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We have a lowered ceiling in the kitchen and I am currently raising it. By doing so, I am having to re-route some of the wiring. I have drilled 1 1/4 in. holes through some of the rafters and fed 5 wires through the whole. My question is if this is ok. I was told by someone before that there was a limit as to how many wires could run through a conduit, but was unsure if 5 wires bunched next to each other in this fashion was exceptable.
 

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Lic Electrical Inspector
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If you bundle more than (2) 14/2 romex for more than 24" it will have to be derated. Five cables will have to be derated. What are the gauges of each cable? I am more concerned about the 1 1/4" hole through the rafters. You may have weakened the rafter.
 
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Discussion Starter #3
12-2 wire. Actually it was 2x12 floor joists for upstairs. How would you re-route wire? How many wires can be bundled for how many feet?
 

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IMO, running wires through bored holes is not bundling, the joist are typically 1.5" thick, thus does not meet the 24" length requirement to be considered bundled, you can run as many wires as you wish in bored holes, the only time this is an issue is when fire stopping is required, then you run into the max. 9 current carrying conductor rule, and are limited to that or derating must take effect.
 

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What would be the problem with the wires being bundled anyway? Of course we have to describe "bundled" Five 12-2's running through several 2x12's for approx. 14 ft. would be ok then?
 

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What would be the problem with the wires being bundled anyway? Of course we have to describe "bundled" Five 12-2's running through several 2x12's for approx. 14 ft. would be ok then?
The problem with bundling, when cables and wires are actually bundled, is heat dissipation...

And I don't see an issue at all with what you propose.
 

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So the heat issue is really dealing with the "length" in which the wires are "enclosed"? (Cannot be enclosed for more than 24") The wires touching one another wouldn't be an isssue? Hey. I'm a truck driver, not an electrician! HA HA
 

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electures said:
If you bundle more than (2) 14/2 romex for more than 24" it will have to be derated. Five cables will have to be derated. What are the gauges of each cable? I am more concerned about the 1 1/4" hole through the rafters. You may have weakened the rafter.
I agree with electures on this. I usually run 2 cables per 3/4" hole. That's the norm where I'm from, inspectors will fail it if we don't. Also a 1 1/4" hole in your 2x10 joist is a very big hole, I would be worried about the structural strength now of those joists
 

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stickboy1375 said:
Then the inspectors are morons... so which code section did they fail you on?

EDIT

Eh. you're canadian... that changes things.
I've never heard of anyone running that many wires thru one hole.
 

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As far as derating is concerned, I wouldn't be concerned with it. But as you add cables to a hole, you build up more friction as you pull each additional cable through. I've seen the outer shell of romex worn away and all the way through the THW insulation as well (yeah, I'm an old electrician). So I always limit myself to two.

Adding more holes in the joist (within reason) won't hurt anything.But do yourself a favor, drill every other joist as you drill your holes, and at the end, turn around and go back and drill the joists that you skipped. This will make pulling the romex through your holes much easier.

And I always unroll my roll of romex on the floor and never pull it directly from the center. This will add a twist that will act as a "rasp" that can damage existing cables in a given hole.
 

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Then the inspectors are morons... so which code section did they fail you on?


EDIT

Eh. you're canadian... that changes things.
Unless its a manitoba thing, in Ontario, we can run it the way you propose. Has to be bundled for more than 2 feet here, as well. Running it through joists doesn't count as bundling. (I'm not 100% sure, but I think we have to start derating at 7 conductors though.)
 

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I agree with electures on this. I usually run 2 cables per 3/4" hole. That's the norm where I'm from, inspectors will fail it if we don't. Also a 1 1/4" hole in your 2x10 joist is a very big hole, I would be worried about the structural strength now of those joists
As a general rule, you can make large holes within the middle 1/3rd of a joist. It's notching or making holes in the top or bottom 1/3 that rapidly destroy the load bearing capacity of a joist.
 

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FRom the 2011 NEC;

334.80 Ampacity.​
The ampacity of Types NM, NMC, and
NMS cable shall be determined in accordance with 310.15.
The allowable ampacity shall not exceed that of a 60°C
(140°F) rated conductor. The 90°C (194°F) rating shall be
permitted to be used for ampacity adjustment and correction
calculations, provided the final derated ampacity does not exceed
that of a 60°C (140°F) rated conductor. The ampacity of
Types NM, NMC, and NMS cable installed in cable tray shall
be determined in accordance with 392.80(A).
Where more than two NM cables containing two or
more current-carrying conductors are installed, without
maintaining spacing between the cables, through the same
opening in wood framing that is to be sealed with thermal
insulation, caulk, or sealing foam, the allowable ampacity
of each conductor shall be adjusted in accordance with
Table 310.15(B)(3)(a) and the provisions of 310.15(A)(2),
Exception, shall not apply.
Where more than two NM cables containing two or
more current-carrying conductors are installed in contact
with thermal insulation without maintaining spacing between
cables, the allowable ampacity of each conductor

shall be adjusted in accordance with Table 310.15(B)(3)(a).

As long as the holes are not sealed, or the cable is not in contact with thermal insulation, no derating is required.
 
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