how do you decide if a pressure is neutral or positive?

[Yordlezeus]

hey just want to know how things like push pull effect the pressure. does it count as 6 fans of pressure?

im planning to have my powersupply facing up to stop causing a hot air loop where i will be putting it. then i have a 3 radiator in the top and the back of the case is basically fully open. so im planning for 4 exhausts with 3 on the gpu doing their own thing (i dont know how they effect air apart from cooling the gpu, they are not blower but the normal fans) and 6 as intake though a radiator. would this be balanced? 

[Willium_Bob_Cole]

as far as i know, blower GPU cards exhaust, but otherwise GPU coolers spread their hot air to the case and let the case cooling jettison it. As for pressure, I think so long as all fans are equal, 1 in and 1 out is neutral, near enough. If you have any kind of filters on your intakes, that will impede airflow however, so best practice (and I'm no pro so don't take what I say as gospel), have filtered intakes, and a slightly higher number of intakes than exhaust fans. The locations of the fans shouldnt matter much except like, if you have your rig on the floor, you will want to either have nothing on, exhaust only, or very filtered intakes, on the bottom of the case. Especially if its a high traffic area like a workshop where you do some kind of dusty craft work, or have a bunch of furry housemates. Hope this helps

[samcool55]

Well usually it's fine to have a bit of positive pressure in the case (so more air goes in than comes out) because that will stop dust creeping into the case through small gaps.

 

So if you can't get it perfectly balanced, go with a positive pressure setup.

[dfsdfgfkjsefoiqzemnd]

push-pull will move more air than just a fan pushing or one pulling, but not twice as much.  A lot depends on the thickness and fin density of the radiators too. 

 

So let's see if I understood that correctly ...

 

- triple rad in the front, with 6 fans in push-pull as intake

- triple rad in the top, with 3 fans exhausting.

- PSU with the fan on the inside of the case, acting as an exhaust

- also the GPU is using 3 fans, so it's an open air card rather than blower style. 

 

Sounds like it's going to be close.

 

Personally I wouldn't worry too much about having a pocket of hot air above the PSU.  The GPU will suck the air from there and exhaust it to the side.  Some of it will get sucked back into the GPU (that's normal for those cards), the rest goes upwards where it gets picked up by the normal case airflow.

I'd put that PSU in the normal position, where it draws in air from underneath the case.  That should put you in positive pressure territory. 

[Willium_Bob_Cole]

 

 

 

4 minutes ago, Captain Chaos said:

push-pull will move more air than just a fan pushing or one pulling, but not twice as much.

good point, it's almost like the SLI argument for graphics cards. Two cards WILL (or yknow, should) be better than one, but not TWICE as good.

[WoodenMarker]

4 hours ago, Willium_Bob_Cole said:

good point, it's almost like the SLI argument for graphics cards. Two cards WILL (or yknow, should) be better than one, but not TWICE as good.

Kind of..? Two fans won't move air faster than just the single fan unimpeded. 

At best, push / pull on a rad would still be worse than a single unimpeded fan for system airflow. 

[Willium_Bob_Cole]

7 hours ago, WoodenMarker said:

Kind of..? Two fans won't move air faster than just the single fan unimpeded. 

At best, push / pull on a rad would still be worse than a single unimpeded fan for system airflow. 

Right, it won't move the air faster, but it helps direct it the way you want, ie out of the system. I don't know HOW big a difference it can make, but like, only having intakes will recirculate way more hot air inside the case than a balanced push-pull that is able to force hot air out to make way for fresh. Intakes only would "work", it would just be relying on PASSIVE venting, thus less efficient. About neutral pressure is optimal, slightly positive preferred over slightly negative because of the dust benefits, but any airflow is better than none.

[WoodenMarker]

4 minutes ago, Willium_Bob_Cole said:

Right, it won't move the air faster, but it helps direct it the way you want, ie out of the system. I don't know HOW big a difference it can make, but like, only having intakes will recirculate way more hot air inside the case than a balanced push-pull that is able to force hot air out to make way for fresh. Intakes only would "work", it would just be relying on PASSIVE venting, thus less efficient. About neutral pressure is optimal, slightly positive preferred over slightly negative because of the dust benefits, but any airflow is better than none.

Push / pull isn't the same as intake / exhaust. Push / pull is referring to a fan relative to a heatsink or rad as opposed to an intake or exhaust on a case. 

[Willium_Bob_Cole]

oh okay, I see what you mean, although I'm a little lost on how it is relevant to system pressure in that case. edit: I don't know why replying with a quote messes my post formatting up lol

[WoodenMarker]

6 hours ago, Willium_Bob_Cole said:

oh okay, I see what you mean, although I'm a little lost on how it is relevant to system pressure in that case. edit: I don't know why replying with a quote messes my post formatting up lol

Did you quote before typing and click outside of the quote to start typing?

 

Push / pull can help increase airflow and pressure where obstructions like case panels and rads would otherwise reduce performance. Push / pull on a rad would provide more airflow than the same rad with a single fan in push.