Is it legal (from a code point of view) to use the bare wire in a 14/2-w/gnd if there is another cable (14/2-w/gnd) going to the same Junction box?

I want to separate the light and fan in my ceiling fan.

Currently, there is a 14/2 w/gnd leading from the switch to the junction box. In the j-box is a semiconductor switch that allows me to pulse the hot to toggle either the light, fan, or both. Turn it on get the light. plulse it off for a sec then back on gives the fan, pulse it again gives both fan and light.

I want to remove the device, and run a second cable (14/2 w/gnd) to control the fan, and leave the existing 14/2 for the light.

The fan is a PSC type motor, so to achieve reverse, I need access to all four ends of the two windings, one of which may be common neutral as the light.

In the existing cable, I would use bare and white as ground and neutral for both fan and light, then black for the light.

In the addition cable, all 3 would get used for the fan. This would put 120V on the bare wire in the second cable some of the time.

Thanks, Mark.

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14-4 isn't expensive

Just use 14-4 NM for the new run instead of 14-2 to get yourself the extra wires. It's not like it's not available or hideously expensive!

Bare is always ground; when it's not ground, it must be neutral, never hot

Under the NEC, bare wires are reserved for grounds, end of story. This is because they only have the cable jacket to protect them from human contact, and nothing to insulate them from any metal junction boxes they may enter. In the only exceptions to this rule, they are a neutral or multiplexed neutral and ground in type SE cable as per the Exceptions to 250.140 and 250.32(B)(1) -- never a hot wire, as bare conductors are not recognized as a current-carrying means in Article 334 Part III, or in the other similar parts of the Code unless you're dealing with open wiring on insulators or knob & tube wiring.

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TLDR: Seek out 14/4 cable, or run conduit and individual wires. The neutral must be in the same cable or conduit with its partner hots. Neutrals and grounds cannot be borrowed (for your application). Ground cannot be used as a conductor. Or, use a smart remote.

If you're an electronics guy, Code is full of weird idioms that don't make sense until you get deeper into the craft of it.

Neutral is not Ground

It's common in DC electronics to use "ground" as both RF shield and current return.

Code electrical is wired the same as if it were a fully isolated system with equipment ground/shield only as a safety device. To keep voltages from floating/rattling, it is bonded to earth in one location. Only hots or neutral may return current, never ground unless you want a GFCI trip.

Because many people must service a circuit, colors are standardized: Neutrals are always white or gray; grounds are always green, green/yellow or bare. Any loose ground wire (not in one of the unusual, grandfathered applications) will be added to the ground bundle by the first competent electrician who sees it attached to anything else.

You can't use ground as a conductor.

That bare wire can only be ground except in a very narrow list of exceptions. All of which involve grandfathering old work. So forget it. Ground as a conductor is not gonna happen.

Only when you are retrofitting ground to old (1970s> work) can you steal ground from another circuit. When doing new work, you must "do it right".

You especially can't steal neutral

Your original scheme, and ThreePhaseEel's modified scheme with 14/3, involves stealing neutral from the light circuit. Nope. You need to put your neutral in with your partnered conductors. Your best bet is to find 14/4 or 14/2/2 cable. It's a bit harder to find but is a Code requirement for what you are doing. Either will have 4 conductors and a ground wire. Alternately, you can run it in conduit and use single conductors, as many as you need/like.

Your motor control needs one neutral and three hots in a single current loop. All of these conductors must be inside the same cable (or raceway/conduit).

It is absolutely not permitted to share a neutral wire out of a different cable. That's because in any cable, the current of all the conductors must be equal/balanced (or to be more precise, sum up to zero when flow direction is accounted for). In this way, the magnetic fields from all the wires cancel each other out. Otherwise, a magnetic field forms around the cable and particularly between the unbalanced cables, and that will inductively heat anything with the misfortune to be metal. Remember, we're dealing with AC here. This is a big deal. This sort of thing is why AC motors need laminated field windings, and DC motors do not, even though the motors are identical in every other respect.

A good litmus test of this principle is to imagine what happens if you put a GFCI on the device/circuit in question. If hot and neutral current are unequal, it will trip. If neutrals are borrowed or ground is used as a conductor, it will trip. Every Code installation should pass a GFCI test.

Like I say, a lot of Code stuff seems weird... or even dumb. "But you can do that!" Actually, get into the gory details and you find out when people did that, houses burned down. The system is intensely designed to save lives and be maintainable by any licensed electrician or Code-respecting hobbyist without obsessively googling every product they might find or weird installation they might uncover.

Plan B: use a smart module

A much better way to do this thing is to use a smart device which is made to control fans and lights, and a partner "remote" that sits up in the fan cowling. The smart control communicates with the remote using fewer wires. In a perfect world, it uses radio or inducts signal onto the power line, in which case you only need to bring always-hot and neutral to the switch and fan location.

The remote sits between the hot+neutral and the fan, switching (dimming?) the light, and selecting the various fan speeds.

Much better!

I assure you this product exists, so search for it before you launch a Kickstarter.

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  • Good catch re: the neutral -- I didn't catch\ that he was tapping it in the switchbox for the fan reversal function – ThreePhaseEel Jan 6 '17 at 0:03

Use #14/3 wire for the addition. It will have three insulated conductors, plus an uninsulated ground wire.

The bare ground wire may only be used as a grounding conductor.

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