Positive vs Negative Pressure?

[Dubesta11]

I have had both positive and negative pressures in my case. The only difference I see is that with negative pressure I get less dust. In my Inwin 303, I have room for 4 exhausts and 3 intakes. Would it be best to keep it with the 4 exhaust I currently have and 2 intakes, or reduce exhausts to 3 and add another intake? Or reduce to 1 exhaust and have 2 intakes? Or change the fan speeds?

[laushik]

I reccomend having 3 intakes and two exhaust as that will give you positive air pressure which prevents dust and also promotes air flow

 

[Trey222]

 

[Groundedbeef]

More Filtered intakes, less exhausts, positive pressure for sure!

[aisle9]

Positive pressure = less dust

Negative pressure = ever so marginally lower temps 

 

I usually set my systems and fan curves up for positive to neutral pressure during normal operation, shifting to negative pressure above 60-ish C. 

[AresKrieger]

Positive or neutral, never use negative unless you want dusty parts

[AresKrieger]

2 minutes ago, aisle9 said:

Positive pressure = less dust

Negative pressure = ever so marginally lower temps 

 

I usually set my systems and fan curves up for positive to neutral pressure during normal operation, shifting to negative pressure above 60-ish C. 

Why would it get lower temps, that doesn't make any sense from a chemistry perspective due to there being more air molecules to transfer heat to.

[Dubesta11]

12 minutes ago, aisle9 said:

Positive pressure = less dust

Negative pressure = ever so marginally lower temps 

 

I usually set my systems and fan curves up for positive to neutral pressure during normal operation, shifting to negative pressure above 60-ish C. 

Damn, I like the way the top LED fans look. I guess I will put them on the bottom.

 

Also, I might be able to draw in air from the back and exhaust in the top, that way the CPU will get even cooler air.

[WoodenMarker]

35 minutes ago, laushik said:

I reccomend having 3 intakes and two exhaust as that will give you positive air pressure which prevents dust and also promotes air flow

24 minutes ago, AresKrieger said:

Why would it get lower temps, that doesn't make any sense from a chemistry perspective due to there being more air molecules to transfer heat to.

Cooling is the removal of heat from the components. 

Having more exhausts is usually better because it's a lot easier to have them properly placed whereas intakes are usually farther from the heat source. 

Positive airflow doesn't 'promote airflow' any more than a neutral or negative configuration. The only difference between the two is dust buildup. 

[AresKrieger]

3 minutes ago, WoodenMarker said:

Cooling is the removal of heat from the components. 

Having more exhausts is usually better because it's a lot easier to have them properly placed whereas intakes are usually farther from the heat source. 

Positive airflow doesn't 'promote airflow' any more than a neutral or negative configuration. The only difference between the two is dust buildup. 

I was aware it shouldn't matter for cooling I was just questioning the idea (from aisle's post) that negative would give you a slight cooling gain. Preventing stale air is key but pressure wise it is irrelevant so positive is generally better unless you want to clean out your PC often

 

Generally I just make a wind tunnel across the CPU's path, and make sure the GPU has a intake vent

[Dubesta11]

1 hour ago, AresKrieger said:

I was aware it shouldn't matter for cooling I was just questioning the idea (from aisle's post) that negative would give you a slight cooling gain. Preventing stale air is key but pressure wise it is irrelevant so positive is generally better unless you want to clean out your PC often

 

Generally I just make a wind tunnel across the CPU's path, and make sure the GPU has a intake vent

 

1 hour ago, WoodenMarker said:

Cooling is the removal of heat from the components. 

Having more exhausts is usually better because it's a lot easier to have them properly placed whereas intakes are usually farther from the heat source. 

Positive airflow doesn't 'promote airflow' any more than a neutral or negative configuration. The only difference between the two is dust buildup. 

 

This is my current setup:

 

The LED fans are mainly for looks, and the intake fans are for performance. There is not a whole lot of space to mount more fans on the bottom, and the current fans already barely fit. So my best guess would be to remove the top LED fans all together, but there would be less airflow and possibly higher temps.

 

Or, flip around the rear fan and CPU fan for a near even pressure: 

[aisle9]

1 hour ago, AresKrieger said:

I was aware it shouldn't matter for cooling I was just questioning the idea (from aisle's post) that negative would give you a slight cooling gain. Preventing stale air is key but pressure wise it is irrelevant so positive is generally better unless you want to clean out your PC often

 

Generally I just make a wind tunnel across the CPU's path, and make sure the GPU has a intake vent

The more hot air you yank out... 

 

Seriously though, this method seems like it gives me temperatures better by a degree or so (yes, that little) under load while not creating dust problems at idle. When my AIO arrives later this week, I'm going to experiment with making the rear fan into an intake and having everything exhaust through the top radiator. We'll see how that works out lol

[AresKrieger]

7 minutes ago, Dubesta11 said:

 

 

This is my current setup:

snip

 

The LED fans are mainly for looks, and the intake fans are for performance. There is not a whole lot of space to mount more fans on the bottom, and the current fans already barely fit. So my best guess would be to remove the top LED fans all together, but there would be less airflow and possibly higher temps.

There would be less airflow if you removed the top fans however what is the air going out the top cooling? The only thing it passes over is the SSDs, though I will say it really doesn't matter since pressure will not prevent dust getting in if you have no filter on the intake, it's also rather unfortunate that your case doesn't have a fan spot on its front

 

1 minute ago, aisle9 said:

The more hot air you yank out... 

 

Seriously though, this method seems like it gives me temperatures better by a degree or so (yes, that little) under load while not creating dust problems at idle. When my AIO arrives later this week, I'm going to experiment with making the rear fan into an intake and having everything exhaust through the top radiator. We'll see how that works out lol

In that case neutral is the best, not negative since you don't have to overcome a pressure difference, but regardless it's not a deal breaker either way

[aisle9]

1 minute ago, AresKrieger said:

In that case neutral is the best, not negative since you don't have to overcome a pressure difference, but regardless it's not a deal breaker either way

No, it's not at all. It's really a difference of about one degree under heavy load, and that's it in my case.

 

True neutral pressure is virtually impossible to attain, courtesy of things like speed variance in the same model of fans, dust filters, CPU cooler exhausts aimed at the rear fan and hard drive cages. For that reason, if I can find a way to get two intakes and one exhaust into a case, I always will. One and one of the same size typically guarantees negative pressure. 

[Dubesta11]

14 minutes ago, AresKrieger said:

There would be less airflow if you removed the top fans however what is the air going out the top cooling? The only thing it passes over is the SSDs, though I will say it really doesn't matter since pressure will not prevent dust getting in if you have no filter on the intake, it's also rather unfortunate that your case doesn't have a fan spot on its front

 

In that case neutral is the best, not negative since you don't have to overcome a pressure difference, but regardless it's not a deal breaker either way

 

The top is weird, it exhausts towards the back side panel, as well as the top mounted PSU. The bottom IS filtered, I just happened to take it out for pictures and movement of it. I will experiment with swapping the top and bottom fans for now.

[Marinatall_Ironside]

Another thing to factor in is the resistance dust filters introduce. In my case, I have three intakes (all 120mm Noiseblocker NB-BlackSilentPro PL-2 1400 RPM fans) and three exhausts (one 140mm Noctua NF-A14 "Special Linus Tech Tips Edition" fan on PWM and two Corsair AF120 Performance Edition fans on DC fan control mounted onto a Cooler Master MasterLiquid Pro 240 AIO cooler). From what I can understand, my 140mm fan has the least amount of resistance as it's not pushing or pulling air through a dust filter while the rest has resistance through either a dust filter or a radiator.

[Dubesta11]

Just now, JurunceNK said:

Another thing to factor in is the resistance dust filters introduce. In my case, I have three intakes (all 120mm Noiseblocker NB-BlackSilentPro PL-2 1400 RPM fans) and three exhausts (one 140mm Noctua NF-A14 "Special Linus Tech Tips Edition" fan on PWM and two Corsair AF120 Performance Edition fans on DC fan control mounted onto a Cooler Master MasterLiquid Pro 240 AIO cooler). From what I can understand, my 140mm fan has the least amount of resistance as it's not pushing or pulling air through a dust filter while the rest has resistance through either a dust filter or a radiator.

Yes, I do understand dust filters, I am more concerned about creating a positive pressure AND having adequate airflow.

[airdeano]

2 hours ago, Dubesta11 said:

I have had both positive and negative pressures in my case. The only difference I see is that with negative pressure I get less dust. In my Inwin 303, I have room for 4 exhausts and 3 intakes. Would it be best to keep it with the 4 exhaust I currently have and 2 intakes, or reduce exhausts to 3 and add another intake? Or reduce to 1 exhaust and have 2 intakes? Or change the fan speeds?

negative pressure you should have more dust as the amount of exhaust overcomes the inlet air and finds any opening (non-filtered) to draw air into the case.

also, take into account that an intake fan that has a filter is reduced in amount of airflow into the case. by as much as 50%.

 

2 intakes and one exhaust fan (same rpm/fan model) would be neutral, slightly positive.

what you have now is 2 intakes and 4 exhaust fans which is over-negative.

[Dubesta11]

Just now, airdeano said:

negative pressure you should have more dust as the amount of exhaust overcomes the inlet air and finds any opening (non-filtered) to draw air into the case.

also, take into account that an intake fan that has a filter is reduced in amount of airflow into the case. by as much as 50%.

 

2 intakes and one exhaust fan (same rpm/fan model) would be neutral, slightly positive.

what you have now is 2 intakes and 4 exhaust fans which is over-negative.

What would the best method be in my case? 3 bottom filtered intakes with a more aggressive fan curve, one rear exhaust supporting the CPU cooler, and passive top exhaust? Or keep the top fans, but reduce the RPMs to minimal lighting? Why is this so complicated lol.

[Marinatall_Ironside]

3 minutes ago, Dubesta11 said:

Yes, I do understand dust filters, I am more concerned about creating a positive pressure AND having adequate airflow.

Okay just making sure. Also what I'm speculating in my case would be that I have negative pressure as my fans has to work through dust filters. If I were to remove them and do what @JayzTwoCents is doing by winging it with no dust filters, I may very well have what I am going after, positive air pressure with more intakes than exhaust.

[airdeano]

3 bottom fans intake, rear i/o flipped to intake (needs air filter), three top exhaust (fan speed play).

[Marinatall_Ironside]

1 minute ago, Dubesta11 said:

What would the best method be in my case? 3 bottom filtered intakes with a more aggressive fan curve, one rear exhaust supporting the CPU cooler, and passive top exhaust? Or keep the top fans, but reduce the RPMs to minimal lighting? Why is this so complicated lol.

The reason why it's so complicated is because of the number of factors to take into consideration. My three intakes are all running at 100% RPM while the rest is on some kind of fan control (DC or PWM) running at lower RPM's.

[Dubesta11]

8 minutes ago, airdeano said:

3 bottom fans intake, rear i/o flipped to intake (needs air filter), three top exhaust (fan speed play).

Any suggestions for dust filters? Like, can I get a magnetic one for the back?

[airdeano]

yeah, the silverstone seems to readily available: http://www.newegg.com/Product/Product.aspx?Item=9SIA4TZ2SN7500