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From: johnboyd@LOGDIS1.OC.AFLC.AF.MIL (John Boyd;CRENP)
Newsgroups: comp.sys.misc
Subject: Fan direction
Message-ID: <9012211500.AA06021@logdis1.oc.aflc.af.mil>
Date: 20 Dec 90 12:30:16 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 41

In msg:<1990Dec17.015530.17483@bilver.uucp>(Bill Vermillion) quoting:
>In article <6606@suned1.Nswses.Navy.MIL> zaft@nswses.navy.mil (Gordon C Zaft) writes:
>>In article <9012130133.AA24147@polar.bowdoin.edu> poulin@POLAR.BOWDOIN.EDU (Jeff Poulin) writes:
>>>Here's a dumb little question that I'm not sure of the answer.  Which
>>>direction should the fan be blowing: into the power supply or out of it?
>>>My computer came configured with the fan blowing in (presumably to keep
>>>the stuff in the power supply cool), but I noticed the cards become quite
>>>warm and one of the hard drives starts sounding like a car going 40mph in
>>>first gear if I leave the computer on for more than 12 hours.  Otherwise
>>
>>	Fans on power supplies should never blow into the cabinet, always
>>OUT.  The idea is to draw cool air into the cabinet, across the cards,
>>through the power supply and out.

>Just because IBM screwed up the original design there is no reason the
>world has to follow.  Fans should always blow IN to a system.  And ideally
>they should have a replaceable filter.

>The problem with blowing out is that the air comes in at ALL entrances to
>the system.  Venturi effects create higher velocities nearer smaller
>openings and you such dirt into such thinks as chip sockets, and worst of
>all THROUGH floppy drives.  That's a killer. 

I had argued this point back and forth with myself for a long time, (no
snickering B-) ) until I realized that here where I work, the electronic
assembly 'clean rooms' are ALL positive pressure rooms; i.e. a 
fan/air conditioner blows air from inside the room - OUT - for all the 
reasons Mr Vermillion sited!  Before I changed the fan direction in my
computer, I had to regularly vacuum my floppy drives and the boards.

On the comment regarding the replaceable filter, I whole heartedly agree!
I've gotten tired of 'lint picking' mine.  I hope that this issue has been
settled to everyone's satisfaction.  Happy Holidays; whatever they may be.

               johnboyd@ocdis01.af.mil            
============================================================================
 "Preserve your memories...
     The rest ends up in a garage sale" - Ferris Beuller

  Disclaimer - If I express an opinion, the Air Force will deny I know
               what I'm talking about.