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Thread: Ground Ring

  1. #1
    Join Date
    Jun 2007
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    Baltimore
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    Ground Ring

    The buildings (3) that I am currently inspecting have the following set-up for a grounding/lightning protection system; a ground rod driven at each of the three main power panelboards and connected as required to the proper size grounding conductor and interconnected to a ground ring which encircles each building. Each ground ring is interconnected and the entire system is connected multiple times to building steel and driven ground rods. Additionally, the rooftop air terminals are connected to the ground ring.

    Here is my issue: as per NEC 250:53F, the ground ring is to be buried at a minimum depth of 30". It is nowhere near this depth; 20" would be the maximum at any point in the system.

    I received a response from the designer which stated that the ground rods driven at each of the 3 distribution panels are sufficient and that the ground ring only needs to be at a depth of 18" (?) as it is only being used for a lightming arresting system.

    My concern is that because the ground ring (at less than 30") and the rods at each of the 3 panels are tied together through building steel the entire grounding system has been compromised.

    Thanks in advance,
    John

  2. #2
    Join Date
    Feb 2003
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    Your designer is correct and you have nothing to be concerned with IMO

  3. #3
    Join Date
    Feb 2003
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    Ohio
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    If the ground rods and building steel qualify as grounding electrodes then it would seem that your service is grounded properly. Just by making an attachment to a "ground ring" that is not at the NEC required depth doesn't compromise the grounding electrode system it just simply means you do not have what the NEC would qualify as a ground ring.

    My 2 cents...

    Pete
    Experience is something thats gained shortly after you really needed it.

  4. #4
    Join Date
    May 2005
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    John, I have to agree with the others. The rods are the required electrodes; the rings and interconnecting conductors are jumpers.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  5. #5
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    Jul 2003
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    New Jersey
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    This question reminds me of when someone pulls an undersized EGC in a metal raceway. The response is usually that "the raceway is the EGC and the undersized conductor is for a little extra protection". Wouldn't the ground ring, if present, need to follow the required burial depth listed in Article 250?
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  6. #6
    Join Date
    Feb 2003
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    Illinois
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    Trevor,
    Wouldn't the ground ring, if present, need to follow the required burial depth listed in Article 250?
    No because if it doesn't meet the rule in 250.53(F), it isn't a grounding electrode...it is just a bonding jumper.
    Don
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

  7. #7
    Join Date
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    Florida
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    7,637
    See 14.3.4 of the NFPA 780. 18" burial depth is sufficient for a ground ring used as the grounding terminal of a LPS.
    Bryan P. Holland, MCP
    NEMA - Codes & Standards

  8. #8
    Join Date
    Jul 2003
    Location
    New Jersey
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    So you're saying that once we define this particular ground ring as part of the LPS the 30" burial depth no longer applies. Thanks for the clarification.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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