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I have 2x 3-gang boxes, each with 3x 3-way switches in each box. All are on the same 15A breaker.

I have wired them together and I'm just connecting the switches now. I have:

                 --------              ---------
BREAKER --14/2-- |3x-3WAY| --3x14/3-- |3x 3-WAY| ---3x14/2-- LIGHTS
                 ---------             ---------

The 3-gang boxes are connected with 3 runs of 14/3 cable.

My question is: should I splice the neutrals together (and the grounds) at the second 3-gang box (load side)? It seems like it doesn't matter, since they could just as well be going to 3x 1-gang boxes on the load side in which case they would NOT be connected.

To clarify - I'm not asking if I should connect neutral to ground (I know I shouldn't do that). I'm asking if I should connect all the neutrals together and pigtail off that or just treat each switch independently on the load side.

Is there a standard way to do it?

  • Is there a reason you're using triple runs of 14/3 instead of say a 1/2" ENT with 14AWG THHNs in it to connect these switch boxes together? That would simplify neutral routing considerably, and also give you the ability to wield the rainbow of colors THHN comes in to your advantage ;) – ThreePhaseEel Jul 15 at 2:36
  • If I'd ever heard of " 1/2" ENT with 14AWG THHNs" I might have done that. What is it and how does it provide an alternate solution? (I've never seen 3-way switches connected with anything other than 14/3 or 12/3. – Harold Jul 15 at 3:39
2

If you have an electrical box at the second switch bank location with enough cubic inch volume you should really keep each circuit separate (i.e. not inter tie the neutrals). The primary reason is that you want the current in the hot line (in this case the travellers) and the neutral of each cable to be the same.

Another good reason for that would be that at some time in the future it may be desirable to bring an alternate power feed to the first switch bank location to feed one lighting circuit separately. You do not want to intermix the neutrals from two separate circuits.

  • Thanks for your rapid response! That's along the lines of what I was thinking. I just wired it and kept everything separate at the second switch box as you suggested. – Harold Jul 14 at 19:16
6

Neutral is not ground

Neutral is the normal path of current return. Ground is an emergency path, only used if something is seriously wrong (in lieu of sending power through a human, and it helps to get breaker to trip). Because of that, it's OK to spiderweb all grounds to each other. This should never be done with neutral.

Currents must be equal in each cable or conduit

Because AC current in wires causes AC magnetism, and the wires' magnetism must cancel each other out. If it doesn't, it will cause eddy current heating, and noise/vibration leading to fatigue, breakage and arcing, both of which can start fires.

It's a lot to sort out. Mark the wires.

They sell 5-packs of colored electrical tape for about $5 at the hardware store. Typically blue red yellow green white.

So you might do something like this in box 1

enter image description here

and this in box 2

enter image description here

*The neutrals will be a wire from each cable that need be wire-nutted; I simply didn't bother drawing the wire nuts.

Note how the 2 travelers are color coded the same. That is because there is no need to distinguish travelers from each other.

I also spiraled the travelers' markings quite some distance, but the switched-hot only the width of the tape.

Now that looks super clear on the drawing, however in the box, things may be so confusing you need to mark the neutrals too. But you cannot use red, yellow or blue (hot colors) on a neutral wire, or you will inadvertently redefine it as a "hot" wire, which is wrong. White, gray and green don't have that problem. They won't redefine a hot because you're not allowed to redefine a hot to a neutral or ground. White and gray are neutral colors, and green won't redefine a neutral to ground, because that's not allowed either. So brace for an argument with the inspector, but I say using white, gray or green on both hot and neutral does not change the purpose of the wire, therefore is only marking for identification.

  • That's exactly how I did it. Thanks! – Harold Jul 15 at 3:36
0

Conduit...on the cheap!

One of the great advantages of the conduit systems used for industrial and institutional wiring is the ability to wrangle complex wire runs like the situation between your two switch boxes without having to worry about mixing up wire colors, retagging wires, or splitting neutrals up on the same circuit. However, typical metal conduit is expensive and requires special tools and skills to install, so it's not used in residential wiring unless called for by local Code provisions or the need to run wiring in unfinished areas.

Still, this does not mean we cannot take advantage of conduit's pros here. One relatively little known fact is that ENT ("smurf tube") is legal to use for mains wiring, not just telecom/datacom work. A 1/2" ENT can be run and fished with little difficulty compared to a bundle of NM cables, and then you can pull individual stranded THHN wires through it, giving you the ability to put in exactly the wires you need without much more cost or work over having to wrangle 3 different NM cables with the perils of duplicate neutrals and crossed travelers that entails.

In your case, I would take that 1/2" ENT and run in it a 14AWG bare ground, a 14AWG white neutral, and 3 14AWG traveler pairs, with both travelers in each pair the same color, which can be any color other than white, grey, or green. (For instance, you could use two wires each in yellow, blue, and pink.)

  • Fascinating! I might have done that had I heard about that technique before I wired my whole basement! Live and learn. – Harold Jul 15 at 4:12

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