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Thread: Ground Rods

  1. #1
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    Ground Rods

    Can a single Ground Rod be used to Bond more than 1 transformer?
    I'm installing a new 480-208/120 transformer to feed a Loadcenter; there's a Ground Rod next to this installation used with another transformer.
    Can I Bond the new transformer to the existing Ground Rod?

  2. #2
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    I don't know of any reason why you cannot use a ground rod for both transformers. Is one rod enough?
    They say I shot a man named Gray and took his wife to Italy
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  3. #3
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    Quote Originally Posted by dasarmin View Post
    Can a single Ground Rod be used to Bond more than 1 transformer?
    I'm installing a new 480-208/120 transformer to feed a Loadcenter; there's a Ground Rod next to this installation used with another transformer.
    Can I Bond the new transformer to the existing Ground Rod?
    Unless it has been tested to show the ground resistance < 25 Ohms two ground rods are required.

    All grounding electrodes associated with a single structure have to be bonded together.

    When you create a new SDS it has to be connected to the structure's grounding electrode system (GES).

    250.30 is the answer.
    Bob

  4. #4
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    I think the post may be confusining. If there is only one rod then the first transformer probably needs 2- rods at least 6' apart and bonded together. Then, you can use those same rods for the second transformer also.

    I
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  5. #5
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    Neither transformer needs to connect to a rod.

    They need to tie into the grounding electrode system, which 480 volt system that supplies the transformer should already be connected to. Even if you desire to add additional rods or other electrodes for whatever reason - they still need to also be bonded to the GES.
    I live for today, I'm just a day behind.

  6. #6
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    Quote Originally Posted by petersonra View Post
    Unless it has been tested to show the ground resistance < 25 Ohms two ground rods are required.

    All grounding electrodes associated with a single structure have to be bonded together.

    When you create a new SDS it has to be connected to the structure's grounding electrode system (GES).

    250.30 is the answer.

    Just a note - 2017 NEC changed the definition of 'Structure' to; "That which is built or constructed, other than equipment."
    I take this to mean, pump, skid and transformer pads no longer require bonding of rebar.

  7. #7
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    Quote Originally Posted by Dennis Alwon View Post
    I think the post may be confusining. If there is only one rod then the first transformer probably needs 2- rods at least 6' apart and bonded together. Then, you can use those same rods for the second transformer also.

    I
    I know the Code requires 6 feet separation for supplemental electrodes (rods) however rods are frequently driven one on top of the other to achieve 25 ohms. The average, single ground rod in the US is about 40ohms.

  8. #8
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    Quote Originally Posted by Dale001289 View Post
    The average, single ground rod in the US is about 40ohms.
    Please provide the source of that statistic.

    Roger
    Moderator

  9. #9
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    Quote Originally Posted by roger View Post
    Please provide the source of that statistic.

    Roger

    Mastering the NEC - Mark Shapiro

  10. #10
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    Quote Originally Posted by Dale001289 View Post
    I know the Code requires 6 feet separation for supplemental electrodes (rods) however rods are frequently driven one on top of the other to achieve 25 ohms. The average, single ground rod in the US is about 40ohms.
    The ones driven one on top of the other are coupled together to create a single longer rod aren't they? You can't do this with the typical 8 foot rod without some sort of coupling method be it integrated into a rod or an additional fitting.

    40 ohms average is nothing more then trivia information. Doesn't mean if I go outside my front door and drive a rod there it will be 40 ohms.
    I live for today, I'm just a day behind.

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