Bathroom exhaust fan turn on with light or independent switch

Question

I have two toggle switches, one for the bathroom light and one for the exhaust fan to operate independantly. Each has it's own 14-2 wire run to it from the switch. I want the fan to come on always with the light (which it does not now) but also keep the ability to turn on the fan and let it run longer with the lights off (use it independantly). Is there some way to wire this or use 3-way switches to accomplish it as the kids do not always turn on the fan when showering...

Answer 1

Install a humidity sensor fan control, like this one from Leviton. It will automatically turn on the fan, when it senses excess humidity in the room.

humidity sensor fan control http://www.homedepot.com/catalog/productImages/300/43/43ea781d-e83f-41d3-98c2-90fec341f3c6_300.jpg

You should be able to find them from other manufacturers as well, this was simply the first example I found when searching.

Answer 2

To actually do what you asked, rather than push a different solution...

You can't simply tie the two switches together, or the light will come on with the fan (as well as the fan coming on with the light.)

While my default in this sort of situation is to reach for a relay, there is a simpler solution for the specific case you ask for.

Replace the light switch with a DUAL-POLE (or double-pole) switch (not a 3 or 4 way.) That's one switch with two independent single pole switches operated in tandem by one handle. Wire one side to the light, wire the other side to the fan. The fan switch and the fan side of the dual pole light/fan switch can be tied together, and will not cause the light to come on when only the fan switch is on, since the two sides of a dual pole switch are independent of each other.

They are very common in "not a lightswitch" format but findable in lightswitch format, usually with the intent of switching 240V loads, but you don't have to use them that way (and would not be in this case.)

Answer 3

Double-pole solution (Ecnerwal's answer):

light   fan
switch  switch  operation
------  ------  ------------------
off     off     dark and quiet
off     on      fan on
on      off     light and fan both on
on      on      light and fan both on

With this design, the FAN switch is usually off and most bathroom users flip the LIGHT switch when entering and leaving.

PRO: Operation is very natural. When you have the fan running independently and someone uses the bathroom, they will habitually flip the LIGHT switch when leaving, and your fan will keep running.

CON: You must find and purchase a double-pole switch.

Single-pole solution (for the genuine cheapskate):

light   fan
switch  switch  operation
------  ------  ------------------
off     off     dark and quiet
off     on      fan on
on      off     dark and quiet
on      on      light and fan both on

With this design, the LIGHT switch is usually left on and most bathroom users flip the FAN switch when entering and leaving.

PRO: Only a single-pole switch is needed, which you already have.

CON: Operation may confuse kids. Your leaving the fan run independently will not survive the kids next visit to the bathroom, because when entering they will habitually flip the FAN switch but the light won't come on. They will then mess with the switches until the light is on (with the fan). Then, when leaving, they will habitually and thoughtlessly flip the FAN switch, turning everything off.