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Old 08-24-2009, 10:40 PM   #1
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


There's a light fixture in my house where wires come out of one hole and they're twisted to wires that come out of another hole. Piggybacking on those twists was a light fixture. None of the wires have a color and all are jacketed in felt or something like it.

I'm sure I'm not explaining this right so I made a diagram with super cool mspaint:


The socket was disconnected from the wiring when I was painting and I don't remember how to reconnect. I've read that the base wire is supposed to go to hot and the thread wire is supposed to go to neutral. So naturally I tested the twists for hot and neutral and this is where I had a problem.

I used this device:


I tested the wiring by holding one of the twists to the right/hot prong and the other to the left/neutral prong. It tested as open ground so I assumed that I had correctly identified both hot and neutral twists. Just for the hell of it I reversed them and what is weird is that it also tested only as open ground, when I expected to see hot/neutral reverse indicator.

So I'm wondering, is maybe my tester bad? Is there some wiring anomaly that would explain what happened? I tried it several times with the same result. No matter which way I do it, there is no hot/neutral reverse. Could there be two hots, would that explain it? Wouldn't I have seen some indicator for that though?

I have a multimeter and I guess my next step is to try and use that to identify the hot wire(s). What I'm going to do is run an extension cord from another part of the house and then stick one probe needle in the female ground hole of the cord and the other probe needle on one of the twists. Any advice on using a multimeter? Should I be looking for a specific reading or just anything?

I've noticed some people connect light fixtures any old way, doesn't matter which wire runs to hot or neutral. But with these new fluorescent lights and their starters, and frankly as a matter of best practice, doesn't it make sense to make sure the base of the socket is to the hot wire?

I welcome any advice and suggestions. Thanks guys
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Old 08-24-2009, 10:47 PM   #2
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


the shell of the socket is connected to the neutral


simple test since you have a voltmeter

check from the bare wire to a ground source. If it show power, it is the hot. No power would be neutral.

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Old 08-24-2009, 10:51 PM   #3
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


Hi, I just registered here to ask a question and noticed your question. The three wire tester you used needs the ground to be able to tell the hot from the neutral, just like you need a ground to decipher which is which with your multimeter. If you have a sensitive digital multimeter you can usually tell which is hot just by probing with one lead. The hot one will read a very small amount of voltage while the neutral won't. Your idea to bring a ground to the area with an extension cord is sound, obviously the hot should read 120 volts and the neutral should read zero with reference to an earth ground.
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Old 08-25-2009, 07:51 PM   #4
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


You probably answered the question already using your multimeter (use only the AC volts settings when measuring with the power on).

But to use the orange receptacle tester you would do this:

Stretch a ground wire across the floor to the work location (junction box for the light), either a plugged in 3 wire extension cord or a long single conductor wire connected to a known ground. Connect the grounded wire to the round ground prong of the tester.

Connect one of the existing wire bundles (ends already twisted together) up in the junction box for the light to one flat prong of the tester. Connect the other bundle to the other flat prong. Hold the tester with prongs pointing away from you with the ground prong below the other two and wires or wire bundles connected to each prong not touching one other. Turn on the power.

If the colored lights on the tester now register "correctly" then the bundle connected to the flat prong on the right is hot and the other bundle is neutral.
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Last edited by AllanJ; 08-25-2009 at 07:53 PM.
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Old 08-25-2009, 09:43 PM   #5
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


Thanks guys. Allan, I did already use the multimeter. I was skeptical that the other tester was working properly.

I did suffer a very mild electrocution. I was undoing a mounting screw for the sconce and my hand brushed against the hot wire. Luckily my hand was dry and I was not sweating, which could have been much worse and I assume could have killed me (water=conductivity; conductivity + electricity + you = death). I tell this story because I would like to stress to other DIYers just how important it is to be patient and take the proper precautions(POWER OFF AND THEN DOUBLE CHECK WIRES ARE NOT ENERGIZED). Overnight I had covered the twists with wire nuts which was good for safety. And if you have kids I'd be careful because they like to unscrew stuff and play around(not an issue this high up).


EDIT (08/26/09): As noted in the posts below, electrocution is not the proper term when you are shocked. The proper term is electric shock. Electrocution means death by electric shock.

Last edited by Deck; 08-26-2009 at 07:45 PM.
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Old 08-25-2009, 10:32 PM   #6
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


Unless you're standing barefoot on the concrete or otherwise well grounded a shock like that is generally an annoyance. Like you said, best to be careful to begin with though. Glad you got it sorted out. Electrocution isn't the right term. If you've been electrocuted, you're dead. That term was coined after the electric chair was invented and is a modified form of the word execution.
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Old 08-25-2009, 11:13 PM   #7
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


Quote:
=Deck;319413]

I did suffer a very mild electrocution.
and you are now speaking to us from the dead?

an electrocution is death by electrical shock.


Quote:
I was undoing a mounting screw for the sconce and my hand brushed against the hot wire. Luckily my hand was dry and I was not sweating, which could have been much worse and I assume could have killed me
given the proper circumstances, absolutely.

Quote:
I tell this story because I would like to stress to other DIYers just how important it is to be patient and take the proper precautions(POWER OFF AND THEN DOUBLE CHECK WIRES ARE NOT ENERGIZED).
DIYers? Dang guy, that is preached continually at my work as well. In fact, it is more apt to happen to an electrician due to complacency.

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Overnight I had covered the twists with wire nuts which was good for safety. And if you have kids I'd be careful because they like to unscrew stuff and play around(not an issue this high up).
If you have kids, plain and simple; you do not have exposed energized conductors or an easily exposed energized conductor accessible to them, period.
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Old 08-25-2009, 11:21 PM   #8
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


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Originally Posted by mmccarty View Post
Unless you're standing barefoot on the concrete or otherwise well grounded a shock like that is generally an annoyance. .
You are so misleading here. There are many places to be grounded. 120 volts is the most common voltage involving electrocutions. It is attitudes like what you have stated here that is what gets a lot of people into trouble.

In basis it is true but unless you can verify you are not going to be a current path, you need to have a little more respect for electricity than that.

the last guy I knew that was electrocuted was neither barefoot nor standing on concrete.
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Old 08-26-2009, 08:08 AM   #9
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Light fixture: Does hot&neutral designation matter, and possible wiring anomaly.


If you were undoing a bolt attached to framework or other grounded parts and the wrist of the same hand brushed a live wire or metal part then the electricity goes from your wrist to your fingers and won't kill you although it could make muscles jerk and propel your hand against something sharp.

But if some other part of your body, say, your left hand, was touching something grounded and your right wrist touched a live wire, then electricity will in this example go from one hand to the other, likely passing through your heart and interfering with your heartbeat, thus killing you.

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