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Old 03-24-2015, 06:44 PM   #1
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How many cables in a hole?


I am replacing old cable and putting things on their own circuit etc, so I am in attic drilling holes in the top plate over the main panel. I do not want to drill too many holes in the 2 x 4, so I am wondering how many 12 ga. cables I can pull through one drilled 1" hole. Some of the holes appear to be only 3/4".

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Old 03-24-2015, 07:01 PM   #2
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How many cables in a hole?


Not sure what code says but I wouldn't do more than 2. More holes won't hurt anything.

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Old 03-24-2015, 07:25 PM   #3
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How many cables in a hole?


Bottom line is you can have up to four cables in a hole before you have to worry about anything.
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Old 03-24-2015, 08:33 PM   #4
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How many cables in a hole?


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Not sure what code says but I wouldn't do more than 2. More holes won't hurt anything.

The main panel is in the wall and the cables are coming up into the attic via two 2 x 4 top plates. I am concerned about putting holes in these top plates. Won't his weaken the 2 x 4s?

I have encountered this concern before.
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Old 03-24-2015, 08:44 PM   #5
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How many cables in a hole?


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The main panel is in the wall and the cables are coming up into the attic via two 2 x 4 top plates. I am concerned about putting holes in these top plates. Won't his weaken the 2 x 4s?

I have encountered this concern before.
Only if you drill one continuous hole from one end to the other. You are over thinking this. Just make sure when you drill, that you are not going to drill into any electrical wiring on the other side.
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Old 03-25-2015, 06:33 AM   #6
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How many cables in a hole?


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Bottom line is you can have up to four cables in a hole before you have to worry about anything.

Speedy, as I recall from my 2014 code class, the instructor said only 2 cables per hole were now allowed. Offhand I don't know the section in the book.
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Old 03-25-2015, 06:46 AM   #7
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How many cables in a hole?


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Speedy, as I recall from my 2014 code class, the instructor said only 2 cables per hole were now allowed. Offhand I don't know the section in the book.
This two cable limit is not accurate. After two you need to start derating. He is talking about the last sentence in 334.80.
With #14, 12 & 10 you do not need to worry about derating until you get to nine current carrying conductors, hence the four cable number. Neutrals of a multi-wire branch circuit do not count as CCC's.
240.4(D) limits the ampacity of #14, 12 & 10 considerably, and since we can derate newer NM cable from the 90 deg C column you get quite a difference between the two.
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Old 03-26-2015, 06:24 AM   #8
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How many cables in a hole?


A 1" hole can easily take 4 wires of 12 or 14 or combination. We do it all the time, no inspectors ever said a word about it. 1" is a good size hole and 4 wires fit very loosely.
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Old 03-26-2015, 12:25 PM   #9
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How many cables in a hole?


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A 1" hole can easily take 4 wires of 12 or 14 or combination. We do it all the time, no inspectors ever said a word about it. 1" is a good size hole and 4 wires fit very loosely.
1" is a bit close with 2x4 framing. You don't have much room for being off center and staying legal.
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Old 03-26-2015, 05:54 PM   #10
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How many cables in a hole?


Not being an electrician, will nail plates take care of that off-center hole? Or is there yet another chunk of code covering drilling??

To the OP, don't think of taking a chunk of two bye four, supporting it over two others, drilling a bunch of holes in it and jumping up and down in the middle of it. Think instead of the overall load distribution of what is on top of it, the distance between supports and the strength of two boards them selves. Different story. ron
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Old 03-26-2015, 09:07 PM   #11
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How many cables in a hole?


ront02769, that is why new construction you will see the main wiring trunk using 2x6 framing, so you can get around the issue with 2x4's.

You cannot use nailers, because the holes would be through the bottom & top plates. As for Vertical strength, you could just double the joists on either side, to help strengthen the area that would be pretty much cut away if it is a large amount of Romex.
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Old 03-27-2015, 07:12 AM   #12
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How many cables in a hole?


Missing your point. The metal nailing plate would go against the edge of the two bye plate keeping sheet rock screws etc. from hitting the wire.. That's how I've seen it done in residential work...but perhaps there is a specific guide that tells you where you. Can and cannot drill holes in two byes....like that six inch bye six inch prohibited space in the web at each bearing end of an i-joist?
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Old 03-27-2015, 08:58 AM   #13
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How many cables in a hole?


Nail plates are used any time the minimum 1.25" clearance cannot be maintained.

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