Figuring out build airflow

[jfredson]

I just received all the parts to start my first build and I’m starting to think about air flow and it isn’t making sense.

I’ve got a Corsair 270R case with a single 120mm exhaust fan in the back. I’ll be using a Noctua D15S cooler with two 140mm exhaust fans that I plan to mount on the top of my case.

The only other fan is the fan on my PSU which I plan to mount upside down on the bottom of the case and I believe will then pull air into the case? I bought a Corsair RM750X which I believe has a 135mm fan.

So that gives me one 135mm intake fan on the PSU, one 120mm exhaust fan at the back of the case and two 140mm exhaust fans on the cooler on the top of the case. I assume this will give me a very large negative pressure pulling air into the case through all the cracks to keep up with all the exhaust fans.

Do I need to add additional intake fans to balance out my exhaust fans or is this normal for a first time build?

I know that you can manage the air flow by tuning up or down different fans but from a hardware perspective this build seems very lacking on intake fan potential. Or am I understanding this wrong?

 

[scottkendall]

You can add fans or you can not add fans. Normally your PSU flipped upside down sucks air in from the bottom and blows it out the back. I have three 120 fans on the front, two on the radiator and one below. The one below supplies fresh air to my video card that has a blowrer fan facing down. I fashioned a shroud below the radiator to keep the air separate. I have two 120 fans in the top of the case and 120 at the back of the case. Basically front/bottom in - top /back out. You could reverse it if you like but the back of the case normally does not have a dust screen.

 

[theruck]

you are gonna be ok with the setup as is.
the psu fan will kinda operate in its own circuit and cooldown only itself - that is the better way.
the blowout fan will suck in the air from the front of the case and keep it filled with fresh air which will be used by the GPU and CPU coolers
if you have a mainboard with power modern management you can set it for silent or more aggressive cooling profiles with this setup

 

[jfredson]

I ended up going with two 140mm Noctua NH-A15 fans on the front and two more on the top keeping my stock 120mm fan in the back. I mounted the CPU cooler (Noctua D15S) with the fan blowing up directly to one of the top exhaust fans (there's about an inch between them) so it is exhausting straight out the top.

I'm seeing temps hover around 67-70C while stress testing my CPU without overclocking. Gonna tinker with some overclocking this weekend and see how it performs.

 

[theruck]

you are most probably overkilling it with those fans. you will just get louder. the biggest affect on your CPU temperature is the CPU FAN, not the case fan

 

[nicksoph]

• One of the rules of thumb of PC air flow design in normal cases is that you generally want the same or more fan pressure out than in.
• Check your temps with the CPU fan facing both ways (up/down) - Ive found that blowing down onto the cpu generally reduces temps more. (If your fan blows across the cpu then leave as is blowing directly towards exhaust)
• Larger and more fans at lower speeds is generally the way to go for quieter machines.
• Hackintoshes often have limited fan control and separate pwm fan controllers can sometimes be helpful.

 

[percussive]

Do I need to add additional intake fans to balance out my exhaust fans or is this normal for a first time build?

I know that you can manage the air flow by tuning up or down different fans but from a hardware perspective this build seems very lacking on intake fan potential.

As others have said, it's fine to have fewer intake fans. Having a pair in Top/Back exhaust configuration, or two on the back is usually fine (especially if adjustable RPMs).

• Check your temps with the CPU fan facing both ways (up/down) - Ive found that blowing down onto the cpu generally reduces temps more. (If your fan blows across the cpu then leave as is blowing directly towards exhaust)
• Larger and more fans at lower speeds is generally the way to go for quieter machines.

Nick is totally correct about multiple "larger AND slower fans" for a cool and quiet machine. I think you'll like the Noctua D15S, I have the D15 on my OC'ed 4790K with two PWM fans, cool and super-quiet!

 

[jfredson]

Yeah, I’ve been running this setup for about a month now and it’s super cool and quiet. I can’t even hear the fans with the computer sitting on the floor next to me.

I might have gone a bit overkill with the extra case fans but I’m not regretting it at this point. My CPU temps are hovering around 70C while benchmarking, although I haven’t managed to get my i7-9700K to remain stable above 4.6ghz yet. Still need to do more testing on that, but I’m a total overclocking noob and haven’t had the time to really dig in yet.