# # of conductors in a box



## Speedy Petey (Jan 10, 2007)

There is NO "maximum". You are on the right track with 314.16 for conductors up to #6. 
For boxes not on the list on T314.16 you have to know the volume of the box and us the "Minimum Volume" column for the conductors.

_*314.16 Number of Conductors in Outlet, Device, and Junction Boxes, and Conduit Bodies

*Boxes and conduit bodies shall be of sufficient size to provide free space for all enclosed conductors. In no case shall the volume of the box, as calculated in 314.16(A), be less than the fill calculation as calculated in 314.16(B). The minimum volume for conduit bodies shall be as calculated in 314.16(C).
The provisions of this section shall not apply to terminal housings supplied with motors.

FPN: For volume requirements of motor terminal housings, see 430.12.

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



For conductors #4 and larger you have to go to:

_*314.28 Pull and Junction Boxes and Conduit Bodies*

Boxes and conduit bodies used as pull or junction boxes shall comply with 314.28(A) through (D).

Exception: Terminal housings supplied with motors shall comply with the provisions of 430.12.

*(A) Minimum Size *For raceways containing conductors of 4 AWG or larger, and for cables containing conductors of 4 AWG or larger, the minimum dimensions of pull or junction boxes installed in a raceway or cable run shall comply with (A)(1) through (A)(3). Where an enclosure dimension is to be calculated based on the diameter of entering raceways, the diameter shall be the metric designator (trade size) expressed in the units of measurement employed._


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## BackInTheHabit (Apr 12, 2008)

First: Welcome to the forum.

Second: When posting, break up your post so that it's not one long paragraph. This will help others when reading your post.

See T. 314.16(B) Metal Boxes
See T.314.16(B) Volume Allowance Per Conductor

"fill" refers to what type of wire, etc. can be put into the box legally. All boxes have a cubic inch rating on then. Use the cubic inch rating of the box to determine the number of allowable conductors.

http://mikeholt.com/reprint_request2000.php?id=2975

http://mikeholt.com/reprint_request2000.php?id=2974


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## michaeljr7249 (Aug 7, 2008)

*boxes*

Speedy,
To my knowledge we do not derate wires because of the number of them in a box. If I am mistaken, please tell me. 
I guess I am putting myself in the inspector's shoes and trying to come up with a reason to limit the number of wires in a box. These are all #12 wires, some mc and some thhn. 
Thanks.


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## Speedy Petey (Jan 10, 2007)

No, we do not derate because of box fill, and your inspector cannot simply institue his own rules on a whim. 
The ONLY limit to box fill is the volume of the box. There is no magical "maximum number" for all boxes. Each one is different.


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