Multiple NM cables through common hole in studs

[roger]

I took my drywall down and noticed there are multiple(2-3) romex cables running horizonal through the same holes in the wood stud. Is that allowed oer NEC? Thanks.

When was the house built and what code cycle was in place at the time it was built? If it was before the 2005 was adopted you're fine.

Roger

 

[jap]

334.80 (2011)

Wow, I wasnt aware of that,I was spouting off from the hip, not knowing this was already addressed.
It seems you have to derate if theres any caulk around a cable regardless of the number.
This makes me glad I'm in Industrial not Residential.
They have too much to keep up with.

 

[roger]

I retract my earlier post, I was stuck on the sealed penetration issue.

Roger

 

[jap]

Wow, I wasnt aware of that,I was spouting off from the hip, not knowing this was already addressed.
It seems you have to derate if theres any caulk around a cable regardless of the number.
This makes me glad I'm in Industrial not Residential.
They have too much to keep up with.

I may have worded this wrong about the number of cables, but I get the Point now.

 

[guschash]

The way I see it if he has 2 or 3 NM going through the hole, I wouldn't derated them.

 

[infinity]

To me this is a contradiction of terms.
what does the "Caulked Hole" have to do with it?
Are you saying that I can run 12 cables "Without Spacing" together for 23 15/16" inches without having to
derate, but I cant run the same 12 cables through a bored hole through an 1 1/2" wide stud if I caulk the
hole after they're installed?

You may actually be able to bundle those cables for 10' without any derating if 310.15(B)(2)Exception applies.

310.15(A)(2) Selection of Ampacity. Where more than one ampacity
applies for a given circuit length, the lowest value shall be
used.
Exception: Where two different ampacities apply to adjacent
portions of a circuit, the higher ampacity shall be permitted to
be used beyond the point of transition, a distance equal to 3.0
m (10 ft) or 10 percent of the circuit length figured at the
higher ampacity, whichever is less.

 

[kwired]

Yes, you do. That's what I'm saying. If you consider several cables that pass through horizontal bored holes and touch each other for at least 24" as "Bundled" then you would have to consider the several cables that
come out of the top of a loadcenter as bundled also if they are all touching each other for 24" and between
2 studs from the top of the panel to the top plate, therefore requiring derating right from the git go regardless of what they do down the line.

There were some previous responses that indicated they thought since the cables were running through
horizontal bored holes it was safe to assume that the cables were still touching each other or "Bundled"
between the studs beyond the bored holes.

I don't know how you route NM cables when coming to something like a panelboard, but when I do so they are not just free flying on their approach to the panel. They are generally bundled in groups of 2, 3 or 4 cables. (I use the staples designed for stacking them in these configurations) This maintains spacing and each bundle has less conductors than 10 conductors which will keep you out of the 50% deration where you will end up having to increase conductor size.

The way I see it if he has 2 or 3 NM going through the hole, I wouldn't derated them.

It is not that they don't need deration, it is that until you get more than 9 current carrying conductors in the bundle does the deration value make you start increasing needed conductor sizes. If you have 7-9 conductors the factor is only 70%. At 70% your 14, 12 and10 AWG conductors still are allowed on 15, 20, and 30 amp circuits. Add a 10th current carrying conductor and your deration factor is now 50%, and an increase in conductor size is going to be necessary.

 

[RustyShackleford]

Add a 10th current carrying conductor and your deration factor is now 50%...

Don't seem like it'd be that tough to have a few more rows in Table 310.15(B)(3)(a), does it ?

 

[kwired]

Don't seem like it'd be that tough to have a few more rows in Table 310.15(B)(3)(a), does it ?

Looks to me like adding a row with 60% would be the main place where one might make a change, but after doing a few quick calculations with common applications of conductors up to 6 AWG copper, it doesn't seem to matter if you go 50% or 60% you are going to end up increasing the conductor size, so they maybe realized this when making the table.

 

[infinity]

Looks to me like adding a row with 60% would be the main place where one might make a change, but after doing a few quick calculations with common applications of conductors up to 6 AWG copper, it doesn't seem to matter if you go 50% or 60% you are going to end up increasing the conductor size, so they maybe realized this when making the table.

60% helps if you're not using multi-receptacle circuits. i.e.- #12 THHN = 30 amps * 60% = 18 amps next size up 20 amps.