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Thread: 250.53(F), 2017 NEC

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  1. #1
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    250.53(F), 2017 NEC

    The above article states:
    "The ground ring shall be installed not less than 750mm (30 in.) below the surface".

    If the ground ring is supplemented with ground rods, does it still have to be buried 30"? Both qualify as grounding electrodes.

    In my industry, i.e. refineries and chemical plants, we frequently use a #4/0 bare copper grounding conductor as the so-called 'main ground ring' with taps to equipment usually @ #2 AWG or #2/0 AWG.
    To obtain the required resistance of (usually) less than 5 ohms, the #4/0 is typically supplemented with ground rods to form the overall equipotential grid. Is the #4/0 therefore, really a bonding jumper between rods? And if that's the case, is it no longer the 'ground ring' and can it be buried at a much lesser depth, of say 18"?

  2. #2
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    You stated it was a ground ring therefore it has to be 30" down.

    Ground rings do not require supplemental electrodes, that is your spec.
    "Electricity is really just organized lightning." George Carlin


    Derek

  3. #3
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    If the GECs/bonding jumpers connecting the rod electrodes happen to be bare copper and circle the building, then they do not have to follow the 30" specification for a ground ring. You just cannot take credit for having a ground ring if the contract calls for one.

  4. #4
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    Quote Originally Posted by GoldDigger View Post
    If the GECs/bonding jumpers connecting the rod electrodes happen to be bare copper and circle the building, then they do not have to follow the 30" specification for a ground ring. You just cannot take credit for having a ground ring if the contract calls for one.
    If grounds rods are all over the place, (as is usually the case with large chemical plants) whether or not we call it a 'ground ring' sounds like semantics.
    I happen to agree with you (BTW), the problem I have is convincing the Client that 250.53(F) is not applicable.
    Any suggestions?

  5. #5
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    Quote Originally Posted by Dale001289 View Post
    If grounds rods are all over the place, (as is usually the case with large chemical plants) whether or not we call it a 'ground ring' sounds like semantics.
    I happen to agree with you (BTW), the problem I have is convincing the Client that 250.53(F) is not applicable.
    Any suggestions?
    Does your contract/specs say to install a "ground ring" or not?

    As I stated earlier, you called it a ground ring.
    "Electricity is really just organized lightning." George Carlin


    Derek

  6. #6
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    "Electricity is really just organized lightning." George Carlin


    Derek

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