Is this fan setup fine?

[Xdrone]

Front intake: 3x SP120 Rgb DC

Back exhaust: 1x ML120 Pro PWM

Top exhaust: 2x ML120 Pro PWM

 

This should probably have positive air pressure if everything runs at even rpm, but all I'm worried about is that when the pwm exhaust fans ramp up speeds, there will be negative air pressure? Is this correct? And is it really that bad, because the negative air pressure is coming from exhaust so the hot air would just get pulled out faster?

[Helix_Exton]

1 hour ago, Xdrone said:

Front intake: 3x SP120 Rgb DC

Back exhaust: 1x ML120 Pro PWM

Top exhaust: 2x ML120 Pro PWM

 

This should probably have positive air pressure if everything runs at even rpm, but all I'm worried about is that when the pwm exhaust fans ramp up speeds, there will be negative air pressure? Is this correct? And is it really that bad, because the negative air pressure is coming from exhaust so the hot air would just get pulled out faster?

It doesn't really matter. All that maters is that air is both entering and exiting the case.

[LogicalDrm]

Unless you have these fans with radiators, you can do some testing. Disconnect some, or change speeds and see how temps change. Or with longer run check how much dust is gathering.

[thedons1983]

I think if all fans were running at the same RPMs you will end up with negative air pressure, as the MLs produce more airflow at almost any RPM than the SP120s do.  Running the SP120s at the front slightly faster than the exhausts would make up for this though I would think.

 

I've currently got a Fractal Node 304, which has 2x 92mm intakes and 1 140mm exhaust, and I have a negative pressure problem with my case unless I run the exhaust slow enough that they don't overwhelm (for want of a better word) the 2x intake fans.  At the moment I have all three fans connected to the cases fan controller and run them at constant 7V, which results in negative air pressure and a lot of dust.  I think it's all about fan control really, and I'm sure you can achieve largely positive air pressure if you adjust your fans accordingly.  You'll have to test different configurations to test for sure though.

[HisEvilness]

SP fans are built for Static Pressure there for will offer lower CFM thus this will give you negative pressure.
And negative pressure is not bad at all helps with cooling just make sure you got proper dust filters on the intake fans.

[Xdrone]

2 hours ago, thedons1983 said:

I think if all fans were running at the same RPMs you will end up with negative air pressure, as the MLs produce more airflow at almost any RPM than the SP120s do.  Running the SP120s at the front slightly faster than the exhausts would make up for this though I would think.

 

I've currently got a Fractal Node 304, which has 2x 92mm intakes and 1 140mm exhaust, and I have a negative pressure problem with my case unless I run the exhaust slow enough that they don't overwhelm (for want of a better word) the 2x intake fans.  At the moment I have all three fans connected to the cases fan controller and run them at constant 7V, which results in negative air pressure and a lot of dust.  I think it's all about fan control really, and I'm sure you can achieve largely positive air pressure if you adjust your fans accordingly.  You'll have to test different configurations to test for sure though.

 

36 minutes ago, HisEvilness said:

SP fans are built for Static Pressure there for will offer lower CFM thus this will give you negative pressure.
And negative pressure is not bad at all helps with cooling just make sure you got proper dust filters on the intake fans.

Would it be fine to just switch around the exhaust and intake so the ML are intake and the SP are exhaust? 

[HisEvilness]

Just now, Xdrone said:

 

Would it be fine to just switch around the exhaust and intake so the ML are intake and the SP are exhaust? 

Ideally, you want to use SP fans as intakes to get the actual air to your hardware past any cages or the distance it needs to travel.
and just use high CFM fans to get the hot air out since hot air tends to rise anyway, all those fans need to do scoop up the hot air and remove it.
Why negative pressure is so nice because it speeds up the process, hot air rises towards the top where you have fans and the top back of your case.

[thedons1983]

32 minutes ago, HisEvilness said:

Ideally, you want to use SP fans as intakes to get the actual air to your hardware past any cages or the distance it needs to travel.
and just use high CFM fans to get the hot air out since hot air tends to rise anyway, all those fans need to do scoop up the hot air and remove it.
Why negative pressure is so nice because it speeds up the process, hot air rises towards the top where you have fans and the top back of your case.

This just isn't true, the ML fans are better optimised for more airflow and more static pressure at any RPMs than the SP series, Corsair even handily shows you that on their website, so I'm sorry but you're just wrong.

 

http://www.corsair.com/en-gb/air-series-sp120-high-performance-edition-high-static-pressure-120mm-fan

http://www.corsair.com/en-gb/ml120-pro-120mm-premium-magnetic-levitation-fan

 

38 minutes ago, Xdrone said:

 

Would it be fine to just switch around the exhaust and intake so the ML are intake and the SP are exhaust? 

Yes, I think that would be the best way to do it, but I will add that the SP120s make poor exhuast fans as they are just too loud, and are tuned for static pressure over airflow, something hisevilness did correctly flag.  Ideally you should get rid of the SPs and buy better exhuast fans, such as the Fractal Design X2 GP series.

[thedons1983]

1 hour ago, HisEvilness said:

SP fans are built for Static Pressure there for will offer lower CFM thus this will give you negative pressure.
And negative pressure is not bad at all helps with cooling just make sure you got proper dust filters on the intake fans.

I'm sorry but this is incorrect.  At any RPMs the ML series fans offer more airflow AND more static pressure than the SP series does at the same RPMs, because the ML series fans are an upgrade on the SP series.  The ML series are also quieter too.

 

http://thermalbench.com/2016/07/12/corsair-ml120-pro-120-mm-fan/3/

[HisEvilness]

5 minutes ago, thedons1983 said:

I'm sorry but this is incorrect.  At any RPMs the ML series fans offer more airflow AND more static pressure than the SP series does at the same RPMs, because the ML series fans are an upgrade on the SP series.  The ML series are also quieter too.

SP vs ML line up yes, but in general SP are for Static Pressure.
The problem with the ML fans it also gives allot of static pressure thus will attract even more dust, they will do fine as intakes but not such a good idea for exhaust.

[thedons1983]

Just now, HisEvilness said:

SP vs ML line up yes, but in general SP are for Static Pressure.
The problem with the ML fans it also gives allot of static pressure thus will attract even more dust, they will do fine as intakes but not such a good idea for exhaust.

No that's not true, and you are getting too caught up in the Corsair naming convention.  The ML fans are better than the SP or AF series in every single way, but do lean towards static pressure.  They produce more static pressure than the SP series at any RPM, that is fact.

 

But yes, static pressure optimised fans are not the ideal for exhausts, as you say.

[HisEvilness]

SP = Static Pressure not the branding name in my case, i use SP fans as intake no matter what brand and CFM fans as exhaust just to clarify that.

[thedons1983]

1 minute ago, HisEvilness said:

SP = Static Pressure not the branding name in my case, i use SP fans as intake no matter what brand and CFM fans as exhaust just to clarify that.

Nope, that is not true, SP is a Corsair naming convention for their static pressure optimised fans and is not an industry standard term.  Also using static pressure optimised fans is not even always advised if the front of your case has good intake vents, just so you know.

[HisEvilness]

Just now, thedons1983 said:

Nope, that is not true, SP is a Corsair naming convention for their static pressure optimised fans and is not an industry standard term.  Also using static pressure optimised fans is not even always advised if the front of your case has good intake vents, just so you know.

Just to clarify Static Pressure is the actual measurement in mm/h2o to give a calculable number to pressure generated by fans.
It is not a naming convention from Corsairs at all, and static pressure is only useful for intake since it cooler air needs a push to get to the hardware or to bypass any obstruction in the case.
And keeping the case fans is a good idea only if they offer a good amount of static pressure, rule of thumb 1.5 mm/h20 or more.
Case Cooling Pressure Calculator.ods

[thedons1983]

Yes 'static pressure' is a quantifiable thing, but using the term "SP", as if it means something, is just because you have bought Corsair fans and nothing less.  Using "SP" to refer to static pressure optimised fans generally, is the same as referring to all smartphones as iPhones.  I know what static pressure optimised fans are by the way thanks.

 

Using static pressure optimised fans is a use case basis, and is not universal as you seem to suggest by the way.

 

And for the record, Corsair SP fans are crap.  If you think they're good, then this conversation will be very short.

[HisEvilness]

SP = Static Pressure not the branding name in my case, i use SP fans as intake no matter what brand and CFM fans as exhaust just to clarify that.
Cooler master has SP fans, Phanteks has them as well etc etc.

Edited August 14, 2017 by wkdpaul
Cleaned up

[SpaceGhostC2C]

11 hours ago, Xdrone said:

This should probably have positive air pressure if everything runs at even rpm, but all I'm worried about is that when the pwm exhaust fans ramp up speeds, there will be negative air pressure? Is this correct? And is it really that bad, because the negative air pressure is coming from exhaust so the hot air would just get pulled out faster?

That's not how positive/negative pressure works: it's not "coming out of" or "coming in nowhere".

 

Positive or negative pressure refers to the air pressure inside the case as a whole. An inflated balloon has positive air pressure, meaning its inner air pressure is higher that the atmospheric pressure. If you make any opening in the balloon the pressure difference will make air go out the balloon without any additional force needed. Similarly, if you create a negative pressure in any container (in the extreme, a vacuum), it will tend to suck air in. An example would be a vacuum cleaner, which expels air at high speed, causing the inside to have lower pressure and suck air in from through the nozzle (since everything else is sealed). Another example are suction cups: when you press them, you reduce the volume and displace air, so that inner pressure is equal to outside pressure. But if it was to expand back to its original shape, inner volume would increase, which for a given amount of air means lower pressure. Therefore, it will tend to suck air (but because its sealed, it just sucks the surface you put it on).

 

Now, going back to computer cases: "negative pressure" simply means that you exhaust air faster than you pull it in through intake fans. It would cause the inner pressure from the case to be lower than the outside pressure, which means that more air will be sucked in to compensate. If the case was sealed, with the only opening being the intake fans slots, you would ultimately have as much air going in through intakes as going out through exhausts, regardless of the fans used. You could even have no intake fans, just like a vacuum cleaner. But because computer cases are not perfectly sealed everywhere else, air will come through the path of least resistance, meaning every opening in the case, however small, will act as a slow speed intake (rather than more air coming from the already pushed intake). This is why, despite having filtered intakes, a negative pressure configuration will lead to more dust buildup over time, unless you filter every tiny opening (or the case as a whole for that matter). On the other hand, if you achieve positive pressure, air will slowly leave the case through every small crack, leaving only intake fans as the only entry place for air. Because it's easier to control dust buildup when you have fewer entry points for dust, most PC builders prefer a mild positive pressure setup.

The main reason why you don't want crazy positive pressure, and some prefer to have negative pressure indeed, is cooling: in every test I've seen, negative pressure tends to make temps somewhat lower, as hot air is typically moved away from the heat source faster in that case. A very high positive pressure has the opposite effect, with air not being removed from the immediate vicinity of the heat source as quickly (and in general higher pressure means higher temperature, but make no mistake, you are not going to turn your case into a pressure cooker ).

The difference is not big between slightly positive and slightly negative, and because of the dust issues, most consider "slightly positive" as the sweet spot, though.

[LogicalDrm]

On 8/13/2017 at 5:45 PM, thedons1983 said:

....

SP = Means nothing, it never has and it never willl.  You only think of it as a term, because you are a Corsair user.

To be fair, while SP isn't really any measured value, it is common abrevation used to describe fans which are oriented for static pressure. No, it doesn't mean Corsairs SP line up are absolute static pressure fans. Nor does ML mean that fans blades of those fans are really levitating. But its been used as synonym. Just like AF is used for Air Flow, because Corsair was first/loudest in their naming scheme. Its not first time marketing term will become synonym to something and won't be last. We could take PC as example. It was IBM's marketing term to make difference between consumer computers and supercomputers. Yet it doesn't mean "Box you connect to TV to do stuff" but rather is used for wider range of products.

 

Rather than fighting over terminology, you two should have just kept arguing what makes Corsairs SP line up static pressure optimized, or why ML line up is has better optimization. Or why some other manufacturer is using P or F or other naming scheme while they could (or rather can't) use SP.

[WkdPaul]

Thread cleaned.

 

Please leave the useless arguments out of this thread and focus on helping the OP.

[thedons1983]

On 8/14/2017 at 5:24 PM, wkdpaul said:

Thread cleaned.

 

Please leave the useless arguments out of this thread and focus on helping the OP.

Duly noted!