MC cable in wood studs
- Thread starter jonny1982
- Start date
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John120/240
Senior Member
- Location
- Olathe, Kansas
How big is the hole ? Seriously when using a 3/4" or 7/8" hole drilled in a wood stud One per hole would be what I would do.
Fifteen Years Ago
A green helper (he knew enough to be dangerous) drilled all of the basement joist with a 2 1/4" self feed bit. Still 3 cables max is all that were allowed through these holes. Needless to say some of his holes were too close to the edge & sister joist had to be installed.
- Occupation
- Licensed Electrician
The bundling rules don't apply to MC until you get up around 20 CCC or so, so you can stuff as many as will fit. That is only about three MCs in a one inch hole to avoid having to use nail guards.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Running cables through a hole is not automatically considered bundling if there is air space between the cables in the areas between the studs. Also there is no 3 cable limit for NM cable.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Do stud holes have to be 2" apart like joist holes? and johny1982, you could get a few sections of your 12-2/3 MC and drill holes in a scrap of 2x4 to see how easy they are to pull thru. A drill bit that leaves clean holes (no splinters on the backside) will make cable pulling a lot easier regardless the cable type.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Agree, also don't know where people keep coming up with 3 cable limit. If you do require ampacity adjustment most of the time you can still have 4 cables before you need to upsize anything, unless there is more then two current carrying conductors in any of the cables. The key here is number of current carrying conductors not number of cables.
- Occupation
- Licensed Electrician
I agree with you, but my inspectors don't.
- Location
- Massachusetts
I am not sure the NEC agrees with you.
Consider that the NEC considers MC run through bridal rings as bundling as evidenced by this.
Notice it says without maintaining spacing OR supported on bridal rings.
In my mind running through a stud every 16" is much more bundled than running through a bridal ring perhaps every 6'
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I would disagree, just because that section mentions bridle rings does not mean it applies to all similar installations like running through stud holes. Although I do agree with your logic it simply says that if you use bridle rings then you consider them bundled.
- Location
- Massachusetts
How can something held loosely together every 6' be bundling while something tightly bundled every 16" is not?
I can't follow that logic.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Same here, I also think the could use a little work to clarify better. Use of bridal ring in the wording is too specific for something likely intended to be more general in nature. If it said "including but not limited to ... or similar" it would be some improvement.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I agree with your logic but what you're saying (that the cables between the studs are bundled) is not supported by any wording in 310.15(B)(3)(a). In fact the section that you've mentioned is a specific allowance to the modify the derating required by the first paragraph in 310.15(B)(3).
Bridle ring installations only fall within that allowance {310.15(B)(3)(a)(4)} for #12 MC or AC cables and is not applied universally to all installations under 310.15(B)(3)(a).
If that section had some wording similar to what Kwired mentioned then I would agree but currently it does not and is therefore not enforceable.
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