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Thread: Understanding Arc Flash rating requirement

  1. #21
    Join Date
    Mar 2013
    Location
    Rutland, VT, USA
    Posts
    228
    Quote Originally Posted by MikeChaco View Post
    Thankyou for the replies.

    The image of the Arc rating label did not get uploaded.

    I am doingvarious maintenance procedures, including adjusting packings but that isdone with pump running.

    My issue is I have been told 2 different things from ourelectricians. 1 says hazard is only when cover is off, I asked anelectrical engineer and he agreed. The other says a Cat 2, 25cal suit isneeded to throw the disconnect with door closed. I read NFPA 70e Table 130.7to require Cat 2. For Metal Clad switch gear 1kV and above.

    Our labels do not say with cover on or off. To me that should mean asconditions are currently.

    My goal here is to start an Arc Flash PPE program. I am attempting to have my company supply, or assist in the cost, of Arc Flash clothing. We work in buildings that are full of equipment. Just being in the building makes us in the boundaries.

    I am not trying to rewire cabinets here, just trying to understand these labels correctly. I feel throwing a disconnect puts me in harms way, and I am trying to validate or dismiss these concerns.


    One of the labels on our gear reads as follows;

    QUALIFIED WORKERS ONLY
    PPE REQUIRED
    438 inch Flash Hazard Boundary
    13.6 cal/cm2 Flash Hazard at 36 inches

    Category 3
    FR Shirt & Pants with FR Coverall with combined AR of at least 25, Hardhat, Hearing Protection, Safety Glasses, Flash Suit Hood, Arc-rated Gloves & leather work shoes

    4160 VAC Shock Hazard when cover is removed
    1 Class Glove with Leather Protectors
    60 inch Limited Approach (Fixed Circuit)
    26 inch Restricted Approach
    7 inch Prohibited Approach

    How old is the study that determined the incident energy levels and generated the labels? Was actual utility available fault current used? I ask because I have seen studies that did not use utility fault current and the results were erroneous when compared to using the actual fault currents.

    There seems to be a lot of confusion and mis-understanding in your company on arc flash. For instance the statement about being in the boundary just because you are in the building is erroneous.

    I would highly recommend that you and others in your company take an 8hr NFPA 70E training course before you implement anything as you want to do it right the first time.

  2. #22
    Join Date
    Sep 2003
    Location
    Connecticut
    Posts
    225
    Quote Originally Posted by MikeChaco View Post


    438 inch Flash Hazard Boundary
    13.6 cal/cm2 Flash Hazard at 36 inches

    Category 3
    FR Shirt & Pants with FR Coverall with combined AR of at least 25, Hardhat, Hearing Protection, Safety Glasses, Flash Suit Hood, Arc-rated Gloves & leather work shoes

    4160 VAC Shock Hazard when cover is removed
    1 Class Glove with Leather Protectors
    60 inch Limited Approach (Fixed Circuit)
    26 inch Restricted Approach
    7 inch Prohibited Approach

    A 13.6 cal./cm^2 arc flash hazard at 36 inches seems to be assuming a working distance for an arc in open air.

  3. #23
    Join Date
    Dec 2011
    Location
    Ocala, Florida, USA
    Posts
    2,095
    Quote Originally Posted by iwire View Post
    Besides what other people have said I will ask you this.

    When you turn off the switch how do you do the next required step which is verifying the power is off?

    You are required to wear PPE for that step.
    I agree with that. But that was not what the OP was asking. From a mechanical perspective I have not been aware of a requirement that they verify that the power is off when they are using a disconnect to isolate a motor to change a belt or something. Perhaps they are required to, but I'd bet that is even less likely than a residential roofer wearing a harness.


    I know what I don't know, and I know where to go to find it!

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