Home>Discussions>ELECTRICAL & LIGHTING>12 wire V. 14 wire for circuits
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charleswaz
12 wire V. 14 wire for circuits

This is what I get for over thinking again. I was all set to use 12 wire, 20 amp breakers, for the new circuits going to the bedrooms, however, i read that any lighting should be placed on 14 wire, 15 amp breaker, to limit the current passing through the filaments.

Would it be better to run a single 15 amp circuit for the lighting then seperate 20amp circuits for the outlets? Or just 15 amp all around?

JLMCDANIEL
Re: 12 wire V. 14 wire for circuits

The size of the wire will not noticably limit the current going through a filament. Cost is usually the factor for using 14 instaed of 12.

I like to have the lighting and the outlets on seperate cuircuits but it is not required.
Jack

NEC
Re: 12 wire V. 14 wire for circuits

[QUOTE=charleswaz] however, i read that any lighting should be placed on 14 wire, 15 amp breaker, to limit the current passing through the filaments.
QUOTE]

Now in 30 + years in the electrical trade I've never heard that one!

Jack offers good advice.

Fencepost
Re: 12 wire V. 14 wire for circuits

It won't limit the current going through the filament, unless there is noticeable voltage drop in comparison to using 12 gauge wire. The voltage drop would happen because of excessive distance (in which case you would be required to upsize the wire anyway) or continually running the circuit near capacity.

sparky1
Re: 12 wire V. 14 wire for circuits

some one filled ya with aline about more current running through it.. i persoanlly run as much 14 as i can to make it easy on myself making up devices.. and it is also a bit cheaper, but for me its the ease of it!! feel free to run 12 all day long to your lights thou..

Re: 12 wire V. 14 wire for circuits

If you have 12 in allready dont change it. Its fine. The biggest disadvantage to using 12 over 14 is the way it eats up the wire fill in a givin box, and as someone else said a bit harder to make a termination on a device (requires a little extra squeeze to make sure its wrapped around the screw all the way) cost advantages and ease of pull fall toward 14 as well, but none of these make enough of difference to really matter in an attic.

Does bring up a good point with wire fill tho, look inside those plastic boxes it will tell you how many individual conductors you can have per box. Dont forget to subtract 2 for each device, and all of your equipment grounds count as 1. Overfill is a pretty common fail around here. You can get quite a bit of 12 wire in those plastic round boxes you would typically be using for lighting, but the single gang plastic you are using for a switch is another issue, only allows you 9 -2 for device -1 for ground thats 6 or 3 12/2 so feed in feed out and switch leg, if its a 3 way you would have to drop the feed out and leave a feed in traveler and switch leg. Of course all depending on the size of the box your using.

edited to add
I hope we get some pics of all this at some point.

Ernie_Fergler
Re: 12 wire V. 14 wire for circuits
NEC][QUOTE=charleswaz wrote:

however, i read that any lighting should be placed on 14 wire, 15 amp breaker, to limit the current passing through the filaments.
QUOTE]

Now in 30 + years in the electrical trade I've never heard that one!

Jack offers good advice.

I believe it is "The Completion Backwards Principle" first written in the late seventies by those electrical pioneers, The Tubes !!!!:D

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