Can I pull a new single conductor alongside an existing 14/2 wire for a fan+light install?

Question

In my bathroom, I have a 2-gang switch box. One switch controls the light bar above the sink, and one controls the fan. I have a new fan, which includes a light. I want to wire the light on the fan to be on the same switch as the light bar, and so this requires 2 switched hots in the fan box; I only have 1.

Do I need to pull a new 14/3 wire from the switch box to the fan box, or can I just pull a new single conductor and use it alongside the existing 14/2?

Located near Houston, TX, not sure what version of the NEC we have to follow.

Answer 1

Not under the code.

NEC 300.3 (B) - All conductors of the same circuit ... shall be contained within the same raceway ... [or] cable ...

The additional hot you need is a conductor that must be in the same cable or raceway as the neutral for that circuit.

Additionally, in general, you cannot run single/solo wires that are not in a cable, a raceway, conduit, or some similarly approved protective covering.

NEC 300.3 (A) - Single conductors ... shall only be installed where part of a recognized wiring method described in Chapter 3.

Answer 2

You cannot pull a single conductor. (Retrofitting grounds is another story, that's allowed now.)

However, there may be "smart devices" to help you solve that problem, such as Infineon modules which which sit up in the fan/light and listen to electronic signals from a matching light/fan switch. They are most commonly used on tavern style slow spinning ceiling fans, but I believe they make them for bathroom fans also. Some also work with wireless remotes, smartphone and home-automation systems.

Answer 3

ANY version of the NEC prohibits a single THHN conductor or other type without an outer jacket to be run with the 14/2.

NM cable (your existing cable) is approved for residential use. Single conductor wires are made to be installed in a raceway.(conduit)

If you need to turn the light on and off without running another cable there are many wireless switch options for sale at your local box store or online.

Good luck with your project!