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Old 11-14-2008, 01:49 PM   #1
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Electrified Wall?


I have an 100 year old house that has one lighting circuit that controls most of the ceiling lights in the entire house. Yesterday all lights on that circuit stopped working so I checked the breaker but it was not tripped. I pulled a three way switch to check for power at that location (using a Fluke VoltAlert) and found out that not only was there power at that box but I would get an alert if I moved the tester anywhere within 4 inches of wall (up to 3+ feet away from the box). Seeing as the minimum reading to activate the VoltAlert is 90 VAC I am guessing I have a melted/ broken/ damaged hot wire somewhere in the wall that is touching the inside of the wall. I have since turned off the breaker and want to start troubleshooting the circuit tonight.

The circuit only has a hot and a neutral. There is no seperate ground.

Why didn't the breaker trip?

I am guessing that I need to figure out where power is fed from then check for continuity between each wire from fixture to fixture to see where there may be a break? If so then open up the wall and replace the wire?

Any other possible senarios to cause this type of issue? Thanks.

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Old 11-14-2008, 02:01 PM   #2
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all lights on that circuit stopped working
the breaker . . .was not tripped.
Why didn't the breaker trip?

There was no short or the breaker is bad, either one or both.

Any other possible senarios to cause this type of issue? Thanks.
Breaker contacts have failed to an open state?
Try slamming the breaker handle on and off a few times. A guy at the electric supply counter did this once, which taught me something and saved my customer $38.

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Old 11-14-2008, 02:57 PM   #3
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Electrified Wall?


First I'd try slamming the breaker like yoyizit said. (no, don't hit it)

What you need to do is check for voltage with a multimeter, I do not trust those touch meters. It could be a bad splice...have you done any drilling, nailing, working in the attic, etc.?

The wall (assuming it is sheet rock) can't conduct electricity unless you put 7.2 kv trough it or something, thats 7080 more than your standard outlet voltage!
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Old 11-14-2008, 04:32 PM   #4
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Electrified Wall?


Jeez how many times does this problem occur? 4 or 5 a month on this site maybe more.

If you have power present in your electrical device boxes but nothing works you have an open neutral in the branch circuit somewhere. In this case it sounds like he has lost the entire branch circuit. So his open is between the first device box on the circuit or junction box and the panel.
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Old 11-14-2008, 04:32 PM   #5
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...
The wall (assuming it is sheet rock) can't conduct electricity ...
The OP has a 100-year-old house. The wall is not likely to be sheet rock unless it's a recent addition. It could very well be plaster over metal lath.
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Old 11-14-2008, 04:46 PM   #6
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Very true and he has no equipment ground to trip a breaker so it is possible that he is faulted to the metal lathe and lost the hot to the circuit. I would check to see if I had power in some of the other boxes on the circuit. If so I'm still betting on open neutral. But it sure sounds like the metal lathe might be energized. I didn't catch the 3 foot from the box statement.
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Old 11-14-2008, 04:56 PM   #7
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Oh, I didn't catch the 3 ft away part...is there any chance you could shut the circuit off and carefully chip away some plaster to get to the lath? Then use a multimeter to test between the lath and a neutral.

I do not recommend anyone looking in the panel while its energized! Unless they are experienced and comfortable with electrical work.
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Old 11-14-2008, 05:28 PM   #8
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Electrified Wall?


Before tearing open your wall, I would suggest testing other switches and see what you get. Also trace wiring in the attic/basement if you can.

The wiring should go in some logical manner from one device to the next. So you would get power up to a certain point, then no power.

If you verify that power is in fact lost at that point and the wire is not going into another wall on the back side of that wall or terminating on the back side of that wall at a light fixture, etc., then maybe there was a splice in the wall at that location.

This was common with knob and tube wiring, although all the splices I have seen were done quite well! But who knows what someone else might have come along and done later (inside the wall).

FYI - A circuit breaker will only trip if there is a short. Not if a wire breaks.
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Old 11-14-2008, 06:33 PM   #9
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FYI - A circuit breaker will only trip if there is a short. Not if a wire breaks.
Not likely if he has an fpe...
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Old 11-14-2008, 10:34 PM   #10
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but I would get an alert if I moved the tester anywhere within 4 inches of wall (up to 3+ feet away from the box)
About the voltage detector, static charge can set them off. I have those white plastic tables with folding legs, and if I move my voltage detector across the plastic surface, it goes off.

Without knowing more about the situation, you should assume it's a true reading though, until proven otherwise. Best to be safe.
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Old 11-15-2008, 04:53 AM   #11
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I carry a light stick (fluke non contact AC detector) in my pocket all the time, but I don't use it to troubleshoot. If you were testing it at a 3 way switch, both of your travelers will always set it off, and both sides of any switch leg (once you get used to this you can figure it out by spreading the wires apart and seeing which one lights up first). The cable doesn't even need to have any power on it and your light stick will go off if it is run next to (bundled) another cable for any length (induced voltage).

The point about "3 feet away" I wouldn't worry about either because you might be reading the cable feeding the box through the wall.

Sometimes you can put it close to the conductor, get it to light up, and then pull it much farther away and it stays lit.

In other words, nobody can give you a true answer, without guessing, as to what is really going on until you get a "contact style" tester and check the circuit out.

Go and get yourself a solenoid style tester if you're going to do any electrical work.

Now I know you're going to go out and get a Digital multimeter because it looks much cooler, but you're going to have the same problem because the "Dead" leg will still show a voltage only a few volts less, or you're going to see 115 and then miss the little "mv" next to it.
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Old 11-15-2008, 04:55 AM   #12
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Now I know you're going to go out and get a Digital multimeter because it looks much cooler, but you're going to have the same problem because the "Dead" leg will still show a voltage only a few volts less, or you're going to see 115 and then miss the little "mv" next to it.
That never happens with my analog!
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Old 11-15-2008, 05:07 AM   #13
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One of the best industrial electricians I've ever worked with did the little "mv" error many times. The guy was practically a genius when it came to troubleshooting, but I guess because he was always in such a hurry he missed those little things some times. That's why most maintenance electricians keep the fluke in the shop on the bench.
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Old 11-15-2008, 05:09 AM   #14
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That never happens with my analog!

I missed the "analog" part, You really are old school. Cool
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Old 11-16-2008, 12:56 AM   #15
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I missed the "analog" part, You really are old school. Cool
I keep meaning to get around to buying one of those fancy auto-scaling digitals, but I never get a round-tuit. So I have cheap digitals that I hate and a nice analog that I love.

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