Need a neutral in a switch loop

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Old 02-24-11, 04:02 AM
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Need a neutral in a switch loop

I have all switch loops in this old house and am needing to replace a run this weekend due to probable mouse activity. The issue is I'd like to upgrade this X10 switch to a newer type which supports CFLs, but in order to do that I need a neutral at the switch.

Am I allowed to run 12/3 for the switch loop and bring down the neutral like that?

This is not in conduit, but seems like it would all be balanced anyway under all conditions. Right? (And is it possible for an inline switch to change the phase angle? (intentionally or not))

EDIT: Bah, NEC '11 answered my question quite firmly in the affirmative. I think. Sorry for the needless post guys.
 
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Old 02-24-11, 04:13 AM
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Am I allowed to run 12/3 for the switch loop and bring down the neutral like that?
Yes. In fact a neutral is required in the switch box by the 2011 NEC. http://forum.doityourself.com/electr...ml#post1787270

Of course it will probably be a while before the AHJs actually require it.
 
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Old 02-24-11, 11:23 AM
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Originally Posted by core View Post
(And is it possible for an inline switch to change the phase angle? (intentionally or not))
To my knowledge the extra length of copper in the hot side of the switch loop compared to the length of copper in the neutral side does cause a very slight angle shift because of the imbalance in capacitance, but not enough to be concerned with in residential distances. I have heard of some problems given very long switch loops (100s-1000s of feet commercial bldg.).
 
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Old 02-24-11, 11:44 AM
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Originally Posted by ibpooks View Post
To my knowledge the extra length of copper in the hot side of the switch loop compared to the length of copper in the neutral side does cause a very slight angle shift because of the imbalance in capacitance
Wow, I hadn't even considered that. I may have to ponder that one. But what I _was_ getting at was the impedance of the X10 switch (or anything else with a lot of "meat" to it). Which those X10s, by the way, are deep as heck and chock full of capacitance.


Originally Posted by ibpooks View Post
I have heard of some problems given very long switch loops (100s-1000s of feet commercial bldg.).
Now this I think is even more interesting than my original question. How would these problems manifest themselves? Between the dist. panel and the fixture, or between the fixture and switch? That sounds like one fun barrell of monkeys! Do tell!
 
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Old 02-24-11, 02:33 PM
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I think the new code is good in this point. I did a remodel a few weeks ago and ran 14-3 (just for grins) for the switch loops, capping the white. It makes for easy identification of a current carrying wire without having to remark them, and it gives you the neutral for future use like dimmers, etc. Customers will ask, and I think there should be a tag created to keep confusion down....."this is a neutral, it is supposed to be here, capped off. If you need it use it, if you don't, leave it alone." Hundreds of questions will arise later on for sure.
 
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Old 02-24-11, 03:09 PM
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Originally Posted by core View Post
How would these problems manifest themselves? Between the dist. panel and the fixture, or between the fixture and switch?
Overheating and voltage drop on the conductors makes it hard for ballasted lighting (fluorescent, metal halide, etc) to start correctly. The best thing to do for a long switch run is to put in a contactor (relay) and switch a small control current instead of the full lighting load.
 
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Old 02-24-11, 04:34 PM
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What's an X10? never heard of one.
 
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Old 02-24-11, 04:42 PM
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Originally Posted by Justin Smith View Post
What's an X10? never heard of one.
http://en.wikipedia.org/wiki/X10_(industry_standard)
 
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Old 02-24-11, 04:46 PM
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X10 is for home automation devices.
 
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Old 02-24-11, 04:46 PM
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I would agree that this is a good thing overall. Then again I may be biased because I'm cursing whoever put in these switch loops in the first place.

Originally Posted by chandler View Post
I think there should be a tag created to keep confusion down....."this is a neutral, it is supposed to be here, capped off. If you need it use it, if you don't, leave it alone."
Hmmmm not quite as pithy as "NO EQUIPMENT GROUND". Shorten it up, and you may have a trademark.

What I'm worried about is all the installations in which the TOP end of the neutral will be capped as well, by well-meaning folks. Recipe for later disaster and/or death.
 
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Old 02-24-11, 05:27 PM
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How about "CODE REQUIRED NEUTRAL - DO NOT REMOVE". Printed on double sided laminated 'flag tags'.

And to be code compliant, the top end must be actually connected to the same neutral as the light fixture. It can only be capped in the switch box.
 
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Old 02-24-11, 05:42 PM
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If I can't remove the wirenut how am I supposed to use the neutral?

And SURELY you didn't mean that they weren't supposed to yank the neutral conductor out of the NM-B cable. heheh
 
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