Negative or positive pressure? Does it matter?

[AusWolf]

The title says it. In case any of you are unfamiliar of the topic, here are some great videos:

As a starter, let me present my case:

System in my profile - I have it all in a Corsair 280X chassis. My cooling setup is composed of a 240 mm AIO with the radiator at the top of the case, fans working as exhaust. I also have the 2x 120 mm fans that came with the case in the front as intake. They work at similar RPMs, so it's a fairly balanced pressure setup. I've been wondering how to improve the cooling performance, as by taking off the side panel of the chassis, I'm shaving 8 °C off of both the CPU and GPU (62 °C CPU instead of 70 and 66 °C GPU instead of 74 in Metro: Exodus). In terms of performance, it's only a couple of extra boost bins on the GPU which isn't noticeable at all, but the noise, I mean silence! It would be nice to have it with the side of the case on too.

The 280X chassis has 14 cm fan mounts both on top and in the front, so a fan upgrade is evident. What I thought about is getting a 280 mm AIO to improve CPU temps at the same time. But then, I probably wouldn't be able to install 14 cm fans in the front for a balanced setup (not enough room), resulting in a negative pressure setup.

My other idea is not giving a hoot about CPU temps, as they are OK anyway, but to just install 14 cm intake fans in the front, resulting in a positive pressure setup.

Which path would be more beneficial in your opinion?

Also feel free to turn the thread into a general discussion with your own questions and stuff.

 

[newtekie1]

Which path would be more beneficial in your opinion?

Always go positive pressure. The actual temperature difference is minimal, but the much lower dust with a positive pressure case is so worth it.

 

[mtcn77]

Always go positive pressure. The actual temperature difference is minimal, but the much lower dust with a positive pressure case is so worth it.

It is good to see the community picking up on the notice. It actually stems from less temperature gradient at fin arrays, somehow the uniform cool air lessens the heat interface temperature gradient and airborne dust doesn't drop from suspension when air isn't vented so hot.

 

[pavle]

I have an old IBM server (dual Pentium3 450) that from factory used to have all the fans turned the way they blow air out of the case and it didn't have hardly any dust in it when I got it. And those fans are Delta 12mm and with high RPM too - all were connected to 12V, so there goes the theory of positive pressure out the window.
I of course turned them the way there's more of them to direct air in, put them all on 7V and only PSU one for out, but that's besides the point.

 

[mtcn77]

all the fans turned the way they blow air out of the case and it didn't have hardly any dust in it when I got it

I think it happens when the components are hot, thus the case ambient gets hot. Maybe yours was not.

 

[Shrek]

I would argue that the fan is where the air runs fastest, so blowing out (negative pressure) would result in the least dust intake.

 

[Vya Domus]

Dust will make it's way into the PC anyway, no matter what you do.

 

[freeagent]

I like positive pressure. Dust is in your environment.. sweep, vacuum, and don’t leave your pc on the floor..

 

[Shrek]

All the more reason to worry about dust.

Early PCs had the power supply blow into the case; modern PCs have it blow out.

I was wondering about a sealed PC case with fans blowing air around internally and the case itself a giant heatsink.

 

[AusWolf]

OK, so the consensus is: for dust protection, positive pressure is optimal.

What about temperatures? Obviously, my CPU would be a tiny bit cooler with a 280 AIO instead of my 240, but would the bigger fans help extract more hot air from the case?

Or is it better to have 140 mm intakes, pump in as much cold air as possible, and leave the 240 AIO as exhaust?

I would argue that the fan is where the air runs fastest, so blowing out (negative pressure) would result in the least dust intake.

I used to think the same before dust filters were a thing. Now I'm not sure.

Edit: These are the two designs I could easily build with my chassis (I currently have 12 cm fans in all of these mounts):

 

[eidairaman1]

Vaccum is negative.

Id say use high static pressure fans up front and bottom and high cfm fans in back and top.

 

[mtcn77]

OK, so the consensus is: for dust protection, positive pressure is optimal.

What about temperatures?

No, this is inconcise. When you are installing intake filters, running positive pressure is less dusty since air will find ways 'out' of the case, not in places where there are no dust filters.
Temperature wise negative pressure has a lead.

 

[TheoneandonlyMrK]

Always go positive pressure. The actual temperature difference is minimal, but the much lower dust with a positive pressure case is so worth it.

Agreed I would add, it's always possible to adjust fan speeds to accommodate different fan sizes so as to make positive pressure setups, though it can cost time and money.

 

[freeagent]

It’s tough to have negative pressure in a case full of holes

 

[mtcn77]

It’s tough to have negative pressure in a case full of holes

Just have all fans exhaust, that's it.

 

[freeagent]

Just have all fans exhaust, that's it.

that would mess with my ocd big time

 

[ThrashZone]

Hi,
You post two tubers, praise them and ask for opinions lol

I make all radiators front/ top intake because they are both filtered by design period :doh:

 

[Deleted member 24505]

Here's mine, not sure if it's positive or negative. apart from the psu, fans are are you see.

 

[MentalAcetylide]

I guess it becomes more of a question of how picky you want to be in regards to airflow & dust. In my opinion, I don't think it really matters unless you're using some completely foreign(like way out there on Jupiter) fan setup and like cleaning old chalkboard erasers in the same room. I would try to have airflow slightly on the positive side but closer towards having equal air coming in & going out. If dust is such an issue, I would just get an appropriate air purifier for the room and practice good computer case hygiene.

 

[AusWolf]

Hi,
You post two tubers, praise them and ask for opinions lol

I make all radiators front/ top intake because they are both filtered by design period :doh:

I shared some videos in case someone is new to the topic and wants to know what's going on. What's so lol about that?

I guess it becomes more of a question of how picky you want to be in regards to airflow & dust. In my opinion, I don't think it really matters unless you're using some completely foreign(like way out there on Jupiter) fan setup and like cleaning old chalkboard erasers in the same room. I would try to have airflow slightly on the positive side but closer towards having equal air coming in & going out. If dust is such an issue, I would just get an appropriate air purifier for the room and practice good computer case hygiene.

That's good advice, but again...

Everyone: Dust is not my issue! I want to make my PC as cool and quiet as possible. I want to know what setup would be best especially for GPU thermals. That's it. Please stop telling me about dust. Thank you.

 

[freeagent]

The attitude I have towards airflow is the overclocker in me. I tend to think everyone who visits tech sites shares the same mindset as me.. but that is not always the case. I have learned my needs are not everyone else’s needs.. and sometimes that can be a bitter pill

 

[AusWolf]

The attitude I have towards airflow is the overclocker in me. I tend to think everyone who visits tech sites shares the same mindset as me.. but that is not always the case. I have learned my needs are not everyone else’s needs.. and sometimes that can be a bitter pill

Considering how many "I've got a fake GPU, how can I make it work?" kind of threads I've visited lately, I'm definitely sure that not every one of us is on the same wavelength.

 

[claes]

I would try running all of your fans as intake, including the radiator, and removing any PCI brackets. Sure, you’re pushing warm air in, but you’re getting more airflow to the GPU rather than pulling the front intake up and out.

Or get a new case. That thing is anemic.

 

[AusWolf]

I would try running all of your fans as intake, including the radiator, and removing any PCI brackets. Sure, you’re pushing warm air in, but you’re getting more airflow to the GPU rather than pulling the front intake up and out.

Hmm... I've never considered something like this. It sounds silly, but interesting. I might test it when I've got some time.

 

[ThrashZone]

Hmm... I've never considered something like this. It sounds silly, but interesting. I might test it when I've got some time.

Hi,
Watch out you might upset your tubers thinking against the grain like that lol