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Thread: 705.12(D)(3) “Exception”

  1. #1
    Join Date
    Mar 2018
    Location
    Carlsbad California USA
    Posts
    4

    705.12(D)(3) “Exception”

    NEC Article 705.12(D)(3) “Exception”

    I am having trouble interpreting NEC Art 705.12(D)(3) “Exception” specifically the Exception.


    the following code: 2011 NEC 705.12(D)(3) Exception: “Connection shall be permitted to be made to the load side of ground-fault protection provided that there is ground-fault protection for equipment from all ground-fault current sources. Ground-fault protection devices used with supplies connected to the load-side terminals shall be identified and listed as suitable for backfeeding.”


    I have a 480V/277V Solar Switch Switch Board rated 1600A, which has a 1600A Bolted Pressure Switch with a GFP device.
    The Long time setting of the Switch is 1000A.


    The Switchboard has 10 -100A interactive utility connection (solar Inverters from solar arrays) which are connected on the load side of the BP Main GFP sensor.


    The exception permits this stating “provided that there is ground-fault protection for equipment from all ground-fault current sources. Ground-fault protection devices used with supplies connected to the load-side terminals shall be identified and listed as suitable for backfeeding.”


    My interpretation of the exception, is that the 10-100A breakers would also have to provide a level of GFP and the breaker and GFP sensor within the downstream load side connected Branch feeder breakers be listed for back feeding.


    This would provide the switchboard from Ground fault protection from the solar arrays (other than Utility ground fault current sources).


    Is this correct?


    Currently the 10-100A installed breakers are molded case fixed curved breakers that do not have GFP capability.




    The contractor’s argument is that due to the fact the inverters shutdown on a loss of Utility then the switchboard would be protected by the inverters GFCI devices. I do not agree with this due to the fact that the inverter (ungrounded inverters) GFCI devices sense current on the DC side of the inverter only.


    The EOR has written a letter stating that he has designed the system to code and excepts the installation as is.


    Please respond ASAP if possible and help us understand this Article.


  2. #2
    Join Date
    Feb 2003
    Location
    Seattle, WA
    Posts
    18,968
    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

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