stacking case fans

Ruthless Brad · 08-17-2004, 10:36 AM

The AIRFLOW does not increase, only the PRESSURE does. Stacking two 30cfm fans, whether they spin in the same direction or not, will not increase airflow beyond 30cfm, only the pressure. Increased pressure helps with heat sinks, radiators, or in any other places where there are obstructions. I believe opposite rotation directions help increase turbulence to get rid of that dead spot in the middle.

**Duke3d87** · 08-17-2004, 10:43 AM

what about having one fan on each side of a radiator? would i be better off stack fans on one side or having having on fan on each side of the rad?

renegade_ewok · 08-17-2004, 11:13 AM

my friend has a ghetto CPU cooling setup because his Volcano 7 doesnt work on his NF7-S...whenever he tries to boot up the mobo alarm goes off for some reason and it wont boot...then we changed fans and its fine...he took 2 smaller fans and stacked them on top of the Volcano HS...hes got high temps now...im telling him to get a new fan but he wont listen

**Duke3d87** · 08-17-2004, 11:20 AM

I have the same problem with the alarm. it seems to be a thermal alarm. I get that when i overclock too much. I just put the AS5 on so temps are high, but this is the first time its happened to me.

Zyphron · 08-18-2004, 07:06 AM

..... ok now im sure most of us have 2 fans ..... go a head an put them together ....... it creates cancelation effect ...... the fan on the bottom gets too much restance from increased airflow (from the fan on top) ..... so your bottom fan cant pull as much air and your top fan has more restance because of the blades obstructing the way ..... either way no matter how u do it ..... putting 2 same rotationg fans together does not work ... in fact it makes it worse....

Ematep · 06-08-2009, 02:42 PM

ok... so im suprised no one has asked this yet, but what about rewiring a case fan? ive done alot of work rewiring simmilar motors for different devices and you would swap the pollarities (pos to neg, neg to pos) and get the desired affect, opposite spinning fans. now in case fans its not the same, you have a 12v wire and a 5v wire with a ground. DO NOT SWITCH WIRES the will burn up your powersupply. but does anyone know of way to do it? rewire case fans i mean

RcRon7 · 06-08-2009, 03:31 PM

I had a post, but deleted it, it was not helpfull.

You could rewire a fan, sure. But for the purpose of the original post, it will not work.

If you want to change the air flow direction, turn the fan around, much simpler.

Ematep · 06-08-2009, 09:07 PM

when stacking fans you cant just turn one around though. then you dont go any where. the fans are either blowing air towards eachother or away. the ONLY way to do it is to create a turbine affect and thats through opposite spinning fans. now alot of case fans have curved blades which mean rewiring them to make them spin the opposite way will not create airflow. but with flat casae fans you can switch the ground wire(black) with the yellow one. this will cause the motor to run backwards.

oh dang · 06-08-2009, 09:24 PM

Maybe its just me but...isnt rewiring them that way the same as RcRon said...would be just the same as flipping a fan around...?

RcRon7 · 06-08-2009, 09:26 PM

Yes it would, that is the point I was making. That was also kind of pointed out earlier (2004) when thread was first posted.

The fan blades would have to be reversed in order for stacking to have any effect.

Ematep · 06-08-2009, 10:10 PM

no... why is this so hard to understand the fan mounts one way so removing the rudder and reattaching it isnt possible

but look f-> that is the fan and the dirrection. lets stack them now f>f>
because these are the exact same fans and they spin the same way they have NO increased airflow.

now "flipping the fan" <-F F-> they are blowing opposite directions!! what good does that do? flip them both? ok....? F-><-F still nothing.... if you flip the fan you change the direction of airflow.

changing the wiring keeps the blades in the same place, mounts in the same place but reverse airflow.
essentials you will mount like this <-f f-> but because the blades spin opposite air will acutally travel f->f-->

Ematep · 06-08-2009, 10:11 PM

i mean we can arrgue about this all day but iv got 2 turbines runing in my cpu now and it wont happen by flipping a fan.

oh dang · 06-08-2009, 10:25 PM

lol I didnt mean take the blades off and flip them, i ment flip the entire fan its self. Im still not seeing how your way does anything different.

Ematep · 06-09-2009, 02:50 AM

haha yea i added that because i wasnt postive witch you meant, but if your flip a fan you also chage the direction of airflow. and the idea is to stack two identical fans to increase airflow. leaving one fan alone and flipping one will create the f><f affect that i mentioned before. i honestly thought the same thing when i came acrross this idea in a physics class but youll have to try it i guess to see exactly. flipping a single fan wont create the desired affect.

well look at it this way say your sitting infront of a house fan on a hot day. what happens when you turn the fan around and face it away from you? well the fan isnt blowing on you thats for sure. or at lease thats what RCron is saying, that no matter which way his fan is facing it will always blow on him

but even with turbines its not that much more airflow your still better off with 2 fans side by side. if your limited on mounts and have the watts on your power supply then i would mount a second fan on all of them

Ematep · 06-09-2009, 03:01 AM

the only way and this has been confirmed by other forums, is to change the spin on the fans. the problem doesnt ly in the direction of the air flow its the fact that the fans have to spin opposite directions.
the airflow provided by two i dentical fans will slow after the first.
when air pases through the first it will maintain the same speed through the second because they are the same fans. then why the second fan? in this case there is no reason for the second fan.

now adding a second, yet faster fan also will NOT increase the airflow because the first, slower fan is restricting the air from the second and vis versa the first fan being faster up front and the second being slower wouldnt do anything but slow the air before it inters the case.

and apperantly my major isnt spelling and grammer. hahaha

p4_2.4 · 06-21-2009, 06:39 PM

Well, I've been gone for years, and now I find one of my threads has been shot back to the top.

Anyway, I have new ideas on this point. What about an air redirector? I'm thinking about something like one the back of a tornado fan. I was thinking this might fix the opposite spin issue.

Ematep · 06-23-2009, 06:29 AM

did some recon on that... turned up nothing. sounds interestng though. explain more plz

Ematep · 06-23-2009, 06:31 AM

what i did find as far as "air redirectors" are to power hungry and not small enough to be a better solution.
still way easier to cut a couple of wires and switch and crimp em'.

vsop · 08-06-2009, 03:08 PM

If you put a fan on each side of lets say a radiator and have a proper spacing you COULD see an increase in CFM but only to the Max that the fan can produce when running with out any restriction. The only way you would see the increase is if the Rad that you are using is restrictive enought that the static pressure causes the CFM to drop when using just 1 fan.

Ematep · 08-07-2009, 03:58 AM

X2 I agree with previous