Best location for an extra fan?

[cva1077]

While clearing out my stuff, I found a 120mm PC case fan, and am wondering whether it is worth installing it into my new PC. When connected to 12V, it spins a lot faster and seems to move a lot more air than the fans I have installed now. The case has 3 existing fans plus the fan on the CoolerMaster H212 CPU cooler. They are front, side (intakes) and rear (exhaust). There is provision to put another fan at the front of the case or to mount one on the opposite side of the CPU cooler (in a sucking configuration).

 

What would be the best place to mount this extra fan?

[vololiberista]

What are your temperatures? Download this programme. It's very useful and gives you a good idea of what's going on inside your case.

http://www.almico.com/sfdownload.php

 

I have a single 4" fan at the back drawing air out of the case. Plus obviously a fan for the power unit and CPU. Also for the GPU and 2 fans under the HD. Both the CPU and HD come out at 40c. The GPU at 60c (it's rated to 105c). It's a lot cooler than my old system that used to have 60-68c for the CPU and much the same for the HD. I'm Planning on adding a card to one of my PCU Express slots right next to the GPU. I'm a little concerned that it might interfere a bit with the GPU's airflow.

[cva1077]

After using FSX, the max temps of my system (according to HWmonitor) are:

 

CPU 62

Mobo 55

GPU 50

HDD 32

 

Yes, my PSU and GPU also have dedicated inbuilt fans.

[martin-w]

Your motherboard seems a tad warm. Although it does depend on the motherboard model, some boards have the temp sensor in a warmer location.

 

Which CPU, motherboard, GPU etc? A photo of the inside or your case would help. And are you overclocking, if so how much?

 

ideally we should go for a somewhat negative, or balanced case pressure. Positive is not a good idea, yes it can reduce dust, but to generate a positive case pressure one must restrict the rate at which warm air escapes...obviously thus increasing temp.

 

Make sure all cables are neatly tied up out of the way to promote airflow. Feed air in from the front, out from the back, and ideally the top.

 

The point, is that your components should be within the manufactures recommendations, it's not necessary to go crazy with cooling and simply generate needless noise.

[cva1077]

From what i've read the mobo is a bit warm, but its not that bad IMO. Unfortunately the case does not have a top exhaust vent, so top fans aren't an option. Cables are quite neat, not obstructing airflow much a all. The components do get a bit warmer (compared to FSX temps) when playing games such as BF3 and COD, so maybe that is a factor to consider?

 

specs are:

 

cpu: i5 4670k (stock 3.4ghz)

gpu: Gigabyte GTX560ti (factory OC)

mobo: Gigabyte z87m-d3h

hdd: WD 1tb blue

[vololiberista]

 

ideally we should go for a somewhat negative, or balanced case pressure. Positive is not a good idea, yes it can reduce dust, but to generate a positive case pressure one must restrict the rate at which warm air escapes...obviously thus increasing temp.

 

That's a good point and probably why my inards are not that hot! But My case is quite wide so there's plenty of space for air to circulate.

[martin-w]

It's something that always generates arguments on forums. There are those that adamantly proclaim positive case pressure as best, and those that advocate the opposite.

 

I used to work in a dark room many years ago, it housed a big waist high camera with two banks of powerful halogen lights. The temperature in the darkroom was colossal. Finally my company agreed to install a fan in the wall. The fan had two settings, extract and intake. Others that used the darkroom always set the fan to blow in cool outside air. Guess what, when they did so the temperature in the room hardly changed. My approach was different, I always set the fan to extract the hot air. When I did so, there was a huge gust of cool air from around the gaps in the door frame and the room was cool in seconds. Easy to understand why, each one of us has a ton of atmospheric pressure pressing down on our heads, thus nature abhors a vacuum and indeed negative pressure. The huge weight of the atmosphere will equalise that negative pressure very quickly and efficiently. 

 

So negative pressure is the most efficient way to cool an enclosure. However... PC's are somewhat different, in that we like to spot cool various components like VRM's, CPU's and GPU's. And that's something that a purely negative pressure can't do efficiently. So we add fans to spot cool, to feed air where we need it, and thus pressure increases. I have no problem with this as long as the internal case pressure doesn't become positive. Because by definition, to generate a positive enclosure pressure we must restrict exhaust air, so that air is fed in more quickly that it's exhausted. Easy to see how that's a bad idea.

 

One of the things positive case pressure advocates proclaim, is that positive pressure decreases dust build up. They may be right, but in my opinion they vastly overstate their point. My current enclosure has a very negative pressure, and the only dust that seems to ingress, is straight through the front filters, a very fine dust that passes straight through. Clumping does occur in places, but that's more to do with the fact that dust is electrostatically charged, so naturally clumps.

After using FSX, the max temps of my system (according to HWmonitor) are:

 

CPU 62

Mobo 55

GPU 50

HDD 32

 

Yes, my PSU and GPU also have dedicated inbuilt fans.

 

 

It would seems you have  a somewhat positive case pressure, depends on the CFM and RPM of the fans of course. You seem to have a front fan as intake, a side fan as intake, and only one fan as exhaust. Ideally I would say you need the new fan installed as exhaust.

 

Having said that, how is your PSU configured, is it mounted with the fan directed into the case? In which case, if it is, then the PSU will be exhausting warm enclosure air too. And yes, your graphics card too.

 

If the above is true, then you may be closer to a balanced case pressure which is fine.

[vololiberista]

My case using negative pressure has little or no dust on the inside. But plenty on the outside around the fan mountings. Easier to clean methinks!

[martin-w]

Yes, mine too. Just a case of vacuuming the dust from the front of the case where it sticks to the front, filtered grill. The positive case pressure advocates claim tons of dust gets sucked in from cracks and crevices with a negative pressure. I have never seen this, only the dust that passes through the filters, and perhaps a tad from a gap here or there.

 

Ideally I would prefer it a bit closer to balanced, or balanced. You get the best of both worlds with balanced, in as fast as out, plus minimising dust ingress.

 

Fans mostly blowing in doesn't necessarily equate to an "extreme" positive pressure by the way. As long as there are plenty of vents to allow the air blown in to escape, it can be only somewhat positive. It can never be totally balanced though with just fans blowing in, regardless as to how many escape vents there are, because obstructions within the enclosure slow the airflow down.

[cva1077]

Thanks for all the comments.

 

 

 

It would seems you have a somewhat positive case pressure, depends on the CFM and RPM of the fans of course

I don't think my case has a positive pressure, as on of the side panels is half mesh. Unless I block it up, I dont think there will be positive or neagtive air pressure in the case.

 

 

how is your PSU configured,

PSU is installed with the fan facing the bottom of the case (there is a hole with a filter there). I assume it sucks air into the PSU, but I'm not sure.

 

 

Ideally I would say you need the new fan installed as exhaust.

As there are no more places to mount the fan as an exhaust, is it better to leave it off?

[martin-w]

I don't think my case has a positive pressure, as on of the side panels is half mesh. Unless I block it up, I dont think there will be positive or neagtive air pressure in the case.

 

 

Regardless of your mesh side panel, the enclosure pressure can still be somewhat positive. The air being fed into your enclosure will meet obstructions and be decelerated, thus air will be leaving the enclosure slower than it enters. Place a strip of paper by the mesh side panel. Does the paper blow away from the case or suck toward it? Away, and your case pressure is positive, toward and it's negative.

 

PSU is installed with the fan facing the bottom of the case (there is a hole with a filter there). I assume it sucks air into the PSU, but I'm not sure.

 

 

In that case your PSU is not helping to extract enclosure air. So more likely you have a positive enclosure pressure.

 

It's nothing to be concerned about, temps of internal components are the key. If all is stable, you don't have an issue. What we are debating here is the optimal set up.

[cva1077]

The paper is ever so slightly pushed away, but is basically falls straight down when I release it, so there is not a massive pressure difference between the inside and outside of the case.

 

If I had another exhaust mount I would put it there to get a more balanced case pressure, but I don't so I think I'll leave it off.

[martin-w]

Yes, as I thought, your enclosure pressure is positive.

 

Pressure differential will never be massive in any scenario.