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Thread: Clearances to meet Phase-to-Phase for Bus Bar

  1. #1
    Join Date
    Aug 2016
    Jackson, NJ

    Clearances to meet Phase-to-Phase for Bus Bar

    Our plant has a 3-phase, 480 VAC transformer with copper braids coming off of the transformer to outdoor bus bar that feeds into a bus duct. One of the braids had faulted and burnt through, and we are now in the process or replacement. The contact pads on the new braids are much thicker than the existing ones (Most likely the reason for the fault; wrong size was installed). My concern is the distance of the new, contact pads, with bolts heads, between phases where it comes up into the bus duct.

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    With the bolt head sticking out, I am slightly worried about a possibility of arcing over if a bolt head was too close to an adjacent phase, only slightly as there is still some gap.

    I was wondering is there is any guidance through UL, NEC, etc on clearances, distances, etc? Any feedback you may have is greatly appreciated.

  2. #2
    Join Date
    Feb 2003
    New York, 40.7514,-73.9925
    Table 408.56 addresses it for SWBDs, SWGR and Panelboards, but those are enclosed.

    I'm sure your exterior condition has a special situation to consider

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