Fan 3-way switch wiring - questions on your diagram

[diyadmin]

Received by email...


Grand Palmetto Custom Homes


Good morning, viewing your website for three-way wiring a fan light kit

https://www.wiringdoneright.com/m/fa...itch-nec-2011/

a few questions If you would kindly help me to understand:


1) What is the source of the BLUE wire you reference in your illustration and instructions? Standard for a 14/3 are of course black, white, red, and copper... curious why the use of the blue wire in this demonstration?

2) Is this wiring diagram still legal as of NEC 2017 (and now NEC 2020)? I noticed you have the power source coming to the fixture box, but the NEC seems to prefer pushing power into the switch boxes now.

Thanks in advance,
Dave

[diyadmin]

Thank you for your email.

The website was built when earlier versions of NEC was current.

I will follow up later in the following week as I have to check on any changes in NEC in uniited states [i am in canada]

Don

[suemarkp]

The diagrams are correct, but may be difficult to implement. Note it is indicating using cable with 4 insulated wires. This is now available in two varieties -- black/white/red/blue and black/white/red/white with red stripe. The latter was designed for two separate circuits in one cable, or GFCI LINE/LOAD in same cable. The one with the blue wire is for circuits like this. It may be difficult for you to find this cable (I've never seen it in stores myself) in which case a different diagram would be more helpful.

The NEC has no prohibition on running power to a light first then looping to a switch. However, code does now require a neutral in most switch boxes and there are various ways to do that and some exceptions. In the old days, it was also discovered that running a full power circuit to a light fixture and continuing on to another from there was cooking the wires. That caused NM cable to get upped to a 90C rated conductor instead of 60C to help alleviate that in 1986. Personally, my preference is to run power to a switch box first and not the light.

To wire a fan/light combo with 3-way control of the light and a separate on/off switch, I would do the following if on a 15A circuit:
Power to on/off switch with 14-2
Power out of on/off switch with 14-2 to the fan (connecting to the black/white of the fan motor)
Add another 14-2 cable from this power switch box to the first light switch box.
Run 14-3 between the two switch boxes with the neutral a neutral, and red/black as travelers.
Run 14-2 from 2nd switch box to fan. This connects to the light black/white.

Note - fan wire colors for the light and motor could be anything, although each should have a white. Many fans today use a remote control module so you just power the whole fan and either leave it on all the time and use the remotes for control, or wire like just the light portion if multiple switches and then the remote works for dimming and speed control (the wall switches will complete turn it off or on).