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  1. #1
    Join Date
    Jan 2011
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    Marietta, Georgia
    Posts
    93

    Default How many conductors can we get in one box?

    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.

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  2. #2
    Garry Blankenship's Avatar
    Garry Blankenship Guest

    Default Re: How many conductors can we get in one box?

    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.


  3. #3
    Join Date
    Jan 2011
    Location
    Marietta, Georgia
    Posts
    93

    Default Re: How many conductors can we get in one box?

    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.


  4. #4
    Join Date
    Apr 2008
    Location
    Western Massachusetts
    Posts
    536

    Default Re: How many conductors can we get in one box?

    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.


  5. #5

    Default Re: How many conductors can we get in one box?

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

    Egbert Jager
    Diamond Home Inspection
    http://www.diamondhomeinspection.ca

  6. #6
    Join Date
    Apr 2008
    Location
    Western Massachusetts
    Posts
    536

    Default Re: How many conductors can we get in one box?

    Quote Originally Posted by Egbert Jager View Post
    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.


  7. #7
    Garry Blankenship's Avatar
    Garry Blankenship Guest

    Default Re: How many conductors can we get in one box?

    Quote Originally Posted by Michael Bronner View Post
    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


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