3 way switch and power.

Status
Not open for further replies.
K

K2X

Senior Member
Location
Colorado Springs
The other night in class we went over the fact that the travelers and the power had to be in the same conduit for a 3 way switch but how about NM. In otherwords if I had a 3 way in a small bathroom and i didn't have any 12-3 could I just use 2 12-2's and cap one off?? Thanks..
 
K2X said:
The other night in class we went over the fact that the travelers and the power had to be in the same conduit for a 3 way switch but how about NM. In otherwords if I had a 3 way in a small bathroom and i didn't have any 12-3 could I just use 2 12-2's and cap one off?? Thanks..
Click to expand...

This "fact" you are speaking of is a myth, not a fact. There is no such requirement.
 
mcclary's electrical said:
This "fact" you are speaking of is a myth, not a fact. There is no such requirement.
Click to expand...

NEX300.3(B) requirs that allconductors of the same circuit, and where used, the grounded conductor, all equipment grounding conductors and bonding conductors shall be contained within the same raceway...... exceptions for nonferrous wiring methods....
 
K2X said:
The other night in class we went over the fact that the travelers and the power had to be in the same conduit for a 3 way switch but how about NM. In otherwords if I had a 3 way in a small bathroom and i didn't have any 12-3 could I just use 2 12-2's and cap one off?? Thanks..
Click to expand...
It sounds like you were studying, at least, practice based on NEC 300.3(B), if not the actual passage itself. Some people speed read it, missing or ignoring following thru on the last nine words of the passage.

Pay particular attention to NEC 300.3(B)(3) and the links to other articles.
 
K2X said:
The other night in class we went over the fact that the travelers and the power had to be in the same conduit for a 3 way switch but how about NM. In otherwords if I had a 3 way in a small bathroom and i didn't have any 12-3 could I just use 2 12-2's and cap one off?? Thanks..
Click to expand...

In conduit: you must have a supply and return path. Typically, you will pull two travelers and a switch leg to one three-way switch (no power feed).

Your question about 12/3 or 2 12/2s is a question I suppose many have asked themselves at the moment they ran out of 12/3. However, I consider it unprofessional. I'll be looking for NEC reference.
 
So many big commercial and industrial jobs you find the incorrect practice of bundling a whole bunch of neutrals in one conduit and the hots in some other conduit.

The conduits can get pretty hot!
and watch out for theEMF.

But think about the old K&Tube method.
Those shacks are full of EMF!!
 
roger3829 said:
NEX300.3(B) requirs that allconductors of the same circuit, and where used, the grounded conductor, all equipment grounding conductors and bonding conductors shall be contained within the same raceway...... exceptions for nonferrous wiring methods....
Click to expand...

Read the op again, he's not talking about that, there is NO SUCH REQUIREMENT as the one he mentioned.
 
K2X said:
I think I meant the grounded conductor not the power or ungrounded conductor. I've done 3-ways but i always have to think about them.
Click to expand...
For NM, your answer lies in 300.3(B)(3). When one starts understanding that exception to 300.3(B), you will have even more to think about.

Oh, and as far as I'm concerned, one is never too old (or experienced) to NOT think about threeways. It gets easier to hold the circuit in the head, with practice, but the opportune variation of the circuit that is the sweet solution to the structure one is wiring, keeps one on one's mental toes, so to speak, lest a detail be missed.
 
wyreman said:
So many big commercial and industrial jobs you find the incorrect practice of bundling a whole bunch of neutrals in one conduit and the hots in some other conduit.

The conduits can get pretty hot!
and watch out for theEMF.

But think about the old K&Tube method.
Those shacks are full of EMF!!
Click to expand...

With your first scenario, the problem arises because the conduits are a ferrous material and a current induced in the conduit is not counteracted by an equal and opposite force because the neutrals are not contained in the same conduit. Eliminate the ferrous conduit (ie. use PVC) and there is no problem.

Thus, you can see that the second scenario you mentioned with K & T is not a problem, either.
 
al hildenbrand said:
Oh, and as far as I'm concerned, one is never too old (or experienced) to NOT think about threeways. It gets easier to hold the circuit in the head, with practice, but the opportune variation of the circuit that is the sweet solution to the structure one is wiring, keeps one on one's mental toes, so to speak, lest a detail be missed.
Click to expand...

Al, you have a way with words.:grin: I can do a conduit threeway in my sleep (still thinking, of course), but I always have to think about a Romex 3way.
 
iMuse97 said:
Al, you have a way with words.:grin: I can do a conduit threeway in my sleep (still thinking, of course), but I always have to think about a Romex 3way.
Click to expand...

In a conduit 3-way if you forget a wire you can usually pull in another wire but in a romex 3-way in a finished dwelling you could run into major problems if a wire is missed.
 
Something I've done on lighting circuits with several 3-ways, such as a kitchen/dining room/hallway/foyer type circuit, is to bring the 2-conductor supply into the first room's first 3-way switch box, run two 2-conductor cables to the second 3-way switch box, then a 2-conductor on to the next room's pair of 3-ways.

Now, I can bring the switch leg out of whichever 3-way switch's box I like, picking up the grounded conductor there, and feed the other 3-way of the pair in the other switch box, where I pigtail the hot. Obviously, the second of the two 2-conductor cables is the travelers, in which I recolor the white either red or blue with a Sharpie.
 
I have heard that eventually it will be code that all switch boxes will have to have a neutral (grounded conductor) available, the reasoning is for occupancy sensor switches and other devices that control lights to save energy.
 
Status
Not open for further replies.
Top