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Old 11-04-2007, 07:12 PM   #1
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diagnose house wiring problem


All outlets on one circuit are dead. I have located the outlet closest (in the network) to the breaker box. At this outlet (two cables, each with one white, one black and a copper wire), testing with a digital multimeter shows 120V across the black line wire and the copper wire. All other combinations show 0V.

Two questions:

1) Am I correct in assuming that the voltage should be across the black and white wires (within one cable), and the lack of this probably points to the problem? (And is the voltage across black and copper normal?)

2) What problem am I likely seeing?

Notes:

I have replaced the breaker and tested for voltage there. I have tested an outlet on another circuit and found 120V across the white/black pair. Nothing obvious changed on the bad circuit before the problem appeared.

Thanks for any help.

Bruce

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Old 11-04-2007, 07:58 PM   #2
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diagnose house wiring problem


The neutral is loose, either at the panel or at another receptacle, switch, or light closer (electrically) to the panel. The problem has nothing to do with the breaker.

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Old 11-04-2007, 08:48 PM   #3
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diagnose house wiring problem


Definitely the neutral is loose or not connected under the screw at the main panel. (provided you are in fact at the outlet closest the electrical panel).Sometimes the neutral is in the neutral bar, but the screw is not tightened or the stripped part of the white wire breaks off (because of being nicked ).
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Old 11-04-2007, 09:08 PM   #4
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diagnose house wiring problem


Hi Bruce.. I'll add this to the other advice


Quote:
1) Am I correct in assuming that the voltage should be across the black and white wires (within one cable), and the lack of this probably points to the problem? (And is the voltage across black and copper normal?)
Yes you are correct also 120 volts black to bare ground is what you should be getting. This also proves you have power to the receptacle.

Quote:
2) What problem am I likely seeing?
O volts black to white is telling you that you have an open in the white wire or commonly called an open neutral as househelper and Mike have already stated.

If you determined that this closest to the panel outlet receives power first before the others then your open white is upstream of it as you are measuring O volts black to the white wire here. But you need to make sure you have the incoming power cable isolated when you test it. All power should disappear from the other recepatcles if they are daisy chained to that outlet and with the cable isolated its black should be constantly hot and measuring 0 volts to the neutral of that cable.

Would this be what you have determined?

If so the problem is not in any of the non working receptacles so you will need to see what is working on that circuit and look in the switch box or light box for a bad connection or open with the neutral white wire. Remember while your looking not all whites are neutrals and can be used as hots...like in switch loops so don't let this confuse you. To find what else is on the circuit turn off the breaker and see what else stops working look in the electrical boxes of these areas for the open white wire.

If you have determined that this is the first device the circuit hits before going anywhere else then isolate the incoming power cable and test it.. if 0 volts between black and white then problem exists between there and the breaker. Now something to watch out for if this is the case. When you replaced the breaker did you notice if there was a red wire in the cable with the black when it exited out of the breaker panel? I'm asking because you may be dealing with a multiwire circuit and there will be a junction box somewhere you will need to find. I will pursue this further if that is your case...check for that red wire.
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Old 11-04-2007, 09:25 PM   #5
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diagnose house wiring problem


Yes, all the outlets downstream from this are dead also. I isolated each and tested.

As it turns out, I misspoke. There appear to be two devices (at least) upstream from this outlet. (These die when I turn off the pertinent breaker.) One is an outlet. This is working correctly. The other (I would assume, based on geography, between the working outlet and the broken outlet) is a multiple light/light/fan unit, which I have adjusted for various purposes, so this is where I will focus. The hypothesis: the line cable is intact, and then something is screwed up at the load connections. Right?

I don't see where the white neutral from the bad circuit (or any circuit) arrives at the breaker. There is an aluminum bar that serves as the neutral, and then the black wires arrive from their respective circuits. I won't touch any of that unless my hypothesis doesn't pan out.

Thanks a bunch!
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Old 11-04-2007, 09:39 PM   #6
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diagnose house wiring problem


We didn't mean the whites arrive at the breaker...but arrive at the neutral bar.

Sounds like a reasonable plan go to that last working receptacle next.

EDIT: Sorry I guess you won't have any choice since it will be that last outlet...
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Old 05-06-2009, 01:21 PM   #7
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diagnose house wiring problem


I'm inclined to go with mp1 and HouseHelper's advice. Since this is (according to your determination) the first outlet downstream [of the panel] and you have power in the Black to (bare) ground wire, but not in the Black to White (neutral) wire. There is one additional test that you can make to isolate the problem. After looking at physical damage or loose connection (which I doubt, because you would then have intermittent contact with flickering lights on that circuit) of the neutral to the NEUTRAL bar in the panel, you could have a CONTINUITY test on the white wire between the panel and the [first] junction box! Caution. Make sure that ALL power to that circuit is disconnected!!!

Last edited by spark plug; 05-06-2009 at 08:36 PM. Reason: typographical error
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Old 05-06-2009, 09:03 PM   #8
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diagnose house wiring problem


Quote:
There appear to be two devices (at least) upstream from this outlet.
The problem is in the last working outlet, before the dead ones.

White wire disconnected/burned.

Happens all the time.

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