J box sizing

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dt08

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I have an issue with a new contractor at our site ,They have 21 #12 THHN conductors in 4 square box.I called to his attention that this is undersized and his solution is to provide an extension box.This is a new raceway,box and I want the correct size pull box installed, It is my feeling that he must change it. Am I correct , Thank you for your Advice
 
after re-reading your post, if this is just a pull box and no splices, it depends on the largest sized conduit going into the box, you multiply the largest conduits diam. by 6 to get the proper sized box.
 
ultramegabob said:
after re-reading your post, if this is just a pull box and no splices, it depends on the largest sized conduit going into the box, you multiply the largest conduits diam. by 6 to get the proper sized box.
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help me with a Code reference on that, please.
 
dt08 said:
I have an issue with a new contractor at our site ,They have 21 #12 THHN conductors in 4 square box.I called to his attention that this is undersized and his solution is to provide an extension box.This is a new raceway,box and I want the correct size pull box installed, It is my feeling that he must change it. Am I correct , Thank you for your Advice
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Even if it is a 4 11/16 x 2 1/8" deep it will only hold 18 #12's. See table 314.16 (A)
He needs a 6x6x4 if you won't let him use the extension ring.

Also sizing a pull or junction box by the size of the raceway only comes into play when the conductors are #4 and larger. see 314.28 (A)
 
Why can't he use an extension ring? That's exactly what they're made for. :-? What code article would you quote to say that he must use "the correct size pull box"?
 
infinity said:
Why can't he use an extension ring? That's exactly what they're made for. :-? What code article would you quote to say that he must use "the correct size pull box"?
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I dont think the issue with sizing a box for pulling is so much the volume of the box, but he distance from connector to connector to allow for the wire to be manipulated without scraping the insulation off.
 
ultramegabob said:
will his splices extend 6 inches past the outer edge of the extension ring?
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Hate to rub salt in your wounds but 3 inches is good.

300.14 Length of Free Conductors at Outlets, Junctions, and Switch Points.
At least 150 mm (6 in.) of free conductor, measured from the point in the box where it emerges from its raceway or cable sheath, shall be left at each outlet, junction, and switch point for splices or the connection of luminaires or devices. Where the opening to an outlet, junction, or switch point is less than 200 mm (8 in.) in any dimension, each conductor shall be long enough to extend at least 75 mm (3 in.) outside the opening.
Exception: Conductors that are not spliced or terminated at the outlet, junction, or switch point shall not be required to comply with 300.14.
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chris kennedy said:
Hate to rub salt in your wounds but 3 inches is good.
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I would think that, if the extension is easily removable, the 3" can be from the front of the original box. Pop off the extension, make your changes, pop it back on.
 
I understand what dt08 is saying. The extension ring is fine but it looks shoddy. If they used different depth boxes accordingly throughout the job but this one is wrong, then someone just miscalculated.Changing the box could be a very time consuming job for something that is not really necessary.
Gene
 
Ebow said:
I understand what dt08 is saying. The extension ring is fine but it looks shoddy. If they used different depth boxes accordingly throughout the job but this one is wrong, then someone just miscalculated.Changing the box could be a very time consuming job for something that is not really necessary.
Gene
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Basically he's telling them to change it for these reasons:

This is a new raceway,box and I want the correct size pull box installed
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If there's a code issue then he at least owes the installer the Article number that backs up his request.
 
infinity said:
If there's a code issue then he at least owes the installer the Article number that backs up his request.
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I agree with that,the OP may want to re-think his new hire if he is that unhappy with there wiring methods...
 
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