bundling romex wires

[dave81]

What is the harm in bundling romex wires together in a single family home. Is their that much heat created to lower the ampacity of branch circuits in a home, I just can't see it, unless someone can enlighten me, lately inspectors around here don't want any bundling of romex even if its just 3 or 4 wires other wise they want you to derate them but I was under the impression that wires of these kind of circuits have already been derated for safe operation. I was also curious as to what section in the code you find this under. Any comments would be appreciated. Thanks

 

[don_resqcapt19]

Re: bundling romex wires

See 310.15(B)(2)(a). Note that there is no real issue unless you have more than 4 cables bundled. With 4 or less cables the derating is 70% from the 90?C column so youcan still use 15 amp breakers for #14 and 20 amp breakers for #12.
Don

 

[throttlebody]

Re: bundling romex wires

I agree with Don, but..........Exception 3

Anything over 24" in length would need to use that table. A 1" drilled hole in a 2x12 with 10 NMs is not defined as bundled.

Very seldom will you see anything of that stature in a new SFDwelling, unless you are drilling vertically or using conduit hanging from the joist for the panelfeeders.

 

[mdshunk]

Re: bundling romex wires

Even if you do bundle them somehow, if the ties/straps/whatever are more than 24" apart, and you have a little air space between the cables between the ties, my inspectors don't consider this bundling. It is interesting to learn how this stuff is handled in other lands, though.

 

[dave81]

Re: bundling romex wires

Lets say you have a 3wire romex white, red, black, ground, is the neutral considered to be a current carrying conductor since its carries current or not. Does the NEC outline exactly what they consider to be "bundled"?

 

[throttlebody]

Re: bundling romex wires

Originally posted by dave81:
Lets say you have a 3wire romex white, red, black, ground, is the neutral considered to be a current carrying conductor since its carries current or not. Does the NEC outline exactly what they consider to be "bundled"?

No. When it carries ONLY the unbalanced current from the other conductors of the same circuit.

Definition of Bundled can be found @ 520-2

Originally posted by mdshunk:
Even if you do bundle them somehow, if the ties/straps/whatever are more than 24" apart,

Derating would only apply in a bundle of more than continuous 24 inches. Ties that are 24" apart may be called "bundled" according to the definition, but there is no violation that I can find.

[ February 01, 2006, 10:29 PM: Message edited by: throttlebody ]

 

[LarryFine]

Re: bundling romex wires

Originally posted by throttlebody:

Originally posted by dave81:
Lets say you have a 3wire romex white, red, black, ground, is the neutral considered to be a current carrying conductor since its carries current or not. Does the NEC outline exactly what they consider to be "bundled"?

No. When it carries ONLY the unbalanced current from the other conductors of the same circuit.

In other words, feeding four circuits via two 3-conductor cables results in 4 current-carrying conductors, while using four 2-conductor cables results in 8 current-carrying conductors.

 

[macmikeman]

Re: bundling romex wires

Definition of Bundled can be found @ 520-2

That is for theater, places of assembly, and similar places. So if you are installing romex in multiples in a theater thru holes close together, and tightly wrapped up with tape or tie wraps, you messed up because romex is not allowed in these places. Otherwise that definition of bundling is not applicable to other locations.

 

[bphgravity]

Re: bundling romex wires

Don't forget about the exception to 310.15, this option will generally negate any bundling derating over 24" but not longer than 10'.

 

[Paul B]

Re: bundling romex wires

One inspector that I have been putting up with lately will not allow 9 CCC throught a drilled hole in a 2x no matter what. Yes the neutral is considered a CCC. So 3 14/2's and a 14/3 your done.

Paul

 

[pierre]

Re: bundling romex wires

"Don't forget about the exception to 310.15, this option will generally negate any bundling derating over 24" but not longer than 10'."

Bryan
would you mind elaborating on this?

 

[ryan_618]

Re: bundling romex wires

I made a proposal to delete the new part of 334.80, using the same logic as Bryan. I am curious to see what panel 7's take is on the issue.

 

[don_resqcapt19]

Re: bundling romex wires

Paul,

Yes the neutral is considered a CCC.

The neutral conductor of a 3 wire cable on a 120/240 volt single phase system is not a current carrying conductor for the purposes of derating.
Don

 

[Paul B]

Re: bundling romex wires

Don,
I understand your point, but you get the idea.

 

[dave81]

Re: bundling romex wires

So "bundled" is or is not clearly defined in the NEC or is that left to inspectors to decide because my bundled romexs were never that tight they always had air space between them when they were not going through a hole in the wood. Is their much heat created from NMSC romex when under load I thought if the conductors were in metal conduits then you tend to have heating alot more than you would with non-metallic sheathed cables.

 

[throttlebody]

Re: bundling romex wires

Does the NEC outline exactly what they consider to be "bundled"?

Definition of Bundled can be found @ 520-2

Originally posted by macmikeman:

Definition of Bundled can be found @ 520-2

That is for theater, places of assembly, and similar places. So if you are installing romex in multiples in a theater thru holes close together, and tightly wrapped up with tape or tie wraps, you messed up because romex is not allowed in these places. Otherwise that definition of bundling is not applicable to other locations.

Exactly.

 

[iwire]

Re: bundling romex wires

The definition of bundling is what the inspector determines it to be.