Can I wire 3 switches to 3 devices through conduit with a single hot and ground?

Question

I have a bathroom fan/light/night light combo unit that allows for all 3 features to be switched separately (a connector for each). I want a timer for the fan, and separate switches for each light. I'm wondering the best way to wire that.

I could just add a 12/3 cable with two hot wires and a 12/2 cable to control all three features. Or 3 12/2 cables. But I was wondering, if one were starting from scratch would they run 3 separate cables from the switch to the fan combo? Or something else?

So my thought was, could I run conduit and put a ground, neutral, and 3 hots through it, between the switches and the fixture. I realize that would mean all 3 things going through the same neutral, but that would be the case anyway if I just ran 3 cables from the switches.

So is that a valid use of conduit? I also looked for existing cables with 1 neutral and 3 hots (grounded). I think they exist but I can't tell if they're for home wiring or to any sort of electrical code or anything.

I'm having a hard time finding the answer because I don't know how to ask. Being an amateur, I want to go with something I know is correct so I'm wary with this.

Answer 1

Conduit is a fine way to do it. One of the luxuries of working in conduit is you can install any wires the circuit requires. This is safer too, because it assures that hots and neutrals actually are together. There's no problem with transitioning between cable and conduit of any kind, so long as you are in locations appropriate to both types.

It's also easier to wire, since you aren't stuck with red and black (or marking white or gray neutrals). You can use any color you please; brown, orange, yellow, blue, purple or pink. Even my local lumberyard sells several of those by the foot. Of course green can never be anything but ground, even in a conduit. (thanks gregmac for reminding me to specify what I assume you know, but the next reader might not.)

In metal conduit you must bond the conduit to ground, but you also can let the conduit be the ground, so one less wire to pull. To make a transition from wired ground to conduit ground, the boxes have a hole tapped for 10-32 for attaching the ground wire. For convenience, they sell green screws 10 for a buck, and pre-made ground pigtails 10 for $3.

Answer 2

If you use conduit you can run a neutral ground and 3 hots. Since these are all fed from the same hot. Flexible non metallic would be the easy way since it will be concealed in a wall it is legal as long as not above 3 floors above grade NEC 362.10. Table 1 chapter 9 says over 2 conductors the max fill is 40%. with 1/2" there is room to spare according to table 5 with #12 wire (table C-1 allows for a total of 9 ea 12awg conductors).

Answer 3

If the power is at the switch box, you could simply run a single 12/4 (with ground) nonmetallic sheathed cable between the boxes. You might not find 12/4 at your local big box; or maybe not even at the local electrical supply, but you should be able to order it. Another option would be to use 12/2/2 (with ground) nonmetallic sheathed cable, which is more widely available. Though with 12/2/2, you'll have to reidentify one of the neutral conductors.

Of course as you mentioned, you could always install conduit and pull individual conductors.

You don't have to worry about sharing the neutral, as long as all the "hots" are from the same circuit. The neutral is rated for 20 amperes, and there'd be no way to pull more than that without tripping the breaker.

NOTES:

• You might find 12/2/2 listed as 12/2-2, or 12-2-2. In any case, it's a cable with two "hots", two neutrals, and a ground.

---

^{example using 12-2-2 NM cable.}