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Thread: Question about Grounding Electrode size

  1. #21
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    Bob

  2. #22
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    Quote Originally Posted by O'donisR View Post
    You right... I missed the key-word Minimum Thank you,, very helpful

    Sorry for mention this again but I think the right size is #3/0 copper as the minimum grounding electrode conductor.. I been preparing myself for the master exam and all the questions from exam preparations that are related with minimum size of grounding electrode conductor are answered based on the information provided, on this Question we only have a 3000 Amps/460V that need a carry conductor bigger that a 1100 KCMIL and table 250.66 show a #3/0 as the minimum size grounding electrode conductor. If electrodes are specified then exceptions and notes shall be apply.

    What is the minimum size of grounding electrode required to handle 3,000 AMPS 460 Volts.

    A. 4
    B. 6
    C. 3/0
    D. 400kcmil

    There is not specification of what type of electrodes will be used, the only info provided was : (what is the minimum size of grounding electrode required to handle 3,000AMPS 460 Volts), table 250.66 show for a 1100 KCMIL OR OVER use #3/0 Copper for grounding ELECTRODE. That would be my answer..

  3. #23
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    Quote Originally Posted by O'donisR View Post
    What is the minimum size of grounding electrode required to handle 3,000 AMPS 460 Volts.

    A. 4
    B. 6
    C. 3/0
    D. 400kcmil

    There is not specification of what type of electrodes will be used, the only info provided was : (what is the minimum size of grounding electrode required to handle 3,000AMPS 460 Volts), table 250.66 show for a 1100 KCMIL OR OVER use #3/0 Copper for grounding ELECTRODE. That would be my answer..
    And you would answer wrong. The simple truth is the" minimum" size GEC for a service be it 400, 1000, 3000, 5,000 amp or what ever is a #6 copper.

    If the question specified an electrode, say a metallic water pipe, you would be right but since there is no specified electrode it is very possible it could be a lowly rod and the Table doesn't come into play.

    Roger
    Moderator

  4. #24
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    Quote Originally Posted by roger View Post
    And you would answer wrong. The simple truth is the" minimum" size GEC for a service be it 400, 1000, 3000, 5,000 amp or what ever is a #6 copper.

    If the question specified an electrode, say a metallic water pipe, you would be right but since there is no specified electrode it is very possible it could be a lowly rod and the Table doesn't come into play.

    Roger
    I agree, unless you had a 60 or 100 amp service then the minimum size is a likely a #8.
    Rob

    Chief Moderator

    All responses based on the 2011 NEC unless otherwise noted

  5. #25
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    This appears to be worded like a WI masters test question. IIRC
    So what is the Most correct answer based on the info given? #6 IMO
    MINIMUM GEC with the limited info.
    Gotta admit my knee jerk thought was 3/0 but the do say Minimum and do not specify the electrodes.

  6. #26
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    Quote Originally Posted by WIMaster View Post
    This appears to be worded like a WI masters test question. IIRC
    So what is the Most correct answer based on the info given? #6 IMO
    MINIMUM GEC with the limited info.
    Gotta admit my knee jerk thought was 3/0 but the do say Minimum and do not specify the electrodes.
    If the question is as posted, it could be possible that there are no other grounding electrodes and two ground rods are required to be installed and the minimum size would be a #6 copper

    (A) Connections to Rod, Pipe, or Plate Electrodes. Where the grounding electrode conductor is connected to rod, pipe, or plate electrodes as permitted in 250.52(A)(5) or (A)(7), that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.

    A poorly written question for a qualifying test.

  7. #27
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    Quote Originally Posted by Gregg Harris View Post
    A poorly written question for a qualifying test.
    We only have the OP's "generalization" from memory. The actual wording of the test question may have been better, and addressed the objections raised about multiple possible interpretations.
    Otherwise, I agree, either poorly written or wrong "correct" answer.

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