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Thread: Welder Ground Lead

  1. #71
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    IMHO the LPS ground system _must_ be bonded to all other grounding electrodes, otherwise earth 'step potentials' could be coupled via the _separate_ grounding electrodes to cause differences of potential on different metal components which are separately grounded.

    With that said, it would seem to me that the bonding and lightning down conductors should be routed so that current is not likely to be coupled into the building electrical system via these bonds.

    When you consider lightning strikes, a direct hit is much less likely than a nearby hit which causes ground currents. You must design for these earth currents, not just the direct hit.

    -Jon

  2. #72
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    Quote Originally Posted by FionaZuppa View Post
    that wasnt the point, and i dont think anyone was stating [that lightning is comparable to welding current]
    MAC702 seemed to be saying so, to me, in posts #42 and #49. This wasn't originally a thread about lightning protection. Regardless of the best practices with respect to bonding an LPS, I hope we can agree that it has little to no bearing on the safety of welding currents such as those brought up in the OP.

  3. #73
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    Quote Originally Posted by winnie View Post

    With that said, it would seem to me that the bonding and lightning down conductors should be routed so that current is not likely to be coupled into the building electrical system via these bonds.

    -Jon
    if the LPS is tied to GEC (and the EGC) how can that also be "...routed so that current is not likely to be coupled into the building electrical system"?? 100kA and 4Mvolts with just a fraction of an ohm in GEC means lots of volts and amps across the GEC & EGC, they are just shunts at that point.

    and if lightning is a ground strike then its not hitting the LPS??


    an isolated LPS that uses say 3/4"dia steel rod in center of a 4"dia pvc pipe filled with glass bead, and then tied to a 20ft ground rod, seems to me a better way. but, if the building is 1500ft tall then obviously not a real ez way to construct it.

  4. #74
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    Quote Originally Posted by jaggedben View Post
    MAC702 seemed to be saying so, to me, in posts #42 and #49. This wasn't originally a thread about lightning protection. Regardless of the best practices with respect to bonding an LPS, I hope we can agree that it has little to no bearing on the safety of welding currents such as those brought up in the OP.
    I don't think I inferred that welding and lightning currents were the same, just that the latter is possibly a noteworthy thing to the discussion. I wouldn't have thought it has "little to no bearing..." I thought I had freely admitted to no expertise in lightning protection.

  5. #75
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    Quote Originally Posted by FionaZuppa View Post
    if the LPS is tied to GEC (and the EGC) how can that also be "...routed so that current is not likely to be coupled into the building electrical system"?? 100kA and 4Mvolts with just a fraction of an ohm in GEC means lots of volts and amps across the GEC & EGC, they are just shunts at that point.
    But I don't believe there's any particular reason why a GEC or EGC should see the full lightning voltage if only one end is connected to ground and it's not a direct strike. In any case, it is an not apples to apples comparison to a welding current.

    Quote Originally Posted by MAC702 View Post
    I don't think I inferred that welding and lightning currents were the same, just that the latter is possibly a noteworthy thing to the discussion. I wouldn't have thought it has "little to no bearing..." I thought I had freely admitted to no expertise in lightning protection.
    'little to no bearing' is my opinion. They are just very different phenomena. If you design a road for racecars, you don't test it by running dump trucks on it, or vice versa. Also, for what it's worth, welding currents are comparable to NEC applications and the NEC can be read to prohibit using random EGCs as a welding return, as Goldigger said a long time ago in this thread (objectionable current). The NEC does not cover lightning protection, so judging EGCs by their performance in a lightning storm isn't a comparable standard. Apples and oranges.

  6. #76
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    Quote Originally Posted by jaggedben View Post
    But I don't believe there's any particular reason why a GEC or EGC should see the full lightning voltage if only one end is connected to ground and it's not a direct strike. In any case, it is an not apples to apples comparison to a welding current.



    'little to no bearing' is my opinion. They are just very different phenomena. If you design a road for racecars, you don't test it by running dump trucks on it, or vice versa. Also, for what it's worth, welding currents are comparable to NEC applications and the NEC can be read to prohibit using random EGCs as a welding return, as Goldigger said a long time ago in this thread (objectionable current). The NEC does not cover lightning protection, so judging EGCs by their performance in a lightning storm isn't a comparable standard. Apples and oranges.
    FWIW, in terms of electrical safely rather than design and use, a transformer-isolated welding machine could be considered to incorporate an SDS.

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