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Thread: What to look for?

  1. #1
    Join Date
    Nov 2007
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    What to look for?

    I got a call from a homeowner who is telling me that the utility somehow energized the neutral conductor with 120V and ruined several electronic items in their home.

    The utility is not denying that it happened. The owners insurance company wants to have the wiring checked to make sure there is not additional damage that is unseen at this point.

    I really don't know what to look for. NM cable is rated for 600 volts so I don't see damage occurring that way.


    What else is there to look for?

    Suggestions appreciated.

  2. #2
    Join Date
    Jun 2012
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    Most likely no further damage to internal wiring as you’ve said, just check all the equipment in the home for damage. Of course this is just visual so you can’t vouch for something that may crap out in a couple weeks because of some weakening effect, And I would state it as such.

    What was the power company doing to accidentally put 120 on the neutral?

  3. #3
    Join Date
    Apr 2009
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    Williamsburg, VA
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    5,238
    Depending on how they apparently miswired a transformer, some 120v devices and breakers undoubtedly saw 240v.

    aside from the customers equipment, I would check all GFCI and afci devices, and all dimmer switches for proper operation. anything that could have been damaged from over-voltage or reversed polarity. I cannot think of any potential problems with the wiring from such an error.
    Electricians do it until it Hertz!

  4. #4
    Join Date
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    I had one of those a while ago, everything metered out fine, made multiple visits, drove me nuts....etc

    Came to realize the tape had worn off the very old OH splices & were clicking together on windy days

    ~RJ~

  5. #5
    Join Date
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    Probably no further damage other than anything electronic or with a digital display is now toast. Damage would be somewhat similar if you lost the neutral at the utility pole.

  6. #6
    Join Date
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    Quote Originally Posted by mopowr steve View Post
    Most likely no further damage to internal wiring as you’ve said, just check all the equipment in the home for damage. Of course this is just visual so you can’t vouch for something that may crap out in a couple weeks because of some weakening effect, And I would state it as such.

    What was the power company doing to accidentally put 120 on the neutral?
    I agree, most damage should already be obvious. Minor damages that may have occurred may not show themselves for years, and by then no one will know any different.

    What did they do - maybe miswired transformer connection, or service drop/lateral connection. (Service drop not so likely simply because neutral is likely a bare conductor, but not impossible).

    They also can on occasion get high leg on the wrong lead on high leg services or wrong rotation.

    Most are pretty good at pulling meters, opening switches, etc. and verifying proper voltage, rotation (when applies) before installing meter or closing switches though.
    I live for today, I'm just a day behind.

  7. #7
    Join Date
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    It's also possible the actual situation was an open neutral which, as we have discussed ad nauseu, can act as an energized neutral under load.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  8. #8
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    Resting under the Major Oak UK
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    You could “Megger” all circuits, then you can give the insurance company measured values. If US insurance companies are anything like the UK they’ll try to wriggle out of paying.
    The reports of my death are greatly exaggerated.

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