3 way switch - 2 wires between

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inspector 102

Senior Member
Location
Northern Indiana
Looked at an existing home (brother-in-laws) and found that the 3 way switch in the dining room only has 2-wire running from 3-way to 3-way. Have not found where the switched leg is being picked up for the receptacles in the room. I have always seen 3-wire to carry current over the "travelers" between switches, then to the fixture on the common leg. Anyone have any thoughts on how this was installed. Never seen before and have not figured out yet. Gong back tonight to open up more boxes. All this work to install an overhead light for the dining room.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
The 2 wires are only travelers. What they do is use the neutral and hots that were already in the 2 boxes. Legal as long as care is taken with what neutral they used. If same circuit fine if not you need be carefull what is on that neutral
 

One-eyed Jack

Senior Member
The 2 wires are only travelers. What they do is use the neutral and hots that were already in the 2 boxes. Legal as long as care is taken with what neutral they used. If same circuit fine if not you need be carefull what is on that neutral

Ditto that. This is seen more with conduit work than with nm. Some just don't want to buy the 3 cond cable.:D
 

Cavie

Senior Member
Location
SW Florida
Looked at an existing home (brother-in-laws) and found that the 3 way switch in the dining room only has 2-wire running from 3-way to 3-way. Have not found where the switched leg is being picked up for the receptacles in the room. I have always seen 3-wire to carry current over the "travelers" between switches, then to the fixture on the common leg. Anyone have any thoughts on how this was installed. Never seen before and have not figured out yet. Gong back tonight to open up more boxes. All this work to install an overhead light for the dining room.

Are you sure you are not looking at the 4way of a 4-way system? system? That takes 2-3ways and 1-4way.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
Emt,rmc,pvc it doesn't matter. Yes. As long as it is the same circuit the runners can travel on their own. Source on one switch,load on the other.

Draw the current flow in a set of three ways out and you will see where the problem and violation occur, so in a metallic raceway, it does in fact matter and is a violation of 300.3(B) as already mentioned by Rick and Chris. Even with out a code violation, inductive heating of the raceway would be an issue.

And, in a non metallic raceway or cable, it is a bad design to run a circuit that won't cancel EMF although the NEC does allow it in NM wiring methods.

Roger
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
A switch for a overhead light is typically wired with a two conductor cable wg. There is no neutral (grounded conductor) present. Source down on white,load back on black. Not a violation.

The grounded conductor (neutral) doesn't have to run with the conductors of a circuit to cancel current, what has to happen is that current flows in two directions in close proximity and this does not happen in your three way configuration.

Roger
 

jwjrw

Senior Member
Alot of the old timers here catch the power etc in the fixture box and just run a 2 wire between 3 way switches. I would rather take 2 switches apart when troubleshooting than pull a fixture down so I DO NOT make my 3 ways up like that.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Often times these switches were done this way. They pick the power feed at one end and the neutral at the other end. If this is NM cable it is legal as long as it is the same circuit but it will cause unwanted electrical magnetic field.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
I've heard it called a "California Three Way" also...

Hmmm...anyone know how Cali got stuck with that? LOL

Icefalcon, the California, Chicago, Missouri, Tennessee, Kentucky, .... version is not what is being discussed here, that is a violation period regardless of wiring method.

Roger
 

busman

Senior Member
Location
Northern Virginia
Occupation
Master Electrician / Electrical Engineer
The grounded conductor (neutral) doesn't have to run with the conductors of a circuit to cancel current, what has to happen is that current flows in two directions in close proximity and this does not happen in your three way configuration.

Roger

If everything is nonmetallic, this is true. If there is metal involved and the current makes a loop around the metal, it makes for inductive heating and a code violation.

Mark
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
If everything is nonmetallic, this is true. If there is metal involved and the current makes a loop around the metal, it makes for inductive heating and a code violation.

Mark

Mark, what do you think I have been saying?

Have you read all the posts?

Roger
 
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