Travelers run in separate conduit

[ElectricMatt]

I have always ran my travelers along with my lighting circuit. I do this because I was taught that way. However, I worked on another mans job recently and he had me run the travelers in a separate conduit from the lighting circuit itself. Will this lead to a potentially higher impedance or is this an acceptable practice?


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[GoldDigger]

Are you referring to switch legs in general or specifically to the paired travelers for a three or more way switch setup?
Whether the travelers are run with other wires or not they almost always end up being a net current flow inside a raceway.

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[ElectricMatt]

Are you referring to switch legs in general or specifically to the paired travelers for a three or more way switch setup?
Whether the travelers are run with other wires or not they almost always end up being a net current flow inside a raceway.

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Not the switch leg, the travelers for a SPDT switch.


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[ElectricMatt]

I understand there is a net current flow in the raceway. I was told it could cause the travelers to get hot. I do not understand why they would get hot being run in a separate conduit, but I wanted some opinions the subject. Is there such an increase in the impedance that it could have a greater potential to heat up.


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[GoldDigger]

I understand there is a net current flow in the raceway. I was told it could cause the travelers to get hot. I do not understand why they would get hot being run in a separate conduit, but I wanted some opinions the subject. Is there such an increase in the impedance that it could have a greater potential to heat up.


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There will be an increase in inductance if you run a net current through ferrous raceway. No extra heating in the wire at all since the extra impedance is inductive.
There will be some small heating in the raceway itself from hysteresis and the corresponding iron losses.
But none of this is significant for the amount of current found in a lighting branch circuit. The effect on fault current is probably irrelevant too.

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[ElectricMatt]

I didn't think it would be significant, but I appreciate the validation!


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[roger]

I have always ran my travelers along with my lighting circuit. I do this because I was taught that way. However, I worked on another mans job recently and he had me run the travelers in a separate conduit from the lighting circuit itself. Will this lead to a potentially higher impedance or is this an acceptable practice?


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See 300.20(A) and 404.2

Roger

 

[Smart $]

FWIW, running the travelers separate from the other circuit conductor(s) is a violation of 300.3(B) when using any ferrous wiring method. It is permitted using nonferrous wiring methods under 300.3(B)(3), but you will then have to comply with 300.20(B).

 

[spark master]

Years ago, I saw a job where the neutral was in a different conduit. About 100' of neutral, all the way back to the panel in a totally separate conduit. I could never figure what they were thinking when they did the lighting.

 

[JFletcher]

Years ago, I saw a job where the neutral was in a different conduit. About 100' of neutral, all the way back to the panel in a totally separate conduit. I could never figure what they were thinking when they did the lighting.

Perhaps the original lighting was all L-L loads and subsequent upgrades/replacements required a L-N connection. or perhaps the neutral was omitted by error and that's how it was 'fixed'

 

[peter d]

You must always run the neutral with the line conductors, or create a switch loop.

 

[Electric-Light]

Though not as a big deal now, this is a great way to cause a CRT to bounce around. The magnetic field does not cancel out if you don't have opposing conductors.

 

[Strathead]

Ok I am thoroughly confused here. If this needs to be moved to a separate thread please do, but I think belongs here.

Doesn't 404.2 exception mean that you DON'T need the neutral (grounded conductor) between the switches? So I can run 2 travelers, and a switch leg between switches?

 

[peter d]

Ok I am thoroughly confused here. If this needs to be moved to a separate thread please do, but I think belongs here.

Doesn't 404.2 exception mean that you DON'T need the neutral (grounded conductor) between the switches? So I can run 2 travelers, and a switch leg between switches?

That's right, as long as you have a feed and return in the same raceway, you're good to go.