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I put in double gang box, second switch, ran second cable from light switch to ceiling. So there are two identical cables from switch to fixture. The existing switch had power in to it. So i need to connect the two switches and at the ceiling use one black for light and presumably black from second cable for fan. How do i connect the two switches?

  • Can you re-run the cabling? That second cable's rather a no-no with most light/fan combos... – ThreePhaseEel Jul 22 '18 at 22:36
  • The fan and light have separate hot wires. Do they also have separate neutrals? – Harper Jul 22 '18 at 23:56
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    This fan speed control / full range dimmer is the best choice for the not enough wires situation. It’s two part, one part (not pictured) installs in the fan canopy. The pictured part replaces the switch. It’s actually marketed under half a dozen brand names (note the coloring of the light button to identify) but the Westinghouse version seems to be the least expensive at the moment. – Tyson Jul 23 '18 at 0:25
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If the line power enters in the switch box, you will have a single (probab black) line hot that you want to connect to one side of both switches. The most straightforward way is to make two pigtails (short ~6 inch pieces of wire) (black) and connect them in a wire nut with the line hot (so three black wires in the one nut). One pigtail is connected to one switch and one to the other.

You could also use a single pigtail and pass it from one switch to the other. This means that this single pigtail would be stripped for an inch in its middle and a loop made which goes around the connection screw for one switch and the same piece of wire carried on to the other switch. This saves on space in the box, if that is a problem. (You could even do this to the line hot and have no pigtail at all, but I don't like to do that because I like to preserve insulated length on the incoming line hot.)

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    He's got a fairly serious Code vio he needs to rectify before he buttons this back up....(300.3(B)/310.10(H) stuff with paralled neutrals) – ThreePhaseEel Jul 22 '18 at 22:36
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    I wasnt able to remove existing cable, pinned down, attic restricted access so i ran a second cable intending to use only one wire. I guess u should have pulled a 14/3 and made existing cable redundant? So using only one of the wires (black) from second cable is a code violation? – Newroof Jul 22 '18 at 22:57
  • Hummm . . . In formulating my answer, I missed the parallel neutrals. Yes you should have pulled a 14/3. Interesting. Now I wonder about our tract house bathrooms with 1970 vintage combined unit of light, exhaust fan, and heat lamp with fan blowing on it. This should be a 12/4 or 14/4. Does your bathroom have a separate receptacle on a dedicated circuit, and is it 20 A? Our two bathrooms are on the same 15 A breaker (now a 15 A GFCI breaker), one receptacle and one lights/fans unit in each! My wife uses a high power hair dryer and we never get breaker trips?! – Jim Stewart Jul 22 '18 at 23:23
  • @newroof you can't do that, you can't run a cable and expect to use only one wire. Every wire in a circuit branch must be in the same cable. – Harper Jul 22 '18 at 23:55
  • This is high vault living room light/fan fixture, 15A. I will use spare cable to pull 12/3 and make original wiring redundant and comply with code! – Newroof Jul 23 '18 at 0:43

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