bundling wires

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daver828

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New to the forum. Also new to trying to learn the code, and need some help please.
I had a discussion with an inspector last week who told me some things I?d not yet heard and cannot find where to look it up in the code book. I do alot of residential work, remodels, etc. So this is about residential and romex.

This inspector was talking about bundling of wires, either under the same staple or with tie wraps, or whatever. What he was telling me is that beginning at 3, and not more than 9 current carrying conductors can be bundled together. He discussed heat buildup and circuit loads. That was easy enough to understand. But he kept saying something about stapling every 24 inches in order to allow the heat to dissipate? I understood that the first staple from the box had to be within 6 inches, and then up to 4 1/2 feet after that. I tend to use much more and try to keep the romex neat. But the inspector was talking about even stapling 2 pieces of 12/2 under the same staple builds up heat, but that he doesn?t enforce the ruling on that because of this 24 inch thing. This is what I don?t understand.

Also he gave me a chart number in the code book that discusses de-rating the ampacity of the circuit when wires are bundled together. He was over my head and I can hardly remember what he was saying. When I asked other guys I work with, they didn?t seem to know of this either, and unfortunately just want to pass inspection.

I don?t want to ?just pass?, I want to understand the process and safety.

If anyone can point me to the rulings in the code about stapling and this ?no more than 9 current carrying conductors? rule, please help me out. Also if you know of this chart to use in order to de rate the circuits, that would be helpful also. Thanks.
 
daver828 said:
If anyone can point me to the rulings in the code about stapling and this “no more than 9 current carrying conductors” rule, please help me out. Also if you know of this chart to use in order to de rate the circuits, that would be helpful also. Thanks.
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Article 310(B)(2)
 
daver828 said:
New to the forum. Also new to trying to learn the code, and need some help please.
I had a discussion with an inspector last week who told me some things I?d not yet heard and cannot find where to look it up in the code book. I do alot of residential work, remodels, etc. So this is about residential and romex.

This inspector was talking about bundling of wires, either under the same staple or with tie wraps, or whatever. What he was telling me is that beginning at 3, and not more than 9 current carrying conductors can be bundled together. He discussed heat buildup and circuit loads. That was easy enough to understand. But he kept saying something about stapling every 24 inches in order to allow the heat to dissipate? I understood that the first staple from the box had to be within 6 inches, and then up to 4 1/2 feet after that. I tend to use much more and try to keep the romex neat. But the inspector was talking about even stapling 2 pieces of 12/2 under the same staple builds up heat, but that he doesn?t enforce the ruling on that because of this 24 inch thing. This is what I don?t understand.

Also he gave me a chart number in the code book that discusses de-rating the ampacity of the circuit when wires are bundled together. He was over my head and I can hardly remember what he was saying. When I asked other guys I work with, they didn?t seem to know of this either, and unfortunately just want to pass inspection.

I don?t want to ?just pass?, I want to understand the process and safety.

If anyone can point me to the rulings in the code about stapling and this ?no more than 9 current carrying conductors? rule, please help me out. Also if you know of this chart to use in order to de rate the circuits, that would be helpful also. Thanks.
Click to expand...
Try looking in 310.15(B)2.
 
implications?

implications?

Ok, ha, now in English. What are the implications of 310.15.B.2?

What does that mean in regard to pulling romex in the same holes? And should each cable be stapled separately? Or just plan on always using those plastic wire stackers, even for one or two wires?

Thank you.
 
daver828 said:
Ok, ha, now in English. What are the implications of 310.15.B.2?

What does that mean in regard to pulling romex in the same holes? And should each cable be stapled separately? Or just plan on always using those plastic wire stackers, even for one or two wires?

Thank you.
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It depends on your jurisdiction. Most areas will allow 2 wires under one staple. More than 2 wires you would need stackers.

It is of the opinion of most of us that you can put more than 2 wires through a bored hole however in Orange county, NC they have been saying no more than 2 wires in one hole. I don't know why. If more than 2 wires are run for more than 2' together than its bundling and you must derate unless there is space between the wires. See article 310.15 (B)(2) exception #3
Table 310.15(B)(2)(A) gives the adjustment factor.
 
Dennis,
If more than 2 wires are run for more than 2' together than its bundling and you must derate unless there is space between the wires.
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Why two cables? While derating starts with the 4th current carrying conductor, there is no real problem until you have more than 9 current carrying conductors in the bundle. That is because, in the case of NM, you start the derating from the 90?C column. In that column #14 has an ampacity of 25 and #12 has an ampcaity of 30 amps. Even when you apply the 70% factor for 7 to 9 current carrying conductors in a bundle you have a final ampacity that is greater than the maximum permitted overcurrent protective device for those size conductors.
Don
 
daver828 said:
What he was telling me is that beginning at 3, and not more than 9 current carrying conductors can be bundled together.
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This is a common misstatement - not more than nine CCC's can be bundled together without upsizing the conductors. You can keep going, but it starts to not be cost-effective after nine CCC's are present.

But he kept saying something about stapling every 24 inches in order to allow the heat to dissipate?
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You probably misheard him - he probably said (or meant to say) that if you stapled every 24", then that would be considered bundling, in his opinion...?

Basically, determining what "bundled" means in a cabled wiring system can be tricky. Take a look at 310.15(B)(2)(a)'s exception 4. MC cables on bridle rings are not crisp and neat and tight together, but are still considered bundled by the NEC.

So, even if you were to staple every 4.5 feet, if the cables run side by side for over 24", then the inspector could force you to begin derating the conductors on account of that. It is a rare jurisdiction to do so, however.

Most folks balk at that, because we can still see air around the cables, to one extent or another. Bundling, being ill-defined in the NEC, causes different interpretations and enforcement.

Invite the inspector to the forum. This is a good place to take your time and explain what you're getting at, without having to run to the next spot in ten minutes. :)
 
thank you

thank you

Thank you gentlemen for your responses. As it turns out, I talked with this same inspector today, again, about another matter. I asked him again about this bundling matter, to which he gladly started all over again. He said exactly what you gentlemen have said about the 3 CCC's and no more than 9. And he explained again the reasons and how to derate, etc.

I asked him specifically what he would prefer, what he was looking for. This is where it got a little confusing to me. Anyway, he said that on one hand 3 ccc's began the process of deration, but that it was okay to staple 2 pieces of 12/2 on top of each other. But no more. Seemed like a contradiction to me. Either 3 was the limit or it is not. However, what he did say was that he was more concerned about more than one circuit being involved. Like, for instance, he said, if you had one circuit feeding 2 4-gang boxes each switch serving a single recessed can light in a room, then it's only one circuit, the heat buildup is still because of 20 amps. But if two or three circuits are feeding switches all over the main floor, then the ampacity starts to multiply, causing the heat to rise exponentially. Then he would turn it down if they were all bundled together.

But, he did say this about running wires through the same hole. What he said was that the NEC doesn't explicitly have anything to say about this, so he personally would not turn it down to have 2 or even 3 wires in the same hole. But in reality he didn't think it was a good practice and would not do it himself. And he said emphatically that drilling extra large holes and stuffing them full he would turn that down too. As well as tie wrapping bunches of wires together going toward and down into the panel. He wanted the wires separated.

Anyway, this is very good for me to learn, not only what this guy wants, but what the book says and why. I am looking for improvement in my own practices. Thank you all for helping. Has given me a newfound desire to learn the code book. Tired of being just an installer.
 
don_resqcapt19 said:
Dennis,

Why two cables? While derating starts with the 4th current carrying conductor, there is no real problem until you have more than 9 current carrying conductors in the bundle. That is because, in the case of NM, you start the derating from the 90?C column. In that column #14 has an ampacity of 25 and #12 has an ampcaity of 30 amps. Even when you apply the 70% factor for 7 to 9 current carrying conductors in a bundle you have a final ampacity that is greater than the maximum permitted overcurrent protective device for those size conductors.
Don
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I didn't say there was a problem with more than 2 cables I just stated that you had to derate after 2 cables. I thought he would figure the rest out. Perhaps I should have told him more.
 
I have always viewed bundling as wiring running tightly together. When you have more than 2 wires through a bored hole in a stud, if you seperate them bewteen the stud spaces to provide air space, then I don't think bundling applies since they are not tight for the 24 inch length. If the cables are zip tied together the full length, then it would be viewed differently. I have seen wires "bundled" from the top of the load center into the attic and had contractors adjust it for air space.
 
daver828 said:
But, he did say this about running wires through the same hole. What he said was that the NEC doesn't explicitly have anything to say about this,
Anyway, this is very good for me to learn, not only what this guy wants, but what the book says and why. I.
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obtw
If you are working under the 2005 take a look at 334.80 regarding more than two cables through the same hole in a framing member.
 
cpal said:
obtw
If you are working under the 2005 take a look at 334.80 regarding more than two cables through the same hole in a framing member.
Click to expand...

Right, but that still allows more than 2 pieces of Romex through a firestopped hole. Each piece of X/2 or X/3 counts as 2 CCCs (assuming the X/3 is a MWBC and yada, yada, yada), the 90C ampacity is sufficient that after derating the ampacity is still greater than the 60C value up to 9 CCCs, which is at least 4 pieces of X/2 or X/3.

Which means, in practice, you don't have to derate until you have more than 4 pieces through a framing member because you're not permitted to use anything more than the 60C value in the first place. The derating from the 90C ampacity to the 60C ampacity is already required -- might as well take advantage of it :)
 
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