Switch polarity question (electrical)

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Up in the attic. Have to bring hot wire to junction box with three legs going out. Each leg goes to ceiling light of different rooms. YES, I can power them up and the wall switch in each room turns on its respective light. BUT, what's an easy way to test that I don't have hot and neutral reversed. The old romex in the attic (two wire, cloth wrapped) is NOT color coded in any way.
Do I simply drag a neutral wire from a different circuit and probe the bulb socket in each room? Is there an easier way? My A.C. voltmeter obviously does not indicate polarity.
All replies appreciated. Sheetrock guy is coming tomorrow a.m. and I have to solve this today!
Ivan Vegvary
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Ivan Vegvary wrote: ...

Every old cable I've seen is coded in some way -- how else could they have kept track originally, either?
Look for a stripe, a ridge, something that distinguishes the orientation of the cable itself.
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Ivan Vegvary wrote:

better, drag a wire from a good ground (water pipe) and check voltage against that. Heck, if you're in the attic, why not just add supplemental grounds and/or pull new romex to replace the old cloth NM? If you can't pull the whole circuit, do what you can and then wire a supplemental ground from where you started repulling. Best would be to take it back to the breaker box but if you can't do that any ground point is acceptable per code (unless they've changed it recently.) Only thing that *wouldn't* be acceptable would be to repull some of a circuit so it would appear to be grounded but to not actually connect the ground wire to a real ground.
nate
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Well, some local codes have problems with things like that, but ... when it's that old you aren't likely to get much objection to improving the safety of the ckt if that's all you can afford or manage. I've even seen some knob & tube with earth grounds.
That's a good point; if the insulation is that old, beware the insulation falling apart in your hands and possibly already being missing from some parts of the wires. Especially if there have been any varmints running around there.
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Ivan Vegvary wrote:

I'll assume that the presence of two wire romex means that none of the outlet boxes themselves are grounded, so you can't use them to test against.
No warranty on this advice, but if you're using an "electronic" (digital) voltmeter, and are standing on something which insulates you from ground, then you can jsut touch one of the voltmeter leads with your hand and probe the shell and center contacts of the sockets with the other lead.
Your body capacitance will provide enough of a load to cause the voltmeter to indicate some voltage when it's lead is connected to the "hot" side iof the line. It probably won't read the full 120 volts, but enough so you can easily tell the difference.
There are commercial testers which will do what you want to do, if you want to spring a few bucks for one:
http://www.tecratools.com/product492.html
But, if you've already got a sensitive AC voltmeter, try my suggestion.
Jeff
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Jeffry Wisnia
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THANKS JEFF!!!!!!!
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wrote:

They also make what is called a touch voltage tester. I don't know if you can get them at builder supplies but you can get them at an electrical supply.
http://www.ehow.com/how_2237961_test-for-voltage.html
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wrote:
[snip]

Would that be the same as the $5 testers sold for holiday light strings?
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Yessir!
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Even if you are using a real cheap neon tester, this method works to find a hot wire, Just hold the end of one lead and touch the other to the wires, the neon bulb will light up dimly when you hit a hot wire. You won't feel a thing.
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Good suggestion; that also helps with the confusion sometimes that phantom voltages present.
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wrote:

There are plug-in inexpensive testers to tell you from hot and neutral. Many just plug into an outlet, but I'm sure you can get one of those screw-in sockets that would allow you to plug the tester in.
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Phisherman wrote:

I believ those only work if they are used on a circuit with a ground available. I don't see how they could work with one of those screw-in socket adapters.
Someone please correct me if I'm wrong, please.
Jeff
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I can't speak for all of them, but mine works on two wire/no earth. In fact, missing earth is one of the light sequences, right along wiht a "missing" neutral. It can identify any of the 3 wires are missing. I suspect they all can, no? This is just a cheapie Radio Shack tester. GB is the only mfg ID I see on it.
It's also my second one; the first one grew legs apparently.
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Twayne wrote:

If there is no ground it will tell you that.
But unless you have one I haven't seen, if there is no ground the tester won't tell you if there is a H-N reverse. That is basically what Jeff asked.
It won't tell you if there is a high resistance (useless) ground.
In an unusual case of N tied to G (which some idiots do when there is no ground available) and a H-N supply reverse it will indicate "normal".
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lol, not for long once the power is turned on!
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On Mon, 1 Dec 2008 15:54:45 -0500, "Twayne"

Semantics. If the "u" ground on the receptacle ic connected to the neutral, either at the plug or the panel, everythiing will work fine except the case of every grounded device connected will be HOT.
If, however, the neutral is connected to a functional ground, and the H-N wires are crossed, breakers and/or fuses will complain immediately upon power-up.
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wrote:

Actually a cheap NEON tester can tell you a LOT. It will tell you which side is "hot", if one is. (capacitive connection with your finger.
It will tell you if the ground is totally open (no "bright" light across the socket) and it will tell you if you have a significant ground problem (the ground side lights capacitively with a load plugged into the socket)
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But the plug-in testers assume that you have a 3-wire outlet to work properly.
Bob H
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I always have my little inductive tester with me to figure out which wire is hot. You just touch it to the insulation and it only gives an indication on the hot wire. It can also read through the outer jacket on Romex. I've used several brands over the years, but have found the Fluke model to give the least amount of false readings. http://us.fluke.com/usen/products/Fluke+1ACII+VoltAlert.htm?catalog_name=FlukeUnitedStates
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