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#20332 - 01/13/03 02:22 PM Finding the other end of EMT
maintenanceguy Offline
Member

Registered: 12/02/01
Posts: 303
Loc: Southern NJ, USA
In a 100K sq ft facility, I've got three breakers that all tripped at once. The only thing common to these breakers is that the circuits they serve all leave the panel through the same conduit and these are the only circuits in this conduit. These serve an area of the building several hundred feet from the panel.

I've been able to isolate the three circuits by disconnecting devices to know that all the wires are probably shorted to ground and each other within this conduit run. I need to pull new wires but I can't find the other end. The conduit disapears into the concrete slap and the circuits show up inside a wall in another area as romex. I spent probably 4 hours today in drop ceilings, and attic spaces trying to follow this circuit and It's just not accessable enough to be sure I'm following the same wires.

I need to find where the conduit leaving the panel ends up. With probably a hundred pieces of emt leaving this distribution room, this is a challenge. Any tips?

Tone generator won't work with the wires shorted to ground. The best idea I've come up with is to blow air through the pipe with an air compressor and walk around listening for the hiss. Pretty poor idea.

Any suggestions appreciated.

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#20333 - 01/13/03 02:53 PM Re: Finding the other end of EMT
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
A circuit tracer (Greenlee) may solve your problem. Or if the run is not too long, how about a fish tape in the pipe.

If the circuits change to RX, did you open any other devices to look for the spot it changes?

A last resort may be to abandon it, and repipe & refeed it.
John
_________________________
John

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#20334 - 01/13/03 03:39 PM Re: Finding the other end of EMT
Wirenuttt Offline
Member

Registered: 11/10/02
Posts: 267
Loc: Massachusetts
Nothing wrong with blowing air in the pipe. I think it's a good way to indentify the run as well as pushing any dirt, dust and possibly water out the other end.
~Ange

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#20335 - 01/13/03 04:38 PM Re: Finding the other end of EMT
lighthouse Offline
Member

Registered: 01/02/03
Posts: 141
Loc: philadelphia pa 19125
maintenanceguy...i have a question.is this a 3phase panel.the reason i am asking is that maybe it's a motor that shorted and someone installed 3 single pole circuit breakers instead of a 3 pole cb.you can check exhaust fans ,pumps,etc..not the first time i seen this happen.if this is a new building check the oringinal prints on the panal circuit layout.you may get lucky.

what equipment is not working?????

the greenlee circuit tracer is a real good idea. ampprobe puts out one too.

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#20336 - 01/13/03 06:16 PM Re: Finding the other end of EMT
maintenanceguy Offline
Member

Registered: 12/02/01
Posts: 303
Loc: Southern NJ, USA
It is a 3Ø panel but these are 120V 1Ø loads, two are for recepticals and one circuit feeds three single phase exhaust fans on the roof. And these aren't adjacent breakers.

The building's aobut 20 years old and the prints show circuit numbers but not conduit runs. And there aren't any as-builts anyway so they aren't real accurate.

We do a little telco work and I've got a couple of toners/amp probes but can't use them here because the wires are shorted to the conduit. So everything in the buildng has tone when I hook it up. Is the greenlee circuit tracer likely to work where these won't?

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#20337 - 01/13/03 06:57 PM Re: Finding the other end of EMT
harold endean Offline
Member

Registered: 02/16/02
Posts: 2248
Loc: Boonton, NJ
I have a crazy idea, (as long as there isn't a lot of smoke detectors that is.) how about blowing an orange smoke through the pipes. You should be able to detect that pipe somewhere. (You also might scare a few people if they don't know about the test.)

Harold

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#20338 - 01/13/03 07:31 PM Re: Finding the other end of EMT
lighthouse Offline
Member

Registered: 01/02/03
Posts: 141
Loc: philadelphia pa 19125
maintenanceguy.the greenlee or ampprobe tracer.(not your voltage/amprobe) will locate the short in the conduit.
ground/floor/ceiling.but you have to follow the path of the signal.

with the wires connected on the circuit breakers did you try to turn on one at a time.?did it hold or trip???

did they pull one neutral for all 3 circuits or 3 neutrals

check the exhaust fans,you said there are 3 of them.go to the first 1900 box closest to the panel and disconnect the wiring for the fans and check again for a short at the panel.

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#20339 - 01/14/03 12:13 PM Re: Finding the other end of EMT
Pearlfish Offline
Member

Registered: 09/12/02
Posts: 83
Loc: Chicago Ridge, Il, USA
Just my $.02

What probably happened is your foundation settled and pinched off your conduit. It wont be any good to you, even if you did find it. In the time you have spent pursuing an un-tamed ornathon, you could have run a new conduit. Put down the tick tracer, go get your bender and get to work!

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#20340 - 01/14/03 01:22 PM Re: Finding the other end of EMT
Wirenuttt Offline
Member

Registered: 11/10/02
Posts: 267
Loc: Massachusetts
Is it just me or is ornathon some word from some other language???

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#20341 - 01/14/03 06:28 PM Re: Finding the other end of EMT
dugmaze Offline
Member

Registered: 12/18/00
Posts: 46
Loc: St. Louis
I work in a factory too and have never had a circuit tracer work one time. I could pick up 3 or 4 good signals out of 50 breakers and still have none of them be the one.

I've even shut off the breaker to turn off lights, went to add in wiring and find it still hot from another breaker. Unforunately there are a small percentage of electricians that do some weird stuff.

I know in my factory we can't get engineering to update prints so when you run into these hard problems it makes it even harder to work on.

I like the orange smoke trick.

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