box fill calculations

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moondog23

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I am calculating box fill requirements for non-metallic sheathed cable in non-metallic boxes in residential construction.

(In California we still only enforce the '99 NEC, so it is article 370-16(b)(1) on page 193 of the '99 edition. I believe it is 314-16 (b) of the 2002 code)

The code says " a conductor, no part of which leaves the box, shall not be counted." Here is my problem: When the grounded conductors are pigtailed together, are any of those white wires counted? Same issue with the grounding and ungrounded conductors. They all enter the box, and no part of any of them leave the box, so does this satisfy the requirements? This seems as though ANY conductor would not be counted, as every wire would either be pigtailed or connected to a device in the box, therefore not leaving the box. The only conductor that would be counted would be those that pass through the box, effectively using the box as a raceway.

Any help?

Thanks -

Mike
 
Re: box fill calculations

Hi Mike,

Prior to making up the pigtail, are any of the connected wires out of the box? If not, what type of wire connector are you using? If so, those wires are counted.

rbj, Seattle
 
Re: box fill calculations

This refers only to conductors that completley remain in the box. Ie, they originate inside the box and they terminate inside box, such a pigtail or a bonding jumper for a steel box.
 
Re: box fill calculations

I think Moondog has solved the problem of box fill calculations for good. "No part of which leaves the box"... the key word is "leaves". All the wires are entering the box and none of them leave. It's as simple as that.
No matter how carefully you draft a law, there will always be a lawyer out there who can nit-pick it to shreds.
~Peter
 
Re: box fill calculations

I am not trying to nit-pick or be funny. I am serious.

For example, I bring the power (line) into the box. I pigtail the grounded conductor, and the ungrounded conductor is secured to the single pole switch. The switch leg ungrounded conductor is secured to the other terminal of the switch. The grounding conductors are pigtailed and a single lead is then terminated to the switch grounding screw.
Two 14/2 w/ground non-metallic sheathed cables enter the box.

How many of these 6 conductors count towards the box fill requirements?
 
Re: box fill calculations

Oh, duh...

I just reread the replies and I understand now. Just had a senior moment, I guess. I don't have all-timers. I must have some-timers!

Thanks for your help!!
 
Re: box fill calculations

With the device, you have to count 7 conductors.


1. Ungrounded.......................2
2. Grounded.........................2
3. Equipment Ground Conductor (2)...1
4. Device (switch)..................2

total...............................7
 
Re: box fill calculations

Ok, maybe I am confused again... Why do I count two for the device? Where can I find that calculation in the code book?

Thanks for your help -

Mike
 
Re: box fill calculations

It is all in 314.16.

Here is the section on device fill.

314.16(B)(4) Device or Equipment Fill. For each yoke or strap containing one or more devices or equipment, a double volume allowance in accordance with Table 314.16(B) shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap.
Click to expand...
Edit or in 370-16 :p

[ October 31, 2004, 05:47 PM: Message edited by: iwire ]
 
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