I installed the Comfort Air fan today.
At first I was disappointed with some noise coming from the motor but after 4 hours of running in both directions the noise has subsided considerably. I expect after additional running things should be fine.
The fan makes little noise until running from medium to high speeds when the blades to beging to shred the air. At lower speeds the air movement is substantial and quiet.
Installation notes:
--The flashing on the vent is larger than the original vent. The predrilled screw holes miss the aluminum square tubing roof frame on two sides. Locating the screws 3/8" in will fixed this problem. Check this out before putting down caulk. Things get very messy.
--I used self leveling lap compound to seal the flashing and fill the unused holes.
--Be careful not to over tighten the screws. Snug is good enough. It is easy to strip the hole in the frame especially with a screw gun. I used the same type of screw that was used in the original installation.
--Inside was a different problem. The roof is 1/2" too thin for the fan unit to trim out without a filler. The simplest way may be to use a foam spacer to fill the gap. The original inside trim may be reused.
--The vent was prewired. There was room to install a blade type inline fuse holder in the gap between the the roof frame and the fan housing. The fuse will be accessable when the trim is removed. No drilling of the fan housing was necessary. The black wire is the ground wire. I would still check the polarity of the wire to prevent damage to the fan.
--Removing the old vent was the usual messy project. I used paint thinner to help in the removal of the old caulk and clean up of tools.
I'm satisfied that the fan is worth the time and money. Now I need to load up and hit the road.
BTW .. thanks for the help everyone.