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Thread: Intent of 110.26 (E), dedicated equipment space

  1. #1
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    Intent of 110.26 (E), dedicated equipment space

    Can anyone direct me to some evidence explaining the intent of 110.26 (E), dedicated equipment space? This has come up on several projects, and it's often contentious. The NEC handbook commentary (2014) is all about the 'how' and not the 'why'.

    Here are the two claims I tend to hear about the purpose of DES, and the problems I see with both:

    A. To protect the equipment from leaks / damage due to failures in other systems.
    1. By the wording, the section only applies to "switchboards, switchgear, panelboards, and motor control centers" as opposed to all electrical equipment. Why would other kinds of equipment not require this basic protection?
    2. Why does DES exclude all "foreign systems," including things that cannot leak? (for example, phone systems or fire alarm devices)


    B. To allow space for future conduits.
    1. Providing space for easy future expansion is not in the scope of the NEC. I can't think of any other code provision based on that concept.
    2. The height of DES is six feet above the equipment - surely future conduits are not the only reason for that much space?
    3. This section also includes the requirement for "protection from damage" and for leak protection when foreign systems are located above the DES. That strongly implies that future conduit space is not the goal here.

  2. #2
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    Part of the reason is that there is never not going to be an install that doesn't need some kind of addition or correction. By keeping the equipment space open it allows us electricians to get in there and do the work we need to do.
    Once in a while you get shown the light
    In the strangest of places if you look at it right. Robert Hunter

  3. #3
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    Quote Originally Posted by ActionDave View Post
    Part of the reason is that there is never not going to be an install that doesn't need some kind of addition or correction. By keeping the equipment space open it allows us electricians to get in there and do the work we need to do.
    Yeah, it's absolutely good practice - but the NEC isn't a good practice guide. If I were going to require open space for future work, it would apply to all equipment, and be based on the size of the enclosure, or number of conductors, or something like that. The way this section is written makes me think the intent is something more specific.

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    ... anybody else?

  5. #5
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    Quote Originally Posted by Electrum View Post
    ... anybody else?
    Sure, while I cannot give you any official view or references and I am too lazy to look up the original adoption of the rule and why in the NEC archives, I agree with ActionDude above.

    I can say there is at least one highly respected EE here that if of the same opinion.

    If you are really curious look up the info at the NFPA website and review the ROPs, ROCs and TC C reports.
    "Electricity is really just organized lightning." George Carlin


    Derek

  6. #6
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    Quote Originally Posted by Electrum View Post
    If I were going to require open space for future work, it would apply to all equipment, and be based on the size of the enclosure, or number of conductors, or something like that.
    The four items to which this article applies are the only ones that are likely to require the future installation of new conduits. Once you install a transformer, an ATS, a VFD, a fused disconnect, or any other item, it will have all the conduits it will ever need. So I will hold on to the opinion (and I know it is nothing more than that) that the reason has to do with future conduits.

    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

  7. #7
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    Quote Originally Posted by charlie b View Post
    The four items to which this article applies are the only ones that are likely to require the future installation of new conduits. Once you install a transformer, an ATS, a VFD, a fused disconnect, or any other item, it will have all the conduits it will ever need. So I will hold on to the opinion (and I know it is nothing more than that) that the reason has to do with future conduits.

    And the EE I referred to shows up and agrees.
    "Electricity is really just organized lightning." George Carlin


    Derek

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