"djay" wrote in message
news:Y4DCj.341$CO3.135@trnddc04...
"John Grabowski" wrote in message
...
"djay" wrote in message
news:gkvCj.4$CO3.1@trnddc04...
"John Grabowski" wrote in message
...
"djay" wrote in message
news:m%nCj.8985$HA3.8232@trnddc02...
I'm installing a Panasonic bathroom exhaust fan - approx fan box size
is 12 X 12 inches and it's replacing a POS nutone NOISE maker that has
an opening about 8 X 10. Panasonic has an approx 1" lip on the
underside that would normally screw right to ceiling joists for new
construction (would need to add a 2X4 to make the 12" span instead of
the normal 16". Anyway, I'm in a quandary as to how to correctly
install this fan.
It came with "joist spanners" that seem flimsy and possibly difficult
to install. Alternatively it has mounting screw holes in the lip. I
want to just cut out the old fan and expand the hole (I have been up
in the attic and inspected. the existing joist/electrical etc before
doing so). One side of the existing fan is already attached to a
ceiling joist. I'd still use this point as a starting point and expand
the drywall hole away from that existing joist accordingly to fit the
new Panisonic box. My goal is to just cut the hole, install an new
spanner joist to snug up to the other side of the box (would cross
between the headers of the two existing walls) and just use some
longer pan head wood screws to screw up through the "lip" with
mounting holes right through the existing drywall ceiling and into the
old existing joist and the newly install joist.
So in my example above after the new hole is cut into the drywall fit
the larger fan, and new joist installed (parallel to the existing
joist but for the other side of the fan hole). I'd push the new fan
up through this hole until the mounting lip rested on the ceiling.
I'd put screws in through this lip, up into the drywall and into the
joist above. Then of course seal in the fan from above and replace
the 3" exhaust duct with 4". Does that sound doable? I guess
normally this lip would be between the ceiling drywall and joist but I
can't see a downside to installing it directly onto the existing
drywall.
That's usually how I do it, but without adding any additional wood
bracing. On the side of the fan housing that will be against the
existing joist I drill a screw hole about three quarters up near each
corner. I use them to screw the fan housing to the side of the joist.
I also screw that bottom lip in from underneath. That gets the housing
up solid enough to where you almost don't need the spanning brace, but
I use it anyway.
The joist spanners that came with the Panasonic fan are quite solid.
You will only need to install one. I usually attach the U bracket
loosely on the side that does not have the duct connector. That makes
it easier to slide the joist spanner in while up in the attic. You can
snug up the screws after the spanner is in place.
When cutting the hole in the ceiling, make a notch for the U bracket.
Also on the side that the duct connector will attach the hole must be
almost the full size of the lip so that the duct connector can seat
properly. The finish trim is big enough to cover the larger opening.
Don't forget to use the thumb screw to secure the duct connector to the
housing. There is a little hole near the internal electrical plug that
it goes into.
I recommend that you use knee pads and a dust mask.
That's good advice and is pretty much exactly what I was going to do. I
like the idea of using the screws through the side of the housing... I
may do that if installing the extra wood brace becomes....
"challenging" 
As the other poster mentioned, I put the plastic fan cover in place and
it looks like it will snug up to the ceiling without a gap. Has that
been your experience too?
I've never had a problem with the plastic trim. It is a little deep to
accommodate the screws that you install from underneath. Make sure that
the extra wood brace does not interfere with the duct connector.
It's all in and operational. Fairly easy installation and would have gone
twice as quick had I had someone helping from underneath! I saw that the
duct flange was going to be impeaded by the joist so I just loosly screwed
in the fan through the side to hold it in place, went above and installed
the second joist and then went back down to screw the box in place.
Worked GREAT!
Now my bathroom is QUIET!
Thanks for the help!
Djay
Now instead of hearing fan noise you will be trying to listen to see if it
is actually working. :-) Congratulations on the install.