Box Fill: Do The "Tongues" Count?

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Old 11-08-11, 06:37 AM
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Box Fill: Do The "Tongues" Count?

When figuring box fill for plastic boxes do the plastic "tongues" count as clamps?
 
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Old 11-08-11, 07:19 AM
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Ray - My guess is that they don't. My reasoning is that the tongues seem to clamp in only one direction and that some brands of plastic boxes have break out tabs instead of tongues.

Was the staple distance reduced for plastic boxes?
 
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Old 11-08-11, 08:06 AM
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Wayne, you brought up my second question. Assuming the cable is stapled if they do count can you break them out to reduce the total box fill.

I was answering a post elsewhere about fill and wasn't sure how to answer when writing about plastic boxes.
 
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Old 11-08-11, 08:13 AM
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Ugh. I always assumed they did count as clamps. I never thought about the fact they only clamp in one direction.
 
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Old 11-08-11, 10:04 AM
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I hope they don't count. If they do I probably should go back and redo a box in my kitchen - not.

My thought was always that the clamps used on metal boxes were mostly to provide a protected entrance into the box and the staples secured the cables. Since plastic boxes don't require any special protection no clamps are required.

Then again the tongues do have volume and that's what box fill calcs are all about?
 
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Old 11-08-11, 10:17 AM
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Another thought, the manufacturer may have already included the tongues in their volume calculations for what gets stamped into the box.
 
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Old 11-08-11, 11:41 AM
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On plastic boxes, the manufacturer has already done the calculation and stamped both the cubic inches on the box and the number of wires allowed.
 
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Old 11-08-11, 02:11 PM
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The toungues on plastic multi-gang boxes are clamps. On plastic single gang boxes they are knockout tabs.

Box with no clamp stapled within 8", with a clamp within 12".
 
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Old 11-09-11, 05:18 AM
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Plastic Box Clamps

Carlon addresses this on pages 3 and 4 of the document below. Be aware that this was written in November 2002.

http://www.carlon.com/FAQs/FAQ-ZipBoxes.pdf
 
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Old 11-10-11, 06:52 AM
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Yes the internal clamps count towards box fill. Not only does the Carlon site above state so, but UL and the NFPA CMP have stated it also.

Now, does anyone actually count them, nope.
 
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Old 11-10-11, 08:10 AM
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Wingz, welcome to the forums. Roll up your sleeves and jump in.
 

Last edited by ray2047; 11-10-11 at 11:20 AM.
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Old 11-10-11, 08:46 AM
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You would have to encounter one stickler of an inspector to ding you on something like that (or to even notice).
 
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Old 11-10-11, 08:56 AM
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Makes you wonder since the clamps are part of a listed assembly. How would UL test for proper cable retention if the clamps were removed or is it two tests?

Sure would be simpler if the volume already had an allowance for the clamp. The clamp volume is the same yet the allowance changes based on conductor size.
 
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