Replies

1. 
   cap | Oct 27, 2005 08:47pm | #1

   Well, you can't do it without using some math. 

   It's simple arithmetic, counting the wires or wire equivalents, and multiplying by a volume factor for each wire (which depends on the gage of the wire).  Or, you could take the box volume and subtract a volume value for each wire or eqivalent.

   Once you calculate how many wires/equivalents are allowed in a given box volume,  you could make a table to eliminate some of the math, but you're still gonna have to count up the wires/equivalents.

   See this link:

   http://www.taunton.com/finehomebuilding/pages/h00134.asp

   Good luck,

   Cliff

2. 
   Hubedube | Oct 27, 2005 09:40pm | #2

   BOXES:

   Octagon, 4x 1-1/2"= 6 # 14 conductors, 5 #12, 5 # 10, 4 # 8

   Square, 4x 1-1/2" = 10 # 14      "        , 9 #12, 8 # 10, 7 # 8

    Note; count all grounding wires in a box as one conductor.

   count each device as one conductor.

   Count each wire entering or leaving box without a splice as one conductor.

   More sizes if needed.

1. 
   cap | Oct 27, 2005 11:19pm | #3

   Each device (strap) is counted as TWO condictors.

    

1. 
   Frankie | Oct 28, 2005 01:10am | #5

   I found the Taunton article soon after I posted. The math is simple enough and actualy is great considering that often there are more than one gauge of wire in the box. Thank you for your responses. I have copied the article so I may include it in my boiler plate info. on the inside cover of all my main electrical files of each project.FrankieThere he goes—one of God's own prototypes—a high powered mutant of some kind never even considered for mass production. Too weird to live and too rare to die.—Hunter S. Thompson
   from Fear And Loathing In Las Vegas

3. 
   DanH | Oct 27, 2005 11:28pm | #4

   Since the NFPA (or whatever it's called) makes money from selling copies of the Code, the verbatum rules aren't online anywhere (at least not legally).

   Even if you had the code book, the rules are often quite indecipherable. A few rules of thumb have been quoted, and likely a few others will be added, but my rule of thumb is that if you can get the wires into the box without the use of some sort of hydraulic press, you're probably code-legal.

   In other words, unless you're doing a hundred boxes, always use the largest box that will fit in the space. It's not a code issue so much as an issue of your own time and convenience.

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   No electrons were harmed in the making of this post.
4. 
   JohnSprung | Oct 28, 2005 01:31am | #6

   Here's the best source for easy to find and easy to understand code info:

   http://www.codecheck.com/

    

    

   -- J.S.