Do I need an extra ntake or exhaust fan to create positive air pressure for my system?

sapped1 · Dec 28, 2016

Hey guys,

I’m thinking of adding more fans to my system, to cool my GPU and more importantly in controlling the amount of dust getting in to my pc case. Thus I’m hoping to set up a positive air pressure with more intake airflow than exhaust.

However I am confused with the following, because I’m using the massive Noctua NH-D15 CPU Cooler to cool my processor, it has two 140mm fans attached on top of the heatsink like this:

http://noctua.at/en/nh-d15.html

So I have a total of 4 fans (140mm) in my system, 1 intake in the front, 1 exhaust in the back, and 2 fans in between attached to my heatsink. What I’m wondering is, because I’m hoping to create the positive air pressure, does the 2 fans attached to my heatsink count as intake or exhaust?

I can’t find any definite info on this, I remember reading an article stating the CPU fans also affects the air pressure. So I’m hoping to ask you guys, do I need an extra intake or exhaust fan in my situation, to create this positive air pressure I’m hoping to achieve?

Thank you so much for reading and I appreciate your responses!

Totally · Dec 28, 2016

No, the heatsink fans don't factor in because they aren't at the boundaries. They are moving air that is already in the system that has already been brought in by the intake fans nor are they aren't directly connected to an exhaust.

Tsukiyomi91 · Dec 28, 2016

Depends.

rtwjunkie · Dec 28, 2016

The heat sink fans don't matter in the equation. To determine whether you will have positive pressure or negative you simply need to know the cfm of air movement by the case fans.

As long as more goes in that out (by fan, don't worry, an equal amount will exit by other openings), then you'll have a positive pressure system. Just be aware, if you don't have intake filters then a positive pressure system will actually be dustier inside.

EarthDog · Dec 28, 2016

Positive 'pressure' (use the term loosely as it isn't sealed so there isn't much pressure difference) prevents dust from coming through the cracks. And really, there isn't a huge difference in my experience. In fact, I prefer negative pressure.

sapped1 · Dec 28, 2016

Ahh thank you so much for your help guys, appreciate it!

Jetster · Dec 28, 2016

EarthDog said:
Positive 'pressure' (use the term loosely as it isn't sealed so there isn't much pressure difference) prevents dust from coming through the cracks. And really, there isn't a huge difference in my experience. In fact, I prefer negative pressure.

It keeps the dust out if you have filters and enough intakes to compensate for the leaks. Like 4 in 1 out

EarthDog · Dec 28, 2016

Well aware you need a dust filter.. it was even mentioned earlier.

As far as 4:1 ratio you are describing, in most cases just 1 more or more cfm will do. You do not need to use that many intake fans over exhaust to get the benefits (dust not coming through the cracks).

phanbuey · Dec 28, 2016

blast the case with some air every once in a while.... dust filters are pointless.

Jetster · Dec 28, 2016

I live in a high humidity environment. Dust is not easily removed with air. Filters are a life saver and keep the parts spotless.

rtwjunkie · Dec 28, 2016

Jetster said:
I live in a high humidity environment. Dust is not easily removed with air. Filters are a life saver and keep the parts spotless.

I can second that where I live as well.

sapped1 · Dec 29, 2016

Btw guys, I'm using an Fractal Design Define R5, with dust filter in the front and bottom.

Just a question though, if I put the new intake fan in the bottom, does it suck in more dust than usual even with the filter?

micropage7 · Dec 29, 2016

sapped1 said:
Btw guys, I'm using an Fractal Design Define R5, with dust filter in the front and bottom.

Just a question though, if I put the new intake fan in the bottom, does it suck in more dust than usual even with the filter?

dust usually accumulated on bottom
so bottom intake fan would take more dust thats why air filter is important so it wont entering your case

Komshija · Dec 29, 2016

You'll need more intake fans than exhaust fans; eg. 3 intake fans and 2 exhaust fans. Another option with 4 fans (2 intake & 2 exhaust) is to increase revolutions for the intake fans and decrease it for the exhaust fans. Either way, there is very little difference between the positive and negative air pressure, because in both scenarios you'll have a lot of dust inside the case after a few weeks. Dust filters are only moderately effective.

sapped1 · Dec 29, 2016

Hey guys, I've got some further questions on the type of fans I'm hoping to purchase.

However I think it really deserve its own thread as I'm hoping to ask some questions regarding the specifics of fan model

so let's continue the discussion here:

https://www.techpowerup.com/forums/threads/static-pressure-or-air-flow-fan.229082/

Cheers guys!

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Do I need an extra ntake or exhaust fan to create positive air pressure for my system?

sapped1

Totally

Tsukiyomi91

rtwjunkie

PC Gaming Enthusiast

EarthDog

sapped1

Jetster

EarthDog

phanbuey

Jetster

rtwjunkie

PC Gaming Enthusiast

sapped1

micropage7

Komshija

sapped1

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