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Thread: Ground Rod - Spacing

  1. #1
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    Ground Rod - Spacing

    Someone please clarify for me for required ground rod spacing, here is what I recalled from NFPA780 and NEC:

    NFPA780 (lightning protection system): the spacing between rods shall not be smaller than the sum of all ground rod length..

    NEC article 250...spacing between ground rod is min. 6 feet.


    So, which rule should we go with? If we go with NEC, we are ok at spacing ground rod 6' apart as minnimum. If we go with NFPA 780, we have to space them at least 24 feet apart (assume 8' long ground rod)...

    Or ground rod spacing rule per NFPA-780 only applies to lightning protection system? I saw several electrical grounding details where they showed the rod either 20' or 15' apart for tri-rods system.

  2. #2
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    NEC 6' apart

  3. #3
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    Quote Originally Posted by dSilanskas View Post
    NEC 6' apart

    That's not necessarily true.

    It depends on what you want and what you are installing them for, if you are looking for the most effective use of your driven electrodes you would go twice the lenght of the electrode 8' X 2 = 16' (not 24'?).
    Brian John
    Leesburg, VA

  4. #4
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    Let's take note that the NEC says "they shall not be less than 1.8 m (6 ft) apart.", it does not say they shall be 6' apart.



    Roger
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  5. #5
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    Quote Originally Posted by roger View Post
    Let's take note that the NEC says "they shall not be less than 1.8 m (6 ft) apart.", it does not say they shall be 6' apart.



    Roger

    VERY TRUE, we had an inspector turning down contractors for spacing over 6'.
    Brian John
    Leesburg, VA

  6. #6
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    Quote Originally Posted by brian john View Post
    VERY TRUE, we had an inspector turning down contractors for spacing over 6'.
    That's ridiculous if you were off by a small amount either way you would fail. As you stated in your other post 6' is not ideal anyway.

  7. #7
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    I belive the op is refering to 'Lightning protection system". that is different than grounding a service.
    Unlimited Electric Contractor/Standard Electric Inspector/Traffic Signal Inspector/Highway Lighting and Level One Traffic Signal Installer.

    I know you believe that you understand what you think I said but I'm sure you realize that what you heard is not what I meant.

  8. #8
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    NFPA 780 is the Standard for the Installation of Lightning Protection Systems. The NEC nolonger has a article on lightning protection I believe it was 280???

    in 780 you probably would have to extend the spacing to 24 or whatever feet.
    Charlie

  9. #9
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    Quote Originally Posted by brian john View Post
    VERY TRUE, we had an inspector turning down contractors for spacing over 6'.

    Let's take note that the NEC says "they shall not be less than 1.8 m (6 ft) apart.", it does not say they shall be 6' apart.
    Roger
    That tells me that over 6' is OK. 5ft 11in is LESS THAN 6ft
    Organized people are people that are just too lazy to look for their stuff

  10. #10
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    hey brian what would be the reason you would want to space the ground rods apart that far? i usually space them 8 feet apart for a house. never really had to do any fancy grounding like you do
    "Most good electricians are pretty sure that they are the best and the great ones never stop trying to be."

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