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Re: [APD] Building a new hood

It ain't the meat it's the motion. It ain't thenumber of fans but the airflow, which can mean ssefveral small  or a few large, or one fast or many slow fans.  The noise will mostly be a factor of the amount or air moved, the velocitiy of the air, and the pressure differentials created.  Big slow fans are the quiest, cubic foot for cubif foot.
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----- Original Message ----
From: Bill Wichers <billw at waveform_net>
To: aquatic-plants at actwin_com
Sent: Monday, June 26, 2006 12:51:19 PM
Subject: Re: [APD] Building a new hood

>Putting one fan blowing in and one blowing out is the equivalent of
>stacking one fan
>on the other in terms of airflow. Stacking fans like that does increase the
>airflow--it's like stacking two water pumps in series; the flow doesn't

Actually, the flow can increase with two fans in "series" this way, but
only if the airflow from the fans is limited by back pressure. Normally
this wouldn't be the case since you should have lots of reasonably
unobstructed space in a light hood for air to move around.

>2) to market to overclockers that think more or something
>is always better.

I think mostly this is the reason for doubled-up fans in computers :-)
There're a lot of products out there for the performance-minded computer
hobbiest that don't actually do anything. Have you ever seen a power
supply review that used an *oscilloscope* for example (the only way to
really make meaningful measurements on switching power supplies)? Sigh...

>I've found that vented hoods, along the design of those that AHsupply.com
>sells do as well passively, by convection, as enclosed hoods with a
single >fan. I'd try a vented hood first, and add a fan if mere
convection proves >inadequate in your situation. Passively cooled hoods
are much quieter ;-)

I find a single quite fan (I've had good luck with NMB and Panaflow fans
being quiet), plowing lengthwise along the bulbs usually makes for a
enough airflow to keep temperatures manageable. I've had trouble with
convection not quite being able to do it. I doubt there'd be need for much
more than one or two small fans even on a fairly large hood unless there
were lots of MH lights.


Waveform Technology
Systems Engineer

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