Neutral/Hot Confusion

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Old 03-24-09, 03:04 PM
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Neutral/Hot Confusion

Hi,

Hope you can help with this mystery.

I was tapping off an existing ungrounded receptacle to add new ones. To check my work, I inserted one of those three prong circuit testers with three lights. It said my neutral and hot were reversed. To help locate the problem, I tested the existing receptacle and got the same reading. I disconnected the wires to the new receptacles so I could eliminate the new work as a problem.

I reversed the black and white wires on the existing receptacle and got the same reading. Thinking it might be the receptacle, I tried a different one and got the same reading. Thinking it might be the tester, I tried it in receptacles on other circuits and got "correct" results. I tried another tester and got the same results (reversed in original receptacle no matter what and good on a different circuit.)

I touched a non-contact circuit tester to the black wire and got a beep. I didn't get a beep when I touched the white wire. I got a reading of 120 volts with my voltmeter.

If the black is hot and I'm getting 120 volts, why are my three prong testers saying the hot and neutral are reversed and why don't I get a "correct" reading when I reverse the black and white wires?

A friend said it might be because a regular or three way light switch on the same circuit may be improperly wired and I'm getting backfeed?????

What can I do to correct this. And, most important is this dangerous!!

thanks,

Mikeyg
 
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Old 03-24-09, 03:38 PM
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Ungrounded circuits are not permited to be extended. The proper way would be to run a new circuit back to the panel.
 
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Old 03-24-09, 03:58 PM
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Originally Posted by mikeyg View Post
If the black is hot and I'm getting 120 volts, why are my three prong testers saying the hot and neutral are reversed and why don't I get a "correct" reading when I reverse the black and white wires?
When used on an ungrounded circuit, the three-prong tester is unable to tell which wire is the hot and which is the neutral. It will read either "open ground" or "hot/neutral reverse" when the truth is that both readings are caused by the lack of ground wire. For some reason, the instructions on those testers do not mention this fact.

What can I do to correct this. And, most important is this dangerous!!
You can install a new grounded cable from the service panel to your new receptacles. The code grandfathers existing ungrounded circuits as long as they are left alone, but they cannot be legally extended or modified in any way.

Based on modern standards, ungrounded circuits are unsafe.
 
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Old 03-24-09, 03:58 PM
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On an ungrounded receptacle, it is impossible for those testers to tell if the hot and neutral are reversed or not. The tester needs a ground to figure it out. Either your circuit is grounded, or your tester is broken, or you are misreading it.
 
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Old 03-24-09, 04:17 PM
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Thanks

Thanks for your quick reply.

I just have to figure out how to get a wire from the existing receptacle on the second floor to a copper cold water pipe or back to the panel without having to drill too many holes!

Mikeyg
 
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Old 03-24-09, 04:53 PM
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Stop right there! You just cannot grab a water line to create a grounded wiring system. If you were to try to do this corrctly it would need to run all the way back to the panel where the circuit originates.

Since this is just as much work as running the new circuit there is no reason not to run the new wiring.
 
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Old 03-24-09, 06:37 PM
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Another option

Thanks for the warning about using a cold water pipe.

I did some exploring and someone ran a grounded circuit in a knee wall just behind the location of the ungrounded receptacle box. The grounded circuit has an accessible junction box. Can I run a ground wire from the ungrounded circuit receptacle to the ground wire in the junction box? To this would require only one hole to run the ground wire about four or five feet and would give me grounded receptacles on two circuits in the room.

Thanks again for your help.

Mikeyg
 
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