0

I'm installing a ceiling fan with a light kit and want to control the fan and light separatly from two separate switches in the same two-gang box via a switch leg (power comes in through the fan). It seems that I need 4 wires for this - one hot, two load, and one neutral. Would it be a code violation to use two 14/2 cables to accomplish this task? I could buy 14/2/2, but it's not widely available and is pricey. Am I over thinking this, or is there an easier way to do it?

Many thanks in advance for the help.

  • Note: my state uses 2014 NEC – Uncle Woody Sep 23 '18 at 12:59
  • Can you get 14/4 NM? – ThreePhaseEel Sep 23 '18 at 14:17
  • Can't find it locally. I'd have to order it online. Do you think the two cable solution is a problem? – Uncle Woody Sep 23 '18 at 14:53
1

Two cables won't fly, most likely

Splitting the wiring here between two 14/2 cables would be a 310.10(H)/300.3(B) violation for having unbalanced currents in each of the cables. Using a 14/2 and a 14/3 is likely to be a non-option as well, as many fan/light controllers assume a common always-hot for both sides of the control, again bringing unbalanced currents into play.

Smurf (tube) to the rescue, though!

While 14/4 or 14/2/2 will definitely work for this application (check with your local electrical supply house -- they should be able to get you decent pricing on this stuff if big-box is gouging you on it), there is another option as well -- running an ENT ("smurf tube") between the switch box and the fan box. A 1/2" trade size ENT can fit 11(!) 14AWG THHN wires alongside a bare 14AWG ground, and also gives you the flexibility to use the rainbow to your advantage, selecting wire colors based on application instead of being bound by the monotone of NM cable. Furthermore, it makes adding additional wires to that loop later trivial compared to ripping out and replacing a cable, alleviating concerns about having to provision an unused neutral now.

You'll need boxes with 1/2" conduit knockouts though, or to carefully make your own KOs with a KO punch set or KO holesaw (a 1/2" trade size KO is 7/8" in diameter to accommodate a standard conduit connector or cable clamp) if you have cheap plastic boxes without conduit KOs. Also, stranded THHN is your friend here -- it is far easier to work with than solid wire due to its flexibility.

  • Great, thanks! My knowledge of electricity is limited, so I don't understand how placing the same THHN wires in the same NM jacket or raceway vs two separate jackets makes a difference, but I shall comply with the code :) If I run the Smurf tube, I don't need a neutral, correct? – Uncle Woody Sep 23 '18 at 15:53
  • @UncleWoody -- you are correct re: the Smurf tube not needing a neutral wire at this point, since it's easy to add one when it's needed :) – ThreePhaseEel Sep 23 '18 at 16:12
  • @UncleWoody because when current goes up one cable and down the other, it means the current is going around something. Current going around something is how electromagnets and transformers work. Any nail between the two wires will enjoy eddy current heating (unless like a transformer core it is laminated to prevent this). There will also be magnetic (i.e. Electro-motive) force which will physically try to move metallic items or the cables, and that creates vibration which creates fatigue which creates overheating and arcing. – Harper Sep 23 '18 at 17:07
  • @ Harper. Thanks for the explanation. In my cursory understanding of electricity, this does make sense. So the same forces are in effect within the smurf tube, but since there are no nails in between the wires carrying current, it's not a problem? – Uncle Woody Sep 23 '18 at 19:29
  • 1
    @UncleWoody the problem goes a lot deeper than nails... Even open space between cables can cause interaction amongst the cables. The difference is when wires are bound closely together, as in cable or how they tend to lay in conduit, there's no space between them. – Harper Sep 23 '18 at 20:55
0

In general you only need 3 conductors and a ground. One neutral, one switch leg for the fan, one switch leg for the light, and of course the grounding conductor. Usually running a 12/3 w/ ground or a 14/3 w/ ground (it depends on the rating of the breaker 12 for a 20A breaker and 14 for a 15A) takes care of this.

Do you need a fourth conductor for anything else, or are you saying you need to pull a hot (line side) conductor from the fan box down to the switch box? If that is the case then you still only need a 14/3 since the NEC 2014 does not require you to pull a neutral to the switch box, but the NEC 2017 does require it.

  • The 404.2(C) requirements for neutral at the box date back to 2011... – ThreePhaseEel Sep 23 '18 at 14:16
  • @ThreePhaseEel - Then I stand corrected. – Retired Master Electrician Sep 23 '18 at 14:18
  • You seem to be forgetting a wire -- supply hot. – Harper Sep 23 '18 at 17:03

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.