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Old 02-21-2012, 09:27 AM   #1
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Finding a back-fed breaker.. stuck!


I'm renovating a mid-50's house cape cod, and I've found a back-fed breaker in the panel. Quite by accident, actually. I'll skip the long story and tell you what I've got.

In the 100a main panel I have 2 20a circuits that I'm pretty sure were on the same phase, and they feed each other. After finding this, I removed one of the two breakers and capped the wire in the panel. So now I've got 1 20a breaker that, when on, causes that capped line to be hot.

I turned off every other breaker in the panel and went around with a voltage sensor and found each receptacle and light fixture (yes, there are both) that this line feeds (actually, these TWO lines). In a ceiling box for a fan/light fixture, there is a junction that sends power upstairs, so I removed the jog upstairs, flipped the breaker back on, and tested the capped line in the panel. Still hot. Confirmed that all the previously hot upstairs receptacles are now dead.

At this point, I started working my way backwards from the ceiling fan to each receptacle (and switch in one case), doing this:
  1. remove the old receptacle/switch
  2. leaving the line open, turn the breaker back on
  3. check the capped line in the main panel for current
  4. install new tamper-proof, self-grounding receptacle (or switch)
Each time I checked the capped line, it would be hot. I worked all the way back to the very first receptacle in the series, and when I did the steps above on that one, the back-feed went away (the capped line stayed dead). But of course, the entire series was unpowered, now. But this means that the only length of line in the whole run that I can say is good for sure is the first 10 feet from the main panel to that first receptacle... how can I find where these two circuits are meeting?



I'm considering doing a continuance test on each leg by disconnecting both ends and using an extension cord and my multimeter. The only thing this buys me over running current over it is isolation and the ability to check the neutral, though. Any better ideas?



Thanks!
Kevin
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Old 02-21-2012, 09:41 AM   #2
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Finding a back-fed breaker.. stuck!


Ditch the voltage sensor and use a meter or Wiggy style tester. The sensor may be giving you false readings.
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Old 02-21-2012, 10:22 AM   #3
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Finding a back-fed breaker.. stuck!


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Ditch the voltage sensor and use a meter or Wiggy style tester. The sensor may be giving you false readings.
yes...do this first. I suspect your "live wire" will go away. If not, check back with us, the connection should be easy enough to find, but it may take a while to trace every connection.
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Old 02-21-2012, 10:40 AM   #4
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Finding a back-fed breaker.. stuck!


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yes...do this first. I suspect your "live wire" will go away. If not, check back with us, the connection should be easy enough to find, but it may take a while to trace every connection.
I suppose I'll need to tell a bit of the "accidental discovery" story after all.

When I redid the kitchen, I ran new circuits to bring it up to code. The panel is an old cutler-hammer with a restriction bar, so until I could remove the bar, I couldn't get new breakers. I borrowed a breaker from another line in the interim, and after removing the black line from the breaker, I shoved it out of the way and it made contact with the side of the panel. Bright spots in my eyes for an hour and a big black scorch mark on my thumb.. could have been a lot worse. So.. it's definitely hot.
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Old 02-21-2012, 11:15 AM   #5
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Finding a back-fed breaker.. stuck!


If you have attic space maybe check there or in a crawl space could be a junction box somewhere.
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Old 02-21-2012, 11:32 AM   #6
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Finding a back-fed breaker.. stuck!


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If you have attic space maybe check there or in a crawl space could be a junction box somewhere.
Crawl space is possible. It was dark by the time I was ready to look in there. If there is a jctn box down there, I don't know what it's feeding, but it's definitely worth checking. Thanks.
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Old 02-21-2012, 11:48 AM   #7
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Finding a back-fed breaker.. stuck!


With AC wiring you cannot easily tell the direction of power flow, so I'm wondering if someone makes a backfeed tracer that uses a heavy DC current. With the main breaker off and a test load in place, DC would be injected into the system and the polarity of the small DC voltage drop along each piece of wire will tell you the direction of current flow.

It can be done with AC, such as finding which outlets are upstream of which others, but the method is hard to explain
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Old 02-21-2012, 12:40 PM   #8
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Finding a back-fed breaker.. stuck!


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Originally Posted by ink View Post
I suppose I'll need to tell a bit of the "accidental discovery" story after all.

When I redid the kitchen, I ran new circuits to bring it up to code. The panel is an old cutler-hammer with a restriction bar, so until I could remove the bar, I couldn't get new breakers. I borrowed a breaker from another line in the interim, and after removing the black line from the breaker, I shoved it out of the way and it made contact with the side of the panel. Bright spots in my eyes for an hour and a big black scorch mark on my thumb.. could have been a lot worse. So.. it's definitely hot.
Yeah, well that's another way to check.

I second the junction box in the crawlspace/attic. Worst case if you can't find the junction, is to connect both wires to the breaker (or pigtail together with a jumper to the breaker). That way you'll know everything is off when the breaker is off.
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Old 02-21-2012, 12:58 PM   #9
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Finding a back-fed breaker.. stuck!


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Yeah, well that's another way to check.

I second the junction box in the crawlspace/attic. Worst case if you can't find the junction, is to connect both wires to the breaker (or pigtail together with a jumper to the breaker). That way you'll know everything is off when the breaker is off.
I hadn't considered that. I'm sure it's bad practice, but now that I know what is on that circuit, I don't think it's going to be a load issue for a 20a breaker. You guys probably know better on that. Everything is 12/2; it's 10 receptacles, one light/fan fixture, and an exterior light.
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Old 02-21-2012, 01:32 PM   #10
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Finding a back-fed breaker.. stuck!


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I hadn't considered that. I'm sure it's bad practice, but now that I know what is on that circuit, I don't think it's going to be a load issue for a 20a breaker. You guys probably know better on that. Everything is 12/2; it's 10 receptacles, one light/fan fixture, and an exterior light.
It's a redundant wire. It's not hurting anything but you aren't allowed to put two wires under a breaker. If either wire is used, not both, are all the devices live when each wire is hooked up?...or just part of the circuit? Shouldn't be too hard to find if you start in the middle of the circuit, then keep going to the middle of whatever works.
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Old 02-21-2012, 01:35 PM   #11
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Finding a back-fed breaker.. stuck!


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It's a redundant wire. It's not hurting anything but you aren't allowed to put two wires under a breaker. If either wire is used, not both, are all the devices live when each wire is hooked up?...or just part of the circuit?
If either one, the other, or both of the breakers are on, then everything has power.

Quote:
Shouldn't be too hard to find if you start in the middle of the circuit, then keep going to the middle of whatever works.
That was my thought, too. 6 hours later, I still haven't found the bastage.
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Old 02-21-2012, 01:39 PM   #12
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Finding a back-fed breaker.. stuck!


If it's not in any of the device boxes, it's in a junction box somewhere.....or is the connection buried in your panel itself?
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Old 02-21-2012, 01:45 PM   #13
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If it's not in any of the device boxes, it's in a junction box somewhere.....or is the connection buried in your panel itself?
I'm holding out hope for a box in the crawl, then. It's not in the panel.. if I disconnect the line out from the first receptacle, keeping the receptacle hot, the back feed goes away. If I do the same procedure on (what I believe to be) the second receptacle, the back feed stays.

Could also be that the way that makes the most sense for the cable run isn't the way it's actually run. I'll need to disconnect all of the receptacles at once to properly check that, I suppose. Ugh.
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Old 02-21-2012, 01:47 PM   #14
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Finding a back-fed breaker.. stuck!


I have seen this before someone did some remodeling and tied two circuits together that were coming from the same bus.

Find a halfway point somewhere disconnect and cap the wires joining the two circuits. Or find the end and disconnect it.

This will require a meter turning both breakers and testing everything in the house marking everything that does not work outlets wall fixtures ceiling lights even check inside closets, attics, crawl spaces, outdoor outlets and cabinets.

Then one at a time take them apart removing one hot wire at a time cap them turn one breaker on. Test both wires and or contacts that you disconnected. and you should be able to find what joins them.
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Old 02-21-2012, 02:02 PM   #15
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Finding a back-fed breaker.. stuck!


Here's one way to do it, using a simple example. This method may work for you.

Let's say CB1 feeds outlets 1, 2 and 3 in order, with 3 being the most distant and CB2 feeds this string by being connected to 1, 2 or 3 but you don't know which.

With nothing plugged into the outlets you turn off CB1 and find that the outlets are still powered with identical voltages, let's say 120v. The voltages are identical because no current is flowing in the wires and so there is no voltage drop.

Put a 10A load on any outlet, let's say #3, and measure the outlet voltages.

-If all voltages are identical at slightly less than 120v, then CB2 is feeding that outlet. The voltage is slightly less because now there is a 10A load on CB2 and its wiring.

-If outlet #3 reads 116v or so and outlet #1 reads the ~120v then CB2 is feeding outlet#1 and the voltage drop across the hot line or the neutral line will be (120-116)/2 = 2v. Even if the ~120v varies a lot this 2v won't vary very much but to measure this along-the-wire voltage drop you may need to use one conductor of an extension cord as one of the test leads for your meter. There is virtually no current in this conductor so you can use any old skinny extension cord.
Outlet #2 will read some intermediate voltage, possibly close to 118v.

-If outlets #3 & #1 read 118v or so then CB2 is feeding outlet #2.

The drop from 120v to 118v will depend on the wire length and gauge.

Last edited by Yoyizit; 02-21-2012 at 02:09 PM.
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