View Poll Results: A 480V receptacle or panel is feed from a MCB located in an MCC. The MCB is 100A and

Voters
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  • Would you calculate the arc-flash level at the panel/receptacle?

    13 86.67%
  • Would you 'assume' that the instantaneous MCB would reduce the available level to 0?

    1 6.67%
  • Would you just take the cal level whatever is at the MCC?

    0 0%
  • None of the above

    1 6.67%
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Thread: Arc-flash

  1. #11
    Join Date
    Feb 2003
    Location
    Illinois
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    18,977
    Quote Originally Posted by weressl View Post
    So how does a sealed load-breaking receptacle offers you more safety than an MCB or MCP behind the MCC's closed door?
    That is a good question but the ads for those products say that they do.
    ... Eliminate the need for arc flash protection boundaries and cumbersome PPE. Decontactors maintain a NFPA 70E "hazard risk category" equal to zero. ...
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  2. #12
    Join Date
    Jul 2004
    Location
    Texas by the Gulf, geat crab, great shrimp
    Posts
    5,407
    Quote Originally Posted by don_resqcapt19 View Post
    That is a good question but the ads for those products say that they do.
    I fail to see how a circuit breaker that is designed to interrupt/withstand 65kA would be less safer. yet the conscensus is that the NFPA 70E says so.....

  3. #13
    Join Date
    Feb 2003
    Location
    Wisconsin
    Posts
    8,711
    [QUOTE=weressl;1496117... yet the conscensus is that the NFPA 70E says so.....[/QUOTE]
    NFPA 70E makes no such claim. You are dealing with people's reluctance to follow the requirements of NFPA 70E that say a risk analysis must be performed.
    Just because you can, doesn't mean you should.

  4. #14
    Join Date
    Feb 2003
    Location
    Portage, Indiana NEC: 2008
    Posts
    9,725
    Quote Originally Posted by weressl View Post
    With the microswitch interlock the switching occurs remotely in the MCC, so the 'interaction' with the device does not represent a danger as the fault would occur remotely at the MCC. In other words the 'interaction' can not produce a local fault unless of course the interlock is faulty, in which case arc fault IS assured.

    With the Square D integrated switch the circuit break would occur locally, at the switch, so the arc-flash hazard is present, level must be determined and posted.
    The integrated Square D ones we have remove the arc flash problem from using the receptacle but does not remove the problem from working on the disconnect as it will still require PPE, this is why it confuses me as to what operation of a disconnect can require PPE's but they design integrated receptacle/disconnects interlocked to make just the receptacle safer???? although I will say that the disconnects are made very strong and even the door is bolted shut, so maybe they can contain the arc flash?
    Wayne A. From: N.W.Indiana
    Be Fair, Be Safe
    Just don't be fairly safe

  5. #15
    Join Date
    Jul 2004
    Location
    Texas by the Gulf, geat crab, great shrimp
    Posts
    5,407
    Quote Originally Posted by jim dungar View Post
    NFPA 70E makes no such claim. You are dealing with people's reluctance to follow the requirements of NFPA 70E that say a risk analysis must be performed.
    Read carefully what I actually said, which is what you're saying.

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