I've heard of bathroom fans which have the blower at the top of the
duct, just under the roof rather than just above the bathroom
ceiling. And I heard a suggestion that they can be used to vent
multiple bathrooms with one blower. But I'm having trouble imagining
how that would be wired so it could be turned on in either of two
bathrooms. That's not a three-way switch.
Correct, it's two single pole switches in parallel. Install a junction box
in the attic with the feed in it. Run a two wire cable to the fan motor. Run
a two wire cable to each bathroom switch. Connect the neutral in the
junction box to the fans neutral. Connect the hot in the junction box to
both white wires going to the switches. Connect both black wires coming back
from the switches to the black that goes to the motor.
I think you wind up throwing out a lot of heat/cold unnecessarily with
this approach regardless of how it's wired. The blower will always
be pulling air out of all the bathrooms anytime one of them needs the
Personally, I think using quiet quality individual bath fans is the
This fan system was used on one of my jobs and I paid
particular attention to it because I had not seen one before.
The fan was not at the roof, but in the attic and fed three
bathrooms. The switch turned on both the fan and opened a
damper which only allowed air to be pulled from the room that
was switched on. The biggest problem was that it was so
quiet, unless you looked at the switch and noticed that it was
in the on position, there was nothing to tell you to turn it
off when you left the bathroom.
re: The biggest problem was that it was so quiet, unless you looked at
A timer or humidistat switch solves that problem. I installed timers
since the kids (and wife) would leave the fan on to finish clearing
their bathroom and then forget about it...and we're not talking about
fans that you can't hear!
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