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Joined: Oct 2000
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I'm supposed to be attending a Seminar (Sat.) being put on by our local Association. We will be "Re-Learning" NEC (1999) Articles 300, 310, 362, 370, 430 and Chap 9.

Anybody got any "hot" topics worth bringing up? (I expect we'll go through the romex sleeved in Conduit issue again ...)
Any Suggestions for others?

Bill


Bill
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Joined: Oct 2000
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Bill;
ask why 300 is 'wiring methods' , it should be changed to 'stuff that don't fit in other articles' or 'NEC dumping ground'

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Joined: Oct 2000
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ask if any AHJ's have enforced 370-21 of other trades!

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I still wonder about low-voltage landscape lighting cable depth requirements. Instructions say no cover required, 300-5 says 6".

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Tom Offline
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I new Sparky was pretty #. I've told plenty of folks, if you can't find it, look in article 300.

As far as 362 is concerned, specifically 362-5, if I have a custom made "junction box"
that is 4" tall and 4" deep and 60" long, i can fit 426 #12 conductors in it without derating, but if it is a wireway, I have to derate when I exceed 30 current carrying conductors. How come? I see absolutely no differance.

Tom

[This message has been edited by Tom (edited 04-20-2001).]


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Thanks Guys,

I don't know if anyone will have answers to those questions, but I bought a new Notebook to jot down interesting stuff for discussion.
I'll 'keep you posted' [Linked Image]

Sparky, hey - weren't We doin Rops'
Where are We up to? How about starting another?

Bill


Bill
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check out log #3908, and others like them that address 310-15(b)(6)
there is a conflict bettween it and 336-26, 338-4(a)
http://www.nfpa.org/Codes/National_Electrical_CodeR_NEC/Proposals?necpdf?A220-310.PDF

[Linked Image]

A
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Quote
if I have a custom made "junction box" that is 4" tall and 4" deep and 60" long, i can fit 426 #12 conductors in it without derating,
But each can be only around 6 inches long.

Quote
but if it is a wireway, I have to derate when I exceed 30 current carrying conductors. How come? I see absolutely no difference.
I do see a big difference.

In your custom box, you probably can have 426 #12 conductors. but they would have to be running across the 4" length and exiting.
That's 213' of wire.

You want them to run along the 60" length.
30 times 5' is 150' of wire.

As you can see, they aren't that far apart.
The 30 wires will tend to lie on each other and not dissipate heat so well as the short wires running through crosswise. So the limit of 30 conductors longwise seems on target to me.

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Tom Offline
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Dspark,

I don't see why the wires in my custom junction box would be limited to 6" long.

As far as how they are run in my junction box, I can't find a single thing in article 370 that tells how they must be run, how short they must be or much else about these #12 conductors. As long as I have provided the needed cubic inch capacity (2.25 cu in per) I feel I'm entitled to put as much conductor as possible in my custom J-box. 5' of #12 thhn occupies .798 cubic inches.

According to my math, I can install 426 x 5' = 2,130 feet of wire, which is considerably more than the 30 x 5' = 150 if this were a wireway.

The 426 #12 thhn's would occupy 5.66 square inches of cross section. Since the wires are round, I suspect that I would need closer to 10 square inches of cross section, but since there are 16 square inches of cross section available, I should be able to get them in there.

Of course I wouldn't contemplate doing such an installation. If I was an inspector, what code rule could I apply to prohibit this installation?

Tom



[This message has been edited by Tom (edited 05-13-2001).]


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