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Thread: Best Grounding for 200a panel.

  1. #11
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    Quote Originally Posted by roger View Post
    The bottom line is the grounding has to all be connected period, no compromise.

    Forget the ground rods and run a isolated EGC straight to the first point of service, that's all you can do legally.

    You do understand that the earth does not clear a fault or provide personnel protection at the voltages you are working with don't you?

    Roger
    Yes of course Roger. I just have little experience with isolated systems. Thats why i am asking.

  2. #12
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    Quote Originally Posted by Dale001289 View Post
    Here's another interesting write-up on isolated grounding systems:
    http://www.ecmweb.com/nec/sensitive-electronic-grounding-industrial-locations

    Thank you Dale for the resource and thanks to all!

  3. #13
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    Using separate ground rods was very common (and dangerous) 25 years ago with serial connected computers, each computer had a different reference and that caused issues. The solution (and dangerous) was to lift the equipment ground (green wire)
    If you lift the green wire or do what you have proposed, if an amp has a short to the case, the little electrons want to go back to the source via the disconnected green wire. When someone touches the amp, they complete the circuit and can easily be electrocuted.
    Section 250.6 (D) Was added many code cycles ago:
    Limitations to Permissible Alterations. The provisions of this section shall not be considered as permitting electronic
    equipment from being operated on ac systems or branch circuits that are not connected to an equipment grounding
    conductor as required by this article. Currents that introduce noise or data errors in electronic equipment shall not be
    considered the objectionable currents addressed in this section.
    Moderator-Washington State
    Ancora Imparo

  4. #14
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    Quote Originally Posted by markebenson View Post
    Yes of course Roger. I just have little experience with isolated systems. Thats why i am asking.
    Isolated grounding basically means you isolate the EGC from other components all the way back to the service equipment or other common point, but it is still bonded to the EGC and GES at or near that point.
    I live for today, I'm just a day behind.

  5. #15
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    Quote Originally Posted by kwired View Post
    Isolated grounding basically means you isolate the EGC from other components all the way back to the service equipment or other common point, but it is still bonded to the EGC and GES at or near that point.
    I've been working with "isolated ground" systems for 30+ years (or so people think).

    I have gotten away from that expression and replaced it with Single-Point Ground (which is what it really is) in curriculum and literature to alleviate the confusion that some still have with specific bonding and grounding methods.

    I wish they had never used the IG designation for receptacles. Either way IG is a receptacle, not a system.
    Kirchoff and Ohm...the only laws that make sense

  6. #16
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    Quote Originally Posted by cuba_pete View Post
    I've been working with "isolated ground" systems for 30+ years (or so people think).

    I have gotten away from that expression and replaced it with Single-Point Ground (which is what it really is) in curriculum and literature to alleviate the confusion that some still have with specific bonding and grounding methods.

    I wish they had never used the IG designation for receptacles. Either way IG is a receptacle, not a system.
    Single point is what is intentionally grounded. Without intentional isolating, you still have other points that may be a non intentional grounding point.

    Steel raceways in steel framed building - you have grounding naturally occurring all throughout the facility even though you may only have limited points that are intended for "grounding" of the electrical system.

    Even if you pull EGC's through non metallic conduits - you bond them to items that may have a ground reference.

    Pull an "isolated grounding conductor" and attache it to an item that has a metal frame and is in contact with building steel or other grounded objects, you sort of don't really have an isolated ground anymore.
    I live for today, I'm just a day behind.

  7. #17
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    Quote Originally Posted by kwired View Post
    Single point is what is intentionally grounded. Without intentional isolating, you still have other points that may be a non intentional grounding point.

    Steel raceways in steel framed building - you have grounding naturally occurring all throughout the facility even though you may only have limited points that are intended for "grounding" of the electrical system.

    Even if you pull EGC's through non metallic conduits - you bond them to items that may have a ground reference.

    Pull an "isolated grounding conductor" and attache it to an item that has a metal frame and is in contact with building steel or other grounded objects, you sort of don't really have an isolated ground anymore.
    It's a lot of work making sure there aren't unintentional grounds.

    That's one of my primary jobs. My facility is less than 100,000 square feet, and only a portion uses single point grounding methods. I just have to keep my head on a swivel, make daily checks and supervise all installs well.
    Kirchoff and Ohm...the only laws that make sense

  8. #18
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    Quote Originally Posted by roger View Post
    As the others have mentioned, the new ground rods from this new sub-panel will still have to be connected to the existing grounding electrode system. Isolated equipment grounding does not mean isolated earthing.

    Roger
    Are these not auxiliary ground rods that don't have to be bonded to the GES?

  9. #19
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    Quote Originally Posted by jaggedben View Post
    Are these not auxiliary ground rods that don't have to be bonded to the GES?
    The way I'm reading the OP is that they want to have a stand alone GES, but regardless, even if they are "auxilaiary rods per 250.54 (take note of the last sentence) they would be connected to the EGC which is connected to the building GES so they would be common to the original system anyways.

    Roger
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