Code or best practice, wiring light fixture with switch.

[WanderingSol07]

Simple circuit, from breaker to light fixture to switch. Do you run the wire from the breaker to the fixture and then two wires to the switch or do you run the wire from the breaker to the switch box and then to the light fixture?

The first may save wire, but there will not be a ground or neutral going to/from the switch. This would make installing a smart switch (one needing power) impossible with pulling additional wire.

For my house I am finding every switch box has a neutral and ground so my smart switch installs are a piece of cake. Others on a home automation forum are not so lucky and only have two black wires to their switch box.

I always thought either way was code, but power to the switch first was best practice. Your thoughts?

Tim.

 

[Gerald O]

The first method is called a switch loop. Generally no longer allowed under NEC. You must now provide a neutral conductor at every switch in a lighting circuit in addition to the switched hot conductor, even if you're not using the neutral.

 

[tyme2par4]

For the first option, you could run 14/3 wire over to the switch and still comply with code.

 

[WanderingSol07]

Gerald O, that explains some circuits I've seen where the wire goes from the breaker to the light fixture and then to the switch. The cable from the fixture to the switch had a white, black, and red wire, white was unused neutral, black was power (live), and red was load.

 

[6PTsocket]

I am the last person to ask about code and I defer to the others that know more about it than me but the idea of the switch not cutting power to the load just feels wrong. Of course, switching off the breaker is proper procedure but if I am working in an overhead switched fixture I want it to be dead if the switch is off. I do like the idea of carrying the neutral to all boxes. There are idiots that have used ground for lack of a neutral.

Sent from my SM-G900V using Tapatalk

 

[CJ7VFR]

For the first option, you could run 14/3 wire over to the switch and still comply with code.

This is the way I would do it. You would still save on the total amount of wire used. And since the new code says you have to have a neutral in every new switch box, then you are going to have to have a supply of some 12/3 and 14/3 anyway.

I have seen people doing this now because according to the latest NEC code you can't just color the white wire "black" at the ends and use it like before, where it meant that the white wire was no longer a neutral but a hot for the switch control.

Is there an actual reason sited somewhere in the NEC code for not allowing the old way to be done anymore? I know it says a neutral is now required in every new switch box, but for what actual reason?

Is it because of newer switches that are out now that have more functions than a regular old snap switch and need a neutral?

Or is it a way to sell more wire, like a few of my old retired electrician friends like to say?

I get the need for it in some instances using newer switches that require a neutral in the box, but what about if you are only installing the old snap switches? Is the old way still allowed for that?

Jim

 

[ishiboo]

This is the way I would do it. You would still save on the total amount of wire used. And since the new code says you have to have a neutral in every new switch box, then you are going to have to have a supply of some 12/3 and 14/3 anyway.

I have seen people doing this now because according to the latest NEC code you can't just color the white wire "black" at the ends and use it like before, where it meant that the white wire was no longer a neutral but a hot for the switch control.

Is there an actual reason sited somewhere in the NEC code for not allowing the old way to be done anymore? I know it says a neutral is now required in every new switch box, but for what actual reason?

Is it because of newer switches that are out now that have more functions than a regular old snap switch and need a neutral?

Or is it a way to sell more wire, like a few of my old retired electrician friends like to say?

I get the need for it in some instances using newer switches that require a neutral in the box, but what about if you are only installing the old snap switches? Is the old way still allowed for that?

Jim

Many switches now require neutrals. Especially LED/CFL-compatible dimmers, smart switches, etc. There is some forethought for future upgradeability and so that people don't cheat by using the ground as a neutral for the switch.

 

[sberry]

I got in to a re wire a while back where I started to fix some issues and I am about half way done before I realize I am re wiring the place. They done it all 60's and like a dipshit I copy it and half was wondering wtf in all the lesson may have been useful. I pulled most new and should have started new from basement. I could have reduced the attic wire by a ton and really saved some effort to imagine it ripped out and all new although the lessons learned may prove out in the next job way more complicated.

 

[CJ7VFR]

Many switches now require neutrals. Especially LED/CFL-compatible dimmers, smart switches, etc. There is some forethought for future upgradeability and so that people don't cheat by using the ground as a neutral for the switch.

That makes sense not wanting people to use the ground as the neutral. Is that one of the reasons sited in the new code not to allow the old switch loop method?

Is the old way not allowed at all anymore? Or can you still use it if you are installing just regular old snap switches and nothing else?

Jim

 

[Gerald O]

That makes sense not wanting people to use the ground as the neutral. Is that one of the reasons sited in the new code not to allow the old switch loop method?

Yes.

Is the old way not allowed at all anymore? Or can you still use it if you are installing just regular old snap switches and nothing else?

Jim

Switch loops are still allowed AFAIK. They just don't save wire anymore when you have to also run a neutral. I believe there are exceptions to the requirement for a neutral when a raceway is provided to make it easy to add a neutral later, or when the wire can easily be fished through a wall cavity.

 

[grantw]

I'm going to have some re-wiring done pretty soon, and will go with a 12/2 home-run from the panel to the light fixture, and 12/3 from the fixture to the switch.

I'm still deciding if I want to run the bedroom overhead lights from the same circuit as the outlets in the same room... in that case, I'd run the branch around the room and T off of an outlet to the switch, and then a normal 12/2 from the switch to the light.

There will be exceptions for 3-way switches, so I'll need to go from the breaker to the first switch and then 12/3 between each switch...

 

[Radix2]

I'm going to have some re-wiring done pretty soon, and will go with a 12/2 home-run from the panel to the light fixture, and 12/3 from the fixture to the switch.

I'm still deciding if I want to run the bedroom overhead lights from the same circuit as the outlets in the same room... in that case, I'd run the branch around the room and T off of an outlet to the switch, and then a normal 12/2 from the switch to the light.

There will be exceptions for 3-way switches, so I'll need to go from the breaker to the first switch and then 12/3 between each switch...

what is behind your preference to do that?

It is a nice feature as noted above to be able to cut off all power to a fixture by running to the switch first. I typically remove or lower fixtures for painting or during construction - much easier to be able to kill power locally than to go find the breaker...

 

[grantw]

what is behind your preference to do that?

It is a nice feature as noted above to be able to cut off all power to a fixture by running to the switch first. I typically remove or lower fixtures for painting or during construction - much easier to be able to kill power locally than to go find the breaker...

Well, Sky is the limit when your roof is off and you're having your house rewired with 12/2 everywhere. Second, I'd run 12/3 anyway to control two loads. If I decide to add a ceiling fan later, I want the wire to be there.

 

[Radix2]

Well, Sky is the limit when your roof is off and you're having your house rewired with 12/2 everywhere. Second, I'd run 12/3 anyway to control two loads. If I decide to add a ceiling fan later, I want the wire to be there.

I agree with all of that but the question is, with new wiring , why go to the fixture first?

Makes sense when fishing and the other route is bad, but if wide open, going to the switch first seems like the obvious best choice IMO.

I run 12-3 to any possible fan spots as well...but seems like 99% of fans now are digital switching and don't need it anyway.

 

[grantw]

I agree with all of that but the question is, with new wiring , why go to the fixture first?

Makes sense when fishing and the other route is bad, but if wide open, going to the switch first seems like the obvious best choice IMO.

I run 12-3 to any possible fan spots as well...but seems like 99% of fans now are digital switching and don't need it anyway.

Yeah, I haven't determined if a always-on hot is needed in the ceiling box, but provides options if I want to do anything I haven't thought of. Now, with 12/2 or 12/3, I'll need deeper boxes for wire fill.

 

[Zeke]

Do it with the least amount of wire and with a neutral run to the switch with a 3 conductor wire if going to the light box first. If going to the switch first you don't need any 3 conductor. If I had gone to the switch first in my recent home rewire, I would have used 2wice as much wire as many of the wires would have doubled back over the same direction.

 

[nehog]

For the first option, you could run 14/3 wire over to the switch and still comply with code.

14/3 only on a 15 amp circuit.