Stacking two fans?

[DesireUnkind]

I just read a post by someone who took the motor out of a housing and used to go inbetween two exaust fans. I was wondering if that would mean 2x's the exaust output?

I am having a problem with heat. If I'm gaming or running Prime95 it doesn't go above 50C and the alarm is set to go off at 55C. But when it's idle for awhile, the alarm goes off and sure enough it's at 55 degrees. I'm not sure what the problem is, exactly. I just came home today and the temp was 55C and I'm sure the alarm went off but no one was home. My first thought was that maybe my vid card (9700Pro) was getting hot because of the screen saver (Aquarium) and throwing off heat, thus triggering the alarm. I haven't had time to test that theory yet, so I'm not quite sure.

My second thought was that this is only a symptom of a bigger problem. I'm not sure that I have enough airflow. My case has only one intake and one exaust, two exaust if you count PSU. The fans are Antec LED 80mm's. I bought them at CompUSA and I'm not sure of the CFM that they deliver.

Will stacking two fans at the exaust help the airflow if I used a shroud as described in the other post? I'm waiting for FedEx to deliver my TT Smartfan2 and I'm going to put that on the cpu heatsink, which is a Zalman 5500 quiet cool, made by PC Maxx if I'm not mistaken. I was hoping that this would help my temps a little but if I've got crappy airflow already, it sounds as if I'm only going to be sucking hot air over the HSF. (The direction of the fan as bought was blowing away from the cpu. I tried reversing, removing the duct but no change in temp really so I just put it back the way it was, with duct pointing to the rear exaust fan.)

Does any of this make sense or am I off track? If I have to mod the case in order to put a bigger fan in I will but would like to try out other ways before I go that far.

I've got a P4 2.4 @3.0 and a Antec Lanboy case. Any suggestions would be welcomed, as would theories on why my temp rises when it's idle and nothing running, cept that screensaver. Which btw, does the screensaver come on when the monitor is turned off?

TIA,
Desire

 

[RA3Skywarrior]

Fan Stacking

I really recommend that you do not stack fans, even with some seperation, they will create quite a bit more noise than if you just left them seperate. The fans will just keep fighting each other's output, and will create an annoying noise. I would recommend that you add higher capacity fans, and if you feel like it add a blow hole or two. Unless you have that window that i think it comes with. Either way you shouldnt be worried, 50+ temps are not going to destroy the chip, but if you must the blow hole is always an option. Just raise the alarm temps and you'll be ok.

N.B. if you turn the monitor off the comp will behave just as if the monitor was on.

 

[HiProfile]

Usually if not always the screensaver comes on if the monitor has been switched off. If it is the screensaver creating the problem, I'd say turn it off completely (you seriously have to TRY to burn one of today's CRTs). If you don't want to do that, you should go into window's power management menu and make it turn off your monitor before it usually hits 55C...I think that might kill the screensaver. Btw, the cpu also does work when doing graphics; its not a vid card-exclusive computing process.

As for the actual topic in the title, stacking two fans nets you more pressure, meaning closer to the actual rated CFM. Side by side might net you more than stacked. Analogy: if you fire 2 bullets into an Ira...erm, piece of wood, 2 side by side would always cause 2 wounds, where as 2 fired in the same line gets you one, but with more damage to that wound. I'd rather wound 2 mid-east "pieces of wood" rather than kill one.


One more thing: do you even have a fan blowing on the zalaman? Not secondary air flow, I mean a dedicated fan.

 

[Crash893]

double stacking the fans only works if the fans are going opposit ways

one clockwise and one counter clockwise

 

[DesireUnkind]

One more thing: do you even have a fan blowing on the zalaman? Not secondary air flow, I mean a dedicated fan. [/B]

Yeah it's the one that came with the heatsink. It's at 3443 rpm's right now. And I disabled the screensaver and so far it's not overheated after being idle for the last four hours or so.

I guess I'll do some drilling and get more fans in the back. From what I've read in other posts, it's better to have more in back, since they can always suck air in thru the cracks. I also read about positive air flow, and I think I took that too seriously and created some dead-air hotspots. What I plan to do is put the Smartfan on the cpu HS, take the Zalman fan that came with the HSF and put that in front, and buy a 'Tornado?' fan at Comp and put that in back with the Zalman. I can't put one in the side because I have a window.

I'm not sure what to do with the Antec LED's though. Blowholes maybe at the top.

It just hit that maybe you meant a dedicated fan, like a side fan, blowing in on the cpu HSF. No I don't, in case that's what you meant.

 

[modenaf1]

how does the clockwise and counter clockwise thing work? i thought that all fans were universal in direction. Unless you
mean to put them blowing away from each other but then they would canceleachother out.

 

[Crash893]

no i dont mean cancel them out

its some physics principle or something you can see it on alot of turbo props

it has to do with something like the first fan spins the air and push is forward but the second span doesnt add any speed to it becuase its already spining ( dont quote me on this)

 

[Samoyed]

You R right on the stacked fans not working. After visiting several of the links given on this issue it's extremely complicated why stacked fans dont work..... but for a computer case, they dont.

Now for the Zalman boys problem. Your fans are fine( they are 2500RPM 35CFM fans BTW ). Rather than mutilate your case or add a very loud fan to the back try this: Add in a PCI slot fan for about 10 bucks online. That will lower your internal case temp a bit. Second thing is that the Zalman products are really quiet but not very great at cooling IMO. Get a more powerful fan for that HS and watch the CPU temps drop!!

A easy way to test what's wrong with your comp is to take off the case cover. If it runs cooler then U need more cooling.

 

[Mark Larson]

http://forum.arstechnica.com/forum/ubb/Forum9/HTML/002416.html

 

[fuzzywuzzy]

There was an article that talked just about that recently.... Can't seem to find it no more...

Basically two intake fans were stacked one behind the other, and case temps went up. Reasoning: the fins from one fan disrupted the airflow of the next. Only way that things would work out (though not tested, just in theory), was if both fans has their fins going the same direction, and more importantly, moving in SYNC....

 

[modenaf1]

well, if they have to move in sync that would be really really hard to do.

 

[DesireUnkind]

Now for the Zalman boys problem. Your fans are fine( they are 2500RPM 35CFM fans BTW ). Rather than mutilate your case or add a very loud fan to the back try this: Add in a PCI slot fan for about 10 bucks online. That will lower your internal case temp a bit. Second thing is that the Zalman products are really quiet but not very great at cooling IMO. Get a more powerful fan for that HS and watch the CPU temps drop!!

A easy way to test what's wrong with your comp is to take off the case cover. If it runs cooler then U need more cooling. [/B]

I was thinking of getting one of those slot fans. I hesitated because I thought that it would suck the cool air coming from the front case fan right out. Am I thinking too much on this?

And I'll get that Smartfan2 on the HS as soon as it gets here

 

[Samoyed]

Yes.

The PCI fan will draw air out but not in a direct line from that front fan. Some air will go from the front fan to the PCI, Rear and PS fans each, creating AIRFLOW!!

 

[Alereon]

Stacking fans is a bad idea. In a perfect world, two stacked 80x25mm fans would work like an 80x50mm: More airflow and less noise for the same airflow than a thinner fan. However, in the imperfect world you actually get if you stack fans, its less effective than simply having one fan. Your fans will perform the best in as close to a free-air situation as possible. Thicker fans are of course better than thinner ones, but stacking fans is a no-go.

 

[nerdlogic]

double stacking the fans only works if the fans are going opposit ways

one clockwise and one counter clockwise

I want to hear more about this theory...

Soy

 

[I.M.O.G.]

Stacking fans does not increase their output above what either fan individually pushes.

A common use of a form of stacking is a push-pull sandwich on a radiator or heatercore. The push pull sandwich is good because it helps to overcome the resistance of the fins and create an airflow that is relatively closer to either fans normal CFM. It is a good way to get more airflow through the small heat exchangers that only fit one fan that water cooling people use in their cases.

There is another use for an old or dead fan that is the same size as your heatsink fan. You can remove the fan and motor and everything except the sides/housing... Then put this piece between the heatsink and your fan and it helps to reduce the effect of the deadspot in airflow that is in the center of axial fans.

 

[Samoyed]

Click on the link MARK posted up a few posts and watch your head spin. It's very complex thread. There is nothing on the opposite direction theory though.

 

[fuzzywuzzy]

Actually, I was watching TLC (the Learning Channel) just last night, and saw something similar to this....

I saw one of those HUGE MOFO choppers, the one with TWO blades, and they were going opposite directions...

(It's one of those long choppers that looks like a hot dog.)

Think of it this way... If it's good for the chopper, it's good for your PC case

I want to hear more about this theory...

re: 2 fans going opposite directions...

Soy

 

[I.M.O.G.]

Actually, I was watching TLC (the Learning Channel) just last night, and saw something similar to this....

I saw one of those HUGE MOFO choppers, the one with TWO blades, and they were going opposite directions...

(It's one of those long choppers that looks like a hot dog.)

Think of it this way... If it's good for the chopper, it's good for your PC case

I don't know if that logic holds up... a lot of car knowledge applies to computer cooling, but a lot of it contradicts also.

Nevertheless the fan direction thing is interesting... I doubt it could be applied usefully in PC cooling however.

 

[Ugmore Baggage]

Unless you have some sort of special left handed fan, with blades angles the opposite way, um (LOL) one fan will be sucking and the other one will be blowing!