Wiring a Bathroom Exhaust Fan and Light

By Dave Rongey Summary: Electrical Wiring Question: Hello, I want to wire a bathroom exhaust fan to come on when the light over the shower is on to exhaust moisture, but also want to be able to operate the fan independently on another switch without the shower light on to exhaust odor.

How to Wire a Bathroom Exhaust Fan and Light

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Electrical Wiring Question:
Hello, I want to wire a bathroom exhaust fan to come on when the light over the shower is on to exhaust moisture, but also want to be able to operate the fan independently on another switch without the shower light on to exhaust odor.
I thought perhaps a 3 way switch for the fan/light combo would work if I wired the common leg to power the single switch for the fan when the 3 way if off (so that single switch would be have no power supply if the 3 way was on), but realized the power from the fan only switch when on would only be back fed to the light/fan connection illuminating the light again.
I guess I basically need to isolate the fan and light connection so when I power the fan switch the light won't go on. I assume a relay could be used, but not sure what type or where I would install it.
I have never used a 4 way switch and don't know the principles of how they work and didn't know if it has 2 outputs to power devices that may be split in the switch but power on together when in the on position? Short of buying one and experimenting I thought I'd ask someone who knows better!
Thanks Much Bob V.


From Dave:
Hi Bob - Great Electrical Repair Question!
Lets look it over:
You'll need either 2 separate switches or a stack switch that has the line jumper removed. Wire the First switch to turn on the Exhaust Fan AND send the power to the Second switch on the Line Side to be used for the Shower Light. The Shower Light will not function unless the Exhaust Fan is on, but the Exhaust Fan will work by itself. Let me know if this helps or if you need a wiring diagram.

 

From: Bob
Hi Dave,
I kept on scratching my head and came up with another possibility that seems like it would enable the fan and light to come on with one switch and the fan only on another so I won't have to rely on the fan to power the shower light.
Please let me know if this sounds legit so I won't burn the place down. Use a double pole switch to operate the fan and light. Connect power in to one bottom pole in and a jumper line to the other bottom pole in, connect one top pole out to the light and the other top pole out to the fan. This will turn on the light and fan with this one switch and keep them on separate poles.
Use a single pole switch for fan only, connect power in from same hot leg on same circuit as double pole power and connect power out to the double pole switch out that operates the fan. This way the single pole switch sends power to the same fan out as the double pole and operates the fan only as the light connection is broken when the double pole switch is either on or off.
This way is appears that there would not be a dead switch for the light when the fan switch is off using the other 2 single pole wiring route, although the fan switch will seem dead if the double pole is on as it would not do anything until the double pole is off.
Will this work?? Much thanks again Bob

From: Bob V.
Hi Dave, thanks again for your feedback. Sometimes I over think things, but this time it paid off! Yep I do much of my own electrical, as well as everything else under the sun, but I know my limits and when to ask or call in someone for backup . and yep we have all the current codes covered for updated GFCI's, hardwired smokes, etc.

After seeing way too many cracked outlets with singed connections and wires that have become loose to switches and outlets and the arching that has occurred, during unit turnovers I've been going through and updating all outlets to the nylon faced back wired outlets and to HD switches everywhere.

Seems like cheap price for peace of mind. I have been using Cooper devices as they seem well built and have many options available. I will certainly keep you in mind for future electrical quandaries, and I'm sure there will be some as just when you think you have seen and done it all, you find out that you haven't, as in my exhaust fan scenario! A series for landlords would be great info to have out there.

Current electrical code prohibits a non licensed electrician from doing just about anything electrical related in an apartment if the device doesn't simply unplug (in Maine anyway), but common sense prevails on what can be safely done.
Great forum for advice for novices and intermediates,
Many thanks.


From Dave:
Bob Yes - That will work as well - Great Thinking!
No, I don't believe you'll be burning the place down - sounds like you are the careful type, and that's good!
As a landlord just make sure there are GFI's where required and Smoke Detectors etc. That's another Series I need to create - one Just For Landlords.
If you have any suggestions or input please let me know. I really like working with the requests, as one may represent several who may never ask!
Thanks for sharing your thoughts!