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Old 09-06-2010, 07:07 PM   #1
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leakage from 1 house circuit to another


I successfully installed a GFCI in my kitchen, so proceeded to start another in the bathroom. Turned off its circuit breaker and pulled the outlet out of the wall. Happened to switch the light switch on and the light didn't go on but an LED night light in another socket that should have been cut off by the circuit breaker turned on in a flickering way. So I started measuring voltages. Found 120 v from white conductor to ground (bare) even with the circuit breaker off.
I turned off the circuit breaker for the hallway outside the bathroom and now the 120v is gone.
So I'm assuming that somewhere the two have been wired together by mistake. Is there any other explanation? Advice on how to track this down? Just have to start isolating subcircuits, I guess.
TIA, Roy

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Old 09-06-2010, 08:42 PM   #2
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leakage from 1 house circuit to another


Put everything back together and figure out which lights and receptacles are controlled by each breaker.

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Old 09-06-2010, 09:44 PM   #3
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leakage from 1 house circuit to another


I've already mapped the switches and outlets to each breaker. I have the correct breaker turned off but there is still voltage from the white wire to ground (not from black to ground).
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Old 09-06-2010, 10:39 PM   #4
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leakage from 1 house circuit to another


The white wire could be loose somewhere and it fails to conduct current back to the panel neutral bus bar. Then any light or appliance turned on in that circuit will make that part of the neutral (white) wire live relative to ground.

What happens if you connect an incandescent light of at least 25 watts between that white wire and ground? (Use short lengths of wire with alligator clips on the ends)
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Old 09-07-2010, 12:58 AM   #5
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leakage from 1 house circuit to another


Sound like you have MWBC { MultiWire Branch Circuit } there if that the case you will have loose netural somewhere in that circuit so start at the load centre to make sure you have good connetions then work it way out and if you have any backstabbed receptales then it is a good time to move them over to screw connections.

The quickest way to tell if you have MWBC is look at the breaker if you have red and black then it good possiblty that you have MWBC there.

And yeah it is pretty common do that with pretty long runs escpally on second floor. but once you get into AFCI requirement then it will change everything.{ The AFCI do not work very well with MWBC unless you have two pole AFCI breakers that will cost a bit of money for that one ( About 30 to 100 euros or so )

Merci.
Marc
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Old 09-12-2010, 10:26 PM   #6
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leakage from 1 house circuit to another


Thank you all for your helpful suggestions, especially the information about the MWBC which was news to me. I haven't yet resolved the issue and I have limited time to work on it, but I will post a result when I have one. I checked my electrical panel and I don't have any red wire connections. I do have a single black wire amongst all the white & copper wires connected to the ground bus, not sure what that is about. Seems like all of my electrical outlets are backstabbed, so I have a lot of checking and pigtailing to do.
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Old 09-12-2010, 10:31 PM   #7
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leakage from 1 house circuit to another


If they were backstabbed move them to the screws that is the most common cuprit I have see it {the backstabbed devices have spring to hold the conductors and over the time they will loosen up a bit }{ backwired device are diffrent they will use pressure plate with screws }


And make sure you don't run into borrowed circuits or crossed circuits they are very tricky to deal if not carefull but for now let start with basic items and work it way up so do the receptales and switches first and at the same time check the wirenuts inside the junction box to make sure they are not loose at all.

Merci.
Marc
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Old 06-05-2011, 10:56 PM   #8
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leakage from 1 house circuit to another


FYI, I found the source of this problem. A hallway ceiling light has 2 switches. The original installer used only a 2-wire traveler between the switches, so no room for a ground wire. The 2nd switch box also had another circuit running thru it which had a ground, so they borrowed the 2nd circuit's ground (white wire). So power off in the 2nd circuit still left electricity flowing into the white ground wire from the first circuit.
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Old 06-06-2011, 05:39 AM   #9
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leakage from 1 house circuit to another


Quote:
Originally Posted by rdc View Post
....., so they borrowed the 2nd circuit's ground (white wire). So power off in the 2nd circuit still left electricity flowing into the white ground wire from the first circuit.
The white is the neutral, not the ground.
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Old 06-06-2011, 08:01 AM   #10
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leakage from 1 house circuit to another


White is neutral and not ground. Borrowing that from another circuit is not permitted.

Borrowing the ground (bare or green wire) from another circuit is permitted.
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Old 06-07-2011, 02:16 AM   #11
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leakage from 1 house circuit to another


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White is neutral and not ground. Borrowing that from another circuit is not permitted.

Borrowing the ground (bare or green wire) from another circuit is permitted.
That is the best answer in the fourm and I used that golden rules as well.

Merci,
Marc

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