What size box...

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1793

1793

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I have a situation, another thread:http://forums.mikeholt.com/showthread.php?t=85709&highlight=audio+system

I have 30 #12 wires factory twisted and I have the conduit calculation figured out, what I don't have are the pull box calculations. We will be bringing in the 30 pairs to one box and then branch out to other locations. What I need to know is how to calculate the size of the pull box(s)? I've look at 314.16(B) but I'm not sure how to calculate for this.

I see it as 60 #12 conductors, 2.25 so 60*2.25=135cuin

I would appreciate some guidance with this issue.
 
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Norb, I believe you got it. 135 cu. in would give you an 6x6x4 box. Unless space is a problem I would use a 10x10x4 for future use and for my own comfort level.
 
what size box

what size box

Frankly, I don't like the answer given, and it does get grey.
I went back and read the total thread, saw that your using a 2.1/2" or suggested 3" conduit, but I still missed the size of service, (I'll say conduits) down line from the box. 314.28 (A)(2) "the angle pull" is 6 x the largest size plus all additional (i'll say conduit) entries per row/per side & etc. This sets up one side, the perpendicular side is done with the same math & etc. and of course allow for entry spacing.
Since its audio wire where is the Grounding ? 640.7(A), see 640.9 in toto
In using 30 twisted pars in 135in[] be it 12 x 12 box have at it, and its wrong, its a pull box. Based on simple math of 3" conduit x 6, 318.28 (A)(2)
and still required to add the entries per that side or row, and thats the minimum.
The grey areas: no where in the code that I've found will it specify how to apply the third or fouth sides of the pull box being applied, but the closet is 314.28(2) The future also looks bad, U know And I know they will use it for other services as soon it goes in, bring in the Cat 5 throw in some TV wire.

Enjoy;

Having said all that (6 x 3)+15 x 1/2" = 25.5" A side
(6 x.1/2")+15 x 1/2"=10.5" B side

Enjoy:


CADPoint
...........................................
"Be a Free Agent, Get a Trade"
 
Wow, went from 0 responces to three. slow server? Anyway I was going to say the same thing 4X6X6. LXWXH but Cadpoint brings up a good point you need to comply with 314.28. I've always figured it out by doodling on paper. I have not been folowing the situation but what the heck is 318.28? you must be on the 2010NEC.
:roll: I actually tried to look it up.
 
what box size, continued ...

what box size, continued ...

Sorry about the typo I was writing about 314.28(A)(2)

I still say its a grey area.

314.16 - exceptions point to 314.28

314.28(A) states "For raceways containing conductors of 4 AWH or larger, and for cables containing conductors of 4 AWG or larger, etc ..."

314.28 (A) should be corrected to steer a clearer direction and additional verbage to state,
"For raceways containing conductors of 4 AWH or larger, and for cables containing conductors WHICH SUM OF INCHES SQUARES IS EQUAL TO OR GREATER THAN A 4 awg INCHES SQUARE... etc",

BASED ON 314.28 (A) ((Drop the)) Minimun Size.

Note that theres no handy boxes sizes, 8x8x4, 12x12X6, etc. are contained in 314.16, well why ?

I would assume the following:

Based on chapter 9 table 5
THHN #12 = .0133 in[]

60 x .0133in[] = .799 in[] > 1 -#4 =.0824 in[]

Realize that this is inches square and not inches cubed as used in the multiplier of 314.16(B)

I still default to 314.28 in toto... & becasue theres a 2.1/2" or 3" conduit
and other various numbers of entries out the mystery box.

314.28, pushes over to chapter 9, pushes and over to Table(s) 4, 5 & 5A.
which is the bases of my statement :)
Enjoy


"Be a Free Agent, Get a Trade"
 
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cadpoint said:
... 314.28(A) states "For raceways containing conductors of 4 AWH or larger, and for cables containing conductors of 4 AWG or larger, etc ..."

314.28 (A) should be corrected to steer a clearer direction and additional verbage to state,
"For raceways containing conductors of 4 AWH or larger, and for cables containing conductors WHICH SUM OF INCHES SQUARES IS EQUAL TO OR GREATER THAN A 4 awg INCHES SQUARE... etc",...
Click to expand...

Could bend radius, 4 awg, have more to do with it than "cu. in."?

I don't know, just a thought.
 
the only conductor bending radius is 300.34,
which also happens to be under
II. requirements for over 600 volts, nominal,
but found in the index under conductors Bending radius.




"Be a Free Agent, Get a Trade"
 
cadpoint said:
the only conductor bending radius is 300.34,
which also happens to be under
II. requirements for over 600 volts, nominal,
but found in the index under conductors Bending radius.
Click to expand...

I disagree--- Art. 314.28 is only used when #4 or larger is pulled then you must consider the conduit size. I stick by my original post but based on the fact I know nothing about the potential for noise with speakers I certainly could be off.
 
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