boring holes for NM

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iwirehouses

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I am pretty sure there is nowhere in the NEC that states how many NM cables can be run through a hole. I also know that when bundling wires, you have to derate. I use a 5/8" bit for 1 cable and a 1" for two. I never go over three for a 1" hole. Am I being crazy or is this standard?
 
iwirehouses said:
I am pretty sure there is nowhere in the NEC that states how many NM cables can be run through a hole. I also know that when bundling wires, you have to derate. I use a 5/8" bit for 1 cable and a 1" for two. I never go over three for a 1" hole. Am I being crazy or is this standard?
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The only thing I can see you need to watch out for is WHERE you are drilling the holes. There are building code requirements limiting size of holes and location of the holes in the wood.
 
iwirehouses said:
I never go over three for a 1" hole. Am I being crazy or is this standard?
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I think you're being crazy. Multiple cables through a bored hole are not bundled in my opinion. They're bundled for 1-1/2", then they're not bundled for another 14-1/2". This does not meet the definition of bundling, in my opinion. The inspectors in the jurisdictions where I operate agree with me. I am aware that there are certain hard ass inspectors who have a different opinion, but I'm not sure what they base that on. The inspector is not the AHJ.
 
like inspector says its where u drill your holes. there is some inspectors that say u have to derate if u have 3 or more nm cables coming through a hole thats going to get fire calked. i dont know the reason for this but like mdsk says going through bored holes its not called bundling.
 
cloudymacleod said:
there is some inspectors that say u have to derate if u have 3 or more nm cables coming through a hole thats going to get fire calked. i dont know the reason for this
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Thats a 2005 code change, 334.80, the reason is because tests show excessive temperatures occur in the confined space.
 
Marc-
I would have to disagree with you here. If you are drilling across studs with more than three NM cables in a hole then I and every inspector in our area would consider it bundling.

If I tie wrap a mass of wires in an attic and only use a ties wrap every 4 feet I am guessing you would allow this. It won't fly in many areas so be careful or check with the inspector before you do it.

Secondly, you can use 4 2 wire NM cables in a hole since that is only 8 current carrying conductors. If you use #12 then you derate 70% by Table 310.15(B)(2). #12 is rated 30 amps at 90C. 30*.7 is 21 amps -- still good.
 
I figure if the wires move freely in the hole then I feel good. If this is 4-5 wires so be it as long as they are loose and not packed in. I drill 7/8" holes for everything . Burning wire when pulling is more of a concern. I do not consider this bundling. I would consider running a bundle of cables held together with ties bundling.
 
mikeames said:
I would consider running a bundle of cables held together with ties bundling.
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How is that different from running through holes in studs. If you drill 2 bays of 16 OC studs then fill that hole with wires it is no different than tie wrap. The tie wrap is only in one spot.
 
stickboy1375 said:
Dennis, if I was to ask you how many NM cables you could run in a 1" hole, what code article would you tell me?
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Stickboy, you know it doesn't work that way. If you are running horizontal runs the wires will be resting on each other (bundled)
 
Dennis Alwon said:
Stickboy, you know it doesn't work that way. If you are running horizontal runs the wires will be resting on each other (bundled)
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Thanks for your opinion, but I think you know that air space can be maintained between the cables in the space between each stud. You're not pulling al dente pasta... it's copper cable.
 
mdshunk said:
Thanks for your opinion, but I think you know that air space can be maintained between the cables in the space between each stud. You're not pulling al dente pasta... it's copper cable.
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I do if it is a vertical run. How would you keep the spacing on a horizontal run? BTW, al dente paste is as flexible as wire.
 
Dennis Alwon said:
How is that different from running through holes in studs. If you drill 2 bays of 16 OC studs then fill that hole with wires it is no different than tie wrap. The tie wrap is only in one spot.
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It may not be different depending how you look at it. I see it as different

Running for example 20 cables together held together with ties is much different than 4-5 loose cables running through a stud every 16 inches. There will be airflow where as a "MASS" of cables tied together with ties will not.

Dennis Alwon said:
The tie wrap is only in one spot.
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Tie wraps are tight my holes are not as I stated. In addition to that I am not running a "mass" of wires tightly through a hole..... Anyone can pick this apart one way or another. I know what the code says and IMHO I feel safe an compliant with the methods I explained. I have also never failed an inspection for these reasons.
 
Dennis Alwon said:
... If you are drilling across studs with more than three NM cables in a hole then I and every inspector in our area would consider it bundling. ...
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Dennis -
Educate me here. I had always thought that 310.15.A.2 Exception would apply in this case.

carl
 
This qestion of "how many cables can you run through an X sized hole" is one that pops up nearly as frequently as the ground up or down question. It has no resolution.
 
coulter said:
Dennis -
Educate me here. I had always thought that 310.15.A.2 Exception would apply in this case.

carl
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I am not sure how the selection of ampacities applies to "what constitutes bundling"

Carl I am not putting you off I just don't get the question you are asking.
 
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coulter said:
Dennis -
Educate me here. I had always thought that 310.15.A.2 Exception would apply in this case.

carl
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This talks about different ambient temperatures in a run. This is not considered in this discussion.
 
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