Explain negative vs. positive pressure cases please.

[bgc99]

What's the difference between these two? Is it just more fans blowing in that out is Positive Pressure?

Thanks,
BGC

 

[lehtv]

Is it just more fans blowing in that out is Positive Pressure?

Yes, more airflow in than out creates a positive pressure. Doesn't necessarily mean more intake fans, could just mean bigger fans or higher RPM fans.

Here's the reasoning behind it http://www.silverstonetek.com/techtalk_cont.php?tid=wh_positive&area=usa

 

[The Boston Dangler]

i have a positive pressure case now, and i won't go back

 

[DirkGently1]

i have a positive pressure case now, and i won't go back

This. Especially effective if all your intake fans are dust filtered. Best way to reduce the problem. With things reversed, negative pressure and no filters, you may as well be using your machine as a vacuum cleaner!

 

[BFG10K]

I used to get a lot of dust in the front filters of my case, so I turned my Antec 902 into a positive pressure case by turning off the top fan.

There’s much less dust now, and less noise overall. Also temps weren’t even impacted except idle GPU, which is actually lower now.

 

[Subyman]

I used to get a lot of dust in the front filters of my case, so I turned my Antec 902 into a positive pressure case by turning off the top fan.

There’s much less dust now, and less noise overall. Also temps weren’t even impacted except idle GPU, which is actually lower now.

That's my second biggest complaint with my Antec 900. It is a dust trap. Adding another fan to the door still didn't change the dynamics.

 

[aigomorla]

possitive pressure only works if your case has an active wind tunnel, and your feeding air is good.

otherwise, it wont matter if you get possitive pressure if your doing it for dust.

Negative pressure is asking for dust, because its forcing air though any hole you have unless ur case was designed for that feature.

Most gaming cases arent designed for either... they are boxes with holes everywhere, so the notion of possitive pressure vs negative pressure doesnt apply.

They are free flowing because they expect active cooling to pull heat, and then heat to escape the least restrictive means though air movement inside your very open box.
Those wonderful colored diagrams of red and blue arrows of air movement doesnt apply!!!!!

Heat diffuses everywhere, and goes with air movement.. ie.. your open holes, unless you have wind tunnels setup.

if you want to play with a real possitive pressure / negative pressure case, you need to look at a server case like a U series, or you need to start sealing corners and sides up.

Even your front bay can act as air pockets for negative pressure if they are not sealed.



Possitive pressure is easy... put a nice filter on a high powered blower and blow into your case with everything covered up except the fan holes...

But high powered blowers arent quiet.



But anyhow the op's first question.

Possitive pressure means u have more air inside the case then outside.
It means that litterally your blowing so much air inside, every nook and cranny of air holes u have inside the case is blowing out clean air.

This is very effective in a high dust situations because your feeding the system only clean air.

Negative pressure was more used with sound dampening.
Having the least amount of fans pulling air so your case holds a negative pressure.
This allowed less fans to be used, and used wind tunnels up front to pull in the air and then the fans out rear would blow them out.

Once again.. neither of these models can work on modern gaming cases, because possitive vs negative pressure was myth'd out on all gaming cases..

Your trying to carry water inside a window screen.... ummm... OK... i will tell people to keep trying... :X

 

[The Boston Dangler]

possitive pressure only works if your case has an active wind tunnel, and your feeding air is good.

otherwise, it wont matter if you get possitive pressure if your doing it for dust.

Negative pressure is asking for dust, because its forcing air though any hole you have unless ur case was designed for that feature.

Most gaming cases arent designed for either... they are boxes with holes everywhere, so the notion of possitive pressure vs negative pressure doesnt apply.

They are free flowing because they expect active cooling to pull heat, and then heat to escape the least restrictive means though air movement inside your very open box.
Those wonderful colored diagrams of red and blue arrows of air movement doesnt apply!!!!!

Heat diffuses everywhere, and goes with air movement.. ie.. your open holes, unless you have wind tunnels setup.

if you want to play with a real possitive pressure / negative pressure case, you need to look at a server case like a U series, or you need to start sealing corners and sides up.

Even your front bay can act as air pockets for negative pressure if they are not sealed.



Possitive pressure is easy... put a nice filter on a high powered blower and blow into your case with everything covered up except the fan holes...

But high powered blowers arent quiet.



But anyhow the op's first question.

Possitive pressure means u have more air inside the case then outside.
It means that litterally your blowing so much air inside, every nook and cranny of air holes u have inside the case is blowing out clean air.

This is very effective in a high dust situations because your feeding the system only clean air.

Negative pressure was more used with sound dampening.
Having the least amount of fans pulling air so your case holds a negative pressure.
This allowed less fans to be used, and used wind tunnels up front to pull in the air and then the fans out rear would blow them out.

Once again.. neither of these models can work on modern gaming cases, because possitive vs negative pressure was myth'd out on all gaming cases..

Your trying to carry water inside a window screen.... ummm... OK... i will tell people to keep trying... :X

i think you're really overstating the loss of pressure and related noise. with a simple, quiet 2 120mm intake setup i get very sufficient airflow at low rpm. the larger the box is, the more volume of air you have to move, but it's easy to stay ahead of the curve.

 

[rgallant]

just saying
if the case is not a open type

a positive pressure is required for air cooled high end vid. cards [x1,x2,x3] and more intake air is needed to get there , not with less out air for best GPU temps.

 

[tw33ter]

Here's a very informative link from SilverStone explaining positive vs negative pressure in a case.

http://www.silverstonetek.com/techtalk_cont.php?tid=wh_positive&area=usa

 

[aigomorla]

i think you're really overstating the loss of pressure and related noise. with a simple, quiet 2 120mm intake setup i get very sufficient airflow at low rpm. the larger the box is, the more volume of air you have to move, but it's easy to stay ahead of the curve.

no im not.. because this whole negative and possitive pressure nonsense was drafted on cases which looked like closed up boxes with 2 holes.

This isnt the design anymore.

Does a car 10 yrs ago, look the same today? no they dont... tweeks were made from the case to fit application.

the first tweak was trying to make a case quieter...

That was done by poking a lot of holes inside it, because case makers realized the wireing job on novice pc builders were sub par compared to the factory assemblers in india. AKA Dell.

They realized a lot of people were leaving the side panel open to get better circulation.
The cases in design at the time just weren't working with the fans we wanted to use.

Cases evolved to a point where they dont build them like that for general novice use.

There is a reason why a case cost so much on the server line for a U rack case minus the fact its meant for a rack.


You guys are trying to say oh this car can take turbo and u can nos and you can bore out the headders for a better wind tunnel.

Im trying to tell you guys.... NO! wrong car.... the engine is freaken electric and not a gas engine to begin with.

Part2:

on a stock system with stock settings yes...
but if your going this route, once again.. Dell.

Case makers dont assume your going to throw only stock in.
The case is listed as a cool case, which typically follows a case which is used for overclocking.

Once you increase heat in components... again... things are HOTTER on the gpu side, and cpu sinks are also more efficient, you get a bigger heat release from the box.

At this point... once again.. case vendors realized... its easier to blow off a case if it has more holes, and the heat can efficiently escape with the least amount of work.

IE. those big holes u got up top on most cases now. Also unsealed / shielded front bays.
Which also makes holding any pressure nearly impossible.

 

[BFG10K]

Most gaming cases arent designed for either... they are boxes with holes everywhere, so the notion of possitive pressure vs negative pressure doesnt apply.

Huh? Any case can have positive or negative pressure unless it’s a really open one like the Lanboy Air, or a sealed hot-box. All those holes will either intake air or exhaust it.

Previously my Antec 902 would intake air through places like the side panel mesh, PCI slot covers, and through my PSU when its fan is off. Now it’s exhausting air in the same places because I have positive pressure.

The side panel filter never needs cleaning now, and there’s less dust inside the case overall because the only two places intaking air (front fans) both have dust filters.

I also get better idle GPU temps because the GPU fan can actually exhaust hot air at a low rpm; it couldn’t previously due to the negative air pressure sucking it back into the case.

So yes, pressure differential can most definitely apply to “gaming” cases.

 

[aigomorla]

Huh? Any case can have positive or negative pressure unless it’s a really open one like the Lanboy Air, or a sealed hot-box. All those holes will either intake air or exhaust it.

Previously my Antec 902 would intake air through places like the side panel mesh, PCI slot covers, and through my PSU when its fan is off. Now it’s exhausting air in the same places because I have positive pressure.

The side panel filter never needs cleaning now, and there’s less dust inside the case overall because the only two places intaking air (front fans) both have dust filters.

No its not

Go check your front bays in the, see if it has dust near your cd rom.
Then check the corners of your case.

Im not done yet..

Then pull the front plastic plate off and check out how many places you got dust stuck into.

Think im done now?

NO...

Then you can inspect behind your board, and also the floor.


This isnt a sealed case.


Now take your case and look at a U4 case.


What you honestly are doing is telling someone who just entered the hobby that there is such a thing as possitive pressure and negative pressure.

Then he's going to read the old articles regarding + and - and superimpose that.

This is NOT what you should be teaching a new person in this hobby.

8 yrs ago i was using thermaltake cases... now i wouldnt touch them with a 10 foot pole.
8 yrs ago lian li V2000 series was one of the best cases, now its linked to heat traps in most systems because of the way they inverted the board and put that stupid shield over the cpu.
8 Yrs ago.... (meh im sounding like a broken record.. the point being + and - articles were writting longer then 8 yrs ago, and i cant think of case which we use today hasnt changed from 8 yrs ago.

That should tell you enough about the evolution of cases. The side pannel alone has evolved to complete shields.. then they added a small 80mm blow out.. then a 92mm blowout.. and then CM comes around and brings out 2 x 140mm blowout... This is the side panel ALONE evolving.

To anyone reading this thread...
IGNORE + and - pressure.
What works the best is getting cool air direct to your hottest spots, and then letting that hot air naturally escape though your many holes which the case vendors have placed.

This will net you the BEST results then - and + in cooling terms, becuase you get the freshest air.. (also why vendors put holes all over the place.. you can pull air almost anywhere).

Get the coolest air into your hottest parts... the hot air will escape naturally with the least amount of resistance... like a gaming case should do.

final example... b4 when i was a newbie to this area... it would be very difficult to get your case temperature inside near outside. This was typically the product of excellent wiring jobs.

But now. you dont need the wiring jobs anymore, because vendors like corsair and fractile for example design there cases arround wiring.

This leaves a lot of area's open for better circulation.

If a case was designed with pressure states involved... it would have shaped wind tunnels like a dell for example... you think that big green shield only cools the cpu? It uses a tunnel to get the entire board while pulling air from the front. (neg. pressure)

Now is your gaming case a dell case? NO WAY i dont think i would ever build my machine around that coffin.

 

[BFG10K]

Go check your front bays in the, see if it has dust near your cd rom.
Then check the corners of your case.
Im not done yet..
Then pull the front plastic plate off and check out how many places you got dust stuck into.
Think im done now?
NO...
Then you can inspect behind your board, and also the floor.

How are these questions relevant to anything?

Of course there’s dust there – I haven’t been able to completely clean it after months of running negative air pressure. I’d have to strip the case bare and waterblast the insides to get everything clean.

Not to mention that the front filters are not 100% perfect, so a small amount of dust will always leak in. But the dust build-up is far less now that I’m running positive pressure.

This isnt a sealed case.

Nobody claimed it was sealed; in fact that’s exactly the kind of case I said wouldn’t work well with +ve or –ve pressure. The claim was with positive pressure those holes will exhaust while with negative they’ll intake. That makes less dust because most of the gaps don’t have dust filters.

What you honestly are doing is telling someone who just entered the hobby that there is such a thing as possitive pressure and negative pressure.

There is. More air going in = positive. More air going out = negative. Almost every case can be made to behave one way or another, unless it’s completely open or completely closed.

I got positive pressure just by turning off my 200mm top fan; previously I had massive negative pressure. I also get better idle GPU temps as a result, less dust, and less noise. The side fan filter also has zero dust build-up now whereas previously it would need routine cooling, even without a fan there.

8 Yrs ago.... (meh im sounding like a broken record.. the point being + and - articles were writting longer then 8 yrs ago, and i cant think of case which we use today hasnt changed from 8 yrs ago.

This wasn’t written eight years ago: http://www.silverstonetek.com/techtalk_cont.php?tid=wh_positive&area=usa

In fact, diagram B-1 was exactly what was happening to me; I couldn’t feel any hot air escaping when the GPU was at idle, but now it rushes out.

What works the best is getting cool air direct to your hottest spots, and then letting that hot air naturally escape though your many holes which the case vendors have placed.

Gee, that sounds a lot like positive pressure. With negative pressure it won’t be escaping out of those holes; it’ll be getting sucked back in.

 

[bgc99]

Thanks for the replies. I was just curious because it seems every Anandtech case review makes mention of positive pressure.

My current case is an Antec P180. I'm more interested in a quiet case so the cases that appear to be more wire mesh than solid don't interest me.

 

[monkeydelmagico]

I've (over)simplified it to suck vs blow. I think OP has it right.

Lotsa exhaust = negative pressure. Lotsa intake = positive pressure

My rig likes suckage. Runs cooler. Also quieter since I no longer bother with intake fan.