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Thread: Shock from GEC

  1. #1
    Join Date
    Sep 2009
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    3

    Default Shock from GEC

    Hi all - first post here. Long time fan of TOH. I'm pretty comfortable with most home remodel tasks. Started finishing a basement in our 1920's home that was rebuilt 5 years ago due to a total loss fire (before we owned). Most of the wiring for the house and alarm was surface mounted in the basement so my firs step has been to relocate that up into the joists. All went well and was finishing up tonight installing a new wire to the cold water pipe. Here's where things got tricky.

    The system has two GECs - one to a ground rod outside the panel at the back of the house. The second (which is technically the primary according to code?) runs to the front of the house and conencts to the copper pipe where it enters the basement. This conductor is spliced with a split bolt. I had to lenghten it when I relocated it.

    Figuring that I already had one ground (to the pin outside the panel) I did not bother to shut the power down at the service entrance. When I disconnected the splice the lights in the house dimmed a bit. Odd. I ran the new wire and when I reached up to connect the splice - ZAP..not huge but a shock and a small spark when the wires were connected together. I then shut the panel down and connected, re-engergized and all seems fine. Please don't respond that the panel should have been off - I need help figuring out where I'm getting current on the GEC. Now when I touch the GEC - no shock...all seems fine.

    Any thoughts how I am getting current on this wire? How can I measure it? How can I find the source? Is it possible that the water pipes themselves are being electrified by another home on the street? We live in a row home in Baltimore - our place is nicely fixed up but there are some on the street that are probably original.

    Appreciate your help!

  2. #2
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,821

    Default Re: Shock from GEC

    Actually this is not uncommon. Ground has resistance and connecting to ground in different locations can have slightly different potential until connected together. The GEC is for lightening protection only, the safety ground is the bonded ground in the panel.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  3. #3
    Join Date
    Sep 2009
    Location
    jersey
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    Default Re: Shock from GEC

    Quote Originally Posted by JLMCDANIEL View Post
    Actually this is not uncommon. Ground has resistance and connecting to ground in different locations can have slightly different potential until connected together. The GEC is for lightening protection only, the safety ground is the bonded ground in the panel.
    Jack
    The primary purpose of the GEC and grounding electrode system is, among other things, to eliminate the difference in voltage potential between metal non current carrying parts and earth.

    There could be several things causing it, the most likely, and most common in my experiance is a loose nuettral tap at the service drop, meter, or panel. I would suggest letting an electrician handle that because it can't be powered off to service and can cause damage to appliances. The gec, in this case, was doing one of its jobs.
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  4. #4
    Join Date
    Sep 2009
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    3

    Default Re: Shock from GEC

    Sorry - maybe I got my terminology wrong. The wire I got the shock from is the grounding wire from inside the panel.

    Interesting thought about a loose neutral. My girlfriend just told me that a couple of years back (before I lived here) during a wind storm the power flickered off and on - turns out the wires coming from the pole were loose...I'm wondering if that situation still exists?

    Agree we'll have an electrician take a peak. In the short term though is the electrical system safe? Are there some basic diagnostics I can do with my Fluke DVM to try to locate/isolate the problem?

    Thanks!
    Scott

  5. #5
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,821

    Default Re: Shock from GEC

    There may be no problem at all. If you have a loose neutral symptoms will generally manifest them selves in 120v circuits. If Ground potential was the same every where there would be no need to install GEC rod at the house because because the neutral is grounded at the pole. The earth does have resistance and the GEC system references all points connected to the same potential. When you connect the ground wire to the electrode you are connecting a current carrying conductor, the neutral, to the grounding rod.If the neutral was completely disconnected you would have no current flow to ground because there would be no complete circuit.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
    Sep 2009
    Posts
    3

    Default Re: Shock from GEC

    Hi all -

    An update. Talked to an electrican in the family and consensus is a loose neutral somewhere in the system - likely in the places identified here - the panel, meter or possibly the pole. Out of my leauge to play with live power. So....

    I'm looking for a recommendation for an electrician in the Baltimore City area. Anyone got one?

    Thanks!

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