How many conductors can we get in one box?

[Michael Bronner]

Found this at an inspection yesterday, actually there were about 4-5 such junction boxes in the attic, crawl space and semi hidden behind bench seats. One box had 12 conductors entering the box. There are days when I am glad to be able to spot such defects and tell my clients; gives me a warm and fuzzy feeling.

[Garry Blankenship]

There are pretty specific limitations in the NEC about conductor fill in boxes. A more nimble data provider than I, ( like hisbobness ), will probably provide chapter & verse for you. The good news is that all of the ground wires can for wire fill count purposes be counted as only one conductor, ( I think ). The first photo may not exceed code limits because the dark conductors are most likely single wire knob & tube conductors. The second would probably pass muster w/ a full depth extention ring. It is amazing how many conductors you can jam into a box if you are diligent about organizing, splicing lengths, laying / packing in orderly etc. Oh yea; those boxes need to be secured as well as the cables.

[Michael Bronner]

I did not bother measuring the box but it was somewhere around a 4x4+ size and 1-1/2 deep+-. These conductors were either 12 or 14 gauge 3 wire or an older 2-wire (no ground wire) no knob and tube. that would make the box contain about 24 countable wires (not counting any connectors or such inside as I did not remove the lid to see-did not trust it)..way more than the 13-15+- that would be allowed for box fill calculations.

[Corn Walker]

When you say "conductors" do you mean cables? Because there are a lot of cables entering those boxes, and consequently far more conductors than are allowed by NEC 314.16. The solution is a $20 J-box and about an hour or two for each undersized box.

[Egbert Jager]

Or how about just using a box extension?
http://0.tqn.com/d/homerepair/1/0/O/7/-/-/extender_text.jpg

[Corn Walker]

Or how about just using a box extension?

It may not be enough (if 12 cables are entering he could need 50 cu in or more). Plus a j-box just looks more professional in the end.

[Garry Blankenship]

I did not bother measuring the box but it was somewhere around a 4x4+ size and 1-1/2 deep+-. These conductors were either 12 or 14 gauge 3 wire or an older 2-wire (no ground wire) no knob and tube. that would make the box contain about 24 countable wires (not counting any connectors or such inside as I did not remove the lid to see-did not trust it)..way more than the 13-15+- that would be allowed for box fill calculations.

In the first photo I count 15. 6 N/M cables = 12, 2 loomed wires = 2 and one ground wire as allowed by code = 1 and totals 15. NEC Table 314.16(A) indicated a 4" square x 1 1/2" is allowed 9 #12s or 10 # 14s. Most electricians will tell you that is a good start ;)