back feed on k/t


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## hardworkingstiff (Jan 22, 2007)

Great thread, I hope to see the answer Ken.


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