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    NEC 312.8 Question

    NEC 312.8 Question

    New postby RobShepp on Thu Nov 27, 2014 8:57 am

    Good moring Jerry,
    I have a question about this part of the NEC, the first sentence implies that enclosures for switches or over-current devices can not be used as raceways or junction boxes "unless adequate space for this purpose is provided" . I understand that the enclosure is listed under UL 67 which does not test for this type of installation or work space specifically, but I also have come to understand that cabinets listed for UL 67 have been tested for UL 50 indiviually without the internal components that make up the first listing. UL 50, per my understanding, does qualify the panel/cabinet for use as a raceway/junction box. My question is, what is the specific definition of "adequate space" for raceways or splices? Is this defined in the UL listing or the NEC? The second sentence refers to the maximum allowable filling of the space, but does not seem to imply that sufficient space is provided.

    312.8 Enclosures for Switches or Overcurrent Devices. Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless adequate space for this purpose is provided. The conductors shall not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.
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    Re: NEC 312.8 Question

    New postby Jerry Peck - Codeman on Thu Nov 27, 2014 9:38 am

    Rob,

    One of my many favorite sections, however, before I reply, read the rewording of that section in the 2011 and 2014 NEC editions (Florida is still on the 2008 NEC, but the newer editions will show where the NEC is going).
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    Re: NEC 312.8 Question

    New postby RobShepp on Thu Nov 27, 2014 10:02 am

    The 2011 NEC does address this issue as far as "maximum allowable usage of space" by the conductors/connections in question. I believe this reference to usable space doesn't address "working space". Or maybe I'm splitting hairs and they are the same? Thinking out loud, it has been my experience that qualifying entities like UL specifically do not address clear violations of code(NEC) in their applications(or vice versa), but more of the standards of their testing only....if that makes sense? The only refernce I can give is a recent case where a roofing system was improperly installed per the NOA, I contacted the Metro-Dade approval to let them know and they said "all we care about is that the roofing system meets the minimum required uplift". It seems to say(NEC) that their definition of working space is anything that doesn't take up a certain cross section of space in an enclosure or cabinet. Or, deos UL define in another location the term work space?
    I was also wondering what the actual manufacturer's had to say about there cabinets/enclosures being used for this purpose?

    What I'm seeing in the field is complete enclosures/cabinet relocations where the old cabinet is used as a junction box for all of the connections that have been spliced to the new panel location. The use of 1 or 2 spliced connections doesn't really concern me to much, the use of a cabinet/enclosure to house 30 to 40 spliced connections does. I see this quite frequently in older properties.
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    Re: NEC 312.8 Question

    New postby Jerry Peck - Codeman on Thu Nov 27, 2014 11:47 am

    In the 2008 and earlier versions of the NEC that space was, as stated in the NEC section you posted (I've changed the highlighting with bold and underlining):
    - 312.8 Enclosures for Switches or Overcurrent Devices. Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless adequate space for this purpose is provided. The conductors shall not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.

    I contacted UL years ago with that question and their response was, and is unchanged to my knowledge, that no "space for this purpose is provided".

    That NO conductors were permitted to be run through a panel going to or from someplace else and which did not land in the panel. This permitted the panels to have sections of conductors spliced onto existing conductors (such as for repairs or when replacing a panel and the original conductors were now too short to reach a terminal to land on - splice on a short extension piece of conductor to make the existing conductor long enough to reach the terminal. As long as the conductors, their wire nuts, etc., did not fill the wiring space more than 40 percent nor the the wire nuts, splices, etc., fill the wiring space more than 75 percent, that was okay.

    This meant that NO conductors were permitted to be run through the panel which were not supplied by that panel, i.e., when the panel was de-energized all the conductors passing through or in the panel were also de-energized. Makes for good safety sense.

    The revised wording of removing the requirement that the space 'be provided for that purpose' now means (after the 2011 and 2014 NEC) that conductors will be allowed to run through panels even though they are energized from another panel, as long as the conductors, all of the conductors, do not fill the cross sectional area more than is permitted. This does not make for good safety sense, but that is what the change will allow.

    When the panelboard section is removed from the cabinet, the cabinet becomes like any other cabinet without overcurrent devices or switches - it is a large junction box. The deadfront cover needs to have all the open breaker slots / fuse holes filled or covered to restore the deadfront cover to its original intended purpose of closing off everything behind it so no energized components are exposed when the cover is opened.

    Now you just need to make sure that the space in the cabinet is not overfilled - and it takes a lot or conductors and splices to overfill a cabinet which originally had a panelboard in it after that panelboard has been removed.
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    Re: NEC 312.8 Question

    New postby RobShepp on Thu Nov 27, 2014 11:57 am

    So the NEC trumps the UL? The 2011/2014 NEC allow these types of connection, but as you stated above the NEC specifies adequate space as 1 and 2 for spliced conductors. The UL lsiting does not test for this application, or does not require this application to be tested for? I might not be explaining myself correctly, if the NEC says "yes", but the UL listing says "we didn't test or qualify for that"....how does the NEC and UL work together on this?
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    Re: NEC 312.8 Question

    New postby Jerry Peck - Codeman on Thu Nov 27, 2014 3:46 pm

    RobShepp wrote:So the NEC trumps the UL?


    Not really.

    The UL standard is what items are tested and listed to. The NEC permits, does not permit specified uses.

    In this case, the NEC says, in 2008 and before, that cabinets used for overcurrent devices or switches could not be used as junction boxes or (basically) conductors passing through the vertical section of a panelboard unless space was specifically provided for that purpose, and UL did not list a space specifically for that purpose - i.e., UL didn't say that is was specifically allowed (however the UL standard did not say it was not allowed either - the UL standard did not address it or test it in the standard, the UL engineers told me it was not permitted based on the lack of it being specifically permitted, which is what the NEC said it had to be - specially permitted).

    The 2011 and 2014 NEC simply dropped the reference to a space needing to be specifically for that purpose - now the UL standard and the NEC are in sync with each other, neither now says yes or no.

    Think of it as speed limit sign which state 65 mph maximum ... you are allowed to drive 5 mph and it is legal.

    However, if the speed limit sign states 65 mph maximum and 40 mph minimum, then you must drive at least 40 mph, but not greater than 65 mph.

    The NEC simply dropped the minimum speed limit, and the UL standard never addressed the minimum speed limit - which leaves them matching each other.

    (Note: 11-27-14 @ 9:54 pm I tweaked the wording for more clarity by separating the UL "standard" from "UL" by specifying which references were to the UL standard and not to UL engineers themselves.)
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    Re: NEC 312.8 Question

    New postby RobShepp on Fri Nov 28, 2014 8:52 am

    Thank you Jerry.
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