Replacing bath vent fan - No overhead access

[CarlH]

I'm about to replace the ventilation fan in small half bath and the only thing that gives me pause is the fact that I will have no overhead access. I am looking at installing a Panasonic since it can mounted from under to a header. There is a flange on the fan housing for this type of mount. As long as there is enough slack in the existing wiring and I use a flexible duct to connect the van to the existing duct I think I might be able to pull this off. Even though there is no overhead access, the hole will be 10" x 10" with about +20" of space between the drywall and the floor above. This should give me enough space to modify the existing header and duct. If push comes to shove, I can cut out some more of the drywall for access since the room is going to be repainted when I am all done.
Install instructions for the fan:
http://www.panasonic.com/consumer_el...fs/05VK1-E.pdf

There is one alternative, and that is Broan has a retrofit kit that is made for this type of install where you hook up the duct to a frame, prior to putting the housing in place.
http://broan.com/display/router.asp?ProductID=100748
The problem with this fan is that it is a bit of overkill for such a small bathroom and it is a noisier than the Panasonic. One of the main reasons why I am replacing the fan is because the existing fan so noisy and close to the family room. The other reason is that I am not sure it is up to current safety standards.
http://www.electrical-forensics.com/...hroomFans.html

I am open to any thoughts or suggestions before I take the plunge.

[jadnashua]

I'd stick with the Panasonic and cut a little drywall if required, to get a good seal before buttoning it back up.

[CarlH]

Ran into a bit of a snag. I did not completely pull the old fan prior to ordering the new fan. I just pulled back one of the edges and peeked through the gap with a flashlight. If I were to have pulled back a different edge or pulled the existing fan housing I would have found a couple of things running directly above the fan.
I pulled the old fan after receiving the new fan and this is what I found.

I could have worked around the drain line by shifting the fan over a bit and fix the gap in the drywall. The real problem is the HVAC duct.

Low profile Panasonic fan is now on order...

[CarlH]

The deed is done. While I was waiting for the new fan to arrive I enlarged the hole, added framing below the drain line, and patched the drywall in the gap that was left after shifting the hole over to clear the drain line. The Panasonic fans have a removable "adapter plate" which is what is attached to the electrical wiring and duct. In this type of install, it can be put in place before sliding in the fan housing. Here is a picture of the adapter plate hanging from the electrical:

Once the electrical was wired, the adapter plate was put in place and the duct attached and secured to the adapter plate. I slid the housing in place, which pretty much snaps into the housing and put screws in the housing flange to secure the housing to the framing. In my case, the framing was in an "L" shape. Here is the fan in place without the grill installed:

Ah, so much quieter now http://www.terrylove.com/forums/imag...lies/smile.gif