switch legs

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scubadvr_69

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I have a question regarding switch legs. I have recentaly gotten back into residential after being in conveyor controls installation for about 13 years. when I learned residental I we always pulled a 14 gauge wire to the light for switch legs and 12 to the rest of the house. I have recentaly been told that this is wrong and 12 should be pulled all the way through for a 20amp circuit. I know the rule for 14 and 12 gauge wire protected at 15 and 20 but is there an exception for a switch leg? Of course I will change the mistake I made but is there a rule for this or was it just something that was/is done? I know of lots of homes that have this and there has never been any problem with it.
 
There is no exception for switch legs.

You must protect the circuit conductors at the smallest wire ampacity in the circuit. So if you use #14 AWG switch legs and #12 AWG for the rest of the circuit, you must protect the circuit with a 15 amp breaker. Take a look at 240.4(D).

Chris
 
Switch legs are part of the branch circuit, not taps, so taps rules cannot be applied to them.

Probably the only reason it's been done that way for so long is that in 99.99999% of resi wiring, a switch leg will never see more than 15amps.
 
That was my thinkin' 480, that is why I thought there was an exception that I was overlooking. Just goes to show you that "the way I've always done it" ain't always right.
I have looked at 240.4(D) Chris I was just hopeing that a switch leg might be an exception since as 480 pointed out it is only to a light and most residential lights are not large enough to pull anywhere near 15 amps (unless of course you put all the lights in the home on one circuit)
Thank you chris and 480.
 
Your welcome.

I definitely understand what you are saying about the load on a switch leg, but the NEC does not treat a switch leg as a tap. This practice was, and sometimes still is, followed in my area. It is one of though "that's how we have always done it" practice's that get passed down from journeyman to apprentice without ever being the right way to do it.

By the way welcome to the forum.

Chris
 
At least i'm not the only one who got that kind of info passed down. I am currently trying to train someone and that will not get passsed down any farther.
and just an FYI I am going to rearrange some of my circuits and make them 15 amp circuits.
 
It's funny because you'll need 20 amp conductors going to the switch but a 15 amp switch is permitted on the same 20 amp circuit.
 
infinity said:
It's funny because you'll need 20 amp conductors going to the switch but a 15 amp switch is permitted on the same 20 amp circuit.
Click to expand...

Same with receps.
wink3.gif
 
really sad thing is there is a large county that allows the use of a 14 wire for switch legs but will not allow you to feed anything in 14. The first time I saw this was my moms house. I walk in and theres 12 wire everywhere except for the 14 going to the lights. Unfortunately i didnt have a license to redo what I saw as total bs work. We now work in that state and pull 12 to everything.
 
=480sparky;965141]Switch legs are part of the branch circuit, not taps, so taps rules cannot be applied to them.

[/QUOTE]Probably the only reason it's been done that way for so long is that in 99.99999% of resi wiring, a switch leg will never see more than 15amps.[/QUOTE]

What if you have 16 amps worth of recess on the switchleg?:grin:
 
slick 50 said:
=480sparky;965141]Switch legs are part of the branch circuit, not taps, so taps rules cannot be applied to them.
Click to expand...
Probably the only reason it's been done that way for so long is that in 99.99999% of resi wiring, a switch leg will never see more than 15amps.[/QUOTE]

What if you have 16 amps worth of recess on the switchleg?:grin:[/QUOTE]

Exactly! Or what if the wire that fed a light as a switch leg is now re-connected for a different purpose? Now it's seeing greater potential load. This possibilities, and more, are why such a design is not permitted, IMO.
 
There is no technical reason for limiting #14 to 15 amp circuits...just a code reason. There is no question that it is a code violation, however given that the ampacity of #14 in the 60?C column is 20 amps there is no technical reason.
 
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