How can I achieve positive pressure?

Harrada · Apr 3, 2017

I am trying to get positive pressure for better dust management and airflow. Right now I have two 120mm fans as exhaust. (one pushing out the top/back of my case, and one pushing out the top.)

They are both pulling through radiators, so there is some resistance. One is spinning at 1450 RPM, and the other is spinning at 1750 RPM.

My front end 200mm fan, with the dust filter has stopped working, and I need a replacement. However I have a feeling that a 200mm fan spinning at 700 RPM will not be enough to create positive pressure. I plan to mod the 200mm spot to hold another 120mm fan (I wanted 2, but that wont fit.)

I am still worried that it wont be enough for positive pressure, but I don't really have any more room for more fans. Any advice would be greatly appreciated.

Aeacus · Apr 4, 2017

What's your case make and model?

CountMike · Apr 4, 2017

Positive pressure means more intake than exhaust. As simple as that. Not that it makes any large difference anyway, filters are much better solution.

Harrada · Apr 4, 2017

Aeacus :

Corsair Graphite 600T.
The only filtered Fan mount is 200mm front mount.

CountMike · Apr 4, 2017

That's because most manufacturers assume you would mount all other fans as exhaust. There are aftermarket magnet mounted filters for practically any purpose.
http://www.demcifilter.com/c3/Gaming-Filters.aspx
https://www.amazon.com/Computer-Air-Filter-Polyurethane-Protects/dp/B000FJU8BC
Etc, etc.

Harrada · Apr 4, 2017

CountMike :

I don't get what you mean. If I mounted all those slots with exhaust, I would be pulling in dust from every hole in the case. Why would they design it to collect dust?

I will look into the after market filters though. Thanks.

CountMike · Apr 4, 2017

That's how they do it, not everybody has problems with that, dust is awfully difficult to control, high frequency acts same as static electricity and collects small particles like crazy. Ad to that need to push a lot of air and you can see problems. I have serviced computers from hospitals and still found dust in them. Can't win from loosing when it comes to electronics and dust.

raisonjohn · Apr 4, 2017

Harrada :

What's the airflow (in CFM) of your exhaust fans (one spinning at 1450rpm and one at 1750rpm)?

Airflow for fan at 1450 rpm (in CFM) = [~Rated Max. Airflow (in CFM) / Rated Max. Speed (in RPM) ] x 1450 rpm
Airflow for fan at 1750 rpm (in CFM) = [~Rated Max. Airflow (in CFM) / Rated Max. Speed (in RPM) ] x 1750 rpm

If you can get a 200mm fan for front intake that can produce higher airflow (in CFM) on a certain slower speed (say, 700rpm) than the total airflow of the 2 exhaust fans you have, then, you can get "positive airflow" in your case.

Aeacus · Apr 4, 2017

For a replacement fan, i suggest Bitfenix Spectre Pro 200mm.

Specs:
Spin speed: 900 RPM ±10%
Air Flow: 148.72 CFM ±10%
Static Pressure: 1.26 mmH2O
Noise: 27.5 dB(A)
Current: 0.28A ±10%
Bearing type: fluid dynamic bearing

specs: https://www.bitfenix.com/global/en/products/accessories/spectre-pro#specs
pcpp: http://pcpartpicker.com/products/case-fan/#s=200&sort=a9&m=169&page=1
Either go for regular or LED version.

If you plan to mount 2x 120mm in place of 1x 200mm then it takes a nice deal of searching to find two fans, who's combined CFM can outmatch Bitfenix Spectre Pro CFM, while being more silent than Bitfenix. For higher CFM, one 120mm fan should push more than 75 CFM at lower noise than 27.5 dB(A).
Also, you need to jerry-rig your 120mm fans in place since Corsair 600T doesn't support 2x 120mm at front.

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How can I achieve positive pressure?

Harrada

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Aeacus

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CountMike

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Harrada

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CountMike

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Harrada

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CountMike

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raisonjohn

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