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Thread: Bonding XO when not using a neutral conductor

  1. #21
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    Quote Originally Posted by infinity View Post
    I agree that is the reason, I would just use the bar as is from the manufacturer why bother with the extra work?
    i think it is a much more robust installation and it doesn't take much to do it, i keep a little wire wheel for drills in my toolbag

  2. #22
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    Quote Originally Posted by Kinexis View Post
    i think it is a much more robust installation and it doesn't take much to do it, i keep a little wire wheel for drills in my toolbag
    pretty easy to determine if it iscan issue (imo not)
    meter from case/frame to bar

    and is it an issue?
    assume 208 ph-g fault
    assume a bad 0.1 ohm across frame/bar joint
    i fault = 1200 A, should pose no primary tripping issue
    The difference between genius and stupidity is that genius has its limits.

  3. #23
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    If the bolts or machine screws attaching the bar to the enclosure are threaded through the enclosure material itself there's no need to remove paint. That sort of thing is for locknuts without teeth, perhaps especially when using an outdoor fitting with a gasket on one side. My opinion for what it's worth.

    I had an inspector gripe about paint the other day on a 3/4" offset nipple between two bonded enclosures. The locknuts were totally the type that scrape the paint away on their own, so I just ended up adding a grounding bushing cause I really didn't understand how I could improve contact by removing more paint. DMM measured .01 ohms between the nipple and the ground bar in the enclosures before I added the bushing. I was fairly ticked off about it.

  4. #24
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    Quote Originally Posted by jaggedben View Post
    If the bolts or machine screws attaching the bar to the enclosure are threaded through the enclosure material itself there's no need to remove paint. That sort of thing is for locknuts without teeth, perhaps especially when using an outdoor fitting with a gasket on one side. My opinion for what it's worth.

    I had an inspector gripe about paint the other day on a 3/4" offset nipple between two bonded enclosures. The locknuts were totally the type that scrape the paint away on their own, so I just ended up adding a grounding bushing cause I really didn't understand how I could improve contact by removing more paint. DMM measured .01 ohms between the nipple and the ground bar in the enclosures before I added the bushing. I was fairly ticked off about it.
    I agree with you, but also don't see that being universally accepted - especially by inspectors. I will argue with them if attaching said item to a factory provided mounting hole, that is it listed to go there, in fact with loadcenters and grounding bars same thing is sometimes installed in same manner at the factory.

    Will remove paint if mounting it in my own location, though I question whether it is really necessary in many cases, Bigger question may be if enclosure thickness is enough to engage enough threads for reliable continuity. Factory designated mounting holes - often it is.
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  5. #25
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    Quote Originally Posted by Ingenieur View Post
    pretty easy to determine if it iscan issue (imo not)
    meter from case/frame to bar

    and is it an issue?
    assume 208 ph-g fault
    assume a bad 0.1 ohm across frame/bar joint
    i fault = 1200 A, should pose no primary tripping issue


    use a dlro on both types of connections, there will likely be a significant difference, under fault conditions i want as low impedance on the ground fault return path as possible, the overrcurrent protection device is 1. more likely to open and 2. will open quicker and even if it is a millisecond quicker that with high current faults can prevent a lot of damage to equipment and people.

    also you have to consider the possibility of corrosion for the life of the system, the more contact area originally the more corrosion the system can withstand, tha'ts also why i suggested the conductive grease


    to myself i justify it easily with simple cost benefit, it takes me relatively little time to do it and i think it makes the installation much more robust

  6. #26
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    the bar is likely serated for good engagement
    likely attached with boths/washers, unlikely to count only on tapping screws
    I would like to believe the guys designing the gear have minimum competency

    the enclosure is not considered intentionally as part of the egc/gnd fault path, although effective bonding is important

    multiple parallel ground paths (conduit systems out to other enclos where a bond is present to the egc BACK to the gnd bar in question)

    a little impedance may result in a marginally longer trip time but magnitude is reduced, so a wash

    going the extra mile won't hurt, but imo yeilds little (if any) benefit
    I'll need to look at some in the field, never really thought about it
    just measured enclosure to lug R and usually in the few 100'ths range
    the egc itself is much higher
    The difference between genius and stupidity is that genius has its limits.

  7. #27
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    The terminal bar in the transformer bolted to the enclosure is only bonding the enclosure. The transformer with the terminal bar is listed equipment so for me I won't waste a second removing it and scraping off the paint.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  8. #28
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    Quote Originally Posted by infinity View Post
    The terminal bar in the transformer bolted to the enclosure is only bonding the enclosure. The transformer with the terminal bar is listed equipment so for me I won't waste a second removing it and scraping off the paint.
    I agree. I wouldn't waste a second doing it and I wouldn't waste a second thinking about it.
    If you go and decide to dance with a gorilla the dance ain't over till the gorilla decides it's over.

  9. #29
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    i know the bar is only for enclosure for code purposes but good parallel paths lower circuit impedance, i'm not saying it's required or should be just saying that's what i do and why.





    Quote Originally Posted by Ingenieur View Post
    a little impedance may result in a marginally longer trip time but magnitude is reduced, so a wash

    higher magnitude is better, it will trip even quicker (less energy will be released in fault, arc flash/blast, it can be lowered to an insignificant little spark instead of a second long big incident with lower current)
    Last edited by Kinexis; 05-09-18 at 04:04 PM.

  10. #30
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    Quote Originally Posted by Kinexis View Post
    higher magnitude is better, it will trip even quicker (less energy will be released in fault, arc flash/blast, it can be lowered to an insignificant little spark instead of a second long big incident with lower current)
    Until a certain point is reached that equipment can't take the forces imposed on components, which is what SCC and AIC ratings are about.
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