4 14 nmb through 1 drilled hole

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lowlandman

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Charleston, SC
I have in inspector trying to fail me for putting (4)14-2 Romex through 1 drilled 1” hole. Once I go through top plate it is not bundled. 2 wires on 1 stud left and 2 wires on 1 stud right. Nec says it’s fine in 334-80 but there trying to tell me IRC 3705.404 says no. Can anyone chime in on this.
Thanks

mark leppert
 
Well, that's interesting. Both codes say basically the same thing. I'm assuming you're accounting for the ampacity adjustment which gives you 17.5, but you're already covered there if you are using a 15A OCP (as you should be). do you have a nail plate?
 
lowlandman said:
I have in inspector trying to fail me for putting (4)14-2 Romex through 1 drilled 1” hole. Once I go through top plate it is not bundled. 2 wires on 1 stud left and 2 wires on 1 stud right. Nec says it’s fine in 334-80 but there trying to tell me IRC 3705.404 says no. Can anyone chime in on this.
Thanks

mark leppert
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You could put 100 NM cables through a bored hole without derating if there is no fire or draft stop material in the hole.
 
Even with 8 current carrying conductor's there is no issue with what you have there. 8 current carrying conductor's at 70% 12 is good at 90C x.7 = 21 amps.
 
Since there is foam in the hole derating applies. 25 amps * 70% = 17.5 amps. Still fine on a 15 amp circuit.
 
lowlandman said:
So how do I tell inspector without pissing him off. He has been referring to IRC 3705.404. Looks like same thing to me
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Just explaine to him that you have applied the 70% adjustment factor to your cables and that they are code compliant.
 
Even if the inspector does consider this one hole with 4 bundling, use the 24" or less exception. Fine your bundled through one top plate. Its not 24" thick. If you did it through multiple studs it's harder to argue but not one.

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(2017) section 334.80 references Table 310.15(B)(3)(a) directly, without referencing section 310.15(B)(3)(a). So that would mean you need to apply the table factors without regard to the limitations in the text of 310.15(B)(3)(a). The second paragraph of 334.80:

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.

Cheers, Wayne
 
infinity said:
Since there is foam in the hole derating applies. 25 amps * 70% = 17.5 amps. Still fine on a 15 amp circuit.
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Why? Others quote the 24" bundling rule below. I wondered are you citing something that requires derating for an even shorter "bundling distance" with the foam?
 
lowlandman said:
So how do I tell inspector without pissing him off. He has been referring to IRC 3705.404. Looks like same thing to me
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My 'touchy-feely' opinion:

Remember the definition of 'tact'. (The ability to tell someone to go to h... and have them happy to be on their way.)

You need to somehow tell the inspector that they correctly pointed out a mistake you made while also making it clear that your installation is perfectly fine.

Eg. 'You pointed out that I incorrectly did not derate the conductors. I've now done the calculation, and the corrected ampacity of these conductors is 17.5A which is properly protected by the 15A breaker.'

-Jon
 
wwhitney said:
(2017) section 334.80 references Table 310.15(B)(3)(a) directly, without referencing section 310.15(B)(3)(a). So that would mean you need to apply the table factors without regard to the limitations in the text of 310.15(B)(3)(a). The second paragraph of 334.80:

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.

Cheers, Wayne
Click to expand...
so what do we do with 12-2-2 ?

~RJ~
 
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