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Thread: open neutral/s

  1. #11
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    Quote Originally Posted by ptonsparky View Post
    Wouldn't you get an open circuit voltage from failed neutral to EG? Yes, 120v unless the neutral is compromised at the service or before.

    Part of the reason those taking voltage readings have to be very specific as to what they are doing and where they have the probes. I know what I mean when I take a reading to ground, but do you know what I think I mean?
    If you have resistance in the neutral you raise the N-G voltage. This easily can be just a volt or two from basic voltage drop in the neutral of an otherwise good condition circuit. But you can't raise that difference to more than 120 volts without involvement of both L1 and L2 plus a compromised EGC as well. A good EGC will never see more than nominal 120 from another conductor of the system.

    If you have high volts to EGC (like more than 125) make sure that L1-L2 isn't high as well. That will usually be problem with POCO distribution regulation causing that though.
    I live for today, I'm just a day behind.

  2. #12
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    Quote Originally Posted by kwired View Post
    If you have resistance in the neutral you raise the N-G voltage. This easily can be just a volt or two from basic voltage drop in the neutral of an otherwise good condition circuit. But you can't raise that difference to more than 120 volts without involvement of both L1 and L2 plus a compromised EGC as well. A good EGC will never see more than nominal 120 from another conductor of the system.

    If you have high volts to EGC (like more than 125) make sure that L1-L2 isn't high as well. That will usually be problem with POCO distribution regulation causing that though.
    I will start at service turn off all branch circuits probe L1-L2 then L1-N L2-N then L1-G L2-G if there are over or under voltage readings the distribution lines have issue, call Power company. If there are no over or under voltage readings. The next step is re-energize circuits turn off effected probe L1-L2 then L1-N L2-N then L1-G L2-G if there are no over or under voltage readings. circuits remove Duplex and switch devices separate wires in effected rooms. Then re-energize circuits and locate first branch circuit home run and test L-n then L-g if correct readings connect one set of wire locate junction box it leads to and check readings. I will repeat until I find open neutral then replace effected wire. I have a feeling there is a buried junction box, there is no access to attic. thanks for advice.

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