New 334.80 requirement

[bphgravity]

Section 334.80 of the 2005 NEc states, "Where more than two NM cables containing two or more current-carrying conductors are bundled together and pass through wood framing that is to be fire- or draft- stopped using thermal insulation or sealing foam, the allowable amapacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a)."

Couple of issues...

Is this saying 3 or more cables EACH containing 2 or more currrent-carrying conductors? If so, does this mean I don't need to meet this requirement if I have more than 2 cables each having only 1 current-carrying conductor, or 2 cables with 2 or more current carrying conductors along with 1 or more cables with only 1 current-carrying conductor?

Also, does the "bundle" have to be 24" or longer or do the 3 or or conductors just need to be in the same hole?

It seems there are many combinations that would result in ahot spot, but it seems to be specific to only multiple cables of multible current- carrying conductors in the same hole.

I can see this being horribly misinterpreted.

 

[ryan_618]

Re: New 334.80 requirement

The requirement already applies when the bundle is over 24", so I think that is irrelevant.

Also, when (besides a two wire traveller) would you only have one current carrying conductor in a cable?

 

[don_resqcapt19]

Re: New 334.80 requirement

Bryan,
This is not a bundling issue. Tests were done with the NM in holes that were fire stopped. The temperature rose dramatically. According to the substantiation, the cable temperature exceeded 90?C when installed in holes that were fire or draft stopped, even with out exceeding the cable ampacity. I think that the wording could be better, but if you have 3 or more cables and each of those have 2 or more current carrying conductors, then this rule applies.
Don