electrical wiring issues-neutral has voltage?

jmckinneyAugust 4, 2013

So, i had two outlets that stopped working the other day, while running a vacuum on one of them. it stopped about 2-3 minutes after turning it on.. After sitting overnight, they worked again for a minute, but then stopped working when I used a plug in tester to see if they had power. After talking with my father and father in law, they suggested i check connections nearby to see if there was a loose wire connection. I pulled the light switch to see if it was set up with a neutral or if it had power in it. What i found was the switch when on has two neutral wires, when the switch is off, one is reading ground and the other is 119 ish volts. It is only reading with voltage when the light switch is off. This made no sense to me, i was just wondering if it did to anyone else. Does this indicate a problem? or is it normal to get a reading with a voltmeter on a neutral? I am not sure the light is on the same circuit as the outlets, but i think they are. If i get power back to the outlets, i will check for the breaker that controls them, but i dont know of any way to find out without them having power

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In the days before solid-state electronics, say early 1950's and before, testers required significant power just to operate the meter movement on the tester. Testing of solid-state electronics became problematic in the very late 50's as they became more prevalent because the tester used more power than did the device being tested. So testers of incredible sensitivity were developed.
When one conductor is near another and either is energized, a "phantom" voltage is induced in the other. Not enough power to be useful or meaningful-- or dangerous-- but enough to register on a sensitive instrument. I think that is what you are seeing with your tester.
I use mostly testers that are old school and do not respond to phantom voltages. One of my favorites is two pigtail Edison-base lampholders connected in series and fitted with 15 watt incandescents. No way to fool that tester. And if one knows how to use it, it is good for many different tests on both single and 3-phase of 240 volts and below.

    Bookmark   August 4, 2013 at 3:37PM
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While bus driver's response regarding phantom voltages is correct, I don't think this is the problem the OP is experiencing.

It sounds like the measurement is being taken across the two switch terminals - with the switch on, of course there is no voltage - with the switch off, the meter is reading the voltage between the hot and the neutral through the light bulb - as would be expected.

Not sure why you are looking at light switches, which may, or may not be on the same circuit. Troubleshoot the intermittent connection that is going to, or between, the receptacles and place a small load on it - such as a table lamp, to prevent phantom voltage readings.

    Bookmark   August 4, 2013 at 7:25PM
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Thanks for your responses. I have figured out that the light switch is on the same circuit and i think they just used two light switches beside each other as the junction boxes for the outlets further down the line. So i need to figure out which wires here go to the outlet and check the connection. my understand is that most of the time when you lose power it ill be a connection in the junction box. And i believe that this is the closest junction to the outlet. At this point, any load on the outlet causes it to loose power altogether, so i can't plug in a lamp unfortunately.

    Bookmark   August 5, 2013 at 4:58PM
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Loose connections of that magnitude usually have visible and olfactory indications.

    Bookmark   August 5, 2013 at 7:12PM
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"At this point, any load on the outlet causes it to loose power altogether, so i can't plug in a lamp unfortunately."

That is the idea... Load the circuit to eliminate phantom voltages and then to help identify high resistance connections.

Plug the lamp in and follow the circuit until you have no voltage, take a step back, and there is your bad connection.

    Bookmark   August 5, 2013 at 10:25PM
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When you say two receptacles next to each other are you may be referring to a quad receptacle meaning its 4 outlets in the same faceplate and sharing the same box. If you lost power in both receptacles then the best place to look is behind the receptacles themselves. Receptacles have 2 screws on each side one for top plug and one for bottom. Their is a link between the two screws that is designed to be removed if someone wanted one plug to be used by a switch, for example a table lamp that was controlled by a light switch. What happens when you have quad receptacles is some electricians will connect the line side (wires from panel) on the top set of screws then use the bottom set of screws to power the other receptacle. The problem is that when your operating a vacuum motor (higher current draw) on the second receptacle then your actually running all that current through that little link. If you have older residential grade receptacles they may' only be rated for 15A. By pulling that high current through that link it causes it to heat up, over time the receptacle becomes brittle and breaks. The right thing to do is to connect the make joints using wirenuts so that each receptacle is coming from the wirenut and not theoigh the other receptacle. Be EXTREMELY careful taking the plate off and checking receptacle. Power may still be on from panel and appear to be off if you read with a meter through the outlet. If the outlet did heat up and break it would still be not just not connected in the back anymore.

    Bookmark   August 5, 2013 at 11:04PM
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