"Bob" wrote in message
oups.com...
I installed a Panasonic FV11VQ3 110 CFM bathroom vent fan in a small
bathroom. Works like a champ. No steam on the mirror and within minutes
(with door or window open) majority of steam is cleared.

My one problem is this; I get standing water inside the fan. I wrapped
the duct work and unit with insulation; still condensation turning into
small pool of water. I check for leaks in the roof cap... none. I
switch the duct work from the stiff flexible/expanding type to the
smooth normal duct work; still get pool of water.

I researched google groups and some people recommended running the fan
before starting the shower to warm it up. I don't think this is the
issue because I did some "condensation" tests in the middle of the
afternoon and it was not cold in the attic. I will still try this
though. Also another person recommended having a door slightly open or
a window. I will do this as well.

Would anyone have any other suggestions in case this does not work? One
thing I will mention the instructions ask for 2-3 feet of horizontal
pipe before going to the roof cap and I have 1 foot due to space
issues. I mentioned this to some people with building experience and
said this should not cause a problem.

Thank in advance.


It's clear you discovered the reason for the recommendation of having a
short horizontal run. The run should be close to the fan not close to the
vent cap.

Just because the air in the attic in the afternoon is warm, dosen't
necessarily mean the vent pipe and anything it is resting on/against is also
warm. All you need is to have something below the dew point to get
condensation. Since the dew point is relative to the RH, a steamy room
condenses on fairly warm surfaces. At near 100% RH, water will condensce
on just about anything.

Even with a 150W heat lamp in the vent (my setup) I still get condensation
from overflow from my (new) steam room. I may need to move the vent pipe to
mitigate also but I think it does have a horizontal section near the vent
already. I need to look more closely to see how much is condenscing in the
fan housing itself before the pipe.

I may try to put a dip in the vent pipe (using metal flex pipe) to see if I
can make some sort of P trap and poke a hole for drainage to a pan. I don't
expect more than a few ounces per day so it should evaporate without any
further draining (never reaches freezing at my house in CA). Still thinking
of that solution as it could make for a bacterial breeding ground if the
water does not evaporate daily.

Another solution I am considering is to snake a short piece of wire in the
vent to encourage the condensate to drain where I want it (not dripping from
the middle of the heat lamp). I can probably collect it into a sponge which
will be dried by the adjascent heat lamp. ( I will try this first as it
does not require access to the attic)