3 -way switch box location requires a neutral ?

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Scheffler Energy

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Master Electrician
I have been doing some research on 3 way switches. From my research the three diffrent ways to wire a 3 way switch circuit you leave a neutral out of some of the switch locations. Is it a code violation to run a 3 wire nm with a 2 wire nm just to add a neutral In the switch box? Just running a 3 wire you don’t have enough conductors to add a neutral to the switch box? I wanted to know if running a neutral not in the same cable jacket was a Code violation? What’s the standard practice to get a neutral in every switch location.? Would need a 4 wire nm cable.
 
Scheffler Energy said:
Is it a code violation to run a 3 wire nm with a 2 wire nm just to add a neutral In the switch box?
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No, but you could just use two 3-wire cables.

Just running a 3 wire you don’t have enough conductors to add a neutral to the switch box?
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Not unless you bring in a hot and neutral and leave with two travelers and a neutral.

I wanted to know if running a neutral not in the same cable jacket was a Code violation? What’s the standard practice to get a neutral in every switch location.? Would need a 4 wire nm cable.
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I did a house years ago that had several rooms with two-doors in line: mud room, kitchen, dining room, hallway, living room, so each room got a pair of 3-way switches, one at each door.

I ran two 14-2 cables between the two 3-ways in each room. One cable was the hot and neutral that ran from box to box, room to room, and the second cable was the travelers for that room.

I brought out the switched line and neutral to the light from whichever switch box was more convenient, and fed the 3-way pair in the other box for that room. Yes, I colored the white traveler.

To answer you, with non-metallic wiring methods, such as NM cable, cables can be run alongside each other. By the way, not every switch in a given room has to have a neutral present.
 
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LarryFine said:
No, but you could just use two 3-wire cables.


Not unless you bring in a hot and neutral and leave with two travelers and a neutral.


I did a house years ago that had several two-door rooms in line: mud room, kitchen, dining room, hallway, living room, so each room got a pair of 3-way switches.

I ran two 14-2 cables between the two 3-ways in each room. One was the hot and neutral that ran from box to box, room to room, and the second was the travelers for that room.

I brought out the switched line and neutral to the light from whichever switch box was more convenient, and fed the 3-way pair in the other box for that room. Yes, I colored the white traveler.
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I've done it but hate using a 14 2 for travelers incase it throws off a future apprentice.
 
letgomywago said:
Standard 3ways always end up with a nuetral you don't have to dead end them always but if for some reason you need to dead end some so long as it's the same circuit it will work for smart switching
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I have seen a lot where the power hit the light first and there is no neutral at either switch leg.
 
Scheffler Energy said:
Is it a code violation to run a 3 wire nm with a 2 wire nm just to add a neutral In the switch box? Just running a 3 wire you don’t have enough conductors to add a neutral to the switch box? I wanted to know if running a neutral not in the same cable jacket was a Code violation?
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I believe it is a violation of 300.3(b) which says all circuit conductors have to be in the same cable

Scheffler Energy said:
What’s the standard practice to get a neutral in every switch location.? Would need a 4 wire nm cable.
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Standard practice now would be to feed one switch with H+N, then pass the neutral through to the other switch in a 14/3, then switch leg H+N to light

But you could feed and switch from one location and use 14/2/2 for H+N+T+T to the other location. Or pass through multiple lights using 14/2/2

There are at least a dozen different configurations
 
Joethemechanic said:
Carter 3 way has a neutral in each switch box

View attachment 2566748
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Around KC, they would wire those, but didn't "travel" the hot and neutral from one switch to another, they would feed each switch from the closest circuit. On stairs, the top switch would be fed from the attic and the bottom switch would be fed from the basement. Then a single conductor from each switch to the light

It also doesn't work with a modern dimmer 😁
 
James L said:
Around KC, they would wire those, but didn't "travel" the hot and neutral from one switch to another, they would feed each switch from the closest circuit. On stairs, the top switch would be fed from the attic and the bottom switch would be fed from the basement. Then a single conductor from each switch to the light

It also doesn't work with a modern dimmer 😁
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You know having grown up working around stuff like the carter, K&T, fused neutrals, switched neutrals, Philly's 2 phase, high leg deltas, not to mention electrical systems on heavy trucks with some of the worst butchery I've ever seen, and positive ground stuff, and then there is the European stuff with Lucas Electrics.

I think all that taught me to never assume what anything is. I don't care what color it is, what number is on it, or where it's landed
 
230806-2135 EDT

In any circuit you wire there is a source wire and a return wire. These two wires must be in close physical proximity to each other, preferably less than an inch apart for low voltage and current. 120 V and 20 A are low voltage and current for this purpose. None of this current should flow anywhere else. This is to minimize stray magnetic fields that may interfere with sensitive equipment.

An incorrectly wired 3 or 4 way circuit may be easily mis-wired.

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