310.15(B)(2)(a) w/ 240.4(B)(1)

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  #1  
Old 03-23-05, 09:14 AM
Beeek
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Question 310.15(B)(2)(a) w/ 240.4(B)(1)

In "Wiring Simplified" in the chapter on NM wire they state:

Ampacity Restrictions: Although the individual conductors must, by NEC rule, have a 90 oC temperature rating, the final allowable ampacity must not exceed that given in the 60 oC column (refer to Table 4-1). This restricts the number of cables that are "bundled" for longer than 24 inches. This includes routing more than one cable through a sucesssion of single bored holes. You need to consider this requirement in a basement, for example, where you might be tempted to run large numbers of cables back to the panelboard through a set of holes lined up through the floor joists and ending at the panel. As a practical matter, putting NEC 310.15(B)(2)(a) together with 240.4(B)(1) under this restriction means that for common applications you can't put more than four cables together through a common set of holes.

My question is, for the example they used I have a bundle of six 14/2 gauge NM-Bs running through the pre-made holes in 4 or 5 joists back to my panell. Also I have an inspection tomorrow (alterations) on two dedicated 10/2 gauge NM-Bs I installed, and ran through 3 joists (technically just longer than 24") along with one 10/3 and electric range wire. Does this absolutely mean only 4 NMs per joist hole, or do I have my situations mixed up? Did my inspector just miss the 6+ 14s bundled when the house was built/inspected in December?

As always TIA,
Beeek
 
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Old 03-23-05, 10:25 AM
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Beeek in my experience this is an inspectors call on what is bundling in your situation. The four cables referenced is considering that ampacity deration for bundling usually doesnt become a factor until 9 wires (four 14-2 cables would be 8 wires) are bundled. I havent seen an inspector flag cables through bored holes for bundling in quite a while. If you have them cable tied together between the bored holes then he may flag you.
 
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Old 03-23-05, 10:54 AM
Beeek
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Roger, thanks. For the 14/2s I am going to say they were like that when I got here (which is 100% true). After trying to read up further, I had seen a reference to derating (kind of a mystery), which has me concerned on my bundling I did. I have two 10/2s and one 10/3, with a ?8or6?/3 for my electric stove.

So from your post, I guess if he wants to flag me for something, he will find it. Good to know your expirence. No biggie, I'll pop out another set of joist holes, and unhook the two 10/2s from the board. Biggest problem is my board is full and the room and terminals inside are a pain, 10/2 doesn't bend so eaily. I'll find out tomorrow morn, my first inspection.
 
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Old 03-23-05, 11:26 AM
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I really dont think you will have a bundling concern in either case. What are the 10-2's for? Cooking equipment? Remember when you bore holes stay close to the center of your framing members. If you get closer than 1 1/2 inches to an edge you will have to place a steel nailing plate on the joist or stud to protect the wire from driven nails.
 
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Old 03-23-05, 12:04 PM
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The grouping of 14/2 cables is a code violation. But since it is preexisting, and the inspector is there for something else, and it's not a severe hazard, he'll probably let it slide.

But you might not want him to let it slide. I might be inclined to specifically ask him about it and see if he'll write it up. If so, you can use that as leverage to get the builder to fix it. The house should still be under the 1-year warranty.

You didn't run the new cables though the same holes as the old 14/2 cables, did you?
 
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Old 03-23-05, 12:16 PM
Beeek
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Roger, the two dedicated lines (10/2) that I installed were overkill for home theather (20 amp breakers/15 amp duplexs). The other two bundled w/ it are for cooking, dedicated microwave (10/3) and electric range (6-8???/3).

I used the built in holes in my joists (1/3 to <1/2 up), they have knock out holes stamped in them, you just have to punch them out. About 1 1/4" to 1 1/2" inch round, at least 5+" up. Never noticed them until I was tacking and my hammer popped one out onto the floor.
 
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Old 03-23-05, 12:30 PM
Beeek
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Originally Posted by John Nelson

You didn't run the new cables though the same holes as the old 14/2 cables, did you?
John thanks, Nope my 10/2s are with one existing 10/3 and one 240V electric range run for just over 24 inches (~30). Most of my branching from the SE board is along the cement basement foundation at the framing junction (mostly tacked w/ those plastic comb/loom clips). However, these two runs are cut (holes) into the joists for the last few feet. One run of a ton load of 14/2s (untouched by me--fills the entire 1 1/2" diameter solid) and then the one run (10s) I added too.

I'll if this is a safety issue, I'll take your advice and point it out to Bob the township inspector tomorrow. I'll try to phrase it in a way that proves I don't know much, the last thing I want to do is seem like a know it all..cuz I certainly know little.

This is also the case were the casing of the 10/3 was sligthly damaged and I found it only after closing. After looking for conductor insulation damage, I wound it up well with orange 3m tape, as suggested. This inspection should be fun!
 
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Old 03-24-05, 09:29 AM
Beeek
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Inspection was a quick visual, I pointed out the joists sparingly to him, and he counted, and found inside was not a 14/2 actually it was my water pipe bond, so technically it was only 5 sets of 14/2, not 6 (man there looked like more when they were tight at the joist. He let it slide.

He said good job and wrote me my sticker. $40 bucks, I wish he would have grilled me further. At least my insurance company should be cool now.

Looks like the original e contractor knew something was up also, b/c it looks like he tried to "fan" the wires apart from each other once they came out of the joist.

Thanks guys!,
Beeek
 
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