[SOLVED] Negative or positive air pressure for 1 fan?

[UnrezolvedKaos]

I basically am building a matx build with a r5 2600 and an RTX 2060 from Zotac. However, to fit that power into my build, I had to skimp out on the case and a little bit on the mobo. My b450m has only 2 fan headers, and one is for the CPU. My question is would it be better to use a single 120 fan @ the back to pull air out or a spare 140 I have to push air in the front.

 

[Karadjgne]

Neither. With newer pwm fans, you can physically splitter a header and get 3x fans. Or use a Sata powered splitter, and get 4x fans.

So at a minimum, I'd run a 2way splitter to the 1 header and run 1x exhaust and 1x intake. If you have room, and 3x pwm fans, I'd run 2x intakes. If using 3pin analog fans, check the draw on the back label. If it's 3w or 0.3A or less, then you can splitter and run 3 fans, if not then just the 2.

 

[jamesanyoung]

I guess it is marginally better to have an exhaust fan if you are only using one.
But the right thing to do is us a splitter to install more case fans, and get some proper air flow.

 

[UnrezolvedKaos]

Neither. With newer pwm fans, you can physically splitter a header and get 3x fans. Or use a Sata powered splitter, and get 4x fans.

So at a minimum, I'd run a 2way splitter to the 1 header and run 1x exhaust and 1x intake. If you have room, and 3x pwm fans, I'd run 2x intakes. If using 3pin analog fans, check the draw on the back label. If it's 3w or 0.3A or less, then you can splitter and run 3 fans, if not then just the 2.

I don't have a splitter, so it would just be 1 fan max

 

[TJ Hooker]

Splitters only cost a few bucks. If you already have two fans you might as well use both of them.

 

[Solandri]

You probably already have several other fans. Typically the PSU fan is an exhaust fan - it draws air from inside the case, and vents it out the back. The GPU is usually set up to exhaust some air out the edge. And some cases let you place a duct over the CPU which turns the CPU fan into an exhaust fan.

So generally, if you're adding just one fan powered by the motherboard, it should be an intake fan so you're not fighting these other fans. Inflow is generally preferred since it creates positive pressure inside, meaning the dust buildup only happens at the intake fan(s). That makes it relatively easy to clean. If you have negative pressure, the dust builds up at every nook and cranny of the case.

Beyond that, you need to look at what the airflow will be like inside the case. Try to assure the intakes and exhausts generate a simple and orderly flow of air. No sharp bends, no air coming in one spot and going right out an adjacent spot without cooling anything. The flow should be over cooler components first (hard drives, motherboard), hottest components last (CPU and GPU) before being vented out of the case.

 

[UnrezolvedKaos]

Splitters only cost a few bucks. If you already have two fans you might as well use both of them.

the fan is being used & the splitter cost isn't the issue rather the time and availability. What I was wondering is would my system run fine without them?

 

[TJ Hooker]

You probably already have several other fans. Typically the PSU fan is an exhaust fan - it draws air from inside the case, and vents it out the back. The GPU is usually set up to exhaust some air out the edge. And some cases let you place a duct over the CPU which turns the CPU fan into an exhaust fan.

Most cases I've seen have bottom mounted PSUs with a fan grill beneath them, such that the PSU will pull air from outside the case, and then vents out the back. So the PSU provides no net airflow in the case.

 

[Karadjgne]

Psus in most aftermarket cases are omni-directional, the slot in back being fully rectangular to accommodate any psu with any plug location and any switch or lack thereof. So the psu can be either fan-up or fan-down, makes no difference to the psu.

 

[TJ Hooker]

Sure, but if you have the fan pointing upwards you now have the PSU sucking in warm air and working against natural convection.

 

[UnrezolvedKaos]

I ended up putting in the 140 in the front with the psu & gpu as a form of exhaust. Thermals look good so far gpu 60 under load and cpu ~55 with the stock wraith cooler.