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Thread: Bonding of Isolated Grounding system to plant electrode system, i.e. ground loop

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    Bonding of Isolated Grounding system to plant electrode system, i.e. ground loop

    Is it permissible to have a removable link installed between an Isolated grounding system i.e., underground copper conductor off a Triad and point where it ties into the Plant grounding electrode system, i.e. ground ring?

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    Quote Originally Posted by Dale001289 View Post
    Is it permissible to have a removable link installed between an Isolated grounding system i.e., underground copper conductor off a Triad and point where it ties into the Plant grounding electrode system, i.e. ground ring?
    There is no requirement that an EGC be continuous.

    However I'm not sure that what you are describing is even code legal. The so-called isolated ground goes back to the EGC at the service point not to the grounding electrode system.
    Bob

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    Quote Originally Posted by petersonra View Post
    There is no requirement that an EGC be continuous.

    However I'm not sure that what you are describing is even code legal. The so-called isolated ground goes back to the EGC at the service point not to the grounding electrode system.
    The so-called isolated ground goes back to a common EGC point not to the grounding electrode system. Quite often the common EGC point is the EGC/MBJ point at the service.

    @Dale001289
    The electrode triad can be tied to any point on the EGC system, or it can be tied directly to the grounding electrode system (GES). However, once the triad is in place, it must be and remain connected.
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    Quote Originally Posted by Smart $ View Post
    The so-called isolated ground goes back to a common EGC point not to the grounding electrode system. Quite often the common EGC point is the EGC/MBJ point at the service.

    @Dale001289
    The electrode triad can be tied to any point on the EGC system, or it can be tied directly to the grounding electrode system (GES). However, once the triad is in place, it must be and remain connected.

    Smart: Your last sentence is where I want to focus. The triad will remain connected, however, the 'removable link' constitutes a gap between the triad and point where all other grounding cables connect. To me, this would be violation of 250.50, however, 250.6(B) seems to allow it - then there's 250.8(A) to consider...I'm so confused (looking at 2017 NEC handbook)

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    Quote Originally Posted by Dale001289 View Post
    Smart: Your last sentence is where I want to focus. The triad will remain connected, however, the 'removable link' constitutes a gap between the triad and point where all other grounding cables connect. To me, this would be violation of 250.50, however, 250.6(B) seems to allow it - then there's 250.8(A) to consider...I'm so confused (looking at 2017 NEC handbook)
    Any part of the grounding electrode system can be removable other than the one required by 250.64(C) to be continuous. Look at 250.70.
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    Quote Originally Posted by ActionDave View Post
    Any part of the grounding electrode system can be removable other than the one required by 250.64(C) to be continuous. Look at 250.70.
    Removable, yes... provided minimum or required electrodes are maintained. Electrodes have to physically be removed or otherwise rendered 'not an electrode'. They cannot just be disconnected. But Dale wanting a removable link suggests to me he does not want to remove the triad electrodes.

    @Dale001289
    Exactly what are you seeing as objectionable current requiring the application of 250.6(B)? How would 'unlinking' the triad result in stopping objectionable current that isn't also and will remain on the GES in general?
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    Quote Originally Posted by Smart $ View Post
    Removable, yes... provided minimum or required electrodes are maintained. Electrodes have to physically be removed or otherwise rendered 'not an electrode'. They cannot just be disconnected. But Dale wanting a removable link suggests to me he does not want to remove the triad electrodes.

    @Dale001289
    Exactly what are you seeing as objectionable current requiring the application of 250.6(B)? How would 'unlinking' the triad result in stopping objectionable current that isn't also and will remain on the GES in general?

    The sole connection to plant grounding system as required by 250.50 can result both common mode noise and objectionable currents. The removable link allows the field to 'trouble-shoot' the isolated grounding system and theoretically eliminate both.

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    Quote Originally Posted by Dale001289 View Post
    The sole connection to plant grounding system as required by 250.50 can result both common mode noise and objectionable currents. The removable link allows the field to 'trouble-shoot' the isolated grounding system and theoretically eliminate both.
    A single connection (as in sole) of the GES does not cause a ground loop, ground loops are caused by multiple connections. Your best solution would be to remove the "magical triad".

    Roger
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    Mainly it's about common mode noise - not a loop


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    Quote Originally Posted by Dale001289 View Post
    Mainly it's about common mode noise - not a loop
    So why not provide a link to the isolated ground system in the service equipment where it can be accessed for testing? As mentioned in post #2, this isolated EGS should not connect to the GES itself.

    Roger
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