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Thread: Encountering cut panel ground wires

  1. #16
    Radon Contractor and Water Treatment 99k's Avatar
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    Quote Originally Posted by Chris75 View Post
    Its this simple, we (electricians) must bond the water piping system and all available grounding electrodes. Its really not hard to understand, if the water system leaves the house with 10' or more in metal underground piping, then it must be used as an electrode.
    If the system does not have 10' or more of underground metal piping, should it be disconnected? Is there anything adverse that would cause someone to want to cut the ground at the piping?

  2. #17
    Radon Contractor and Water Treatment 99k's Avatar
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    Quote Originally Posted by Chris75 View Post
    That would be a code violation, ALL grounding electrodes must be USED if present, and the water system would still need to be bonded even if not used as an electrode.
    Could you please explain the theory of bonding the water system to the electrodes. I imagined this was done as a safety issue to protect the occupant if somehow a stray voltage entered into the water system piping (i.e. HW heater, frayed wire against a pipe, etc).

  3. #18

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    Usually when I see bond/ground wires cut, there is a piece missing and has been stolen for scrap.

    Sometimes the plumbers will disconnect when working on fittings by the clamp and don't reconnect..

    We are required to bond the metal piping and structure to keep it from becoming energized in a fault condition. Ironicly, a neutral fault can end up energizing the piping, using it as a "return" path.

  4. #19

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    Quote Originally Posted by renaissanceEE View Post
    If I were to hazard a guess that #4 to the plumbing was the old building ground. A new good grounding source was most likely created when the telcom/computer equipment was installed and the old cut at the clamp to stop any possible loops.

    NEC requires that the water pipe be used as a grounding electrode if it is matal and extends into the ground at least 10'. I will look up the section on Tuesday when I go back to tech.

  5. #20

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    Quote Originally Posted by pudge565 View Post
    NEC requires that the water pipe be used as a grounding electrode if it is matal and extends into the ground at least 10'. I will look up the section on Tuesday when I go back to tech.
    In Oregon, we have "amendments" to the NEC. One amendment says "...water pipe shall not be used unless the metal underground water pipe has been verified..."

    Full text of amendment...

    From Oregon Amended Language, 2008 NEC...

    250.52 Grounding Electrodes...
    ...
    (B) Not Permitted for Use as Grounding Electrodes...
    ...
    (3) In existing electrical installations, when a service change or upgrade occurs, an existing metal underground water pipe shall not be used unless the metal underground water pipe has been verified as suitable for continued use as a grounding electrode. An existing metal underground water pipe shall be bonded to the new grounding electrode system as required by 250.104(A).

    Above from...
    http://www.cbs.state.or.us/external/...918-305_pr.pdf

  6. #21

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    Ah yes I forgot about amendments. I also forgot to look up the code today will do it tomorrow.

  7. #22
    DIY Senior Member AcidWater's Avatar
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    Is there any NEC rule that gives the maximum length of 4AWG grounding conductor wire that may be run from the panel to the location of the grounding electrode?
    ***

    Does the code now or in the past, allow the copper piping system to be used as part of the grounding conductor from the electric panel to the grounding electrode?

    ie:
    Panel box
    4AWG wire to nearest point of copper pipe (say 12 feet away)
    copper pipe runs thru house to well pump
    near the pump, 4AWG wire from pipe goes into the wall penetration used by the well pipes
    presumably to either a buried electrode, a metal well casing, or possibly down to be buried in the concrete foundation.

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