Using 12-2 for travellers between two 3-way switches

[Howard Burger]

Is running three way switch travellers on 12-2 legal?

Ran across this in a resi. troubleshooting call: power came into first three way at bottom of stairs, travelled via 12-2 to second three way at top of stairs.

Then, in the second box was another circuit which provided the neutral back to the panel. Ignoring the potential for overloading the neutral with two same-phase circuits, is running the travelers by themselves a violation? Or does 300.3.B.2 allow it?

 

[jumper]

Is running three way switch travellers on 12-2 legal?

Ran across this in a resi. troubleshooting call: power came into first three way at bottom of stairs, travelled via 12-2 to second three way at top of stairs.

Then, in the second box was another circuit which provided the neutral back to the panel. Ignoring the potential for overloading the neutral with two same-phase circuits, is running the travelers by themselves a violation? Or does 300.3.B.2 allow it?

300.3(B)(2) is not for neutrals. Not having a neutral between the switches is not a code violation since a neutral is not needed.

 

[Little Bill]

Is running three way switch travellers on 12-2 legal?

Ran across this in a resi. troubleshooting call: power came into first three way at bottom of stairs, travelled via 12-2 to second three way at top of stairs.

Then, in the second box was another circuit which provided the neutral back to the panel. Ignoring the potential for overloading the neutral with two same-phase circuits, is running the travelers by themselves a violation? Or does 300.3.B.2 allow it?

Not a violation, but I don't see how 300.3(B)(2) applies to the travelers though.

Edit:Sorry Jumper, you type fast tonight!

 

[jumper]

I just checked, the white as a traveler would violate 200.7(C)(2).

 

[jumper]

I think you may get EMF issues here also, but EMF is not a NEC issue.

 

[ActionDave]

If the neutral at the top and bottom of the stairs need to be from the same circuit to be legal. It is a lousy way to wire. Causes high EMF since there is no canceling of the magnetic field.

Some folks believe this can lead to health issues. I know it can really mess with my radio.

 

[jumper]

Is running three way switch travellers on 12-2 legal?

Ran across this in a resi. troubleshooting call: power came into first three way at bottom of stairs, travelled via 12-2 to second three way at top of stairs.

Then, in the second box was another circuit which provided the neutral back to the panel. Ignoring the potential for overloading the neutral with two same-phase circuits, is running the travelers by themselves a violation? Or does 300.3.B.2 allow it?

Where did the neutral in the first box go?

 

[al hildenbrand]

Where did the neutral in the first box go?

Derek,

Aside from saying 14/2, my little diagram is the basic circuit. The neutral goes to the light and then from the light on to the next 3-way switch.

 

[Howard Burger]

Jumper, the first neutral was capped off in the first box.

I had a thought - if the second neutral was from a different phase, the guy who wired this (30+ years ago) created a mwbc, with the posibility of making some real trouble down the road if the neutral should get opened.

Are you staying dry?

 

[al hildenbrand]

. . .my little diagram is the basic circuit.

Thinking about it, I'm wrong. My diagram is of the traveling bus.

If one connects the hot to the first common, the neutral goes up to the light on a 12/2, and the black conductor in that 12/2 isn't used.

The travelers go to the second 3-way on the 12/2. At the second traveler, the common is connected to the black of another 12/2 that goes to the light. The white is this last 12/2 may or may not be connected to the neutral.

What I've just described puts both travelers in a single 12/2.

 

[jumper]

Derek,

Aside from saying 14/2, my little diagram is the basic circuit. The neutral goes to the light and then from the light on to the next 3-way switch.

Wild set up. Never saw it before. Thanks.

 

[hurk27]

You can not use a hot from one circuit and a neutral from another circuit, 300.3(B), it violates a few sections I would believe, one if both circuits originates from the same phase then the home run neutral could be over loaded, if they originate from different phases then you have an illegal multi-wire branch circuit, and the fact that most likely the two different circuits enter the breaker panel through different KO's which will be a violation of 300.3(B)(3) and 300.20(B)

 

[jumper]

Jumper, the first neutral was capped off in the first box.

That was silly.

Are you staying dry?

Yeah, I bailed out of MD and went to western PA till Irene passes.

 

[jumper]

Thinking about it, I'm wrong. My diagram is of the traveling bus.

If one connects the hot to the first common, the neutral goes up to the light on a 12/2, and the black conductor in that 12/2 isn't used.

The travelers go to the second 3-way on the 12/2. At the second traveler, the common is connected to the black of another 12/2 that goes to the light. The white is this last 12/2 may or may not be connected to the neutral.

What I've just described puts both travelers in a single 12/2.

I think your circuit and OPs circuit are violations, even though they work.

 

[Howard Burger]

Thanks, Hurk. When I sort this whole thing out (there are other issues at this house), if I have two opposite-phase circuits involved, I'll try to re-kludge the panel and install a 2-pole breaker.

 

[al hildenbrand]

Wild set up. Never saw it before. Thanks.

The 2011 changes to 310.10(H) - parallel conductors - makes my sketch a violation.

The two wires running between the two switches, in one switching state, will be in parallel connection with each other, and they are smaller than 1/0 . . . not allowed by 310.10(H).

 

[al hildenbrand]

I think your circuit and OPs circuit are violations, even though they work.

The circuit I describe in my text is not the one I drew. I believe it is allowed by today's NEC.

Your point about EMF is correct, but, as you say, it is not a NEC issue.

 

[hurk27]

Make sure you don't have a Chicago 3-way?

In a Chicago 3-way, the hot and neutral home run is fed to the down stairs 3-way and pigtailed to the traveler terminals running up to the upstairs 3-way pig tailed to its traveler terminals, the stairway light is connected to each common at each 3-way, the hot and neutral travelers feed the rest of the up stair receptacles and lights, this circuit was also very common to find between a barn/garage and house switching the outside lights while providing a hot and neutral for the barn/garage loads, very common on old K&T wiring.

There is a diagram of this circuit somewhere here on this forum, but for the life of me I can not get the search function to function:rant:

 

[jumper]

Make sure you don't have a Chicago 3-way?

In a Chicago 3-way, the hot and neutral home run is fed to the down stairs 3-way and pigtailed to the traveler terminals running up to the upstairs 3-way pig tailed to its traveler terminals, the stairway light is connected to each common at each 3-way, the hot and neutral travelers feed the rest of the up stair receptacles and lights, this circuit was also very common to find between a barn/garage and house switching the outside lights while providing a hot and neutral for the barn/garage loads, very common on old K&T wiring.

There is a diagram of this circuit somewhere here on this forum, but for the life of me I can not get the search function to function:rant:

Here is one from Ken/480Sparky

 

[Dennis Alwon]

Let's summarize---This was a common install but usually it was done with the neutrals from the same circuit. It is still legal today if they are on the same circuit and done with nm cable or non ferrous raceways or cables. Now emf's is definitely an issue but for some reason the NEC does not care.

In the op example it is clearly a violation but it would not be a MWBC since there would be no voltage between conductors. There is no reason that the white wire from the 2 wire cable cannot be marked black and used as a traveler. The white conductor can never be re-marked and used as a return to the outlet.