Attach Romex to main beam in basement?

3879 Views 8 Replies 8 Participants Last post by Datawise, Apr 13, 2020

mkmona04

Discussion Starter · Apr 8, 2020

In the basement, I have a suspended ceiling tile system. Above that and along the main load-bearing beam of the house I have a bunch of Romex (see picture).

I am not in love with the idea of attaching all that romex using staples or fasteners but at the same time, do not want the romex hanging loosely on top of the ceiling tiles. I am considering attaching utility hooks (see attached) to the beam and simply letting the romex rest within the hooks.

Is this a good or bad idea? is there s code requirement?

Thank you

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anyacolo

· #2 · Apr 8, 2020

it is against code for romex to be in contact with T-Bar ceiling,

also, by code, i believe those wires need to go THROUGH the beams, they can not hang below the beam, or be fastened to the bottom of the beams, but im not 100% sure on that one

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seharper

· #3 · Apr 8, 2020

That will have the general effect of being a raceway. I can think of 2 things right off the bat which will come to bear.

Mixing: These must be mains power only. You cannot put any sort of data, thermostat, or any other kind of low power circuits among these cables.

Derating: NEC 310.15(B)(7) limits. This contains a great deal of complexity, but for 15/20/30A circuits, it boils down to this in split-phase 120/240V land: No more than 4 circuits per raceway.

(all circuits have 2 wires that count for 310.15(B)(7) purposes as MWBC neutrals do not count; the maximum is 9 for a 30% derate off 90C numbers from 310.15(B)(16); and 30% does not affect you any worse than 240.4 already does).

You can have more than 4 circuits in a raceway if you really really really want to, but you'll have to upsize the wire if you do. And nobody wants that.

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Old Thomas

· #4 · Apr 8, 2020

Bundling wires so they have reduced air contact reduces ampacity, too. Resist the temptation to use zip ties to make them into a bundle.

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rjniles

· #5 · Apr 8, 2020

Google "stackers for electrical'

Sent from my Moto E (4) Plus using Tapatalk

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seharper

· #6 · Apr 8, 2020

Old Thomas said:
Bundling wires so they have reduced air contact reduces ampacity, too. Resist the temptation to use zip ties to make them into a bundle.

Like the way extension cords will infamously melt if you use them coiled up.

Yes, that kind of zip-tie bundling is exactly when 310.15(B)(7) comes into play. It's all about the thermal calcs. When you bundle wires or use a raceway or put them in a conduit, it becomes about the thermal capacity (surface area) of the *package*.

And that is controlled by the surface area not the cross section. Double wire size, you quadruple cross section, but only double surface area. That is why wire twice the diameter doesn't have 4x the ampacity. If you ran 4x amps, the wire would have 4x the heat to remove, and it only has 2x the skin to do it with. And that... is why 310.15 is so complicated!

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Oldmaster

· #7 · Apr 8, 2020

Easiest thing might be to space them out on the beam and staple then. With correct staples you can have 2 cables under a staple.

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Jim Port

· #8 · Apr 9, 2020

3M stak-its are the solution to your issue.

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Datawise

· #9 · Apr 13, 2020

Can't give you a code answer because I don't know where you are from. Is the beam wood or steel?

Stackers are the answer for wood in my area. If on a steel beam, I PL a piece of 2 x 4 to the beam and then either staple or stacker the wires as necessary. I have some pics somewhere, I will see if I can locate and post.

Cheers
John

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