Romex through bored holes

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keith gigabyte

Senior Member
Recently had an inspector "remind" me only 4 nm cables allowed through bored holes in floor joists..or any other bored hole in wood residential. Looked over 334.17 300.4. That mostly referencing dimensions and use of nail plates. Are there limitations similar to those in300.17 which references raceways..wood is not a raceway.
the romexes were not packed tight. I don't recall number in hole but it was definitely full but still each cable was easy to pull back and forth.
Input?
 

ActionDave

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It's in 310.15. Code refers to cables run together more than twenty four inches without maintaining spacing need to be derated.

There is nothing that gives any guidance what 'maintaining spacing" means. Lots of AHJs take this to mean romex run through holes in wood studs.
 

infinity

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If the holes are filled with fire or draft stop material then more than 2 cables would require derating. If the holes are unfilled stuff in as many as you like. :)
 

RICK NAPIER

Senior Member
Location
New Jersey
If you do the calculations required by 334.80 you will discover that in general the derating has no effect on conductor size until you have over four 2 conductor wires. This requirement also apllies to wires in thermal insulation.

Where more than two NM cables containing two or
more current-carrying conductors are installed, without
maintaining spacing between the cables, through the same
opening in wood framing that is to be sealed with thermal
insulation, caulk, or sealing foam, the allowable ampacity
of each conductor shall be adjusted in accordance with
Table 310.15(B)(3)(a) and the provisions of 310.15(A)(2),
Exception, shall not apply.
 

kwired

Electron manager
Location
NE Nebraska
There is no limitation on how many cables can be put through a hole outside of physical size.

There is a possibility of ampacity adjustments being required if there are more then three current carrying conductors passing through the hole though.
 

infinity

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There is no limitation on how many cables can be put through a hole outside of physical size.

There is a possibility of ampacity adjustments being required if there are more then three current carrying conductors passing through the hole though.


That's only partially true, the requirement is for derating when you have more than two cables, you could possibly have more than 3 CCC's in two cables and derating wold not apply.
 
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