# Which way should my fans blow?



## ctech

I have just built a new system and this is how I have the fans laid out:

Two 80mm fans in front pulling air in.

One 80mm fan on top blowing air out.

One 120mm fan on the back blowing air out.

And one 80mm fan on the side blowing air in at the CPU.

I keep hearing conflicting views on this subject so I just used my on judgment. I am thinking about turning the fan on the side around thinking it would pull hot air away from the CPU but I also think that blowing cool air at the CPU is good also? 

The case came with a funnel on the side and I took it off and sandwiched the fan in the middle between the funnel and the panel thinking it would concentrate all of the air at the CPU/Heat sink. Also I have a Zerotherm heat sink (heat pipe) with a fan mounted on top and I can't tell if it blows air at the heat pipes or it pulls the air away??? If it pulls air away from the heat sink then I would think I should turn the case fan on the side panel around...

Thanks for any ideas you can give me on this.


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## manic

Ive found its more effective having side fan blowin out.


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## ctech

With all of the fans blowing out except for the two on the front would there be enough air allowed in to match the air trying to escape? Also the side funnel came with a filter so I figured the side pannel was meant to be an inlet?


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## ebackhus

Front fans should be intake. Side panels should be intake. Rear and top should be exhaust. This creates a stream that evenly flows over the computer hardware and doesn't suck in air already heated by the computer.


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## manic

I know, most cases that have a side fan that Ive dealt with blow in. I
guess the idea is to suck air in and blow in,on,or around the cpu. Imo
and testing this is wrong. Ive tested it both ways using motherboard 
monitor.With a prescott 2.8ghz machine, using a zalmon 7000 hsf.
If memory serves. It was small but I think I got a 2 or 3 degree cooler
reading with the fan blowing out. Mix and match yourself, see what you
think is best. Use mbm or some other temp recording software, then make
comparisons,,,,,A couple degrees can make all the difference.
Ps, when I have a fan with a varible fan control such as the zalmon hsf, 
I always crank the fan all the way up.


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## ctech

Yeah I am tying to figure out how to check my system temps right now but I don't know how yet. I posted a thread in the MB section and was told to find out if my MB had a monitor in the BIOS but I have not figured it out yet:4-dontkno. I would like to know how my system is performing with the CPU cooler that I have (it is supposed to speed up or slow down due to the CPU temp but it looks like it is the same speed all the time to me?)

I have my PC in an enclosed computer desk and my last PC died after only a little over a year so I want to make sure that it stays plenty cool. I will put some fans in the desk to blow out and in to help also.

Do they make fans that plug into USB ports by chance?


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## Tumbleweed36

ebackhus said:


> Front fans should be intake. Side panels should be intake. Rear and top should be exhaust. This creates a stream that evenly flows over the computer hardware and doesn't suck in air already heated by the computer.


This is the proper fan direction schematic as posted by ebackhus. 

Download and run SensorViewPro and it will tell you about your temps. Here is the link:

SensorView Pro 

http://www.stvsoft.com/download.php?id=122


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## ebackhus

ctech said:


> I have my PC in an enclosed computer desk and my last PC died after only a little over a year so I want to make sure that it stays plenty cool. I will put some fans in the desk to blow out and in to help also.
> 
> Do they make fans that plug into USB ports by chance?


Keeping a modern PC in an enclosed area is murder. They simply create too much heat to be kept like that.

There are USB-powered fans, but they're more meant to keep the user cool rather than the PC. :tongue" I do suggest getting slot fans. They fit into the empty slots of your case and do a great job exhausting heat. I installed one in a friend's PC after his kept having heat-related video problems. No problems ever since.

If you still plan to keep your PC enclosed then I suggest looking at liquid cooling.


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## ctech

Do you have a link to the type of fans you are talking about? I have seen narrow slot fans that blow out the back of the case and plug in to the PCI and I have seen some that blow at the video card? I have also seen many brands and most with bad reviews?

I will keep an eye on my temps once I find a good program that works... I have downloaded sensorsview and it only gives me a HDO reading. I have checked my BIOS and I can get my readings from there for now. If I start seeing high temps I will think about getting the liquid cooler...

Thanks,

-ctech


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## magnethead

I went and got a dual slot fan from fry's for 15 bucks, has a switch on the back so you can choose quiet (20 CFM) or high-flow (40 CFM).


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## Tumbleweed36

When you get it in, let us know the results. Have a great evening.


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## Wozer

hey tumbleweed, remember those pm's we shot back and forth about this subject, specifically fans over the cpu?

what I found from experimentation with my box is that the following setup worked the best for my box, which has 7HDDs, floppy and DVD burner.

I have 2 fans in front sucking air in, one in back blowing air out, and 2 fans on the side..the side fans are what I experimented with...I have one over my cpu, and another situated below it which is over the PCI slots, and fairly close to the AGP slot...the fan over the cpu blows in, and the other blows out...

as has been previously noted, take temperature readings to find the best setup for your system...it is 'common knowledge' that the front fans suck air into the case, and the rear blows out, and as noted in my setup the fans on the side of my case are setup as described, which gave the lowest temp readings for me..

good luck, as heat is a killer with computers!


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## Tumbleweed36

Whatever works best for you will do the job. By the way, where the heck have you been Wozer? Seems like you just up and disappeared on us. Have a great weekend.


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## Wozer

well....I got promoted and am now a supervisor (still do most of the actual carpentry work, but I am 'in control' of the crew) and that took a lot of my mental effort for a while...it also cured me of my 'internet addiction' and on this weekend specifically I am taking a break from thinking about projects and find myself back online for a bit...

but, back on the subject of this thread, heat *is* a killer (been lucky as while a drive or 2 has sustained 'aging' because of heat, I caught the problems before they got terminal) and I hope this d00d gets his setch under control..nothing like noticing a drive is wacking out..a drive which in my case had 232GB of 'valuable' data on it:wink:


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## PCG342

I'm not gonna get into the whole "Which setup is better" debate because it largely varies based on case/board/CPU design and you could all very well be wrong, you could all be right. We may never know for sure. What I _will_ do, however, is toss you another nice freebie -- in my opinion, better than Tumbleweed36's link -- download SpeedFan!
Dell notebook users take note: There's a special setting in there just for you! hooray.
For the rest of you, this is a pretty handy utility, but most settings are best left untouched, lest ye knows what ye's doing.... or whatever.


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## magnethead

I use speedfan for my computer. 

As to the slot fan, it's 15 bucks at fry's, and though my temps haven't moved, i can feel a good bit of air coming out of it on full speed.


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## magnethead

ok, i found the spec sheet that was in the packaging:

12 volt molex
130 grams weight
High speed: 37.5 CFM @ 2600 RPM @ 39.0 decibels
Medium Speed: 24.4 CFM @ 2000 RM @ 32.1 decibels
Low speed: 20 CFM @ 1500 RPM @ 24 decibels


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## ctech

Thanks Guy's for the info! I am going to add some slot fans and I am also going to mount a couple of fans to the air vents on my PC cabinet to pull some air thru the enclosure.


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## magnethead

the fan is an Antec by the way..forgot to menion that.


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## PCG342

I may be unobservant [Ha! Good one, me!] but have you tried changing placement of fan/direction of flow? Might just be, for lack of a better term, pulling the cool[er] air out of your case.


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## Kalim

ctech said:


> Two 80mm fans in front pulling air in.
> 
> One 80mm fan on top blowing air out.
> 
> One 120mm fan on the back blowing air out.
> 
> And one 80mm fan on the side blowing air in at the CPU.
> 
> I keep hearing conflicting views on this subject so I just used my on judgment. I am thinking about turning the fan on the side around thinking it would pull hot air away from the CPU but I also think that blowing cool air at the CPU is good also?


You'll hear conflicting news on this because most online "enthusiast" subscribe to a certain "following" and that is it. The fact is, that some setups work in one case and rig and not in another. What works best for you may vary from another so you have to play some trial and error games yourself. :wink:

The first thing I tend to try is to have more air being pulled out round the back/top than the air pressure created from the front/side intake fans. Because your PSU also helps with this and you need to displace the hot air inside the case outside the case in the end. I have the Thermaltake Armor Extreme mainly, which supposedly is the best designed for case cooling as AMD says, and they only recommend this case for the quad father setup; due to the massive volumes of heat it creates. Having 2 cards at the bottom means I don't use a side intake fan because it disturbs the airflow already prevalent and created by the front intakes (mine are watercooled BTW, very different situation to yours). But I do use an intake around the CPU/MOSFETs/VRs and it works well. My preferred exhaust fans are 2x 120mm.

So far I don't see anything wrong with your setup, however I would probably add an exhaust fan round the back if it was me- test result dependent. You need to test out various configs and you'll soon see what a nifty little piece of work it can be. :wink:

Monitoring software like Speedfan, SensorsView, Everest will all monitor the same sensors and it's a good thing to know what your temps are before you try any changeover.


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## Tino87

I just downloaded speed fan and its says that HD0 is hot. Wat is HD0 and wat can i do to fix it


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## ebackhus

HD0 is the first Hard Drive in your PC. To keep it cool you can install fans on the front of the case that suck air in and blow it over the HDD or you can put in HDD coolers.


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## Kalim

You can change the label in Speedfan if you like:

Configure>Temperatures, click one of the labels you'd like change, press F2 and then type the label for that device you'd like.


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## moejama

The BEST way to do it will be to have the side vent blow in and have the cpu FAN blowing toward the CPU pushing air through it.

This blasts the hottest component, which is by far the CPU with the coolest air.

The rest of the fans are really not even remotely as important except the PSU fan. The rest of the components will only need a minor air flow moving through the computer to keep them cool. 

A lot of people get overzealous on cooling in my opinion. You only need minor air movement to stop heat buildup inside the case, beyond that you don't need a jet stream of air but rather a highly quality copper base heatsink with a top quality paper thin layer of thermal paste. ALMOST EVERYONE USES TOO MUCH PASTE. This keeps the heatsink from making proper contact and greatly reduces your cooling and no practical amount of case cooling will compensate for bad heat transfer at the heatsink. 

High airflow in the case will come at the cost of faster dust buildup. The more airflow you have the more you should clean our your PC and keep it up off the floor or even use intake filters which truly keep your PC much cleaner and running longer and cost very little. 

The fact is the hdd and ram can run without much cooling and since they have no heatsinks usually fan cooling really doesn't do all that much for hdd temps. Your graphics card might also amount to some significant heat but rarely do they challenge the CPU in btu output. 

So case fans really need to merely prevent heat build up and that's not going to require a ton of air flow for the tiny amount of volume of your PC. The duct design works very well and tends to produce longer laster and more silent PC's with much less dust buildup. The standard CPU case filled with fans makes a lot more noise and builds up a lot more dust.

I usually do side in, front in, back out, and have the cpu fan blowing in. Since the PSU has it's own exhaust or two you already have exhaust and you have vents in the back so there is no need for extra exhaust fans in most situations. 

However, fan setups can be done almost any way, but the side in, cpu blowing in will usually perform the best. In very dust environments you might only want the side intake so you can just filter one easy to maintain fan rather than pulling in all that dust through the front of the case. It's always better to have more intake than exhaust to help manage dust flow. The back of the case fan is nice to form a nice system for intaking hot air blowing it into the cpu and then exhausting most of it right out through the back case fan and the PSU fan(s). Larger fans will clog up slower, run longer and produce less noise and that does make larger rear fans ideal such as the ones dell uses with their venting hood thang. 

This way a jet of cool air is constantly being injected directly into the cpu. Having a CPU sucking air through the CPU is just not the way to do it and clogs the CPU up with dust faster IMO. If you want to cool your HDD seriously get a heatsink for it and then the fans will actually be cooling otherwise they are merely preventing heat buildup in the case. Which of course is necessary, but only to the degree that you vent heat out as fast as it builds up. That is, it shouldn't take too much ventilation to keep case temps down AND since you have passive exhaust vents and a PSU exhaust you don't really NEED exhaust fans other than to brag about your case airflow. The irony is that you'd probably move the heat out of the case faster by moving it away from the CPU faster rather than simply by moving more air through the case. Hence the boom of water cooling, pelteir cooling, massive copper heatsinks and high priced thermal compounds. The real trick is getting heat OFF the cpu and keeping it's average temp down, that alone will give you more control over the case temps than a extra fan or two.. usually. On the other hand if you have 6 hdds, two video cards, dual cpus and just as much wattage as you can cram in there.. yea extra case fans will be necessary and getting a higher volume air flow will be beneficial BUT still not at the cost of extra dust buildup. 

If you must have all those fans, use intake filters on the side and front and clean them every 3 months or so. There isn't much point in installing extra fans for cooling which ultimately coat your computer with a heat insulating layer of dust, not to mention hdd's, DVD, floppy and other mechanical drives fail far more often in dusty environments. 

Personally I hate that computer need something as unreliable as fan cooling. It's disgusting that your 400 dollar graphic card could go up tomorrow from a failed 3 dollar fan and with little to no warning since graphics cards rarely have temp monitors and I've never seen thermal overload shutoff on a graphics card. Considering they cost more than most CPU's I think it's time manufacturers take cooling more seriously. 

I love water cooling and I hope it expands more. If your running water through the PC, why not cool the graphics card, chipset, ram and hdd all in complete silence. It's less points of mechanical failure and when put together well the cooling system won't leak. 

At the very least fans should be higher quality and dust prevention should become standard along with AUDIBLE warnings build into the fans when they fail rather than complicated monitoring software which most people will never install or use. If they hear their computer beeping on the other hand, they will at least have good warning. 

Unfortunately fans are made cheap and disposable rather than long lasting and made for the job of protecting your rather important electronics. I always try to avoid electronics with fans when I fan as they all collect dust, get loud and fail before the lifespan of the electronics. Worse is the slowly failing fan that doesn't even make a sound just spins a little bit slower every day giving the appearing of working but moving a fraction of the air it did when it was new. 

Slot fans are loud, expensive and move less air for their size. Beyond using them for graphic card cooling you should not need a slot cooler unless you have some crazy micro case. The real key is a well designed copper heat sink and ensuring cool air is being injected into the CPU. Many times people put their systems up against a wall, corner or inside a desk and greatly limit their ability to intake cool air. Most CPU temps are kept up by low quality heat sinks and installing too thick a layer of CPU compound. Rather than using air flow, use better transfer methods to get the heat OUT of the devices if you even need that much cooling. Air flow is overrated as a means to cool the components that truly get hot. 
You really only need minor air flow in the case to keep the heat radiated from the components from building up. Most people are using air flow to make up for a lack of quality heat sinks on their CPU, RAM and GPU. Once you have good heat radiation from the components a slight breeze is all it takes to move the heat out of the case and the PSU is already there as one exhaust. More pressure, less exhaust, I've done cooling for PC, houses and such and it's always more efficient to blow cool air into a space to lower it's temp than it is to pull hot air from the area.

Just put a fan in your window and try it out. Blowing in it will cool your room much faster, blowing out it will be pulling hot air from every corner of the house before a tiny stream of coolness gets to you. You want to deliver the coolness RIGHT to the hottest spot and that will effectively cool your area faster.


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