Fan Configurations

[Pickelhaube]

So I am building a new PC in the Corsair Carbide Clear 400c, and I am going to put 6 Corsair AF120 Quiet fans in it... 

 

Corsair Clear 400C Specs

 

Configuration I am going for:

Front: (x3) 120mm 
Top: (x2) 140mm 
Rear: (x1) 120mm

 

I know that the 3 120s on the front should be intake, and the rear fan (120mm) should be exhaust, but I am wondering what I should do with the 140s.

Spoiler

idk how to get rid of this spoiler

So if I were to put both of the top 140mm fans as exhaust, it would probably create negative pressure inside of the case - I would only have 3 intake 120mm fans, and doing that math, it would make there be negative pressure -

Intake - 3x120mm = 119.64cfm

Exhaust - 2x140mm + 1x120mm = 175.48cfm

175.48 - 119.64 = 55.84CFM of negative air pressure

 

On the other hand, If I were to make the top fan, which is closer to the front of the case/front intake fans, into another intake fan, the CFM of intake would change to 187.44CFM for intake, making it slight positive pressure.

 

175.48 - 187.44 =  -11.96 → 11.96CFM of positive airflow

 

So is this what I should do? I am wondering about it, and how it would affect cooling of the parts such as the CPU cooler (A hyper 212 EVO, blowing hot air through the rear exhaust fan), my GPU (if that front air can at least hit the GPU to give it fresh, cool air, and other parts of the PC.

 

Now when I think about it, would it really affect performance with the first, negative pressure setup? If cool air is being blown from the front, and gets sucked out the rear and top, would there be any problems? (Besides possible dust accumulation)

 

 Thanks! 

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lol this took like an hour to make 

 

[ClownFace1511]

Have your exhaust fans running at a slower rpm than your front fans to balance out the cfm. Therefore you can create a positive pressure if your fans are the front are spinning at 1000rpm where as the exhaust fans are like 600 (example). You are calculating your cfm with the fans running full speed, dropping the speed can fix that. jayztwocents has a video about it.

[Pickelhaube]

1 minute ago, ClownFace1511 said:

Have your exhaust fans running at a slower rpm than your front fans to balance out the cfm. Therefore you can create a positive pressure if your fans are the front are spinning at 1000rpm where as the exhaust fans are like 600 (example). You are calculating your cfm with the fans running full speed, dropping the speed can fix that. jayztwocents has a video about it.

Thanks! I am going to be using an NZXT Grid+ V2, So I could create a fan slope for the fans depending on the temperatures, so they could usually run at 600RPM, only slowly ramping up when a certain temperature is reached. (If i can set case fan slopes)

[rtpb5642]

That looks so complex... you really only need one exhaust fan unless your putting in more than one GPU. 6 fans is overkill IMO.

 

Running a 980ti and a 4790k with a Noctua NHD-15 and for one month i only had an exhaust fan now i have 4 fans and temps are the same as with one. (currently i have negative air pressure and my case doesent have much dust and is maintaining a 4.8ghz OC on the CPU

[DrM]

I think the front filters reduce airflow enough that unless you only have one or two exhausts, its going to be negative pressure, which isnt as bad as everyone says. Also the cpu cooler blowing the air into the rear exhaust fan does reduce airflow. (source: http://www.overclock.net/t/1199135/hyper-212-testing-push-vs-pull-vs-push-pull-also-horizontal-vs-vertical-positioning)

[ClownFace1511]

Its just a game of balancing out the rpm between your intake and exhaust. Sometimes fans have graphs for the cfm every 100rpm and then you can work it out that way but I usually have my intake running at an extra 200rpm than my exhaust if I have a lot of exhaust.