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Thread: What is the larget size of conduit allowed for 24" handhole?

  1. #1
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    What is the larget size of conduit allowed for 24" handhole?

    Need help on the following NEC topic:

    -Which section of NEC refers to the following statement:
    handhole size is not to exceed largest conduit size times 8?

    So, for 24" handhole only 3" conduit allowed (3"x8=24" max), right?

    -Does it apply to any condition? What is the intend of the code? Are there exceptions to the rule?

    Contractors and maintenance teams seems to be more comfortable with 4" conduit in 24" handhole and didn't have any problems so far.

    Thanks!

  2. #2
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    See 314.30 which sends you 314.28.

    Attachment 18480
    Last edited by jumper; 09-13-17 at 05:04 PM.
    "Electricity is really just organized lightning." George Carlin


    Derek

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    Interpretations for NEC section 314.28

    Thx! Are there interpretations for this section in NEC or handbook?

    Quote Originally Posted by gene_b View Post
    Need help on the following NEC topic:

    -Which section of NEC refers to the following statement:
    handhole size is not to exceed largest conduit size times 8?

    So, for 24" handhole only 3" conduit allowed (3"x8=24" max), right?

    -Does it apply to any condition? What is the intend of the code? Are there exceptions to the rule?

    Contractors and maintenance teams seems to be more comfortable with 4" conduit in 24" handhole and didn't have any problems so far.

    Thanks!

  4. #4
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    Quote Originally Posted by gene_b View Post
    Thx! Are there interpretations for this section in NEC or handbook?
    Handbook probably has commentary. Commentary is note code and not enforceable.

    The math is pretty straight forward, not really much to interpret IMO.

    Read the code section and then ask questions here if needed.
    "Electricity is really just organized lightning." George Carlin


    Derek

  5. #5
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    Nice graphic. I wish the NEC could just be more graphic like that, and less text.

    The handbook does have some commentary, but its too long to retype, and not much different than the code. The one note that may be worth mentioning is that if the wires are spliced instead of pulled, the distances are reduced.

    I do think there are a couple of exceptions where the basic sizing rules don't apply:

    314.28 mostly applies to conductors #4 and larger. So if you have an oversized conduit for a bunch of #6's, or smaller wires, then the sizing rules wouldn't apply.

    Also, if the conduits come up into the bottom of the handhole (not into the side), different sizing rules apply.

  6. #6
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    Quote Originally Posted by steve66 View Post
    ...
    Also, if the conduits come up into the bottom of the handhole (not into the side), different sizing rules apply.
    That actually requires a larger enclosure as that would make it a "U" pull requiring 6 x trade size between the conduits. Even with 4" conduits against the far sides, the box would have to be larger than the 32" required for a straight pull with 4".
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

  7. #7
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    Quote Originally Posted by don_resqcapt19 View Post
    That actually requires a larger enclosure as that would make it a "U" pull requiring 6 x trade size between the conduits. Even with 4" conduits against the far sides, the box would have to be larger than the 32" required for a straight pull with 4".
    Even with the "top" of the enclosure being removable?

  8. #8
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    Quote Originally Posted by GoldDigger View Post
    Even with the "top" of the enclosure being removable?
    The exception to 314.28(A)(2) only changes the distance between the conduit and the wall opposite the conduit entry. The required distance between the conduits does not change.
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

  9. #9
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    Handhole size based on conductor 314.28(3)

    Thanks a lot! There is another option to justify a handhole size which based on the conductor(s) size, rather than conduit diameter, but it requires the box or conduit body to be permanently marked This option is not feasible by my agency at this time. Are there examples around the state?

    Quote Originally Posted by jumper View Post
    Handbook probably has commentary. Commentary is note code and not enforceable.

    The math is pretty straight forward, not really much to interpret IMO.

    Read the code section and then ask questions here if needed.

  10. #10
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    Quote Originally Posted by gene_b View Post
    Thanks a lot! There is another option to justify a handhole size which based on the conductor(s) size, rather than conduit diameter, but it requires the box or conduit body to be permanently marked This option is not feasible by my agency at this time. Are there examples around the state?
    I believe that exception is normally used for conduit bodies (Tee's and LB's and such). It's fairly common for those to be marked with a maximum wire size. Its also pretty common for those to be labeled with smaller wire than the conduit capacity. For example, 500KCM wire easily fits in a 3" conduit, but it might not fit in a 3" LB. It all depends on the type of LB - some have more pulling room than others.

    For example, this one will fit larger wires than a standard LB:


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