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Positive or negative air pressure

WolfBlade
By WolfBlade
in Cooling
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Would 2 x 200 mm front intake fans, 2 x 120 mm top exhaust fans, 1 x 120 rear exhaust fan and 2 x 120mm cpu cooler fans make up a positive or negative air pressure ? 

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Pretty sure that'd be on the positive side, unless the front 200mm intakes are against a really restrictive dust filter and the exhausts run at a high RPM.

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18 minutes ago, Mateyyy said:

Pretty sure that'd be on the positive side, unless the front 200mm intakes are against a really restrictive dust filter and the exhausts run at a high RPM.

All the  fans run at the same speed and the front fans are behind a meshified filter panel. 

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Negative.

47 minutes ago, WolfBlade said:

All the  fans run at the same speed and the front fans are behind a meshified filter panel. 

They run at same speed? Would that be 800rpm which is about max 200mm fans run at?

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39 minutes ago, LogicalDrm said:

Negative.

They run at same speed? Would that be 800rpm which is about max 200mm fans run at?

Its not the max. I v just set them all on silent and i think the rpms are pretty similar at that . Would removing one top exhaust fan create a positive pressure ?

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Just now, WolfBlade said:

Its not the max. I v just set them all on silent and i think the rpms are pretty similar at that . Would removing one top exhaust fan create a positive pressure ?

I think it would be closer to neutral. But I can't say without knowing which actual fans and how fast they are spinning. 120mm fans max rpm is much higher than 200mm fans.

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19 minutes ago, LogicalDrm said:

I think it would be closer to neutral. But I can't say without knowing which actual fans and how fast they are spinning. 120mm fans max rpm is much higher than 200mm fans.

They are not at max rpm all fans are configured to have the same rpm. If the temperature increases, the fan rpm of every fan increases by the same value .

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8 minutes ago, WolfBlade said:

They are not at max rpm all fans are configured to have the same rpm. If the temperature increases, the fan rpm of every fan increases by the same value .

I think you don't understand what I'm saying here. Fans have different CFMs, the amount they move air. That number is not accurate, but if all fans come from same manufacturer, it can be used to count how much air fans move at what speed. 120mm fans move different amount of air at 400rpm than what 200mm fans do. Thats why I can't say anything for sure before I know what fans as in how much their CFM is, and how fast they are spinning.

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44 minutes ago, LogicalDrm said:

I think you don't understand what I'm saying here. Fans have different CFMs, the amount they move air. That number is not accurate, but if all fans come from same manufacturer, it can be used to count how much air fans move at what speed. 120mm fans move different amount of air at 400rpm than what 200mm fans do. Thats why I can't say anything for sure before I know what fans as in how much their CFM is, and how fast they are spinning.

Oh, ok. If it helps, all the exhaust fans and cpu cooler fans are coolermaster MF120R and the front fans are also of coolermaster. 

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11 minutes ago, WolfBlade said:

Oh, ok. If it helps, all the exhaust fans and cpu cooler fans are coolermaster MF120R and the front fans are also of coolermaster. 

So its 59 CFM at 2000rpm for 120mms. If 200mms are MF200R, they are 90.3CFM at 800rpm (which is their max rpm).

 

If all fans are at 800rpm (thats ~40% for MF120R), front brings in 180.6CFM (minus filters and other things in the way), rear takes out 23.6 CFM and top takes out 47.2CFM. Thats 70.8CFM out. So at 800rpm which is max speed for 200mm's, you have positive pressure.

 

If all fans are at max rpm, you have negative as exhaust is 177 CFM. This is all theoretical, ofc. So if you keep exhaust fans at lower speeds than intake fans, you will have positive or neutral pressure all the time.

 

At this point I feel obligated to tell you that pressure has really only effect on dust accumulation. It doesn't matter that much on temps, having airflow overall does.

Edited by LogicalDrm

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45 minutes ago, LogicalDrm said:

So its 59 CFM at 2000rpm for 120mms. If 200mms are MF200R, they are 90.3CFM at 800rpm (which is their max rpm).

 

If all fans are at 800rpm (thats ~40% for MF120R), front brings in 180.6CFM (minus filters and other things in the way), rear takes out 23.6 CFM and top takes out 47.2CFM. Thats 70.8CFM out. So at 800rpm which is max speed for 200mm's, you have positive pressure.

 

If all fans are at max rpm, you have negative as exhaust is 177 CFM. This is all theoretical, ofc. So if you keep exhaust fans at lower speeds than intake fans, you will have positive or neutral pressure all the time.

 

At this point I feel obligated to tell you that pressure has really only effect on dust accumulation. It doesn't matter that much on temps, having airflow overall does.

Thanks my man, and i know the only difference is in dust accumulation but you know, wanted to minimize that as well : P 

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It depends on the case and fans. Depending on the fan design and where it's placed, the actual airflow can vary. 

As mentioned, running your intakes at higher rpm than exhausts can help but it's hard to know without testing.

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7 hours ago, WoodenMarker said:

It depends on the case and fans. Depending on the fan design and where it's placed, the actual airflow can vary. 

As mentioned, running your intakes at higher rpm than exhausts can help but it's hard to know without testing.

Thank you for your consideration : ))

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