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

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gene_b

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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!
 
Interpretations for NEC section 314.28

Interpretations for NEC section 314.28

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

gene_b said:
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!
Click to expand...
 
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.
 
steve66 said:
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Also, if the conduits come up into the bottom of the handhole (not into the side), different sizing rules apply.
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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_resqcapt19 said:
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".
Click to expand...
Even with the "top" of the enclosure being removable?
 
Handhole size based on conductor 314.28(3)

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?

jumper said:
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.
Click to expand...
 
gene_b said:
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?
Click to expand...

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:

images
 
gene_b said:
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?
Click to expand...
While the code permits that, I have never seen a box so marked.(this marking must be by the manufacturer of the box or conduit body, it is not a field marking) Conduit bodies are often marked and a change for the 2017 code provides guidance on conduit body fill with conductor sizes or combinations not marked on the conduit body.
 
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