# 3-way switch wiring



## CheapCharlie

I'm new to the site, and a certified electrician. I've been browsing the site and notice alot of people having trouble with 3-way switches. Here are some diagrams for quick reference. Maybe a sticky?


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## Jim Port

Before they get made into a sticky you might want to look at NEC 200.7. The re-identified white needs to the the feed to the switch.


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## CheapCharlie

Jim Port said:


> Before they get made into a sticky you might want to look at NEC 200.7. The re-identified white needs to the the feed to the switch.


I'm from Canada. Must be different here


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## LyonsElecSupply

The New NEC requires a Neutral to be carried throughout the circuit on residential. I think they started this in 2008, I know it is in 2010....

Youll have to use 14/3 or 12/3 romex w/ground for between the switches and anywhere else where you need to.

no reidentifying anymore.....Red and Black are your travelers between the switches.


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## joed

Nope the white needs to FEED the switch in Canada as well.


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## davido30093

This is the drawing that I give to new guys wiring up three way switches,


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## CheapCharlie

davido30093 said:


> This is the drawing that I give to new guys wiring up three way switches,


My bad, misunderstood what was being said earlier....BACK IN BLACK!


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## jlmran

According to my understanding, only the bottom image is non-compliant to the 2011 NEC. Correct?


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## hayewe farm

As I read it all are now none compliant with NEC 2011 which requires neutral to switch boxes. Or am I mistaken?


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## jlmran

hayewe farm said:


> As I read it all are now none compliant with NEC 2011 which requires neutral to switch boxes. Or am I mistaken?


I'm referencing 200.7(C). White conductors can be ungrounded in certain situations. Is there a citation which prohibits switch loops?

Also, what good is a neutral at a 3-way switch? It could work at the switch which receives the circuit feed, but it would serve no purpose to have a neutral at the other switch. Unless I'm blinded by ignorance.


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## hayewe farm

I believe the purpose to to have a neutral available for future upgrades to motion sensor or digital switches. I'm refering to NEC 2011 404.2(c)


404.2 Switch Connections. 
(C) Switches Controlling Lighting. Switches controlling line-to-neutral lighting loads must have a neutral provided at the switch location.


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## jlmran

So, not including the exceptions provided, the only way to correctly (NEC 2011) wire a light circuit with 3-way switches is:

1. Power => switch => switch => light (Like davido30093 said above);

or

2. Use 4-wire cable in other configurations. Do these exist as a NM-type cable?

Is this correct?


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## hayewe farm

By the way all the drawings including #3 are NEC 2008 compliant. The re-designated white wires in drawing three are not used as a return which is the only restriction for their use as a re-designated wire.


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## hayewe farm

jlmran said:


> So, not including the exceptions provided, the only way to correctly (NEC 2011) wire a light circuit with 3-way switches is:
> 
> 1. Power => switch => switch => light (Like davido30093 said above);
> 
> or
> 
> 2. Use 4-wire cable in other configurations. Do these exist as a NM-type cable?
> 
> Is this correct?


Yes. or you could run 2 14-2 cables with one a redesignated white. 
Beldon NM 4 cond comes in both -2/2 (example 14 2/2) an -4 (example 12 4) configurations. -2/2 is 2 pair of whit/black and the -4 is white black red blue.


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## jlmran

hayewe farm said:


> By the way all the drawings including #3 are NEC 2008 compliant. The re-designated white wires in drawing three are not used as a return which is the only restriction for their use as a re-designated wire.


Last OP drawing: Why isn't the RD white wire in the right-side cable a return? Sure, it is feeding a 2nd switch 1st, but it still is returning the current to it's source after a switch.


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## joed

I can't see anything wrong with the drawings either. I believe the code only requires that the white not be used as the switched wire to the light. You don't want two whites connecting to the light. You can use the white for travellers.


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## jlmran

2008 NEC 200.7 (c)

The use of a white conductor for other than a grounded conductor shall be permitted...where a cable assembly contains an insulated conductor for...switch loops and the white conductor is used for the supply to the switch but not as a return conductor from the switch to the switched outlet.

Doesn't the last drawing violate this?


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## CheapCharlie

joed said:


> I can't see anything wrong with the drawings either. I believe the code only requires that the white not be used as the switched wire to the light. You don't want two whites connecting to the light. You can use the white for travellers.


The last picture is wrong, the white and black should be swapped going to the right switch. It should come in from power (black) hook up to the re-identified white, back on black. The black coming back from the right switch should be connected to the re-identified white going to the left switch and come back on black to the light.


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## joed

The white is being used as a traveller. That's not a code issue that I know of. The switched power comes back from the second switch on black as required.


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## LyonsElecSupply

You have to carry a neutral to every box according to the 2011 code. It is wiring practice (at least in this area for new construction) that a neutral gets carried to every location. 

These drawing DO NOT carry neutrals to every location.

In reference to the White carrying current, you are allowed to recolor wires to indicate them as current carrying.

Irregardless, these diagrams are outdated and arent current practice. Carrying a neutral costs more, but in the end it allows for easier upgrades.


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## jlmran

LyonsElecSupply said:


> You have to carry a neutral to every box according to the 2011 code. It is wiring practice (at least in this area for new construction) that a neutral gets carried to every location.
> 
> These drawing DO NOT carry neutrals to every location.
> 
> In reference to the White carrying current, you are allowed to recolor wires to indicate them as current carrying.
> 
> Irregardless, these diagrams are outdated and arent current practice. Carrying a neutral costs more, but in the end it allows for easier upgrades.


Does this requirement include switched receptacles if they are used for a lamp?


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## LyonsElecSupply

My understanding is that ANY place that a wire is run to and junctioned requires a neutral. EVEN 3 way circuits....Its to facilitate upgrades so in the future you just drop a line into that box to make another circuit......Trust me with the way technology is going you want to do this if you are creating a new circuit......Motion sensors, timers, added receptacles.



Jim, ESPECIALLY for what you said. Infact it might make the installation easier....One romex in for service, you switch your legs, wirenut your neutrals and one romex out. No taping no odd wire usages....its simple and safe....


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## jlmran

I thought the NEC only required it for light circuits. Meaning other switched outlets could still have loops, having a switch box without a grounded conductor.


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## joed

Four wire cable is going to be a requirement for wiring jobs now.


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## Hourglass52

*Nec*

404.2(C) Ex(1)
404.2(C) Ex(2)


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## jlmran

Hourglass52 said:


> 404.2(C) Ex(1)
> 404.2(C) Ex(2)


Already noted in post #12.


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## hayewe farm

CheapCharlie said:


> The last picture is wrong, the white and black should be swapped going to the right switch. It should come in from power (black) hook up to the re-identified white, back on black. The black coming back from the right switch should be connected to the re-identified white going to the left switch and come back on black to the light.


Sorry but you are wrong. The RD white is a "feed" from one switch to the other in one position and disconnected in the other position. It is not a return to the outlet. A RD white can be used as a hot except as a return to the oulet.

All the drawings are outdated if your state has adopted NEC 2011, Not because of the RD white but because neautral is not fed to the 2 switch positions.


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## jlmran

hayewe farm said:


> Sorry but you are wrong. The RD white is a "feed" from one switch to the other in one position and disconnected in the other position. It is not a return to the outlet. A RD white can be used as a hot except as a return to the oulet.
> 
> All the drawings are outdated if your state has adopted NEC 2011, Not because of the RD white but because neautral is not fed to the 2 switch positions.


But that RID white is returning power to the outlet from which the power came (or passing through the outlet on it's way to the other switch). NEC doesn't say anything about connections to the device at the outlet...it only references returning to the outlet. The drawing violates 200.7, no? The blk & wht conductors of the right side cable need to trade places with each other at both outlets.


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## hayewe farm

jlmran said:


> But that RID white is returning power to the outlet from which the power came (or passing through the outlet on it's way to the other switch). NEC doesn't say anything about connections to the device at the outlet...it only references returning to the outlet. The drawing violates 200.7, no? The blk & wht conductors of the right side cable need to trade places with each other at both outlets.


No. Look at it this way, with the switch in one position the RD white is connected to the black power lead and is supplying power to the other switch, with the switch in the other position the RD white is connected to nothing. None of the RD white wires are returns to the outlet, in other words providing power to the load.


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## Rich

*Diagrams/information request?*

Hate to revive an old post but this one seemed closest to the question I had. Does anyone have any drawings that show this requirement that there is a neutral in each switch box? I'm doing rewiring and want the power to come in from the light box. From what I read I need a 12/3 to the first switch then a 12/4 to the 2nd switch. Thinking use the Black/Red/Blue to switch the hot and for the travelers, then the whites all just get nutted together in each box with the last box just having the white nutted by itself. Is this right?

Thanks.


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## joed

Sounds correct.


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## Mike Larsen

LyonsElecSupply said:


> The New NEC requires a Neutral to be carried throughout the circuit on residential. I think they started this in 2008, I know it is in 2010....
> 
> Youll have to use 14/3 or 12/3 romex w/ground for between the switches and anywhere else where you need to.
> 
> no reidentifying anymore.....Red and Black are your travelers between the switches.


And this means that the single "Box Diagram" on Davido's reply complies with 2011 code. At least that's how I interpret it.

Mike


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## Rich

Sat down and drew out my words using an old drawing found on this site as reference, since no one was jumping on having a good drawing of it. Everyone still agree this is what is required now.


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## mac10

I have a duplex receptacle and want half duplex on continuously other halfswitched by 2 three way switches can anyone help Thanks


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## stickboy1375

Rich said:


> Sat down and drew out my words using an old drawing found on this site as reference, since no one was jumping on having a good drawing of it. Everyone still agree this is what is required now.


I don't use four conductor, I just feed one three way and take the load out of the other three way, no need to use four conductor.


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## stickboy1375

mac10 said:


> I have a duplex receptacle and want half duplex on continuously other halfswitched by 2 three way switches can anyone help Thanks


Start a new thread.


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## Rich

stickboy1375 said:


> I don't use four conductor, I just feed one three way and take the load out of the other three way, no need to use four conductor.


My problem with this is box fill. This light/switch is in the middle of the lighting circuit. That is at the box where this 3-way is, I'd have a 12/2 coming from the previous light/switch, a 12/2 to this light fixture, a 12/3 to the other 3-way and a 12/2 to the next light/switch on the breaker circuit. There isn't a box out there (that I could find) that could handle this many conductors.


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## Rich

I think I counted wrong in my previous post. This drawing shows what I'm trying to do. I have a light on the 3rd floor and 2nd floor landings. There is a switch on the 3rd and 2nd for the 3rd light and one for the 2nd on the 2nd and 1st floors. If I bring the power into the 2-gang box on the 2nd floor. I think the box fill would be OK. I count 10 conductors + 1 ground + 2 devices = 33.75 cu. in. The plastic box that I found for this is 34 cu. in. and says 15/12s. The other two switch boxes are would be 5 conductors + 1 ground + 1 device = 18 cu in. I'll use a 21 cu. in. box for this. Anythign I'm missing here?

Thanks.


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