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Old 10-12-2011, 06:52 PM   #1
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Outlet - 2 white wires have 10v?


I installed a new outlet (changed colors, same manufacturer) in a wall and made sure I tested the wires with a voltmeter to be safe.

There are 3 wires, 2 white, 1 black.

Voltmeter:
Touching ground to either white wire and the black gets 120v
Touching the two white wires together gets ~10-15v

Why are the two white ones outputting voltage?


Last edited by lferrante; 10-12-2011 at 07:54 PM.
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Old 10-12-2011, 07:08 PM   #2
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Outlet - 2 white wires have 10v?


Digital meter? It will give a phantom voltage from capacitive coupling.
Why only one black? Normally blacks and whites come in pairs.

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Old 10-12-2011, 07:14 PM   #3
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Outlet - 2 white wires have 10v?


You may have broken off the tab between the white wires. You should not get any potential difference between 2 conductors that are physically connected together.

Or are you measuring voltage with the receptacle removed?
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Old 10-12-2011, 07:17 PM   #4
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Outlet - 2 white wires have 10v?


Analog meter.

I didn't take a good look in the receptacle, but what was connected there before was two white to the line side, and 1 black to the hot side. There are no ground wires.

They are probably capped inside, maybe I should go take a picture.

Yes, I tested with the wires exposed.

House is old, 1960's
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Old 10-12-2011, 07:36 PM   #5
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Outlet - 2 white wires have 10v?


Here are photos. First picture on the left is the wall, and you can see the backside from the mirror.

Odd, 1 orange, 1 black, 1 blue, 1 red, 2 white. They come up then down somewhere. Why isn't there a ground?








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Old 10-12-2011, 08:20 PM   #6
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Outlet - 2 white wires have 10v?


It looks like the wire come thru conduit, which which would be the ground path.
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Old 10-12-2011, 08:44 PM   #7
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Outlet - 2 white wires have 10v?


[quote=lferrante;747497]Analog meter.

but what was connected there before was two white to the line side, and 1 black to the hot side.

Huh
The hot IS the line side....what am I missing?
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Old 10-12-2011, 08:50 PM   #8
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Outlet - 2 white wires have 10v?


You have what appears to be an illegal connection there. Those white wires are the neutrals of a multi-wire circuit. Separating them can cause havoc downstream on the other circuit(s), due to backfeeding from the other loads.

The remedy here is to wire-nut those white wires together, along with a single pigtail to your receptacle.

NEVER, EVER, disconnect them again, with the other circuits still live!!
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Old 10-12-2011, 09:24 PM   #9
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Outlet - 2 white wires have 10v?


Sorry, I meant "white wire" which is what's on the back, not "line"

kbsparky- I turn off the other breakers when I do this, just to be safe, but I had no idea that it could be a problem. How does that work? What kind of problem can it cause? I don't think there was anything else on that circuit anyway,at least nothing in sight on an outlet- small place.

I'll get a wire nut and a pigtail.


Any ideas why I get 10-15V when I use the volt meter on the two white wires?


[quote=Missouri Bound;747557]
Quote:
Originally Posted by lferrante View Post
Analog meter.

Huh
The hot IS the line side....what am I missing?

Last edited by lferrante; 10-12-2011 at 09:33 PM.
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Old 10-12-2011, 10:54 PM   #10
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Outlet - 2 white wires have 10v?


"Any ideas why I get 10-15V when I use the volt meter on the two white wires?"


Ill take a semi-educated guess here. Your two white wires are neutrals. The reason they only measure 10-15v is they are not "hot" wires and never were intended to be. Your measuring a voltage potential between your neutrals . And that shouldnt ever be a large number unless you have seriously imbalanced the load on the panel. Someone got sloppy and landed them both under that terminal. They should be pigtailed as Sparky suggested.
The reason you shouldn't EVER pull a neutral off a "hot" circuit is it can arc, and really mess up your day.

If im off course here, any pros feel free to correct me
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Old 10-13-2011, 01:23 AM   #11
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Outlet - 2 white wires have 10v?


Quote:
Originally Posted by socketman View Post
"Any ideas why I get 10-15V when I use the volt meter on the two white wires?"


Ill take a semi-educated guess here. Your two white wires are neutrals. The reason they only measure 10-15v is they are not "hot" wires and never were intended to be. Your measuring a voltage potential between your neutrals . And that shouldnt ever be a large number unless you have seriously imbalanced the load on the panel. Someone got sloppy and landed them both under that terminal. They should be pigtailed as Sparky suggested.
The reason you shouldn't EVER pull a neutral off a "hot" circuit is it can arc, and really mess up your day.

If im off course here, any pros feel free to correct me
Well, not really. If this is a multi-wire branch circuit (MWBC) as was suggested, then the neutral carries load current from more than one circuit on opposite legs of the service. Disconnecting the neutral of a MWBC can be catastrophic. First, if you only turn off the breaker that feeds one half of the circuit, the neutral may still be carrying load current from the other half even though you think the circuit is de-energized. If you open the neutral and touch it, you'll get shocked. Second, interrupting the neutral on a MWBC while both circuit breakers are on will place both halves of the circuit in series with each other and a 240V source. Thus, the voltage on each half of the circuit can vary wildly from zero to 240V - which can instantly destroy anything you have plugged in to either half of the circuit. You are measuring 10-15V across the opened neutral connection because you got very lucky - the loads on the two halves of the MWBC were well balanced, so the voltage swing when the neutral was opened was rather small. If some different lights or appliances were turned on, the result may have been rather damaging.

Long story short: don't mess with the neutral connections on a MWBC. Learn to recognize when you're dealing with a MWBC and make sure you shut off both of the breakers feeding it before you do anything.
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Old 10-13-2011, 07:44 AM   #12
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Outlet - 2 white wires have 10v?


Quote:
Originally Posted by lferrante View Post
Any ideas why I get 10-15V when I use the volt meter on the two white wires?...
You are separating current-carrying conductors of a multi-wire circuit mid-stream.

First thing I want to know is why you even think you need to measure the potential between separated circuit conductors. Any measurement you get is irrelevant to the proper operation of the circuit(s).
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Old 10-13-2011, 10:06 AM   #13
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Outlet - 2 white wires have 10v?


Cool, thanks everyone. Makes sense.

Just need to wire cap those two white ones and run the pigtail so it's properly wired.

Thx


KBsparky - just to do it, curiosity. I'm not an electrician obviosuly haha.


Last edited by lferrante; 10-13-2011 at 10:12 AM.
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