T314.16(B)

[Dale001289]

The above table gives cubic inch requirements for conductor sizes 18AWG thru 6AWG. What about larger conductors, 4AWG thru 4/0AWG for example? Does anyone have a chart or calculation to extrapolate the larger cubic inch capacities?

Thanks.

 

[Dennis Alwon]

For that size wire the box size is based on the conduit sizes... Look at 314.28

 

[don_resqcapt19]

314.16 ... Boxes and conduit bodies enclosing conductors 4 AWG or larger shall also comply with the provisions of 314.28.

I had a proposal to delete the word also in the above sentence for the 2011 code cycle. My substantiation was that there is nothing in 310.16 that applies to the box size where conductors 4 AWG and larger are used. That proposal was rejected by the code making panel with the following comment.

Although there are no prescriptive requirements in this section that apply to large conductors, the parent language about sufficient size does apply.

 

[kwired]

If you size the box per the rules that are based on raceway sizes - you generally have plenty of room for the volume of the conductors that will be contained.

Generally speaking if you are using 4 AWG conductors you will have at least 1 inch raceway - minimum box dimension for that will be 6 inches, 8 inches if making a straight pull. 4-11/16 box is too small - next most common thing you typically see is 6x6x4 - quite a bit more volume then a deep 4-11/16 box.

 

[enjuhnear]

The above table gives cubic inch requirements for conductor sizes 18AWG thru 6AWG. What about larger conductors, 4AWG thru 4/0AWG for example? Does anyone have a chart or calculation to extrapolate the larger cubic inch capacities?

Thanks.

To piggy back onto this question....

Does the code make any special considerations for industrial plug and receptacle back boxes? When looking to terminate to a device mounted to that box, is there a different set of rules as opposed to pulling through? I understand the 6x for 90s and 8x for straight through. I am struggling to find the minimum volume for a box that may receive as much as 5#2 and 4 #14.

I am attempting to find the minimum volume for a box that will be custom designed for cast aluminum, so standard box dimensions do not apply. The box is to allow for connecting with RGS up to 1.5". Conduit connections will be only via the side walls of the box, with no provisions for entry on the back plate. For a visual representation, the C-H AJ57 box and adapter is of similar application.

http://www.cooperindustries.com/con...atalog-pdfs/pr/back-boxes-arktite-devices.pdf

314.27(E) directs me right back to 314.16(B)(4).

Thank you for your time.

 

[JoeStillman]

To piggy back onto this question....

Does the code make any special considerations for industrial plug and receptacle back boxes? When looking to terminate to a device mounted to that box, is there a different set of rules as opposed to pulling through? I understand the 6x for 90s and 8x for straight through. I am struggling to find the minimum volume for a box that may receive as much as 5#2 and 4 #14.

I am attempting to find the minimum volume for a box that will be custom designed for cast aluminum, so standard box dimensions do not apply. The box is to allow for connecting with RGS up to 1.5". Conduit connections will be only via the side walls of the box, with no provisions for entry on the back plate. For a visual representation, the C-H AJ57 box and adapter is of similar application.

http://www.cooperindustries.com/con...atalog-pdfs/pr/back-boxes-arktite-devices.pdf

314.27(E) directs me right back to 314.16(B)(4).

Thank you for your time.

Sounds like a generator portable hookup box. You can buy them off-the-shelf instead of designing it from scratch.

 

[enjuhnear]

Sounds like a generator portable hookup box. You can buy them off-the-shelf instead of designing it from scratch.

That's where my issue comes in, I am with a mfgr and we are designing a new box that meets code which fits our specific device. I need to design the box that will be bought off the shelf.

However, since I posted this question, I have been provided new information which renders the question moot. However, if anyone has any ideas to get to the bottom of this topic for future purposes, I would love to read your opinions.