# Fan blowing direction?



## Stildawn

This may sound like a silly questions haha, but....

With case fans how/is it possible to change direction it blows??

Is it just the way you mount it to the case or cant the blades spin both counter/clockwise?

Cheers


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## Euklid

Most fans can only be installed correctly facing one direction. And most will not allow you to change the direction. 

With that said, I'm sure there's nothing wrong with having all the fans blowing out  Maybe the power supply blows in?


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## bomberboysk

Stildawn said:


> This may sound like a silly questions haha, but....
> 
> With case fans how/is it possible to change direction it blows??
> 
> Is it just the way you mount it to the case or cant the blades spin both counter/clockwise?
> 
> Cheers



Unscrew it and screw it back in facing the opposite direction


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## Stildawn

Yeah I thought you'd just spin it around.

Now for another question regarding fan lay out.

Ive got a CM690 case.... which as we all know comes with a front fan, a back fan and a side fan.

Tell me what directions are the existing fans blowing (in/out etc)

I also have a further 2 140mm fans to install in on the top and a 80mm fan for behind the mobo, which direction should I have these extra fans?

Cheers


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## epidemik

Front should be sucking in and drawing cool air across the motherboard.
Fan in the rear should be blowing air out (because the air is heated as it goes across the mother board) 

I believe top fans should be blowing out of the case as well.

Im not sure about behind the mobo. 

I'm not a cooling guru but i think your supposed to have abalance (to some degree) of in and out to achieve maximum cooling so you may want to consider putting more fans in the front (since you have 2 140s and a 120 going out and only 1 120 going in). But im not 100% sure on this...


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## Stildawn

I assume the stock side fan (120mm) is also blowing in. Theres no room for another front fan.


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## epidemik

My bad, I was thinking antec (currently trying to decide between a300 and CM590  and everythings getting mixed up in my mind )

So just disregard the last part of that post.


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## viper110110

to tell which way a fan is blowing, you can take a tissue and hold it near the fan.


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## Vipernitrox

the fan has somewhat of a grill on 1 side. That's the direction it's blowing.


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## bomberboysk

Vipernitrox said:


> the fan has somewhat of a grill on 1 side. That's the direction it's blowing.



Not really a grille, but the side that holds the motor to the fan is the direction it blows. As far as fans, negative pressure is better than positive, more fans blowing out is better than having more fans blowing in, due to the fact that through all the nooks and crannies and vents in your case it will also suck in air. usually i would do Front intake, side intake, top exhaust, rear exhaust.


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## Vipernitrox

bomberboysk said:


> Not really a grille, but the side that holds the motor to the fan is the direction it blows. As far as fans, negative pressure is better than positive, more fans blowing out is better than having more fans blowing in, due to the fact that through all the nooks and crannies and vents in your case it will also suck in air. usually i would do Front intake, side intake, top exhaust, rear exhaust.



yea that's what i ment 

best way to test your airflow is to light a smoke in front of your intake fans and the faster it gets out the back the better it is


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## Stildawn

> best way to test your airflow is to light a smoke in front of your intake fans and the faster it gets out the back the better it is



Haha got to give that a try...

Yeah ok so Ill put the top and back as exhust, what bout the little fan behind the mobo?


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## Vipernitrox

well you've got 2 x 120mm intake and 1 x 120mm + 2 x 140 mm + psu outtake
simple math. i'd put the 80mm intake.


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## Okedokey

Vipernitrox said:


> well you've got 2 x 120mm intake and 1 x 120mm + 2 x 140 mm + psu outtake
> simple math. i'd put the 80mm intake.



lol, if only 

W=(1/2)mv^2 is the work produced by the fan. It makes sense that the mass of the air moved by the fan times the velocity of that air equals the work of the fan. It is simply the amount of air moved multiplied by how fast it is moved.

P=((1/2)(mv^2))/t is the power consumed by the fan during operation. Basically the amount of work done by the fan on the air divided by the amount of time the fan has done the work will equal the amount of power the fan consumes. This also implies that you can find how much work the fan produces if you multiply the power it consumes by how long it consumes.

A=D^2/1974 is simply the outlet area of the fan set equal to the diameter of the fan blade squared divided by 1974. This equation by itself is not important but it helps you find terminal velocity which is important.

V=.932(cfm/D^2) is the terminal velocity equation. Terminal velocity being when the fan has reached its max push/pull at which the air is no longer accelerating. This equation multiplied by 1/2 of 1 cfm equals the power consumed by the fan. Think of this as the terminal velocity (max output of the fan) has a direct relation to how much power is consumed by the fan.

Reworking the last equation gives you cfm. I don’t know if that helped you any but hopefully it makes a little more sense now.

Simple mathematics...



Stildawn said:


> This may sound like a silly questions haha, but....
> 
> With case fans how/is it possible to change direction it blows??
> 
> Cheers



*Anyway, to answer the original question, swap the wires, its dc so if you swap the polarity, it will spin the other way.*


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## Stildawn

> swap the wires, its dc so if you swap the polarity, it will spin the other way.



Lol thanks for that, are they ment to spin the other way?


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## StrangleHold

Stildawn said:


> Lol thanks for that, are they ment to spin the other way?


 
It will work, but the fan blades are not curved to spin the other way, not as good air flow. If its not blowing the way you want, just flip the fan around.


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## PohTayToez

Marcin said:


> Most fans can only be installed correctly facing one direction. And most will not allow you to change the direction.
> 
> With that said, I'm sure there's nothing wrong with having all the fans blowing out  Maybe the power supply blows in?



Since when?  The only fans I've seen that couldn't be installed either way were crazy LED fans.  All of the standard, cheap 80mm and 120mm fans I've owned could be easily installed either way.

Also, having all of the pointing outward wouldn't be very good for air flow.  Ideally, you'd want to try and form an air current going through your case, coming in at one end and being blown out the other.


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## Mitch?

The best setup would be:
Rear Top Fan Out, Front Top Fan In (in front of CPU)
Rear Fan Out
Side Fan Out (videocard will need to be exhausted, trust me )
PSU Fan Out
Front Fan In
Behind-Mobo Fan Out
It'll create a pseudovacuum, but the negative pressure will be okay because it'll bring more hot air out than bringing in more room temp air, and will also make the 80mm mobo fan more effective.


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## Stildawn

I hope this works lol first time using Photobucket.

Ok the picture above is all my fans that I have.

As you can see the CPU will go over that vent thing that is Fan 4. I dont know which way my Cooler Master V8 fan blows but the fan in that is mounted vertical in between the heatsinks.

Im doing the build tomorrow so could you all please write up which direction each of the labeled fans should be haha.

Cheers


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## Vipernitrox

1,4,6: intake
2,3,5: outtake
psu is probably outtake to


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## PohTayToez

I would say that you would only have Fan 1 as intake, like Mitch said, creating a nice airflow from the front of the case to the back.  Fan 6 should always be outtake, so that it expels hot air coming off of the CPU and GPU.  I would also say that 4 should be outtake.  Having it blowing in would mean that the air would come and hit the hot part of the motherboard on the other side of the CPU, but then the air would have no where to go.  Making it outtake would create a current coming from the edges of the motherboard and exhausting the hot air from the other side of the CPU.


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## Stildawn

So the stock 120mm side fan (fan 6) as a exhust? I would have thought to have it as a intake? Its more to the front of the case than the back?


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## Mitch?

Green for intake, Gold for exhaust. I also drew you a pretty sweet PSU, which will be exhaust no matter what, if the fan faces the ground it'll take most from outside the case anyway, if you get it to face up (which i'd try, it's way more functional and prettier) then it'll also help take any heat away from the generally >80*C videocard.

You also have a spot for an optional bottom mounted 120mm fan. If you choose to install it, have it as intake.  Without a fan, the vacuum effect created by the negative draw of your exhaust fans will take alot of air from this hole anyway, so a fan isn't necessary at all.

The side mounted fan is about 4/5th to the back of your case, and vertically centered, and should be exhaust, primarily for the videocard.

So it's:
1,2, possible bottom 120mm fan = Intake
3,*4*,5,6,PSU = Exhaust


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## Stildawn

And what about fan 4 lol.

Man this stuff is complex, way more than I imagined. lol.. 

Do you happen to know the airflow direction of a V8? Cause wont your diagram above only work if the V8 fan is blowing towards the back?


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## Mitch?

sorry. 4 is exhaust also. edited my post to state that just now 
and the V8 will either blow to the back or the top, either way, the fan layout i have will work.
I'm PRETTY sure (>95%) that it blows to the rear though.


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## Stildawn

If its this way, depending on the fan direction will blow either forward or front. If it blows front will ruin airflow hard out.

I might do some more research on it surely it must say somewhere.


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## Stildawn

This looks promising... Ok your plan looks good haha sounds like you know your sh*t lol.


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## PohTayToez

In reference to Mitch's diagram, I would say that having Fan 3 and Fan 4 blowing different directions would be a bad idea, and most likely just waist air flow.


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## bomberboysk

Id say fans 1,4,5 intake and the rest as exhaust, side should be exhaust also to remove heat from gpu/etc.


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## Stildawn

I think the idea of fans 2 and 3 being opposite is to cycle the air through my Cooler Master V8 which will draw the "cool" air coming in from fan 2, use it and then fan 3 will get rid of the hot air.


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## StrangleHold

1. Intake
2. Exhaust
3. Exhaust
4. Exhaust or Intake. Doesnt really matter
5. Exhaust
6. Intake


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## Ramodkk

bigfellla said:


> W=(1/2)mv^2 is the work produced by the fan. It makes sense that the mass of the air moved by the fan times the velocity of that air equals the work of the fan. It is simply the amount of air moved multiplied by how fast it is moved.
> 
> P=((1/2)(mv^2))/t is the power consumed by the fan during operation. Basically the amount of work done by the fan on the air divided by the amount of time the fan has done the work will equal the amount of power the fan consumes. This also implies that you can find how much work the fan produces if you multiply the power it consumes by how long it consumes.
> 
> A=D^2/1974 is simply the outlet area of the fan set equal to the diameter of the fan blade squared divided by 1974. This equation by itself is not important but it helps you find terminal velocity which is important.
> 
> V=.932(cfm/D^2) is the terminal velocity equation. Terminal velocity being when the fan has reached its max push/pull at which the air is no longer accelerating. This equation multiplied by 1/2 of 1 cfm equals the power consumed by the fan. Think of this as the terminal velocity (max output of the fan) has a direct relation to how much power is consumed by the fan.
> 
> Simple mathematics...



Or, you could flip the fan 



Mitch? said:


> The best setup would be:
> Rear Top Fan Out, Front Top Fan In (in front of CPU)
> Rear Fan Out
> Side Fan Out (videocard will need to be exhausted, trust me )
> PSU Fan Out
> Front Fan In
> Behind-Mobo Fan Out
> It'll create a pseudovacuum, but the negative pressure will be okay because it'll bring more hot air out than bringing in more room temp air, and will also make the 80mm mobo fan more effective.



Best setup is simple. 1 x 120mm intake and 1 x 120mm outtake


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## Stildawn

So I just found out much to my disgust that my 80mm x 25mm case fan can not fit in the behind mobo position as its too large (needs to be 15mm)

So Im left with a rather expensive 80mm fan.

What would you guys do? Is there away to front mount it in the CM690 to help out the front fan?

Cheers





Fan 4.


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## bomberboysk

Hmm, maybe find a way to mount it so it blows into the intake of your graphics card?


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## Stildawn

Lol like underneath it? 

I could mount it in the bottom slot near the front. Using cable ties or something.


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