NM cable bundled

[nizak]

I’ve got a home I’m working on that has NM cable running in soffits that is boxing in HVAC ductwork in a finished basement.
There are about 15 cables 14 12 10 8 gauge all mixed together. One soffit down each side of basement .

The cables are just laying on the flats of 2x4’s that make up the framing.
Would I be in violation if I tie wrapped the cables together every 3’ just for purposes of neatness and to keep them away from the sheet metal or would that be bundling?

They do not pass through any bored holes in framing nor is there any draft stop or caulking surrounding them.

Thanks

 

[kwired]

If you put them in smaller bundles where you have no more than 9 current carrying conductors in any bundle and maintain spacing between bundles you likely have no ampacity adjustments that will require increasing size of any of them. If you have one large bundle your ampacity adjustment is at least 50% maybe more depending on how many current carrying conductors as defined for the sake of ampacity adjustments are actually present.

 

[nizak]

If you put them in smaller bundles where you have no more than 9 current carrying conductors in any bundle and maintain spacing between bundles you likely have no ampacity adjustments that will require increasing size of any of them. If you have one large bundle your ampacity adjustment is at least 50% maybe more depending on how many current carrying conductors as defined for the sake of ampacity adjustments are actually present.

If you put them in smaller bundles where you have no more than 9 current carrying conductors in any bundle and maintain spacing between bundles you likely have no ampacity adjustments that will require increasing size of any of them. If you have one large bundle your ampacity adjustment is at least 50% maybe more depending on how many current carrying conductors as defined for the sake of ampacity adjustments are actually present.

If you put them in smaller bundles where you have no more than 9 current carrying conductors in any bundle and maintain spacing between bundles you likely have no ampacity adjustments that will require increasing size of any of them. If you have one large bundle your ampacity adjustment is at least 50% maybe more depending on how many current carrying conductors as defined for the sake of ampacity adjustments are actually present.

Is there any distance between tie wraps ( I stated using 3’) that would allow for all 15 NM cables to be grouped together and not subject to de rating?

 

[kwired]

Is there any distance between tie wraps ( I stated using 3’) that would allow for all 15 NM cables to be grouped together and not subject to de rating?

No. Only thing not subject to adjustment would be a bundling of a section of 24 inches or less, though that still may not apply to type NM cables if they are in contact with thermal insulation, see 334.80 for this.

And technically your cables need secured (not just to each other) at minimum of 4.5 foot intervals even if laying on top of framing members.

 

[infinity]

Is there any distance between tie wraps ( I stated using 3’) that would allow for all 15 NM cables to be grouped together and not subject to de rating?

There is no definition in the NEC of the word bundled so it's open to interpretation. IMO a cable tie every 3' would leaving spacing between the cables.

 

[kwired]

There is no definition in the NEC of the word bundled so it's open to interpretation.

True. If you had them just laying freely in a tray or the mentioned "soffit", they will require securing every 4.5 feet as I mentioned. If you secure by tying all 15 of them together at least every 4.5 feet then all 15 will in most cases be considered to be bundled for the sake of applying ampacity adjustments. Now take same cables and organize them in that same location in a manner so you have maintained spacing between small enough "bundles" no ampacity adjustments that would force you to increase any conductor sizes is required.

 

[LarryFine]

My recommendation is to leave them alone, especially if they're going to be enclosed.

 

[nizak]

If you put them in smaller bundles where you have no more than 9 current carrying conductors in any bundle and maintain spacing between bundles you likely have no ampacity adjustments that will require increasing size of any of them. If you have one large bundle your ampacity adjustment is at least 50% maybe more depending on how many current carrying conductors as defined for the sake of ampacity adjustments are actually present.

My recommendation is to leave them alone, especially if they're going to be enclosed.

Thank you.

 

[kwired]

My recommendation is to leave them alone, especially if they're going to be enclosed.

Might be what I would do as well, especially if no inspector is going to see them.

Years back we used to drill 2 inch holes on new homes and run all the home runs through them. Wasn't really NEC compliant but never given any thought until they started inspecting dwellings in my area and inspectors were enforcing this. I don't know of any those homes I worked on at that time that have burned down. I think the NEC is very conservative on this, though the rule is basically one size fits all. In a dwelling about the only circuits that will present much heating issue in that bundle is HVAC loads or maybe a pool pump if you have one. Most everything else doesn't run long enough or is such a light load that it isn't contributing any significant heat to the bundle.

Run same cables but in commercial/industrial that may have more continuous loading and things heat up more in same bundle.