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Posted by on February 6, 2007, 8:33 am
On Feb 6, 4:32 am, you...@comcast.net wrote:
> On Feb 5, 12:53 pm, you...@comcast.net wrote:
>
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> > > you...@comcast.net wrote:
>
> > > >>>The one thing I did which made it not leak at all, was to leave a
> > > >>>space heater on while taking a shower....thefandid operate much
> > > >>>better not even letting thebathroommirror to fog up. So in this case
> > > >>>your theory proves correct except it wasn't just any air....it was
> > > >>>WARM air I was adding into thebathroom. Any thoughts about this as
> > > >>>well?
>
> > > >>>thanks so much for the prompt response
>
> > > >>Pondering your duct sizing, could there be a mismatch? 3 x 14's are
> > > >>42" sq,, 4 x 10's are 40"sq., 7" round 38.5" sq., Many bath fans use
> > > >>4" round outlets (12.6 sq.") which prompted the question. Might be
> > > >>your moist exhaust air is meandering down the ductwork and being over-
> > > >>cooled on the trip.This suggests a) increasing the velocity with
> > > >>smaller ducting, b) using fiberglass or insulated ductwork or, c) all
> > > >>of the above and paying atterntion to makeup air, of course. HTH
>
> > > >>Joe
>
> > > > Nope thisfanuses a 3" duct and says so in the manual. its a
> > > > panasonic model FV-08VS1,,,,and for some reason they don't have it on
> > > > their website. Since it is a smallerfan(fits in a 2 x4 joist instead
> > > > of a 2x6 joist), that is the reason for the smaller ducting. The
> > > > makeup air does not seem to help, as leaving thebathroomdoor wide
> > > > open still results in a good amount ofcondensation. Thecondensation
> > > > is definitely coming from thefanhousing itself as the duct slopes
> > > > downward AWAY fromfanand has fiberglass insulation wrapped around
> > > > the ducting. Are you saying that by using even smaller ducting, that
> > > > it will increase the overall velocity?
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> > > > I should also mention that we had the same problem using a nutone
> > > > model 695 which had 70cfm.
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> > > > Perhaps we just need a stronger vent like 110 cfm?
>
> > > It would appear that since the duct slopes away from thefan, thefan
> > > housing is cold enough to condense the moist air right away. If you
> > > cannot insulate around it you may just have to deal with it.
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> > > BTW, I noticed mybathroomfogs much less with the door closed than
> > > open. It is my thought that the easily available [dry] air from the
> > > bedroom gets to thefanbefore all the air in thebathroom. Closing the
> > > door makes it draw from the room more, perhaps.- Hide quoted text -
>
> > > - Show quoted text -
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> > I can try insulating around it, but am fearful that the insulation
> > will just absorb moisture leading to mold.
> > I also notice that thebathroomfogs a tad less with the door and
> > window closed, but still fogs and the fan still condensates big time(a
> > few tablespoons actually).
>
> > I am pulling my hair out trying to find an answer to this tough puzzle.-
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> > - Show quoted text -
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> do you mean my duct run is too long?....i'm not sure where you get the
> 14" measurement from.
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> The 3 " duct size fits the opening perfectly on the housing.- Hide quoted text
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> - Show quoted text -
I don;t see why you;'re reluctant to insulate around the fan
housing. The exhaust pipe slopes down, so we know the water isn't
condensing there and running back. It has to be condensing inside the
fan. Putting insulation around the fan will keep the fan from
getting cold. Any moisture should be reduced and it should be
contained on the inside of the fan housing and will not get the
insulation wet. I would check any electrical rating concerns related
to how close insulation can be to the fan housing.
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