Reducing 6" to 4" on exhaust duct
I just got a NuTone QTXEN110 and it is much larger than the old fan and also uses a 6" exhaust. The old fan is connected to a 4" exhaust duct. Is it OK to use a reducer and go from 6" to 4" or would that be bad for the fan? The bathroom is 45sqft with 8' ceilings so I believe the 110cfm exhaust is more than large enough, therefore, if it did not function to capacity, I dont see it as a total issue, although I dont want this to stress the fan causing issues. Although, I will leave it to the folks with experience to get the right solution.
Also, the exhaust duct appears to just run to the eave/ridge/(I dont know the exact term) There is no actual cap at the end as far as I can tell, so I believe it is just venting out the ridge vents. Is this OK? It is in my attic and just want to confirm that the configuration and setup is OK and done in such a manor that will lead to moisture being pumped into the attic as opposed to outside.