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Posted by # Fred # on December 26, 2006, 1:23 pm
>
> # Fred # wrote:
>> Wife purchased three of the quiet Broan QT080L bathroom exhaust fans with
>> light and night light. I tested it out on the kitchen table and it was
>> quiet
>> so then I proceeded with the installation in the downstairs 1/2 bathroom.
>> The bathroom is down to studs and subfloor with all insulation removed
>> for
>> remodel. The Broan has a 4" duct connection but the house has 3". Once
>> everything was connected, the fan wasn't all that quiet. The noise was
>> from
>> both fan vibration and wind. Its still more quiet than the old noisy fan
>> but I could hear the new fan from upstairs. The mounting is solid to
>> joist
>> per instruction and the connection to the 3" duct is tight. I suppose
>> once I
>> close up the ceiling and walls with insulation it would not be as bad.
>> Are
>> quiet fans really all that quite? Maybe should have purchased Panasonic
>> fans
>> instead - its the same price.
>
>
> I was unable to find the specs for the model you metntioned
>
> QT080L
Sorry, typo on my part: its QTR080L
>
> maybe a letter is missing from the model number?
>
> in any case..........one of the design features of the quieter fans is
> the use a a larger duct size.
>
> The quiet ones use a 4" duct & the really quiet ones use a 6"
> duct....to keep the air velocities & the back pressure on the fan low.
>
> By using the exisitng smaller duct you are negating some of the quiet
> fan's benefit.
>
> Addtioning most of the quiet fans have some sort of resiliant mounting
> system...does yours have that & is it working?
No.
The second floor is above this bathroom. The existing 3" duct runs along the
joists and punch out on one of the outside walls. The 3" duct has a 25' run
and its the flexible kind so more air restriction. There are blockings
between the joists and seems not possible to upgrade to 4" ducts without
tearing out the family room ceiling. Bathroom is small so I don't need a lot
of CFM - perhaps I could reduce the motor speed.
.....hard mounting allows
> more sound to be transmitted through the framing.
>
> cheers
> Bob
>
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