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Re: [APD] Canopy Cooling



You have to consider the output of the fan. Generally, the
smaller the fan, the faster it needs to spin to produce a
given airflow. Higher rpms mean more noise. Other things,
like bearing quality also affect the amount of noise a fan
produces, but speed is the most important factor, ime.
Usually, for any given fan, you will read a manufacturer's
boast that it is very quiet or that very powerful. Very
rarely will you see both boasts side by side for the same
model, since one is trade-off for the other.

It's not hard to make a quiet fan regardless of the size --
if it spins slowly enough, it will be virtually noiseless.
The important thing is to find the desired airflow and then
find a fan rated for that airflow and with a low rated
noise level. But beware, the standards for the published
specs are apparently rather loose. some fans that are rated
extraordinarily quiet for a given airflow are "relabeled"
fans that have much less optimistic ratings when sold by
other vendors.

Since it is the tips of the blades of a tubeaxial fan that
move most of the air, the diameter makes a big diff. A 4"
fan is not 33% larger than a 3" fan, it's something like
about 80% as large in terms of effective area. So a 4" fan
can spin about a half as fast as 3" fan to move the same
amount if air (other things being equal).

Some very good fan makers, imo, are EBM-Pabst & Panasonic
(Panaflo) -- ADDA and Bi-sonic are pretty good too.

You can check out a lot of diff fans, along with their
manufacturer-stated specs at mouser.com

http://www.mouser.com/?Ne=101&handler=data.listcategory&N=352

With the free Adobe Reader installed, you can view the
Mouser catalogue pages and make a reasonably well-informed
decision.

If you are interested in low voltage fans (wall warts are
cheap these days), you can find lots of good and bad info
from the computer community. There's some good info here:

http://www.silentpcreview.com/article63-page2.html

I wouldn't spend extra money for a fan that has a thermal
speed controller unless I had good reason to expect widely
varying temps for the application. Hood temps are
reasonably stable and a single speed fan is, imo, a good
choice.

Good luck, good fun,
Scott H.

--- Jerry Baker <jerry at bakerweb_biz> wrote:

> I see that the IceCap fans are horribly expensive at some
> $45, and loud 
> at 47.8dBA. I can put together a 35.5dBA fan and a 12VDC
> transformer for 
> about $13. True that the IceCap is variable speed, but
> the whole point 
> of variable speed is to be quiet. When the fan I'm
> talking about is 
> 12dBA less than the IceCap (less than half loud as
> perceived by the 
> ear), I don't see where the IceCap has an advantage. Is
> there something 
> critical I am missing, or is this another case of the
> aquarium hobbyist 
> being gouged?
> 
> -- 
> Jerry Baker
> _______________________________________________
> Aquatic-Plants mailing list
> Aquatic-Plants at actwin_com
> http://www.actwin.com/mailman/listinfo/aquatic-plants
> 


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