I am converting an existing single switched light/fan combo to separate switches for each function. There is already a light/fan combo on the circuit, wired with 14/2 Romex. Power comes in at the switch box. The existing fixture branches off of that power. The switch is in the middle of the run, so power also continues from the switch on to several outlets down the line. The circuit has a 15A breaker and the circuit is wired with 14 gauge throughout.

My question is this: is it permissible by code (local code is NEC 2017) to use 12/3 gauge wire to power the light and fan? Are there any additional considerations I need to take into account?

1 Answer 1


Yes, using 12/3 into a 15 Amp circuit of 14/2 is OK. You could not go the other way and add a 14/3 to a 20 Amp circuit of 12/2.

  • Thanks. I’m assuming I can connect all 3 neutrals together at the box (one from the 14/2 coming into the box, one for the 14/2 leaving the box and one for the new 12/3)? The fan/light kit’s neutral will be connected to the other end of the 12/3’s neutral.
    – Rudy
    Commented Dec 22, 2021 at 23:55
  • Yes, you can and need to connect the 12/3 and the (2) 14/2 neutrals together. Commented Dec 23, 2021 at 0:18

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