New Bathroom Exhaust Fan

[FredM]

My bathroom presently has one wall switch which controls one wall mounted light fixture located over the lav. The existing switch is a middle-of-the-run switch which has two cables in the box. The blacks are connected to the switch and the whites are connected together. I want to install an exhaust fan on a separate switch in the bathroom. I am hoping to replace the single wall switch box with a double switch box. One switch will continue to control the existing light and one switch will control the new fan. I think I can get power for the fan switch by tapping into the supply line which presently feeds the existing light switch before it reaches the light switch by connecting blacks together and whites together. I'd like to know if what I am proposing is the right way to go, and, if it is, how can I determine which of the two cables in the present switch box is the power supply line I should tap into. Any help would be appreciated.

[Wgoodrich]

I believe you can do as your wish without changing the existing switch box at all. Just use what is called a piggy back switch that is two switches in a device that is the same size as your old single switch device is.

Install a new 12 or 14/2wGrnd cable from your new fan down the wall into that existing switch box. Then wire nut the new white wire of the fan to the other two white wires wire nutted together now.

Then connect one of the two existing black wires to the side of that piggy back switch that has a jumper connecting the two screws. Then connect the second existing wire to the opposite side to one of those two screws on that opposite side of that piggy back switch. Then connect that new black wire to the remaining single screw on that same side of the piggy back switch.

Turn your power back on and test to see if the fan and light switch on and off separately.

If the work fine you got it made.

If either the fan or light does not turn on and off with those switches on that on device then exchange where the two eixsting black wires are connected reversing the two existing wires. Then test again.

Let us know how you come out.

Good Luck

Wg

[Wgoodrich]

COPIED REPLY FROM A DIFFERENT POST TO KEEP SAME SUBJECT ON SAME POST.

COPIED REPLY

Thanks for the advice. I had never heard of that type of switch. It sounds like it would be a nice practical solution to my problem. I'll have a look to see if I can find one at the local supplier. In the meantime, if I was under instructions to install two separate switches for decorative reasons, would I be okay to proceed with the re-wiring as per my original posting.

[Wgoodrich]

You will most likely have some trouble removing that old box and installing a double gang box without having to patch your wall finished surface due to damage to the wall and getting the new remodle box to mount securely.

You might consider cutting in a remodle single gang box in the same stud space but separate from the old box by at least 8" or so. This would allow you to install the second box without damaging your finished wall surface. Then fish a cable between the two boxes taking your black, white, and bare power conductors of the existing box making power in your new box.

Your choice. name your own poison in this depending on how much work you want to do.

You have two cables entering that existing box. One cable will be your power in and the second cable will be your switch leg to the light.

Fish your new cable into the new box or added box.

If you add on and make a double gang box then you would just wire nut the white to the other existing whites now wire nutted.
Then you would install two short black jumpers from the hot black existing wire wire nutting the two pigtails to that black power conductor. You have a 50/50 chance that can be corrected later as to which black wire is the existing power wire. Then connect one black pigtail to the existing switch then the second pigtail to the new switch connecting the black wire of the new fan cable to the second switch.

If you install the new separated box then just find the power in cable in the existing box and fish a cable to the second new box. This will put power into the second box. wire nut the two white wires in the new box and install the two black wires to the new switch.

Let us know how you come out

Good Luck

Wg