If its on a motion sensor, what does it matter how loud it is unless you're depending on the fan to drown out in user" noises

Correct. I've read in many places where bathroom fans are discussed that you should put a fan with some volume in the "public" restroom for precisely that reason. Especially for me where the powder room is central to the kitchen, living room and den. The rooms are like spokes fanning from the powder room.

You know how some people are so sensitive about this they'll turn the faucet on while taking care of business. There can also be a gross factor to people within earshot depending on what sounds emanate from there. Gaseous sounds. Plopping. Grunting. Splashing... Not something you want to hear while dining. And maybe not something you want others to hear if you're the emanater ;-)

Uhhhhhhhhhhhhh, why do you need a motion sensor at all ???

Just have the sparky make the fan come on with the light and poof - no need to worry about whether the sensor is working, or sensitive enough or to high or beam spread is wide enough ,or ........

Fan wired to light is an excellent idea

My thought was that if it is on a motion sensor then it can be timed to run for a few more minutes after the person leaves to make sure the air is cleared. If the fan is tied to the lights the fan goes off right away.

If there is a way to have the fan keep running for a bit after the lights are turned off then yes, I would prefer that solution.

You could have both on a vacancy sensor.

I don't think vacancy sensor will accomplish what I want. As I understand it, a vacancy sensor will turn light/fan off *IF* the person forgets to turn off the switch. Then after a preset time it will turn it off automatically if there is nobody in the bathroom.

However, if the person leaving remembers to turn off the light (almost everyone turns off the light when exiting) then both will go off immediately with no delay for the fan.

I want the fan to come on when the user enters. The fan can come on by motion detection or when the light switch is turned on. But I want the fan to keep running after the user exits even if they turn the light off. Is there a way to wire the fan into the light switch and make this happen?

Psycho - you're makin this waaaaaaay to complicated .

Your friends must really stink to be this concerned about all this fan gizmo stuff.

It's simply a switch controlling a load , be it a light or five or a fan , or a fridge compressor . That switch can be a single throw, a mechanical timer, digital timer, an occupancy sensor, a vacancy sensor , a remote controlled relay, or........

The simplest and most reliable way to accomplish what you want is to put a digital timer switch on the fan leg . Min. time of ten minutes ought to be enough to satisfy you . Occ / vac sensors can be finicky to dial in for what you want . Your users turn the light on, and press the fan button and it 'll turn itself off five minutes after they leave .

YOU may want to look into a toilet with built in odor control for your situation .

Motion sensors used in offices run for 15 minutes before turning off. Not so great when you're seated at your desk for a few hours. Good for bathrooms though.

I can't help with your other questions but here is an answer to #4

Google is your friend! delay switch for light and fan

Here is another link. It seems as if you can forgo the motion sensor using this type of set up and choose whatever fan you prefer. I had a house with a broan once and it was sufficiently loud, but not sure it was sufficiently efficient. I mean it sounded like it was sucking air, but not sure it did.

Air King

ETA. I missed that you mentioned the Air King in your op, but the one I linked is a delay shut-off timer combined with the light switch, not motion activated.

One more idea =)

http://www.themarysue.com/toilet-sound-blocker/

uscpsycho, I'm glad that works for your situation - it may not be the solution you imagined, but you just never know what's out there. I think I remember reading someplace about a system that turned on music when the light switch went on, to muffle any sounds. A little overkill for me; I'm not so sure why we have such awkward sensibilities about such natural things, but most of us seem to! My main bath is close to the living area and another thing that I think helps is a solid core door, along with a good size area rug in front of the sink.

After talking to my electrician and lighting designer, that timed switch actually won't work for me. I'm installing Lutron RadioRa lighting control and that switch would take whatever light it controls off my system.

It appears the solution is to just get the right size fan and put it on an independent motion sensor. That was always my assumption and I have no problem with it. It would have been nice to find a 50 CFM 3-4 sone fan with a built in motion sensor but that animal doesn't seem to exist.

Hopefully that timed switch will help someone else when they come across this thread.

Olychick - Yes, definitely using solid core doors for the bathrooms. Not really a fan of bathrooms rugs though. And automatic music? Oh my! That sounds crazy.

This is one of those things that, when everything is done, you don't think about much. But it's better to plan these detailed design elements while you can than look back and wish you had done it when you had the chance.