three way switch wiring

kwired

Electron manager
Outside of the non code compliant "Chicago" or "California three way setups, the wiring logic of three way/four way switching circuits is always the same. Start at one of the three way "common" terminals, run two "traveler" wires to the other three way and continue on to the load from the second three way "common" terminal. Insert how ever many four ways you want in the traveler wires between the two three way switches.

What can vary is how you route cables and conductors depending on physical relationship between source, load and switching components. You use one method or another to use less copper or the installation but the logic of the switching still is the same when you break it down, and is easy to see if you draw it out in a ladder logic type diagram as it will be same diagram every time.
 

rjniles

Member
A true California 3 way is compliant as it never switches the neutral which is always connected to the shell of the light socket.
It is wired with the hot wire connected to a traveler terminal in both switches and the load is connected to other traveler in both switches. The commons are connected together. The neutral is wired to the fixture neutral. It only requires 2 wires between the switches, the common to common conductor and the load conductor.


As long as the neutral is is present in both switch boxes it is compliant.

I would never use it because it confuses the hell out of me.

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PaulMmn

Senior Member
A true California 3 way is compliant as it never switches the neutral which is always connected to the shell of the light socket.
It is wired with the hot wire connected to a traveler terminal in both switches and the load is connected to other traveler in both switches. The commons are connected together. The neutral is wired to the fixture neutral. It only requires 2 wires between the switches, the common to common conductor and the load conductor.


As long as the neutral is is present in both switch boxes it is compliant.

I would never use it because it confuses the hell out of me.

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I followed your description and drew it on paper. It works, but it's a strange looking thing! Power to the load always flows on the link between the 2 commons.

I think a lot of the confusion for 3 or 4 way switches is the number of variations depending on where the power comes from-- switch A, switch B, or at the light fixture.
 

synchro

Senior Member
I wonder if there's a California 4-way circuit? It seems like it would be difficult to do that with just a single traveller. With a normal configuration all of the switches are cascaded in series between the line and load, making it straightforward to extend it to more switches.
 

al hildenbrand

Senior Member
Power to the load always flows on the link between the 2 commons.
Except when the load is turned off.

There are two switching states where the load is turned off. Only one of these states runs afoul of 310.10(H)(1). This one switching state puts the common to common conductor in parallel with the un-switched hot conductor that is connected at one traveler terminal on each three-way switch. Any downstream load connected to the un-switched hot and neutral will have its load current split between the hot and the common to common conductor.
 

rjniles

Member
Ignoring the California, there is only one way to wire a 3 way. The hot goes on one common, the load goes on the other. There are different ways to get to that arrangement.

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cdslotz

Senior Member
Ignoring the California, there is only one way to wire a 3 way. The hot goes on one common, the load goes on the other. There are different ways to get to that arrangement.

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I learned that as a second year apprentice.......
 
Does anyone have an illustration of how a California 3-way would actually be installed with 2-conductor NM cable? The diagrams with hots and neutrals make sense, but I have a hard time envisioning the actual cabling layout. It seems like you'd have an extra conductor for at least part of the circuit if done with 2-wire cable.
 

romex jockey

Senior Member
Yes, that would be correct, thx Al

as to the vids (2019) what stands out is lack of or recommissioned noodles , bit of a possible art 200 identity spat
~RJ~
 

rjniles

Member
I have always known the Carter as a three-way that reverses the lampholder polarity, depending upon the switch position.
True, the hot and neutral at each box are connected to the travelers. One common is wired to the shell of the lamp, the other wired to the center pin.

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al hildenbrand

Senior Member
I see how that works, but don't see it complying with 300.3(B) unless you route the two separate cables in close proximity to one another, and even then there is going to be some debate as to whether that complies.
And just WHY does 300.3(B)(3) NOT allow 14/2 NM to be wired as my little post-it diagram illustrates?
 
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