Testing +ve and -ve air flow

beany_bot

beany_bot

beany_bot

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Hi,
I know in theory we can plan our cases around +ve or -ve airflow. (more fans in than out for +ve airflow for example). If there a way of "testing" that we are indeed getting positive pressure in the case? Is there a way people do this? Im setting up what I hope to be a very mildly +ve pressure on my case and would like to test that it is indeed doing it.
 
If you have any open route for air to flow through (as in, a hole but not filled by a fan) then you can hold a piece of think material, paper, or something similar and see if it gets sucked in/blown away slightly. It'll obviously be affected by any fans pointed toward/away from the opening so you'll have to bear your specific layout in mind, but it's the only thing I can think of bar just assuming based off "more fans in than out", taking in to account their CFM of course.
 
another quick question I will just ask here instead of starting a new thread.

If I plug a 4 pin PWM fan into a 3 pin mobo connection. Will it run at full speed?
and if I plug a 3 pin fan into a 4 pin PWM mobo connection will it run at full speed?

I ask question about pressure because I currently have 2x120 out and 2x120 in. Im planning to replace the in fans to 2x140. Hoping this will give me positive pressure due to the fact they are bigger.
 
Last edited:
beany_bot said:
1) If I plug a 4 pin PWM fan into a 3 pin mobo connection. Will it run at full speed?
2) and if I plug a 3 pin fan into a 4 pin PWM mobo connection will it run at full speed?
Click to expand...

It depends how the headers are controlled. Voltage control on any header will allow control of 3 or 4 pin fans. PWM only control headers will run 3 pins at max, only 4 pinners will be controllable.
 
Does anyone have any thoughts on running 6 fans pulling air in vs. 1 rear exhausting out? My current build has 2 x 360mm rads with 3 x 120mm fans on each - the front pulling in cool air, the top exhausting out. At the moment the top of the case is pretty much a hot zone where the front is like an damn fridge its cold to touch... If I were to switch it up and run the rear exhaust at a higher RPM do we think this is a better option. The case is part mesh part covered (though raised from the mesh) so i'm thinking it could be more effecting drawing in more cool air. Or i'm just being fussy? :)

I wouldn't worry about the pressure too much, as long as you can feel the air flowing in/out of the relevant points it is moving through the case and therefore doing its job.
 
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