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#129998 - 01/05/06 05:48 PM odd voltage readings
JohnnyGreenbomb Offline
Junior Member

Registered: 07/03/05
Posts: 2
Loc: Seattle, WA USA
In a new house I've been wiring I came across the following problem...
I was swapping some breakers around in the panel when I disconnected a neutral from the the neutral bar and I realized that the wire was energized. After testing voltage to this wire I read 120v to ground, minimal voltage to L1, and 240v to L2. I did some troubleshooting and found if I turned off the breaker to the circuit it shared the wire was no longer energized. next I pulled out all the plugs a switches on this circuit to check for a loose wirenut, scarred wire, and incorrect wire terminations on devices. Everything looked fine.
At the panel I retested to see if there was any change. there was, now from the problem nuet. to ground i read 14.6v, from L1 to the problem nuet. was 106.9v, and from L2 i got 135.1v. At the main lugs it all tested fine at 120v/240v.
the next step I took was to go to the outlet where where the homerun was first connected and disconnected the HR from the rest of the circuit. At the panel nothing had changed with a retest of voltage from before. also I did a continuity test between the black and the white and there was none.
In the attic I found the wire and began to inspect it. I found a spot where the insulation installers drove a staple into my cable. I pulled out the staple, stripped back the outer sheathing about 4" in each direction from the impact point, and seperated the conductors so they were no longer in contact. So I figured I had found the problem. How wrong I was. At the panel I retested again and still no change from my last reading.
1)What would cause the funky measurements of voltage that i have of 106v, 135v, and 14.6v?
2)Why wouldn't my problem have been resolved with removing the staple and seperating the wires from contact?
3)How come I never read continuity between blk and white with the staple in or out?
4) Could the cable have gotten damaged futhering into the wall where I cant see from the staple I found?

Any ideas? Suggestions????


#129999 - 01/05/06 08:47 PM Re: odd voltage readings
Joe of NJ Offline

Registered: 12/05/05
Posts: 24
Loc: West Orange, NJ, USA
When you disconect the neutral and the circuit is closed by any conected load (like a light bulb, for example) you read the hot wire voltage in the neutral. There is no current flowing through the circuit, so there is no voltage drop in the load.
From your words, everything looks fine to me.
The staple was never the problem, so the reading didn't change after you removed it.
Connect the neutral again and test, you'll see.


#130000 - 01/05/06 08:57 PM Re: odd voltage readings
JoeTestingEngr Offline

Registered: 11/04/05
Posts: 786
Loc: Chicago, Il.
I wish you wouldn't go lifting neutrals like that unless you want to start blowing up things! The readings you were getting are perfectly normal The neutral was not a problem until you lifted it. Your voltages still added up to roughly 240 volts. If you had lifted a shared neutral, you would have been able to cover the entire voltage swing by switching loads on and off of the 2 circuits. In your case, you lifted a return from a ckt connected to L1. This ckt had some loads on it. The resistance of those loads was close to zero when compared to the very high resistance of your meter. So you would expect to get roughly 0 volts to L1, 120 volts to ground and neutral, and 240 volts to the other leg.

#130001 - 01/05/06 11:14 PM Re: odd voltage readings
JohnnyGreenbomb Offline
Junior Member

Registered: 07/03/05
Posts: 2
Loc: Seattle, WA USA
Just to clear things up I wasn't randomly disconnecting neutrals. As I said earlier I was swapping breakers around. The person that originaly made up the panel placed the wrong circuit on an AFCI breaker. So I was simply going to swap the two breakers. I turned off the two breakers to be switched but the thing that I didn't account for was that the same person that made the mistake in the first place also connected the wrong
neut. to the AFCI breaker. It was connected to a bkr other than the two I had been swapping that was energized.
Also the staple and my questions I understand now are probably unrelated and I thank you guys for clearing the fog in my brain. It was hard for me to clearly think about what was really going on because I was convinced it was all related.


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