How much romex through 1 inch hole through 2x4 wall studs

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If there is no fire or draft stop material then as may as you can fit. If the hole is sealed then you need to derate once you exceed two cables but there still is no limit.
 
To expand on that a little, if the hole is sealed, or if the conductors are bundled for 24" in length including the hole (e.g. two studs in a row with the cables tight bound together in between), then you need to derate when there's more than one cable. But with 12/2 cable (or 14/2 cable), derating for 2-4 cables make no difference.

So 4 is a pretty safe answer to the OP's question, for 12/2 or 14/2 NM cable.

Cheers, Wayne
 
Currently under 2008, but the way I read is - Table 310(B)(2)(a) states that 3 NM cables would be 6 current carrying conductors and 80% of rating on cable. 12 gauge is listed as 25 amp(?) which after adjustment, still maintains 20 amp allowance which is also regulated under 240.4(D). Am I looking at that correctly? Inspector still trying to learn after 30 years.
 
NM-B cable has 90C conductors inside it, so you can start with the 90C ampacity. For 2017 that is 30A for #12 Cu. That means that up to 9 CCCs with 70% derating still leaves you at 21A. As that is above the 20A 60C rating that all NM is subject to, the derating makes no difference.

Cheers, Wayne
 
102 Inspector said:
Currently under 2008, but the way I read is - Table 310(B)(2)(a) states that 3 NM cables would be 6 current carrying conductors and 80% of rating on cable. 12 gauge is listed as 25 amp(?) which after adjustment, still maintains 20 amp allowance which is also regulated under 240.4(D). Am I looking at that correctly? Inspector still trying to learn after 30 years.
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You can derate from the 90 deg column. You could have 4 cables, which would be 8 CCC. #12 would be 30A under the 90 deg column. 8 CCC would require a 70% deration. 30A x 70 = 21A. #12 would still be good for a 20A circuit.
 
As mentioned the magic number is 9 CCC's for #12 and #14 conductors. That means in some instances you could jam in (4)-14/3 or (4)-12/4 maximum before derating lowers the normal ampacity of 15 and 20 amps respectively.

As to the thread title there is no limit in the NEC as to how many NM cables are allowed in a hole. I hear guys say no more than two, no more than 3, but that's nonsense.
 
In my experience the "no more than......" "rule" developed due to the difficulty some folks have in understanding the derating concept.
Unfortunately in this area there are several "rules" inspectors quote (such as "no more than 3; always drive 2 rods, etc.) simply to avoid 'teaching' Code to those not wishing to learn.
 
I understood it from post on here and the article if its not sealed up and then its kinda up to how your AHJ feels. No NEC limit, but his " bundling" might not be the same as yours. You can go infinite on length and amount if they are not bound together but I don't think most AHJ will like that.
 
augie47 said:
In my experience the "no more than......" "rule" developed due to the difficulty some folks have in understanding the derating concept.
Unfortunately in this area there are several "rules" inspectors quote (such as "no more than 3; always drive 2 rods, etc.) simply to avoid 'teaching' Code to those not wishing to learn.
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I get the "rule of thumb" on this one but I wonder why the guys making these rules say no more than 2 or 3 cables, it must be because they don't understand the actual code either. If they said keep it at 4 cables or less then they would be demonstrating that they understood the actual requirment. :unsure:
 
infinity said:
I get the "rule of thumb" on this one but I wonder why the guys making these rules say no more than 2 or 3 cables, it must be because they don't understand the actual code either. If they said keep it at 4 cables or less then they would be demonstrating that they understood the actual requirment. :unsure:
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I think the big problem is code ignorance. Many people read the part in 334.80 that reads "where more than 2 NM cables...are installed....in the same opening in wood framing....the allowable ampacity of each conductor shall be adjusted...." BUT they stop there and dont do the actual adjustment to find it doesnt effect you until over 9 CCC with #12 and #14. Also there is common ignorance that "You cant use or derate NM at 90 degrees....." I seriously wonder of some of these people ever actually open the code book.
 
What most people overlook is the part that says "where firestopped" then you must derate for more than 2 cables. It doesn't say any hole with more than 2 cables, only where they used firestop.
 
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