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-   -   What's the deal with derating (http://www.diychatroom.com/f18/whats-deal-derating-22317/)

James Con 06-15-2008 11:59 PM

What's the deal with derating
 
What's the Max number of 12/2 NM cables I could run through a 3/4 hole? And If I am fire caulking how many of the same could be run, also through a 3/4 hole? If I am reading right, no more than two NM cables through a single hole that is fire caulked. Is this right.
Also I have an 1-1/4" hole in the joist above the main panel, How many 12/2 NM's can I run through this hole to the panel before it is considered bundling? ( No fire caulking invloved) Thanks

James Con 06-18-2008 02:48 AM

Can anyone help me out here. Thanks

chris75 06-18-2008 06:40 AM

Quote:

Originally Posted by James Con (Post 130699)
What's the Max number of 12/2 NM cables I could run through a 3/4 hole? And If I am fire caulking how many of the same could be run, also through a 3/4 hole? If I am reading right, no more than two NM cables through a single hole that is fire caulked. Is this right.
Also I have an 1-1/4" hole in the joist above the main panel, How many 12/2 NM's can I run through this hole to the panel before it is considered bundling? ( No fire caulking invloved) Thanks

This question will be answered will many opinions, here is mine. Bundling does not exist when running wires through bored holes in wood, it just does not meet the definition of bundled, ( The Nec does not define bundled).

As far as the fire caulk, Its when two or more current carrying conductors
pass through wood framing. But, you can use the 90 degree chart to derate, so basically you can run 9 current carrying conductors before the wires actually take a hit.

James Con 06-18-2008 12:28 PM

1 Attachment(s)
Thanks for responding Chris. So I could send a total of nine current carrying conductors through this hole. Now is that 9 conductors meaning 4 -12/2 cables.

chris75 06-18-2008 04:43 PM

If that hole is not getting fire caulked, put as many as you want through it.

James Con 06-19-2008 12:20 AM

Gotcha, Thanks Chris

wirenut1110 06-20-2008 10:15 AM

As Chris said, the keyword is fire caulked or even sealed with insulation.


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