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Thread: Size of ground rod

  1. #1
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    Size of ground rod

    I cannot locate the code reference for sizing of ground rods. 250.52(A)5 says the minimum approved rod is 1/2" but it never mentions when a 5/8 or 3/4 rod would be required.

  2. #2
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    Quote Originally Posted by rookie4now View Post
    I cannot locate the code reference for sizing of ground rods. 250.52(A)5 says the minimum approved rod is 1/2" but it never mentions when a 5/8 or 3/4 rod would be required.
    The NEC never requires those size rods, sometimes engineers specify the use of larger rods.
    Last edited by iwire; 09-09-09 at 03:34 AM.

  3. #3
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    Actually 250.52.(A)(5)(b) says that a ground rod is required to be at least 5/8" of an inch unless the rod is listed, then a 1/2" rod is permitted.

    250.52(A)(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.44 m (8 ft) in length and shall consist of the following materials.
    (a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size ¾) and, where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.
    (b) Grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm ( in.) in diameter, unless listed and not less than 12.70 mm (½ in.) in diameter.
    Rob

    Chief Moderator

    All responses based on the 2011 NEC unless otherwise noted

  4. #4
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    Quote Originally Posted by infinity View Post
    Actually 250.52.(A)(5)(b) says that a ground rod is required to be at least 5/8" of an inch unless the rod is listed, then a 1/2" rod is permitted.
    If I have a listed ground rod (and why the heck wouldn't I) is there anytime the NEC requires the use of a larger rod?

  5. #5
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    There are way more unlisted ground rods on the market than there are listed ones. The cost associated isn't really worth it.

    That being said, ground rod design is perhaps the most commonly over-engineered component of electrical systems I typically see on a daily basis. Engineers must have the inside track on ground rod futures...
    Bryan P. Holland, MCP

  6. #6
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    Everyone I have worked for in the past has specified a 3/4" diameter rod.

  7. #7
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    Thanks for all the answers. At least I know why I couldn't find the code section.

  8. #8
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    Quote Originally Posted by Keri_WW View Post
    Everyone I have worked for in the past has specified a 3/4" diameter rod.
    why not an inch?



    I have never really understood the fascination with grounding electrodes for most electrical systems. It really does not do much for the electrical system, or for safety. Do the minimum and be done with it.
    Last edited by petersonra; 09-09-09 at 02:20 PM.
    Bob

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