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Under our patio, we have a fan and a security light. The fan and the security light are the same light switch, so they are both on, or both off. The only way to run the fan without the security light is to remove the bulbs from the security light, which is highly inconvenient.

By the door, there is a switch for the fan/light, and a three-way switch that controls the dining room light. I’d like to do one of these options:

  1. Replace the dining room light’s other switch by the hallway with a single pole switch and make the dining room light be controllable only from there, then have two single-pole switches by the door to control the fan and security light independently.
  2. Replace the security light’s switch with one of these: https://www.homedepot.com/p/100356887… and have one be the fan, and one be the security light, and leave the dining room light alone.

I fished a romex cable from the security light’s box to the box by the door (about 3 feet), which I’m guessing will end up being the hardest part of this project. I can connect the fan’s cables to the other end of this cable in the security light’s box.

I suspect this is simple, but the way the three-way switch is wired confuses me a little. How would I go about wiring the switches for these options? I think I ultimately would want to go with whichever option ends up with the least number of connections in the box. I have here a picture of the setup and options, as well as a picture inside the box.

Current setup and options

Picture of inside the box

Edit: Going with option 2

So for the wiring portion, I would then do the following (just laying out the steps here):

  1. Get the dual switch (I have this one already: https://www.homedepot.com/p/100356887)
  2. In the switch box, wire the bottom of the dual switch the same as the current single switch is wired now
  3. In the switch box, connect the new cable's white and black wire to the the top of the dual switch
  4. In the switch box, connect all grounds together
  5. In the security light box, connect all white wires together (both the old an new cable, and the security light)
  6. In the security light box, connect all grounds together
  7. In the security light box, connect the black wire for the security light and the black wire on the old cable together
  8. In the security light box, connect the black wire for the cable to the fan and the black wire on the new cable together

Does that seem correct as far as the wiring?

  • Can you post a photo looking into the back of the box? – ThreePhaseEel Nov 6 '18 at 0:18
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I think your description is basically right for wiring another ordinary outlet, but NOT for a switched light. Piece by piece:

In the switch box, wire the bottom of the dual switch the same as the current single switch is wired now

The existing switch should have a black hot coming in and a switched hot going out. The new switch may actually have a common hot coming in, in which case you will have (typically) one screw on one side for the common hot, and 2 screws on the other side for the two switched hots. With the original switch it didn't matter much (if at all) whether you got hot vs. switched-hot correct, but now it most definitely does matter. The switch you linked to has two screws for hot with a piece of metal that connects the two screws. As long as you leave that piece of metal in place, you can connect just one hot wire and share it between the two switches, which is what you want to do here.

In the switch box, connect the new cable's white and black wire to the the top of the dual switch

NO! Connect the black to the switched-hot screw on the top switch. The white will connect together with the other neutral (from the old cable) to the common neutral (i.e., the white wire that is together with the common black hot wire).

In the switch box, connect all grounds together

Correct.

In the security light box, connect all white wires together (both the old an new cable, and the security light)

Not quite. The security light (white wire or screw terminal) connects only to the OLD white wire. The fan (white wire or screw terminal) connects only to the OLD white wire.

In the security light box, connect all grounds together

Correct.

In the security light box, connect the black wire for the security light and the black wire on the old cable together

Correct.

In the security light box, connect the black wire for the cable to the fan and the black wire on the new cable together

Correct.

Does that seem correct as far as the wiring?

I think that covers it. To summarize:

  1. Cable from panel white - currently to white of old cable, now connects to white of old & white of new. (All neutrals together, but only in this box, not in the light/fan box).
  2. Cable from panel black - moved from old switch to common of new switch. If new switch doesn't have a common, pigtail to both hot screws.
  3. In light/fan box - fan connects to old cable (black switched hot, white neutral) and light connects to new cable (black switched hot, white neutral)
  4. Anywhere you find grounds, they all get connected together.

Most important: Do not do ANYTHING with the 3-way switch. In addition to 3-way switches being somewhat confusing (and easy to mess up if you are new to them), if the 3-way is on a different circuit then you definitely can't mix things together.

  • This is great, thank you very much. I think I am following everything, and I'll work on this as soon as I'm off work. One other question: the cable I ran through the wall, is just in the wall coming down about 3 feet from the light's box to the switch's box. Is that fine, or does it need to be in some kind of conduit somehow as the other responder implied? – Allen S Nov 5 '18 at 19:09
  • As far as when Romex is good enough vs. when you have to go to conduit or provide other protection for the cable, I don't know. – manassehkatz Nov 5 '18 at 19:12
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    Thanks a lot! I followed this and was able to get everything up and running. – Allen S Nov 6 '18 at 13:44
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I would get a double switch on a single yoke then put the fan on 1 and the security light on the second. A box extender will allow you to put that romex in a conduit sleeve as it needs to be protected and leaving the existing 3ways will keep you from being confused on the wiring.

  • Excellent, that looks like my option 2--I'll go with that. I've edited my post above to reflect that, with the steps to wire it. Do my steps sound correct as far as the wiring (see above)? It sounds like I need to put the new Romex in a conduit sleeve. I haven't worked with box extenders before. It looks like these will bring the box flush with the wall without replacing the box, but I'm not seeing what steps would be taken to get the new Romex cable in a conduit sleeve or how the box extender helps with that. Would you be able to elaborate on that part? – Allen S Nov 5 '18 at 15:43

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