? about top fans.

rocket · Sep 21, 2001

Q.) Why don't you install a top fan?
A.) Anyone selling a case with a top fan never tested for airflow. Top fans disrupt airflow and increase temperatures. You never want a top fan under any scenario!

is this true because I always thought a top fan <chimney> helped in getting the hot air out. can any one bring some light to this please? I am buying a case and would like on in it but now I am unsure.

Mr.Lansing · Sep 21, 2001

Everybody will haf a different idea because their airflow of their cases will differ from urs
will u need to consider how much cfm is each fan giving out and the airflow pattern of your case!

rocket · Sep 21, 2001

my case is a mid tower pc-66 with the standard fans in front <2> and one in the back. all are 80mm fans.

Kingslayer · Sep 21, 2001

I don't agree with this statement entirely. I use quiet, slow 92mm fans for blowholes. A fast mega CFM blowhole can in fact disrupt airflow. It can suck the cool air coming in from the bottom front of the case and route it to the top, missing the CPU in most cases.

However, we were taught at young ages that heat rises. Therefore a blowhole is a good idea. A slow moving fan will exhaust that hot air efficiently and quietly, without disrupting airflow in the case. And usually do it better than most single fan PSU's. So they do help. Especially when you have alot of hard drives.

AlanSr · Sep 21, 2001

Everything here looks good but you also have to think about the heat from cdroms and psu.
I noticed a few weeks ago that my 16X burner and 16X dvd produce alot of heat.
if you go with the typical S air flow pattern then you would be sucking that hot air right across your HSF.
I think they look cool on top anyway

If I placed on my case I would place it half way over my cdroms so it would pull cool air from the bottom of the case.

I just don't have any juice left in my 300watt psu. My 2 rotrons are sucking the life out of it

CrystalMethod · Sep 21, 2001

All depends on your case design, were your drives, cards, cables, are placed etc... It's not really a question that can be answered "This is the way it is, and there are no exceptions!".
I found that my top fan (exsausting) reduced my CPU temps by 2°C, and case temps by 4°C. Airflow is a very tricky thing to get working in your favor. For the most part, you can map out a general layout of where it's boing to flow, but theres always some thing that will cause it to not go where you want it to. Best thing would be to play with it at stock speed, find out your best setup, and go from there.

CrystalMethod · Sep 21, 2001

Kingslayer said:
I don't agree with this statement entirely. I use quiet, slow 92mm fans for blowholes. A fast mega CFM blowhole can in fact disrupt airflow. It can suck the cool air coming in from the bottom front of the case and route it to the top, missing the CPU in most cases.

However, we were taught at young ages that heat rises. Therefore a blowhole is a good idea. A slow moving fan will exhaust that hot air efficiently and quietly, without disrupting airflow in the case. And usually do it better than most single fan PSU's. So they do help. Especially when you have alot of hard drives.

Shoulda included this in my original post to avoid posting twice...
For the "heat rises" thingy, to take (noticible) effect, you would have to be moving little or no air through your case. The only reason I have my blowhole up top, is that it's the only place I can put any fans, and still be able to take the cover on, and off. My case has the sides and top as one piece.

dimmreaper · Sep 21, 2001

I personally think top fans work rather well. I've had problems with side blowholes disrupting airflow though(they work fine for most people), so I guess it varies from case to case, and fan to fan.

Kingslayer · Sep 21, 2001

CrystalMethod said:
Shoulda included this in my original post to avoid posting twice...
For the "heat rises" thingy, to take (noticible) effect, you would have to be moving little or no air through your case. The only reason I have my blowhole up top, is that it's the only place I can put any fans, and still be able to take the cover on, and off. My case has the sides and top as one piece.

Negative. Heat rises regardless of how much or what temp. Even if you move a ton of air through your case some heat will rise. The only machine that I have a blowhole on is my fileserver. It has 7 hard drives and a cdrw, and a ton of air flow through the case and the top is still 20 degrees hotter than the bottom of the case. Yes, granted 7 hard drives is a ton of heat, but it will still rise. But I still use a slow fan so as not to interrupt the main cooling efforst.

Now with your case design and the top being the only place to put a fan think about this. Instead of routing the air from front to back, why not put a fan on the bottom of your case to move it from bottom to top. This might be the ideal way to handle your cooling effort.

KeyboardCowboy · Sep 22, 2001

IMHO i belive that chimney or stack cooling, having a fan that sucks hot air out of the top of the case, is an excellent way to dissipate heat from your psu and cdrom drives, ect , i have seen drops of 5 degrees in my case temp after i installed 2 92mms at the top of my case, i have also tried using that clothes dryer tubing stuff to make a duct from my psu to my top blow hole, works very good

Phil · Sep 22, 2001

Standard convection doesn't have much of an effect in case airflow as this uses forced convection , the air will flow where ever the fans push and pull it. The only reason I would put a top fan on is due to space.

BrianCapps · Sep 22, 2001

I have a sort of baffle in my case that seperates the MOBO/PCI from the 5 in bays. I also have two 120 mm fans blowing on the mobo from the side, one medium-ish fan on front intake, and several exaust, including the top blowhole.

What I am thinking is: if I put a fan in the cable hole in the 'baffle' of my case that blows up (moves air upward, not explodes

), will this lower core temps?

RocknBull · Sep 22, 2001

rocket said:
Q.) Why don't you install a top fan?
A.) Anyone selling a case with a top fan never tested for airflow. Top fans disrupt airflow and increase temperatures. You never want a top fan under any scenario!

is this true because I always thought a top fan <chimney> helped in getting the hot air out. can any one bring some light to this please? I am buying a case and would like on in it but now I am unsure.

Rocket i bought one of those cases from 3dcool i like it

Tho i did add two toggle switches for the fans on the side if i need them i can turn them on as needed

Crazy Jayhawk · Sep 23, 2001

I have a top fan, but it sucks air in instead of blowing it out. Don't ask me what that does for airflow patterns.

tbirdkiri · Sep 23, 2001

i have one fan in the front and on top done by me and they werk just fine.
i have no air flow before so its a big improvment.
the one on the bottom blows in and the one on top blows out.

Smizack · Sep 24, 2001

Crazy Jayhawk said:
I have a top fan, but it sucks air in instead of blowing it out. Don't ask me what that does for airflow patterns.

My top fan sucks also.

But, I have it right in front of my air conditioner, so my temps are low. the cpu temp is usually around 26-30c

Crazy Jayhawk · Sep 24, 2001

Smizack said:
My top fan sucks also. But, I have it right in front of my air conditioner, so my temps are low. the cpu temp is usually around 26-30c

What a coincidence - mine's right in front of the AC unit too.

RocknBull · Sep 24, 2001

Well Rocket? What are ya going to do?

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