Question about running MC through metal studs.

[Conrad540]

My foreman is having us limit the number of MC's we're running in the studs and it has me wondering. Do you have to limit the amount of MC running through a premade bore hole in a Metal stud to avoid derating it? I'm looking at 310.15 c 1 d and I'm thinking Stainless steel is bad at heat dissipation and maybe it'd create a similar issue to the MC having a overall outer jacket.

 

[infinity]

The question is are they considered bundled. IMO there is enough natural space between the cables that they are not bundled therefore derating does not apply. Others will have a different opinion.

 

[Conrad540]

The question is are they considered bundled. IMO there is enough natural space between the cables that they are not bundled therefore derating does not apply. Others will have a different opinion.

That makes sense. But do you worry about bundling more than 20 of them together or more than 3? I think we're doing it for any spots where we have more than 3 mc runs in the same stud holes.

 

[ActionDave]

You are correct that you can run twenty 12-2 or 12-3 through studs without any derating tax.

 

[infinity]

Yes 310.15(B)(4) allows up to 20 CCC to be bundled. After 20 CCC's the derated value is 60%

310.15(B)(4) Adjustment factors shall not apply to Type AC cable or to Type MC cable under the following conditions:
a. The cables do not have an overall outer jacket.
b. Each cable has not more than three current-carrying conductors.
c. The conductors are 12 AWG copper.
d. Not more than 20 current-carrying conductors are installed without maintaining spacing, are stacked, or are supported on “bridle rings.”
Exception to(4): If cables meeting the requirements in 310.15(B)(3)(4)a through c with more than 20 current-carrying conductors are installed longer than 600 mm (24 in.) without maintaining spacing, are stacked, or are supported on bridle rings, a 60 percent adjustment factor shall be applied.