Negative pressure?

[Derrk]

My case has negative air pressure, which confuses me. I have 5 120mm fans on a 360mm rad for front intake, and 3 120mm fans on a 360mm rad for top exhaust. All the fans run at the same speed via a fan controller, so I'm confused how i have negative pressure. I don't have a rear exhaust fan, but i plan to add a 140mm fan to the outside of the case tomorrow. Does anyone know why my case has negative pressure?

 

the 3 outer-most fans on my case have dust filters, and that rad is about 10mm thicker than the top rad, but i figured the extra fans on the front rad would still give me positive pressure. Also, i would've added the 140mm exhaust fan sooner, but tubes block it from being mounted inside the icase. I didn't want to mount it outside of the case, but i guess now I'll have to if i want positive pressure. 

 

But still, I'm not sure why 5 intake fans don't add up to positive pressure when they're against 3 exhaust fans..?

[Cereal5]

PSU fan possibly? Graphics card might also contribute a bit.

[Derrk]

Just now, Cereal5 said:

PSU fan possibly? Graphics card might also contribute a bit.

hadn't thought of PSU fan.. It's pulling air through the bottom so i'm not sure if it could contribute to negative pressure. The gpu is on a loop, so it doesn't have any fans attributing to pressure.

We spoke last night about my modding intentions and how my front panel is choked for air. The issue occurs even when the front panel is off... Idk why it's negative, but hopefully things will be resolved when i add the 140 to the back, just confused about the situation

[it_dont_work]

Just keep your house clean and don;t worry about it. 

 

[Cereal5]

Worth a watch, if dust is what you're worried about.

[Derrk]

1 minute ago, Cereal5 said:

Worth a watch, if dust is what you're worried about.

Good video, I've seen it before. I'm not too concerned about dust buildup hurting the pc, I'm just a bit anal about keeping it clean. I thought i was running more "inny" as luke would say, but it seems not

[Enderman]

Run your intake fans at a higher rpm and the exhaust fans slower.

[Derrk]

1 hour ago, Enderman said:

Run your intake fans at a higher rpm and the exhaust fans slower.

how would i go about that on a fan controller? all 8 fans run at the same speed except i have 5 intake, and 3 exhaust. Not sure why there's negative pressure.  i plan on adding a rear 140mm fan as intake to help even the pressure out.

[Enderman]

9 minutes ago, Derrk said:

how would i go about that on a fan controller? all 8 fans run at the same speed except i have 5 intake, and 3 exhaust. Not sure why there's negative pressure.  i plan on adding a rear 140mm fan as intake to help even the pressure out.

Depends on what fan controller it is and if it is possible.

Usually people plug their fans into the motherboard and control the speeds through there.

[Derrk]

4 minutes ago, Enderman said:

Depends on what fan controller it is and if it is possible.

Usually people plug their fans into the motherboard and control the speeds through there.

i would, but i don't have 8 motherboard fan headers. i think i have 4, maybe 5.  All the fans run at the same speed, so it's mostly just surprising that i still have negative pressure

[Enderman]

16 minutes ago, Derrk said:

i would, but i don't have 8 motherboard fan headers. i think i have 4, maybe 5.  All the fans run at the same speed, so it's mostly just surprising that i still have negative pressure

You can use fan splitters to run two or three fans off of a single header.

[RejZoR]

What makes you think you have a negative pressure? Dust collection? The pressure thing is frankly a myth because I always ended up having dust inside my case and I had a heavy positive pressure setup (2x140mm intake and only 1x120mm exhaust). I don't have carpets, case is raised roughly 50cm from ground, I vacuum every day with a battery vacuum cleaner and I even run a HEPA air purifier 24/7 and there is still dust inside the case.

 

If that bothers you, then you need to get yourself that Silverstone case that has a HEPA filter on the intake. I have no clue how it affects the airflow, but it has to quite a lot because HEPA is super fine.

[_Hustler_One_]

Maybe sucking the whole air inside case by the top 3 fans freely without restriction and blows it out through rad is much easier task for them than front 5 fans sucking air through filter and blows it in through thicker rad even all runs at same rpm..

 

It's just my thoughts..

 

 

[LogicalDrm]

In theory, you should have neutral pressure. Equal amount of intakes and exhausts. Having 3+2 fans on SAME rad as intake doesn't mean you have move intake. The 3 main fans will still move same amount of air overall, having 2 fans extra just means that rad get cooler quicker.

[WoodenMarker]

5 hours ago, RejZoR said:

What makes you think you have a negative pressure? Dust collection? The pressure thing is frankly a myth because I always ended up having dust inside my case and I had a heavy positive pressure setup (2x140mm intake and only 1x120mm exhaust). I don't have carpets, case is raised roughly 50cm from ground, I vacuum every day with a battery vacuum cleaner and I even run a HEPA air purifier 24/7 and there is still dust inside the case.

The quality of the dust filters also matter -- most don't keep enough dust out of the case to satisfy people who are anal about dust buildup in their system.

[Neo-revo]

1 hour ago, LoGiCalDrm said:

having 2 fans extra just means that rad get cooler quicker.

Yes @Derrk  The push pull does not add CFM together, 

 

TBH HSP fans on both sides of a rad is over kill,  just use  AF-fans on the pull side to encourage the air to move away faster after the HSP-fans pushed it through the Rad.

 

Remember air is compressible so two fans at 100 CFM doesnt not equal 200CFM,  the second fan is useless unless it is overcoming resistance (FPI) or a distance away (in tunnel to encourage air movement)

[RejZoR]

3 hours ago, WoodenMarker said:

The quality of the dust filters also matter -- most don't keep enough dust out of the case to satisfy people who are anal about dust buildup in their system.

My current case, SilverStone Kublai KL-07 has a super fine filter, much finer than Corsair Carbide 330R and I still get dust inside the case. It's just a very fine layer of super tiny dust. I just blow the case with a compressor every couple of months. No other way. I'd have to use the above mentioned SilverStone case with HEPA (or was it EPA, not sure) filter on intake to address that. And then it's a question of case actually being sealed and under actual positive pressure to avoid dust suction through thin cracks in the case.