# how many wires in 3/4" hole?



## Zparme

Someone tried telling me today that you can only run 2 12/2 pieces of Romex through a 3/4" hole drilled through a stud. I said there's no such code. At least I never heard of such a thing but he swears by it. Is there anything that limits the amount of cables through a hole?


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## Pete m.

*334.80 Ampacity.* The ampacity of Types NM, NMC, and
NMS cable shall be determined in accordance with 310.15.
The allowable ampacity shall not exceed that of a 60°C
(140°F) rated conductor. The 90°C (194°F) rating shall be
permitted to be used for ampacity adjustment and correction
calculations, provided the final derated ampacity does not ex-ceed that of a 60°C (140°F) rated conductor. The ampacity of
Types NM, NMC, and NMS cable installed in cable tray shall
be determined in accordance with 392.80(A).
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.
Where more than two NM cables containing two or
more current-carrying conductors are installed in contact
with thermal insulation without maintaining spacing be-tween cables, the allowable ampacity of each conductor
shall be adjusted in accordance with Table 310.15(B)(3)(a)

Pete


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## jproffer

Not for the width of a stud, that I'm aware of.

For longer distances, I think there is a limit of CCC's, but 1.5" isn't where that starts.


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## jproffer

Pete m. said:


> *334.80 Ampacity.* The ampacity of Types NM, NMC, and
> NMS cable shall be determined in accordance with 310.15.
> The allowable ampacity shall not exceed that of a 60°C
> (140°F) rated conductor. The 90°C (194°F) rating shall be
> permitted to be used for ampacity adjustment and correction
> calculations, provided the final derated ampacity does not ex-ceed that of a 60°C (140°F) rated conductor. The ampacity of
> Types NM, NMC, and NMS cable installed in cable tray shall
> be determined in accordance with 392.80(A).
> 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.
> Where more than two NM cables containing two or
> more current-carrying conductors are installed in contact
> with thermal insulation without maintaining spacing be-tween cables, the allowable ampacity of each conductor
> shall be adjusted in accordance with Table 310.15(B)(3)(a)
> 
> Pete


I (somewhat) stand corrected . Thanks Pete.

Still at 80% you're allowed 4-6 CCC's, so that would be 3, 12-2 Romex cables.

Really, in a 3/4" hole, without stuffing it full, I doubt you could get many more than 3 anyway.


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## ceb58

jproffer said:


> I (somewhat) stand corrected . Thanks Pete.
> 
> Still at 80% you're allowed 4-6 CCC's, so that would be 3, 12-2 Romex cables.
> 
> Really, in a 3/4" hole, without stuffing it full, I doubt you could get many more than 3 anyway.


 You can run 4- 12/2's or 4- 14/2's. By derating the #12 would be at 30 amp in the 90 deg column. 8 ccc @ 70% would be 21 amps so you are good. Same with #14 8 ccc @70 of 25 amps would be 17.5 on a 15 amp ocd.


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## SmithBuilt

ceb58 said:


> You can run 4- 12/2's or 4- 14/2's. By derating the #12 would be at 30 amp in the 90 deg column. 8 ccc @ 70% would be 21 amps so you are good. Same with #14 8 ccc @70 of 25 amps would be 17.5 on a 15 amp ocd.


I thought you were required to use the 60 deg column for nm?


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## BBQ

SmithBuilt said:


> I thought you were required to use the 60 deg column for nm?


Yes and no.

For the purposes of derating we can start with the 90C column.


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## mbednarik

What pete posted looked pretty clear.


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## ceb58

SmithBuilt said:


> I thought you were required to use the 60 deg column for nm?


You are. Read the entire code article Pete posted. You can use the 90 deg. column for derating but the ampacities of the wire must not be below the rating in the 60 deg. column. So with derating for 8 ccc #12 wire has an ampacity of 21 amp. So it is above the max ocp of 20 amps. Same with # 14. 17.5 ampacity of the wire on a 15 amp breaker.


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## SmithBuilt

Duh, yes I plainly see it. I'm sure I knew this at one time. Memory is not as good as it once was.


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## sparky402

Weve always ran 4 NM through a 7/8" hole. I never understood that code when we are allowed to put all our hrs through a 2 1/2" pvc sleeve


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## Ultrafault

Sometimes the St. Louis area inspectors will get you on 110.12 if you run more than one per hole. 

Dont get me started on how stupid this is.


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## papaotis

the way im reading petes code quote is 'IF THE HOLE WILL BE SEALED' but sorry ,too tired to look it up.:001_huh:


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## Ultrafault

papaotis said:


> the way im reading petes code quote is 'IF THE HOLE WILL BE SEALED' but sorry ,too tired to look it up.:001_huh:


Indeed. 310.15(B)(3)(a) covers derating for multi conductor cables bundled for more than 24 inches.


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## Cl906um

I said that wrong. Was thinking of the end result after derating.


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## Cl906um

Nmb isn't rated for 90 degrees from the get go.


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## Cl906um

BBQ said:


> Yes and no.
> 
> For the purposes of derating we can start with the 90C column.


yah but my answer is no


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