Computer fan question...which ones should blow air inward, and which outward?

[Delirious]

I just noticed the case on my CM690 on its left side where a fan came already mounted...it's blowing air INTO the case. That is where it is sucking air INTO the case is right in front of my 4850x2...which is right on the vent of the huge sucker, which is blowing hot air OUT of it.

So my case fan is taking cool air from the outside and blowing it on the video card vent which at the same time is blowing hot air right into the case fan...so both fans are blowing against each other.

Is this proper or should the case fan be turned the opposite way and blowing out the video card's vented air outwards?

 

[ROAD_DOGG33J]

I think the sidefan blowing on the video card would have more of a cooling effect on it. Plus you want to keep the airflow balanced in terms of intake and exhaust. I would keep it as is. But you can test it out by measuring the temperatures say with the current setup, no fan, and then with the fan reversed.

What exact card do you have?

 

[Delirious]

Ati Radeon 4850X2 in a CM690 case.

 

[ROAD_DOGG33J]

Is it the Sapphire with two fans?

 

[Delirious]

Yeah the two fans spin in such a way that there's a vent that blows out hot air in-between the fans on the side...which is right in front of the vent where the fan came already mounted on.

 

[ROAD_DOGG33J]

That setup sounds fine to me. The side-fan blows cool air on the graphics card and keeps it cool.

 

[Eric.]

Sounds like you should reverse the case fan. You either want cool air going over components or the hot air being pulled away. Currently you're pulling hot air off the video card and pushing cool air at that hot air. So its just going to mix and be warm turbulence in the case. Powerful video cards make a lot of heat, heating up everything else in there, so if you reverse that fan and pull away a good chunk of that heat you may see a difference in MB and CPU temps also.

Think of your current setup as having your furnace and air conditioner running, such that they end up canceling each other out and you end up blowing air thats the same temp as if neither was on.

 

[ROAD_DOGG33J]

I don't think it should matter that much since the side fan is cooling the card and providing a constant flow of cool air. But like I said before the best way is to look over the temperatures with the different fan configurations. During idle the card's fans will just spin faster so there won't be much of a difference there.

 

[GT3mich]

Here is the card.

I can't see alot of hot air coming out that little hole unless there is a baffle inside for the front fan. Most of the air must get vented out the open end blowing hot air on your hard drives.
That is why I moved my Hdds up in my case.

BTW I'm getting one of these today.

XFX GeForce GTS250 for $114.99 It came with a free copy of COD 5 and a month of WOW that I will be selling for around $40 and I have an 8600 GTS that is being sold for $30 so I upgraded $55.

 

[Delirious]

Ok then now how about two top fans on my case? Should physics speak that hot air rises and have the top fans push hot air out of the case or let the fans blow cool air into the case from the top?

 

[ROAD_DOGG33J]

Ok then now how about two top fans on my case? Should physics speak that hot air rises and have the top fans push hot air out of the case or let the fans blow cool air into the case from the top?

The top two fans are fine. They exhaust the hot air created by the CPU. You want to balance the airflow, exhaust and intake, for the most part. If you set those to intakes, then the hot air would end up all over the place and would most likely raise the temperatures of everything including the hard drives.

XFX GeForce GTS250 for $114.99 It came with a free copy of COD 5 and a month of WOW that I will be selling for around $40 and I have an 8600 GTS that is being sold for $30 so I upgraded $55.

Good choice. That rear exhaust works a charm and it comes with a double lifetime warranty(I think).

 

[Danoff]

Cold air in, hot air out.

If you have an obstruction it's probably better to suck against the obstruction than it is to blow. Ideally, your computer should suck and blow at the same time. Suck into the case, blow out.

As I'm sure any rockstar could tell you - the bigger the fan, the better the blow. Big fans also keep it quieter. I have 5 enormous fans constantly blowing away on my unit. One set of twin fans sucks while another other set of twins blows. The centerpiece is my biggest fan which I have seated directly on my cpu. That one blows the most, but has its own special exhaust.

I hope that answers your question.

 

[Solid Lifters]

And, you want slightly more exhaust than intake. Negative pressure. So check and add up you exhaust and intake CFM to make sure your levels are OK.

BTW, is this typically the 'front' (blow) part of fans? I thought it was the 'back' and therefor (suck) side of my fan. I ended up putting my only fan (the 80mm fan pictured) in backwards.

http://www.newegg.com/Product/ShowI...99&Depa=1&Description=ENERMAX UC-8EB Case Fan

 

[ROAD_DOGG33J]

And, you want slightly more exhaust than intake. Negative pressure. So check and add up you exhaust and intake CFM to make sure your levels are OK.

It has been argued whether there should be more exhaust or intake. From what I read more intake should lead to less dust.

BTW, is this typically the 'front' (blow) part of fans? I thought it was the 'back' and therefor (suck) side of my fan. I ended up putting my only fan (the 80mm fan pictured) in backwards.

http://www.newegg.com/Product/ShowI...99&Depa=1&Description=ENERMAX UC-8EB Case Fan

Generally the fan blows in the direction of the front side or the side where the wire comes out.

 

[opendriver]

Intake fans should be on the bottom and front. Exhaust should be at the top and back. Thats how I have my case (CM690) set up.

 

[Perfect Balance]

I hope that answers your question.

I prefer to have all my fans sucking on my cpu at the same time. My cpu might not last as long that way, but it'd really worth it for the (shorter) time that it does.

 

[Eric.]

I don't know if this ever got settled, but these dual-slot GPUs exhaust air out that second slot with the vents, not back into the case the way you've drawn that arrow above.

 

[ROAD_DOGG33J]

That particular card appears to have 4 DVI ports. Look up 'sapphire hd4850x2' on Google images.

 

[GT3mich]

I don't know if this ever got settled, but these dual-slot GPUs exhaust air out that second slot with the vents, not back into the case the way you've drawn that arrow above.

I looked at all the pics before I drew the arrow for the air flow. That card in fact does have 4 DVI connectors. So it blows ALL the hot air back into the case. If I had that card in my case I would turn the lower front fan around and have it blowing out. I have 2 120 front fans blowing cold air in and one 120 on the back blowing hot air out.