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

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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.

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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.
    If you go and decide to dance with a gorilla the dance ain't over till the gorilla decides it's over.

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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?

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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

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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.

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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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    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.

    I was hoping you'd chime in. If it's space for future conduits, why do you think the DES requirement also triggers the required leak protection for things above? And what do you make of the "protection from damage" wording?

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    Quote Originally Posted by Electrum View Post
    I was hoping you'd chime in. If it's space for future conduits, why do you think the DES requirement also triggers the required leak protection for things above? And what do you make of the "protection from damage" wording?
    As I said, you can read the original proposals with the reasoning/substantion for code sections at NFPA. They give you a free account.
    "Electricity is really just organized lightning." George Carlin


    Derek

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    Well, I did as Jumper suggested and promptly fell down a rabbit hole on the NFPA website, trying to track this code requirement to figure out what it’s “really” supposed to be for. I thought I would share my findings with you all.

    The reason that “dedicated equipment space” only applies to switchgear and panels is very simple and has nothing to do with future conduits: it was originally part of Article 384, and written by that committee. The original proposal (1981) cited a vague safety concern about how pipes and ducts in electrical rooms are a bad idea. The committee agrees, but one member does comment that this is really beyond the scope of 384 and should apply to other equipment as well, giving transformers as an example. Much later in 2002, the text got moved to Article 110 by the Correlation Committee, but the restriction of “only for things under Art 384” was carried along with it when it moved. Various revisions between 1981 and 2002 hash out the exact dimensions of the space and add various exceptions and FPNs that, taken as a group, strongly suggest that protection of the equipment was viewed as the intent during that period. However, starting in 1999 you can see debate on the committee about whether DES is really for equipment protection, or if it is for conduit installation. In 1999 the “equipment protection” side was winning, but since 2002 the “conduit installation” side has been in control, and that’s how our current code is written.

    My opinion – I think the requirement was originally for general equipment protection, but was placed in an inappropriately specific article. Since then, people have taken that over-specificity as evidence of a different intent. But as of today, that is the official position of the NFPA... which is why I’m technically allowed to install unprotected piping over a VFD, but not over a panel. I think that if the person who originally proposed this back in ’81 had submitted it to the 110 committee instead of the 384 committee, we would not have this contradiction today.

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