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Backfeed Mystery?

2751 Views 6 Replies 4 Participants Last post by  Inner10
For those of you who like troubleshooting read on. Those who don't stop immediately.

Brief Summary

Customer leasing space in old house (Built 1892) 3,000 sq ft. Rooms made into offices. 200 amp service with old Wadsworth panel and a 100 amp sub off of that. Luckily, old K&T has been cut out. Unluckily, some hack has rewired the place. Lot's of MW circuits (normally not a problem, but a Hack = MW circuits = Problems). Approx. 90 circuits. Meter was disconnected from last tenant for approx. 1 yr. We just showed up to hang some fixtures and a couple circuits and be on our way. Noticed at least 30+ J-Boxes above acoustical and in basement. Oh, the sub-panel was wired off the line lugs of main with an seu 6-2 bare ground??? We fixed that straight away. I scrounged up an old Wadsworth in garage and at least got it on a breaker with a 4 wire. Basically, this place is a huge electrical booby trap.

Here's what happened:

Meter put back in. Main panel fired up. All's well. As we fired up all circuits (while turned head), no shorts....til the LAST ONE! We were just about to leave job. Anyhow, here's what we do know. It is a 12/3 on 2 Sp 20 amp Breakers. At first, just thought it was a short. After brief looking around went back and phase A conductor was hot even when breaker was off. Turned off phase B and still shorted. Traced the wire forward in basement to a j-box. The 12/3 was spliced to 2- 12/2's. We followed the culprit and the last we saw it turned up into an exterior wall heading upward. We tried locating it by the old fashioned method but to no avail. It could be anywhere. So, basically all the conductors are live now even with the culprit (which we disconnected from breaker). Someone has obviously spliced it somewhere. THe only thing that is off is multiple 2nd fl lights and some kitchen rec. and even and orange isolated ground rec. is not on. Even if we continue on monday this could take days to open up everything in place and even if we look at everything to rule out it could be in a hidden jbox behind drywall in a nightmare place like this. I really love and hate these things. Haven't opened up things yet but it appears the lights and receptacles are probably on some old 50's wiring spliced with 70's or 80's somewhere. It was wired hot to lights first as well. This is like a booby trap minefield. I wanna run...but I wanna fix it as well.

The owner is somewhat frugal on this project so any extra tips to get to the root of this quicker will be appreciated. I had a good streak going for a while getting it in first few boxes but, last couple job's it was like the 30th or last one.

And by the way. This is only from what I hear from others. What is point you cut your losses and refeed from another source (cheat in a sense). 1hr ,1day, 5 days ?? Lately, I've been using the analogy to customers, When you go to the emergency room with a stomach ache, do you want them to solve the problem or just give you some pepto bismal and be on your way. It's your choice. Legally, I should probably just run and have him call someone else because when or if the place burns down they always blame the last electrian there not the 20 hacks that were before them.

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Pigtail both wires to one breaker.
Let me get this straight so we are on the same page, you rewired the sub panel feed from the main panel due to improper installation? The main panel is live/powered up and you are now powering up the sub panel when you find this short/backfeed? If the wire in the sub panel is unhooked from the breaker but still live then i would go to the main panel and begin turning off breakers one at a time until the suspected circuit is dead, this will at least let you know what circuit it is spliced into. I am guessing that when you rewired the sub panel you switched the two hot legs so the splice is no longer on the same feed/phase. I apologize for not using correct terms so i hope you understand what i mean.
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Yes sir. You got it right. The live conductor (short) It's tied into some random circuit from main panel on phase A. That circuit controls a hodge podge of items from basement lights to 1st floor rec. to 2nd and 3rd flr misc things and the mw circuit was on opp phase. We only refed sub panel not rewire.
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I'm no electrician but I'd throw the power on the main breaker and using a toner or continuity meter with one end on hots of the 12-3 and check all the wires going into the main pannel until you find the one that its spliced into.

Then disconnect both from the pannel throw your toner on it and trace the wire until you find where they are both spliced.

Doesn't sound too tricky but things like this can eat up a day REALLY fast.
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Thanks inner. We actually rang the whole thing out initially. There were 17 circuits showing shorts with all switches, pull chains, items off that we could see. There is probably a bunch of plug in air fresheners and padlocked attic we don't know about or something to that effect. We just flipped it all on and I"m suprised only 1 short. I did take that wonderful advice from 480 though. Although, this seemed to happen all over most boxes (below). I told the owner not to worry about it, it's normal operation.


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Thats when you bust out the ohm meter, lights and other electrical gadgets should read much higher resistance then a splice which should be pretty darn close to a dead short.

Like I said I'm no pro but I have to deal with alot of this weird spliced crap in my line of work. Nothing worse then being stuck, but no better feeling when its fixed.:thumbsup:
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