I don't believe this issue is unique, but I'm having trouble finding a solution.

I have a small two piece bathroom existing. It has lighting and an existing in ceiling exhaust fan (which is noisy).

I am adding a shower in the adjoining room and rather than install another ceiling fan, have purchased a 4" inline fan that I will connect to the existing ductwork and run a new line to the shower room. I will be adding another light to the second room, now here is my issue:

I'd like to use the two light circuits to control the fan. I.e. when either or both lights are on. Every drawing I've tried end up with all devices effectively in parallel, which means all would be on when either or both switches are thrown.

I can't access the first circuits anywhere other than at the original fan and all wire is 14/2.

I thought a relay may be an option, using the original fan line as one of the controls, however haven't found any that would fit my application.

Any ideas would be appreciated

Tyrant 53:

You can do this by using a 2-pole switch in each bathroom. On one side of the switch in each bathroom you connect the light for that room. On the other side of the switches you connect the fan, with the switches in parallel. You can pick up the power from the existing fan location or another switch. You will need to get a neutral to the fan motor, and get the fan's switch legs to each bathroom.

I hope this helps. Let me know if you need more assistance.

Thanks for the simple solution Dpfiling! Since the outputs of the fan sides of the switches is the same electrical point, I can run a single 14/2 over to the fan... great solution.

I would assume this would only be safe if both circuits are on the same breaker?

Yes, it's a dedicated 20A line that I was using for a freezer that was in the second room. I'll split the common black across the two switches with some three conductor lines then run the lights and fan from the new switch box. Just need to mark the additional circuit details on the appropriate breaker.

I think I would just put the fans on their own switches and use 3-ways to control them. I hate the added noise of a fan running when it isn't needed which happens when the fans are controlled together with the lights.

You can't hear the inline fan; it's in the furnace room, and I want the fan on when either or both lights are on. These are inside rooms with no other means of ventilation.