Will this fan setup give positive pressure?

[Dagnis]

Front: 2x 140mm be quiet! Silent Wings 3 PWM
Bottom front: 1x 140mm be quiet! Silent Wings 3 PWM

Back top: 120mm radiator with push/pull, Noctua NF-F12 PWM (based of GPU temp)

Top Back: 240mm radiator with push/pull, Noctua NF-F12 PWM (H100i v2)

 

Just in case you need it to help out, 

Case: BeQuiet Dark Base 900.

 

The first three fans, the intake ones, are the fans that come with the case. Just thinking about where to move the back one and put the radiators where I want. I'm not sure if I should get a 4th intake fan for the bottom, I suppose this is my main question. Should I get a 4th intake fan on the bottom? My main problem with doing so is that the case can only control 3 PWM fans. I suppose I could put the extra fan (if needed) onto a 3pin though right?

[GalacticRuler]

This is a good setup, as it is slightly more towards positive pressure as you wanted, while being very close to equal pressure.

[Dagnis]

33 minutes ago, GalacticRuler said:

This is a good setup, as it is slightly more towards positive pressure as you wanted, while being very close to equal pressure.

So,  4th intake fan not really needed? 

[ravenshrike]

Drop the Noctuas unless you go NF-A12x15s since they have the same performance of the F12s and are 10mm thinner each. Your best bet at 120x25 are Enermax Twister Pressures, Noiseblocker eLoop 1300 PWMs, or Gentle Typhoons.

[airdeano]

negative pressure if all fans were 100%

you'd have to lower the exhaust fans speed to match the front intake at 100% for a zero pressure.

[Dagnis]

1 hour ago, airdeano said:

negative pressure if all fans were 100%

you'd have to lower the exhaust fans speed to match the front intake at 100% for a zero pressure.

So perhaps adding a 4th, or even 5th fan might be wise?

[LogicalDrm]

9 hours ago, Dagnis said:

So,  4th intake fan not really needed? 

20 minutes ago, Dagnis said:

So perhaps adding a 4th, or even 5th fan might be wise?

 

How are your temps and dust situation? More fan = more noise, which most don't like. Its usually easier to just control fans than go for even more of them. I would call current setup close to neutral. Exhausts are disrupted by rads so they might as well match with intakes. If temps and dust is fine, I vote for staying with current.

 

[airdeano]

not really, just have to be conscience of the exhaust speed.

 

[Dagnis]

15 minutes ago, LoGiCalDrm said:

 

How are your temps and dust situation? More fan = more noise, which most don't like. Its usually easier to just control fans than go for even more of them. I would call current setup close to neutral. Exhausts are disrupted by rads so they might as well match with intakes. If temps and dust is fine, I vote for staying with current.

 

What if I reduced the 240mm radiator to just a push config? 

[airdeano]

you still have 2x120 exhaust. only reason for p/p fan is too slow the fans down and the extra set is to promote loss in airflow due to the slower speeds.

[LogicalDrm]

49 minutes ago, Dagnis said:

What if I reduced the 240mm radiator to just a push config? 

What about it? Could you just give some reasoning why you need to change anything?

[Dagnis]

1 minute ago, LoGiCalDrm said:

What about it? Could you just give some reasoning why you need to change anything?

I guess I'm just getting the impression I would have a neutral or negative. Taking away from the outtake would solve that no? Or am I being overly concerned and should just manage my intake accordingly? Considering the 4th fan idea will be another silent focused fan, on the bottom of the case, in a sound dampening case, I can't imagine it would cause much noise. 

[LogicalDrm]

Just now, Dagnis said:

I guess I'm just getting the impression I would have a neutral or negative. Taking away from the outtake would solve that no? Or am I being overly concerned and should just manage my intake accordingly? Considering the 4th fan idea will be another silent focused fan, on the bottom of the case, in a sound dampening case, I can't imagine it would cause much noise. 

Removing fans would help. But you could just lower speeds of exhausts. Like run then 30% lower than intakes. In the end it matters most how much dust is issue now vs would it really change that situation at all.

[Dagnis]

10 minutes ago, LoGiCalDrm said:

Removing fans would help. But you could just lower speeds of exhausts. Like run then 30% lower than intakes. In the end it matters most how much dust is issue now vs would it really change that situation at all.

So case pressure for flow only really effects dust, thats it? No real effect on temp? Then I suppose I won't worry too much because I will have dust filters on both bottom and front. 

[LogicalDrm]

1 minute ago, Dagnis said:

So case pressure for flow only really effects dust, thats it? No real effect on temp? Then I suppose I won't worry too much because I will have dust filters on both bottom and front. 

At certain point increasing fans or fan speeds just doesn't have effect. Only way to get lower temps it to increase surface are. AKA bigger rads. So when you have basic airflow working, its all about dust.

[HisEvilness]

Made a excel sheet to calculate this, this will give you a good idea if you wish to use it.

Case Cooling Pressure Calculator.ods

[HisEvilness]

1 hour ago, Dagnis said:

So case pressure for flow only really effects dust, thats it? No real effect on temp? Then I suppose I won't worry too much because I will have dust filters on both bottom and front. 

Positive pressure works best because it will aid the hot airflow away from your components, while hot air will rise anyway given negative pressure outwards will increase the effect.
It will, however, atract more dust to your system where as a positive pressure will reject dust.
Having air filters on the intake is a must either way since it will filter most of the dust out, and leaving it on a desk away from the ground(where dust settles) reduces dust on your filters greatly.