conduit and box fill

[jamesc]

a one inch (1.00") emt conduit can hold 26 #12 conductors at 40% fill, but according to table 314.16(a), for
a (4 x 2-1/8) square box, the maximum fill is 13 #12's.
314.16(c)(1) & (2) state that a conduit body can be filled as listed in Table 1 of Chapter 9, which would allow the same number of conductors in the conduit body as in the conduit of the same size.
am I not interpretating table 314.16(a) correctly? I would appreciate any feedback to help me understand.

 

[raider1]

Box fill and conduit fill are not necessarily going to match up. In your case the box fill will be the limiting factor for the installation.

Chris

 

[jaggedben]

A box is not a 'conduit body', if that helps clarify things. Conduit bodies are LBs, LLs and LRs, LTs, etc.

The fill rules are different for boxes because it is assumed that you will also have splices in them. At least that's my understanding.

 

[iMuse97]

A box is not a 'conduit body', if that helps clarify things. Conduit bodies are LBs, LLs and LRs, LTs, etc.

The fill rules are different for boxes because it is assumed that you will also have splices in them. At least that's my understanding.

If you have splices in boxes, the number of conductors counted for box fill is increased each time you cut a wire that was pulled through.

In other words, if you pull nine #12AWG through a box, you count nine conductors for box fill.

If you then cut and splice three of the original nine, you now count twelve for box fill. If then you cut the additional six, you now count eighteen for box fill.

If box fill is your problem, get a bigger box.