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Thread: 705.12(D)(2)(1)(3) -100% rated breaker exception needed

  1. #1
    Join Date
    Jul 2015
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    705.12(D)(2)(1)(3) -100% rated breaker exception needed

    This code section should account for 100% rated breakers being used.

    690.9(B) has an exception for this, but 705 does not accommodate this.
    690.8(B)(1) Has an exception for 100% rated breakers as well with similar language. I think this should be added here.

    I also think wording for switchboard/switchgear should be added where applicable to (a) thru (d) since some of these sections clearly only apply to panelboards, while this code provision could be used on larger equipment.

    As an example, I have 1440A of PV current, a 1600A 100% rated breaker, but yet I must account for 1800A on the bus which will not exist.

  2. #2
    Join Date
    May 2011
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    I think you must mean 705.12(D)(2)(3).

    I'm not sure I follow your reasoning. Several points:

    - See 705.60(B) for the exception allowing use of a breaker rated for continuous 100% use.
    - The 125% factor for continuous current is something that applies across the board to conductors, overcurrent devices and busbars (except as noted above). It has always accounted for current that doesn't exist. However the breaker rating(s) for inverters no longer play a part in the panelboard calculations as of the 2014 code. So unless the busbar is also 100% rated for continuous use I guess I don't follow the reasoning.
    - The language in 705.12(D)(2)(3) does apply only to panelboards (for the entire section). You have perhaps a good point that by referring entirely to panelboards the code does not give guidance on switchgear and switchboards. But maybe for a project with an 1800A output one can budget for an EE to write a letter that will satisfy an AHJ that the installation is safe.

  3. #3
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    Quote Originally Posted by 310 BLAZE IT View Post
    This code section should account for 100% rated breakers being used.
    It is worth mentioning that any 100% rated breaker you get will have to be mounted in it's own enclosure. You can't gang them up with other breakers.

  4. #4
    Join Date
    May 2013
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    Quote Originally Posted by iwire View Post
    It is worth mentioning that any 100% rated breaker you get will have to be mounted in it's own enclosure. You can't gang them up with other breakers.
    Or possibly in a listed enclosure built for multiple 100% rated breakers. In any case, it is the enclosure as a whole and all products within it, that govern the 100% OCPD rating. It is not plug-and-play in an enclosure that contains standard breakers.

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