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Old 03-31-2009, 02:53 PM   #1
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current carrying conductors - switch loops?


Hi all,

It's my first post - don't hold it against me.

I'm well acquainted with CCCs vs. box and conduit fill and such but am having a brain fart coupled with a lot of unsuccessful googling about switch loops and how they're affected by the rules. Question: if one runs 16 wires back and forth from a central j-box to a pair of 4-gang boxes on a wall thru conduit, does that count as 16 CCCs? I'm assuming yes and derating that way (read also: running another switch loop conduit under the house...grrr.) but thought I would ask just to be sure.

A few specifics:

1) the 16 wires/8 switches would be looping power back and forth from 2 15a circuits (it's a lot of small lights that must be switched separately/decoratively) with all the make-up happening in a (large) J-box on another wall.

2) there's lots of easier ways to do it, but most or all of them are roadblocked for me by structure and detail issues: parallams on top of top plates that I can't drill/notch, wall/ceiling intersections I can't create chases/soffits in, bolts and A35s and holdowns that prevent me from getting in and out of stud bays where it would be easier for electrical, etc.

Looking forward to replies,

WM

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Old 03-31-2009, 02:57 PM   #2
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current carrying conductors - switch loops?


Why 16 wires? Does each switch have to be on a separate circuit? Just run one hot leg to the switch box and 4 switched hots back.

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Old 03-31-2009, 03:55 PM   #3
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current carrying conductors - switch loops?


Yes, each wire in the loop is a current carrying conductor. But since you only have two circuits, just run two hots and 8 switch legs, totaling 10 CCCs.
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Old 03-31-2009, 07:58 PM   #4
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current carrying conductors - switch loops?


Quote:
Originally Posted by HouseHelper View Post
Why 16 wires? Does each switch have to be on a separate circuit? Just run one hot leg to the switch box and 4 switched hots back.
Hmm...I didn't think of that. All the make-up happens across the room in a large j-box, but I didn't think of what you've suggested. You're saying run two hots over - one to each 4gang wall box. line-side loop each group of 4 switches together and run two sets of 4 switched wires back. 10 lines total. I'd still be in the same derating category (10 to 20 CCCs, 12gauge=15a 14gauge=12a) unless i ran another conduit and split it half and half.

The "run another conduit" part is the problem due to floor diaphragm perimeter blocking and hardware (the j-box is in an outside wall) making it a b*tch to get thru the sole plates into the crawlspace. I'll figure something out, or just go with it as each switched run is only 2 to 3 amps max. (2 circuits are CFLs - Aaah, California Title 24.)

the "one rule fits all" nature of the derating schedule has always bugged me. Putting 10 14gauge CCCs in 1" flex (less than half full?) makes you cut the ampacity of 14gauge wire in HALF.

Thanks for the great idea!

WM
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Old 03-31-2009, 08:01 PM   #5
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current carrying conductors - switch loops?


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Originally Posted by InPhase277 View Post
Yes, each wire in the loop is a current carrying conductor. But since you only have two circuits, just run two hots and 8 switch legs, totaling 10 CCCs.
now that I think about it and think about the fact that I work with Theaters and Theatrical lighting systems I realize how stuck in "home run" mode my thinking is. I'm so used to needing full load and single control capability on every circuit, which is SO not the case here. I like this low amp stuff. :D

WM
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