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Question Manage 8 case fans

Apr 4, 2020
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Hi folks

I am currently looking in to my first gaming pc build, and this forum and Google have helped me a lot so far.
My pc case will be a Fractal Design Define 7 xl, which has room for 8 x 140 mm fans and an optical drive.
The attached picture show how the fans can be distributed in the case.
From what I could gather around then the intake should be the 3 in front and the 2 in the bottom. Leaving the 2 in the top and the rear one as outtake.
I would like for all of them to be connected to the motherboard so the fan speed can be regulated depending on the temperature.
The 8 fans I was recommended was Noctua NF-A14 PWM

My question is about how I should manage them in the case. Especially so they do not run at full speed unless necessary. So any comments or tips you have are very welcome.

I also apologize for the many questions below.

Q:
Motherboard:
Will motherboards be able to support 8 fans?
Is it true that only a max of 2 fans should share the same 4 pin on the motherboard?
Airflow:
Will the Noctua mentioned above work as pc fans?
Will this give too much positive pressure with 5 intake and only 3 outtake?
Are the fan placement fine?
Should I get airflow or static pressure fans?
Other:
How else should you manage the 8 fans so they do not run at full speed all the time

Thank you for your help

 
8 fans is overkill.

What is your cpu and cooler?
What is your graphics card?
I would use the three supplied 140mm fans as intake and add an extra 140mm fan for rear exhaust.
That will provide sufficient airflow intake for a strong graphics card and a hot cpu.

You can always change things out later.

To answer questions:
A motherboard header can be split generally to control two fans in the same manner.
The headers have a limited amperage capability.

Yes, the noctua fans are excellent and are good as case fans.
They will include low noise adapters so that you can set a constant lower speed if connected directly to a psu.
I personally prefer a constant drone to fluctuating noise.

Positive pressure is good.
That means that all your intake is from one source and is filtered.
All the fresh air that comes in the front will exit somewhere.
The problem with adding extra exhaust fans is that they will draw in unfiltered air from adjacent opening lowering the cleaning efficiency .

If you bypass motherboard fan control, there are manual rheostat options.
Zalman makes a fanmate for example.
 

Karadjgne

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First, there's a big difference in fan types. Pwm uses a constant 12v and the 'pulse' turns the fan on/off according to its duty cycle. So at 99% or less it'll be in a constant state of trying to get to max speeds. DC fans are voltage regulated, they generally range from 5v-12v so will pull more currant at lower voltages to make up for the wattage difference and keep the fan spinning.

As a result, it's very easy to put 4 pwm fans on a 12v splitter powered from anywhere (molex/Sata) because the power doesn't change, only the pwm signal does. Generally, unless you have a very efficient DC fan, no more than 2 on a single header because they cannot be regulated by any power source, only the header can change voltages.

You are wanting to use PWM fans, so 4x on a powered splitter is fine, you can use 10x on a powered hub with no issues. More than that and the pwm signal is too week to be split further.

As to fan setup, I'd not use the bottom 2x fans, they provide counter airflow, blowing the 3x intake air straight up and away from the gpu. The exception being if they are underneath a shroud, the set at a low rpm will provide a lot of air that can then be pushed up into the gpu if the shroud is vented for such.
An exception for non shrouded would be the rear/bottom at a low/moderate rpm to supply the gpu intakes, but the front/bottom should be avoided.

If aircooling, I'd also not use the front/top fan as exhaust, I'd block that off entirely, you want maximum air availability at the cpu fan intake, and maximum help on the back end.

6 fans total will get you better air FLOW, than just flooding the case with air and exhausting it before it can do anything constructive.

Exhaust should be high cfm fans, you want the fan to be able to move a lot of air, and sp is meaningless as once the air leaves the case, who cares.

Intakes should be balanced or higher sp, it's not so important that air gets moved into the case as it is that that air Move, reach the gpu, push the warmer air towards the exhaust, force its way into a higher pressure area etc.

Exhausts on 1 header, intakes on 1 header. Easy enough for a pwm splitter. Powered splitter or not depending on the fan amperage needs, total for all fans should not exceed @ 0.90A (11w)
 
Last edited:
Apr 4, 2020
14
1
15
0
8 fans is overkill.

What is your cpu and cooler?
What is your graphics card?
I would use the three supplied 140mm fans as intake and add an extra 140mm fan for rear exhaust.
That will provide sufficient airflow intake for a strong graphics card and a hot cpu.

You can always change things out later.
Thank you for your reply. I guess I have a fear of having too few fans. :)
The pc case I the only part I have at the moment. I am awaiting reviews for the 10th Gen Intel CPU's to see if they are worth it. It was recommended to me in another thread. For current Gen comparison I was considering the I9-9900K and the cooler: Noctua NH-D15. For GPU I was recommended GeForce RTX 2080 super.
Does this change your thoughts regarding the fans amount?

To answer questions:
A motherboard header can be split generally to control two fans in the same manner.
The headers have a limited amperage capability.

Yes, the noctua fans are excellent and are good as case fans.
They will include low noise adapters so that you can set a constant lower speed if connected directly to a psu.
I personally prefer a constant drone to fluctuating noise
OK. The 2 limit fans header split is the general rule then. I wanted to connect to the fans to the motherboard to avoid the fans going at full speed when not needed. Do you know how it works with the reduced rpm speed of the fans when connected to the psu? Can you set the rpm? Is the adapter on each fan?

Positive pressure is good.
That means that all your intake is from one source and is filtered.
All the fresh air that comes in the front will exit somewhere.
The problem with adding extra exhaust fans is that they will draw in unfiltered air from adjacent opening lowering the cleaning efficiency .

If you bypass motherboard fan control, there are manual rheostat options.
Zalman makes a fanmate for example.
I was worrying if there could be too much positive pressure and neutral pressure was the aim if possible. I do not understand your last statement with rheostat options. Maybe it is because English is not my native language, but could you elaborate?


First, there's a big difference in fan types. Pwm uses a constant 12v and the 'pulse' turns the fan on/off according to its duty cycle. So at 99% or less it'll be in a constant state of trying to get to max speeds. DC fans are voltage regulated, they generally range from 5v-12v so will pull more currant at lower voltages to make up for the wattage difference and keep the fan spinning.

As a result, it's very easy to put 4 pwm fans on a 12v splitter powered from anywhere (molex/Sata) because the power doesn't change, only the pwm signal does. Generally, unless you have a very efficient DC fan, no more than 2 on a single header because they cannot be regulated by any power source, only the header can change voltages.

You are wanting to use PWM fans, so 4x on a powered splitter is fine, you can use 10x on a powered hub with no issues. More than that and the pwm signal is too week to be split further.
Thank you for your reply. I did not about the difference between PWM and DC fans. So are you saying that if using PWM fans I can use a simple splitter and connect 4 or more to the same pins on the motherboard?
As to fan setup, I'd not use the bottom 2x fans, they provide counter airflow, blowing the 3x intake air straight up and away from the gpu. The exception being if they are underneath a shroud, the set at a low rpm will provide a lot of air that can then be pushed up into the gpu if the shroud is vented for such.
An exception for non shrouded would be the rear/bottom at a low/moderate rpm to supply the gpu intakes, but the front/bottom should be avoided.

If aircooling, I'd also not use the front/top fan as exhaust, I'd block that off entirely, you want maximum air availability at the cpu fan intake, and maximum help on the back end.

6 fans total will get you better air FLOW, than just flooding the case with air and exhausting it before it can do anything constructive.

Exhaust should be high cfm fans, you want the fan to be able to move a lot of air, and sp is meaningless as once the air leaves the case, who cares.

Intakes should be balanced or higher sp, it's not so important that air gets moved into the case as it is that that air Move, reach the gpu, push the warmer air towards the exhaust, force its way into a higher pressure area etc.

Exhausts on 1 header, intakes on 1 header. Easy enough for a pwm splitter. Powered splitter or not depending on the fan amperage needs, total for all fans should not exceed @ 0.90A (11w)
I really like your advice on the fans placement and to avoid having the air be exhausted incorrectly. I just need to understand your last point. Should all the intakes share one pin and all the exhaust share another? And is the 0.90A limit per pin in the motherboard or in both the intake and exhaust together?
 
All the fans tha share the same splitter will be managed to the same speed in the same way.
It is not a requirement, but logically, you would want the two front fans to be managed ti the same speed in the same way.
But, if, for some reason you want one front and one back to run the same way, there is nothing to stop you from doing so.

The amperage spec applies to the total amperage of whatever fans are on the same header.
 

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