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Thread: Good 'ol 250.66

  1. #1
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    Good 'ol 250.66

    Having a senior moment this morning, my brain has slipped a cog, and I am asking for your help.

    I cannot wrap my head around 250.66 (2014).

    First it states to use a GEC at the service using table 250.66.
    Then 250.66(A) tells me so long as it is the sole connection to a single or multiple ground rods it is only required to be a # 6 copper.

    I am thinking about a 3000-amp service. I interpret table 250.66 to mean a 3/0 copper, yet 250.66 seems to tell me I can use a #6 copper?
    How can a #6 be sufficient? if it is, why would I need 3/0?

    I remember it has read this way for many years, but for the life of me I am lost at the moment.
    Do I need more coffee this morning? Send the grandkids home? This makes no sense to me. What am I (obviously) missing?

    Thanks in advance for your help!
    " One of my reasons for success: I learned to feel comfortable being uncomfortable." -- Cal Ripken, Jr.

  2. #2
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    When it comes to a rod, pipe, or plate there is no reason for a larger conductor since they won't do much anyways so 250.66(A) reflects as much. When you go to the other GE's they perform better and warrants a larger sized conductor.

    Roger
    Moderator

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    Quote Originally Posted by roger View Post
    When it comes to a rod, pipe, or plate there is no reason for a larger conductor since they won't do much anyways so 250.66(A) reflects as much. When you go to the other GE's they perform better and warrants a larger sized conductor.

    Roger
    such as Water Main.

  4. #4
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    Quote Originally Posted by mortimer View Post
    such as Water Main.
    Thank you both for the replies. Makes more sense now.

    I appreciate your helpfulness, Merry Christmas and Happy New Year!
    " One of my reasons for success: I learned to feel comfortable being uncomfortable." -- Cal Ripken, Jr.

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