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 DIY Chatroom Home Improvement Forum What's the deal with derating
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06-15-2008, 10:59 PM   #1
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## 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

06-18-2008, 01:48 AM   #2
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Can anyone help me out here. Thanks

06-18-2008, 05:40 AM   #3
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Quote:
 Originally Posted by James Con 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.

 06-18-2008, 11:28 AM #4 Member   Join Date: Aug 2007 Posts: 179 Rewards Points: 150 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. Attached Thumbnails
 06-18-2008, 03:43 PM #5 Electrician   Join Date: Aug 2007 Location: Connecticut, Litchfield Posts: 2,015 Rewards Points: 1,000 If that hole is not getting fire caulked, put as many as you want through it.
 06-18-2008, 11:20 PM #6 Member   Join Date: Aug 2007 Posts: 179 Rewards Points: 150 Gotcha, Thanks Chris
06-20-2008, 09:15 AM   #7
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As Chris said, the keyword is fire caulked or even sealed with insulation.

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