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Old 16-08-12, 05:21 AM
hadbeen hadbeen is offline
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Positive or Negative overall case pressure

I've heard a lot about both..and also heard that you want to keep your case on the slightly negative pressure side of things.. right now on my HAF-X I have stock fans plus the optional 200mm fan up top for upward circulation. In addition I have a 120mm fan in the 5.5in bays for that added direct airflow to the back-to-front facing fans on my CPU heatsink. I have a bgears b-Blaster 140mm as my rear exhaust to give the whole case I'd say about a difference (this is an estimate because I have no idea how much air the bottom front 230mm fan brings in) of 10-20CFM between the air in and the air out..so a slight negative pressure inside the case...thoughts? Also. My thermaltake claims that the frio can move 101CFM at max speed...I'm not understanding this..but I wanted to make sure that the closest exhaust fan (the rear) can pump that kind of air out no problem..again..also..if you're wondering...I do know that I use ellipses incorrectly..and I know proper punctuation..I'm just lazy..

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Old 17-08-12, 03:57 AM
Goldskis45 Goldskis45 is offline
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(Basic pros and cons of positive and negative pressure in a computer case)

Positive air Pressure
Pro- More air for your fans to "grip" as I call it and move it around faster
Con- Dust collects on areas of the case with low airflow

Negative air Pressure
Pro- Dust is generally sucked out of your case and you need to clean it less
Con- you could starve interior fans of air (CPU cooler and graphics card)

That is pretty much all that matters...
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Old 17-08-12, 04:16 AM
hadbeen hadbeen is offline
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Quote:
Originally Posted by Goldskis45 View Post
(Basic pros and cons of positive and negative pressure in a computer case)

Positive air Pressure
Pro- More air for your fans to "grip" as I call it and move it around faster
Con- Dust collects on areas of the case with low airflow

Negative air Pressure
Pro- Dust is generally sucked out of your case and you need to clean it less
Con- you could starve interior fans of air (CPU cooler and graphics card)

That is pretty much all that matters...
Basically what I figured..a slightly negative pressure won't hurt much...and I won't have to worry about much dust hanging around in there..mostly I'm worried about getting the air through the heatsink then immediately out the back (since I've got a AMD APU I don't much have to worry about graphics cooling)
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Old 17-08-12, 04:57 AM
airdeano airdeano is offline
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Quote:
Originally Posted by Goldskis45 View Post
(Basic pros and cons of positive and negative pressure in a computer case)

Positive air Pressure
Pro- More air for your fans to "grip" as I call it and move it around faster
Con- Dust collects on areas of the case with low airflow

Negative air Pressure
Pro- Dust is generally sucked out of your case and you need to clean it less
Con- you could starve interior fans of air (CPU cooler and graphics card)

That is pretty much all that matters...
mmmm, sorta?
positive will not allow air to enter the case other than the filter intakes. so if you are getting
dust collection inside, your filters are crap.
in negative pressure situations dust is never sucked out, it is retained.. meaning the exhaust
pressure is more than the intake and any open grill or mesh without a filter allows dust in.. dust
will not travel to the rear exhaust too much... itll collect on the GPU and recirculate.

positive:
more intake fan pressure than exhaust fan. any open grill/mesh will not allow dust/debris
to enter case. you must maintain the filters regularly.
negative:
more exhaust pressure than intake fan allows dust to penetrate the case without filters on
any open grill/mesh.
both can stagnate air-flow inside the case. the element is to have a tick more positive
for dust protection.

airdeano
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  #5  
Old 17-08-12, 07:09 AM
hadbeen hadbeen is offline
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right now it's pretty clear (by the look of my dust screens) that I've got a positive pressure..though it may go slightly negative once I upgrade my back exhaust fan from 60CFM to 103CFM....if all else fails I'll upgrade the upper front intake..the one I have there is a 120mm cooler master 2000rpm..it was only 2.99 after rebate so I figured why not..plus it'll come in handy when I get a CPU or two when I use it as an internal case fan. As for (semi)stagnant air..I could only really think of two places..behind the mobo back with all the wires..or maybe circling around the PS cable cover..though there are holes for cables to run so I'm not sure about that. Also, I was surprised to see after doing a bit of research..that thermaltake apparently doesn't sell the fans that come on their FRIO heatsink individually...I saw up to 2000rpm in 120mm..not the 2500 that my heatsink gets up to.
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  #6  
Old 24-08-12, 03:09 PM
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NRG! NRG! is offline
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positive with filtered intakes = clean

negative = dusty
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Old 26-08-12, 01:54 AM
Goldskis45 Goldskis45 is offline
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Hmmmm, I may have gotten my dust facts backwards... But I always run positive anyway...
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Old 26-08-12, 03:26 AM
airdeano airdeano is offline
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Quote:
Originally Posted by Goldskis45 View Post
Hmmmm, I may have gotten my dust facts backwards... But I always run positive anyway...
i knew what you were trying to say, but your fingers said s'mthin' else...
its all good!

airdeano
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  #9  
Old 26-08-12, 01:00 PM
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WYP WYP is offline
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my case had a negative airflow at a time, this made dust a problem. i later changed one of my exhausts to an intake and that solved the dust issue and even lowered temps a little. so go for positive pressure.
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