travelers.

[stew]

I sthere any code requirement for travelers in 3 ways having the neutral run with them? or is it just a design consideration? Looking for specifics or your opinions. Thanks

 

[LarryFine]

Not with non-metallic wiring methods and enclosures. Plus, it need not always be the neutral, but any conductor carrying "return" current, as you would have with a switch loop.

 

[Jim W in Tampa]

You need not run a neutral to any switch.

 

[77401]

Why run a neutral if you don't need it?
3way or SP switch leg.

 

[allenwayne]

This topic has come up many times over the years.While not an NEC violation,there are some that belive that there is a health risk in doing this.No cancelling effect.I for one have run 2 wire travellers when I felt it easier,or more economical.Also 3 wire used as a dead ended 3 way.So it`s up to you to decide which way works best in the install.

 

[al hildenbrand]

I sthere any code requirement for travelers in 3 ways having the neutral run with them? or is it just a design consideration?

Stew,

Take a read through in this thread.

 

[stew]

how about when using mc cable?

 

[LarryFine]

how about when using mc cable?

Metallic; it matters.

 

[infinity]

Metallic; it matters.

On a dead end 3-way it would not matter even with MC cable. The neutral is not required.

 

[al hildenbrand]

Metallic; it matters.

Read 300.3(B)(3) last sentence (from the NEC, not my link above).

 

[Jim W in Tampa]

300.3 Conductors

(B) Conductors of the Same Circuit All conductors of the same circuit and, where used, the grounded conductor

WHERE USED

 

[iwire]

On a dead end 3-way it would not matter even with MC cable. The neutral is not required.

I agree with Trevor, you need not always run a neutral with a switch leg.

 

[LarryFine]

On a dead end 3-way it would not matter even with MC cable. The neutral is not required.

Read 300.3(B)(3) last sentence (from the NEC, not my link above).

You guys misunderstood my answer. I wasn't saying that a neutral is required to be run to a switch; I was saying that, in my example of a switch loop, the return leg (and not a neutral) should be run in the same cable, that MC is a metallic method, and therefore these rules apply.

 

[al hildenbrand]

Larry,

The reason I said that wasn't about the neutral, or the "balanced" current (out and back).

Rather:

2005 NEC
300.3(B)(3) Conductors of single-conductor Type MC cable with a nonmagnetic sheath shall comply with the provisions of 330.31, 330.116, and 300.20(B).

The fine print note under 300.20(B) is particularly interesting.

If the MC is aluminum clad, and a, say, 14/2 is used to carry the travelers only between two switches, then, the MC is effectively a single conductor cable.

I'm saying the "non-magnetic" sheathed MC is allowed, with respect to Stew's last query.

 

[ty]

I am probably reading too much into this,
but are you asking if you can feed a 3-way at one end, run a set of travellers, and pick a neutral up from another circuit at the other end??

 

[stew]

yes that was the way they were goig to do it. 3 phase 120/208 and the neutral was going to be the one common to the 3 circuits a,b and c.I ran a 12/3 mc however because it just didnt seem right to me but I again dont really know that it matters except for the metallic wirng method taht has been pointed out.

 

[Smart $]

yes that was the way they were goig to do it. 3 phase 120/208 and the neutral was going to be the one common to the 3 circuits a,b and c.I ran a 12/3 mc however because it just didnt seem right to me but I again dont really know that it matters except for the metallic wirng method taht has been pointed out.

Keep in mind that if the travellers are run between switches "nonferrously" and unaccompanied by other conductor(s) of the circuit, the hot and switch leg must also be run "nonferrously" where they are unaccompanied. Note that "other conductor(s) of the circuit" as mentioned here must be of a conducting portion of the local circuit. Also note that in using the nonferrous method, the individual conductors should not run parallel and adjacent to any ferrous materials, such as a steel stud.

 

[al hildenbrand]

Also note that in using the nonferrous method, the individual conductors should not run parallel and adjacent to any ferrous materials, such as a steel stud.

What is the NEC reference?

 

[al hildenbrand]

but I again don't really know that it matters except for the metallic wiring method that has been pointed out.

If the MC cable is aluminum, there is no "sufficient" induced current in the aluminum to cause heating, even when the circuit inside the aluminum sheath is only a single conductor (worst case).

Note in the Code citations in this thread that there is no limit on the size of the circuit or conductors.

Aluminum MC is common, and it is commonly run between steel boxes and other enclosures. 300.20(B) makes it clear that notches have to be cut in the hole that the MC enters through. The induced current travels in a concentric circle around the edge of the KO that the MC conductor(s) enter through. The induced current concentration is highest, in the box steel, closest to the edge of the KO.

Cutting a notch forces the induced current to take a longer, higher resistance path, thereby reducing the induced current to a level that manages the heat.

The NEC doesn't tell us how long the notch is to be.

 

[LarryFine]

The NEC doesn't tell us how long the notch is to be.

From KO to KO, so the result is effectively a single hole that all of the conductors pass through.