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4 Foot Flash Protection Boundary??

Discussion in 'General Discussion' started by Paul Sedro, Jul 4, 2007.

  1. Paul Sedro New Member

    We are in the middle of conducting our first arc flash study. We are getting many calculated flash boundaries of less than the 4 foot distance that NFPA 70E has. Do any of you use the smaller calculated boundaries or do you use the 4 foot distance as the minimum??
    b.t.w. Nice Forum!
    Paul Sedro, Jul 4, 2007
    #1

  2. JoeB New Member

    4 Foot Boundary

    We started out using the calculated numbers, but then decided it would be more consistant to adopt a standard "minimum" distance of 4 feet. We have a few distances greater than 4 feet but 4 is our minimum.
    JoeB, Jul 4, 2007
    #2

  3. Paul Sedro New Member

    4 Foot Boundary

    Joe B - what do you post on the labels? 4 ft?
    Paul Sedro, Jul 4, 2007
    #3

  4. JoeB New Member

    4 Foot Boundary

    We use the labels generated by the program so the distance will vary. We use 4 ft. as part of our electrical safety standard.
    JoeB, Jul 5, 2007
    #4

  5. kencybart New Member

    Default Arc-Flash Boundary

    The default arc-flash boundary for systems 600V and less is 4 feet. However, it depends on the available fault current and clearing time of the overcurrent protective device. According to NFPA 70E, the combination cannot exceed 300,000 Amp-cycles. What this means - is that if the available fault current is 50,000 amps, then the clearing time cannot exceed 6 cycles (100 milliseconds).
    Ken Cybart
    Littelfuse, Inc.
    kencybart, Nov 20, 2007
    #5

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