My dust puzzle...

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S. Whitmore

I have two PCs that are about 2 or 3 feet away from each other. One
is on a desk, the other is on the floor between two desks. The cases
and fans are fairly different. The PC on the desk is used about 60%
as much as the one on the floor.

The case on the desk is consistently and significantly dustier than
the one on the floor. It's so dusty that dust quickly accumulates in
any/all holes in the case, so I'm ending up cleaning it much more
frequently than I'd like.

I wouldn't expect such a significant difference between the two, and I
would've thought the more heavily-used one on the floor would have
more dust. Is this just a matter of having more airflow through the
one on the desk? Does proximity to a monitor (CRT) make a significant
difference? Is it a case design issue?

Just some late-night curiosity... :-)
 
the low-grade said:
I have two PCs that are about 2 or 3 feet away from each other. One
is on a desk, the other is on the floor between two desks. The cases
and fans are fairly different. The PC on the desk is used about 60%
as much as the one on the floor.

The case on the desk is consistently and significantly dustier than
the one on the floor. It's so dusty that dust quickly accumulates in
any/all holes in the case, so I'm ending up cleaning it much more
frequently than I'd like.

I wouldn't expect such a significant difference between the two, and I
would've thought the more heavily-used one on the floor would have
more dust. Is this just a matter of having more airflow through the
one on the desk? Does proximity to a monitor (CRT) make a significant
difference? Is it a case design issue?

Just some late-night curiosity... :-)
Click to expand...

The problem is one of having negative case pressure.
Regardless of how many fans there are and where they are situated, if the
overall effect of fans drawing air out of the case is greater than that of
fans blowing air into the case then it's going to get full of dust and lots
of it.

Ignore that stupid **** who replied earlier, he obviously thinks you're an
idiot.

What you need to do is make sure that any fans on the front of the case are
drawing air into the case through a filter, it's easier to clean a filter
than it is to clean the cases innards. Secondly you need to make sure that
any fans at the rear of the case are extracting air at a lower volume than
those at the front are sucking in, don't forget to take into consideration
any fans you have in your power supply.

The net effect you're looking for is positive case pressure, that is to say
that all the holes and gaps through or around items such as CD/DVD/Floppy,
blanking plates, Video card, network card etc. have air pushed through them
from the inside towards the outside. The only place dust will then be drawn
to enter the system is through the filter on the front.

Of course, you shouldn't muck about with the fans at the expense of adequate
airflow but if your carefully and skilfully match different fans to your
needs then you will be ok.

You should consider using larger, slower fans if noise is an issue. You can
run fans below voltage fairly easily should you wish to do so. Otherwise
control units can be bought or made to introduce a resistance and thus slow
the fan down. Papst sell some rather nice fans which have a sensor which
increases the speed of the fan if the inside of the case gets too hot. I use
these on the rear of most of my cases.

HTH

--
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in words with even more distinctness than that with which I conceived
it. There is, however, a class of fancies of exquisite delicacy which
are not thoughts, and to which as yet I have found it absolutely
impossible to adapt to language. These fancies arise in the soul, alas
how rarely. Only at epochs of most intense tranquillity, when the
bodily and mental health are in perfection. And at those weird points
of time, where the confines of the waking world blend with the world of
dreams. And so I captured this fancy, where all that we see, or seem,
is but a dream within a dream.
 
Interesting, I appreciate the input. Now that I think about it (and
am awake enough to do so!), the case is definitely pushing more out
the back than is readily coming in the front, which would explain the
dust accomulations in the vents along the back. Unfortunately, the
case is a real piece of crap, so modifying it will not be trivial or
elegant. (Ugh... I knew I was on shaky ground buying this cheap PC
and it's been all grief ever since...)

Maybe I should cut a hole or two through the paper-thin side panels,
toward the front, and build an easily-changed filter setup into it
that way. The CPU is already running on the hot side (well, not
really "hot," but ~10C hotter than the other PC), and that's right
after cleaning the dust out, so I do want to maintain good air flow.

[For noise, the worst part of that PC is the monitor -- no joke. It's
an old Orchestra Tuba II that has been a piece of junk since I first
got it (and it was a warranty replacement for another one that died
shortly after buying it). Replacing the monitor is high on the list
for when I have sufficient disposable income...]

Thanks for giving me some things to think about! A sledgehammer would
be more satisfying, but I'll see what I can do to fix the air flow.
 
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