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Reversing a case fan
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Dagger
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PostPosted: Thu Dec 02, 2004 4:13 pm    Post subject: Reversing a case fan Reply with quote

Can reversing one of the 2 case fans really affect cpu temps that much? My system temp has stayed the same at 32C (89F) but the cpu temp has dropped from 55 to 57C (114F) to 30C (87F) I only stopped the comp for 5 mins while i dropped in a new 3.25 in floppy and changed the one fan around.
The one i changed is now sucking out the hot air about 5 inches from the heat sink. Is this normal?
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PostPosted: Thu Dec 02, 2004 5:14 pm    Post subject: Reply with quote

As regards technical matters, I'm generally regarded as a MORON around here, but that never stops me from posting an answer Razz .

Are the case fans "balanced" ?

That is, are there (and were there) as many sucking air in as are pushing air out ?

If they weren't balanced but are now, then there's your answer Cool .
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Dagger
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PostPosted: Thu Dec 02, 2004 5:47 pm    Post subject: Reply with quote

In the beginning there was the 2 3inch fans blowing in, and the one PSU fan blowing out, plus whatever air leaked out the different openings. Now it's the 1 3inch in and the 12cm and the 3inch blowing out. Running 2 FAH clients at once, (found some timeless WU) i'm running @ 35C on the CPU and 37C for the system, compared to before which was 55C/32C. At any rate colder is better.
[EDIT] After a reboot it's back up to 51 to 54C [/EDIT]
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PostPosted: Thu Dec 02, 2004 7:26 pm    Post subject: Reply with quote

Dagger wrote:
In the beginning there was the 2 3inch fans blowing in, and the one PSU fan blowing out, plus whatever air leaked out the different openings. Now it's the 1 3inch in and the 12cm and the 3inch blowing out. Running 2 FAH clients at once, (found some timeless WU) i'm running @ 35C on the CPU and 37C for the system, compared to before which was 55C/32C. At any rate colder is better.
[EDIT] After a reboot it's back up to 51 to 54C [/EDIT]


It can make a difference... but as you have since noticed it is not generally a huge difference... Wink

Another thing that will affect how well the fans work is their placement within the case... that is, it is somewhat counter-productive to have the PS fan blowing out and a second fan on the back blowing in as there is a reasonably good chance that the second fan will be blowing in warm air that was just expelled from the PS fan (was that clear?)...

Therefore my personal recommendation is to have the fan(s) on the front (or possibly side) of the case blow inwards while the fan(s) on the rear of the case blow outward... obviously it is always important to have the PS fan blow out, never in... Very Happy

Also, since it is difficult to have a truly balanced air-flow system I recommend that you have more air blowing in rather than out... the reason for this is so that you can filter the air coming into the case and therefore decrease the amount of dust (etc.) that accumulates (sp?) inside the case... that is, with a positive pressure system dust will not be sucked into your computer case through the various cracks & crevices as opposed to a negative pressure system where dust WILL be sucked into the case (I may have "+" vs "-" backwards) Cool

#ni-1 #ni-1 #ni-1
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PostPosted: Thu Dec 02, 2004 7:44 pm    Post subject: Reply with quote

The easy way to test is to remove the side panel and observe the temperatures. If you have good air movement, the temperature drop should be minimal. If not, you need to look for ways to improve circulation.
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PostPosted: Thu Dec 02, 2004 8:02 pm    Post subject: Reply with quote

Terry West wrote:
The easy way to test is to remove the side panel and observe the temperatures. If you have good air movement, the temperature drop should be minimal. If not, you need to look for ways to improve circulation.


Hmmm... I would think there would be a (slight) temperature increase when you remove the side panel if you have good circulation to begin with... after all, you really aren't pushing that air away from the CPU much with the case open as opposed to with the case closed (assuming you have a fan blowing air out near the cpu)... this is especially true if (God forbid) you have your computer in an enclosed area (like sooo many of those stupidly designed computer desks) *shrug*
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PostPosted: Thu Dec 02, 2004 8:34 pm    Post subject: Reply with quote

With the above system she was running a lil too hot for my taste (avg 57 to 59C!) So i moved the one fan that was sucking the air out by the CPU up to the top, where it's sucking from the ceiling so to speak. If i need to i can add more fans, i have room for 5 more. (2 front, 2 rear, 1 side.) Current locations.. Bottom side in, PSU out, Top out. The top one doesn't seem to be moving much air though, so i might have to relocate it once again. Is for computer location, my computer desk is an old kitchen table, closest things to it are the monitor, and a wall with a cold drafty window.
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PostPosted: Thu Dec 02, 2004 10:02 pm    Post subject: Reply with quote

Dagger wrote:
With the above system she was running a lil too hot for my taste (avg 57 to 59C!) So i moved the one fan that was sucking the air out by the CPU up to the top, where it's sucking from the ceiling so to speak. If i need to i can add more fans, i have room for 5 more. (2 front, 2 rear, 1 side.) Current locations.. Bottom side in, PSU out, Top out. The top one doesn't seem to be moving much air though, so i might have to relocate it once again. Is for computer location, my computer desk is an old kitchen table, closest things to it are the monitor, and a wall with a cold drafty window.


yikes... that cold drafty window could do horrible things like keep your system a little cooler.... Razz

I would personally add at least one, if not two, fans (really depends on the quality of the fans... ball bearings are the only good choice and something with a good CFM to noise ratio) to the front of the case... are those slots in a location where they could also help to keep the hard drive cooler? Very Happy
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PostPosted: Thu Dec 02, 2004 11:37 pm    Post subject: Reply with quote

Sir Latch wrote:

yikes... that cold drafty window could do horrible things like keep your system a little cooler.... Razz

I would personally add at least one, if not two, fans (really depends on the quality of the fans... ball bearings are the only good choice and something with a good CFM to noise ratio) to the front of the case... are those slots in a location where they could also help to keep the hard drive cooler? Very Happy


Laughing I had to slide the HD back just so i could put 1 of the fans in the front. But i should get at least 2 more, so i can shove on more on the front and the other back on the side to plug up that hole. And that cold drafty window also does horrible things like keep this room 10 degrees colder than the rest of the house.
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PostPosted: Fri Dec 03, 2004 12:06 am    Post subject: Reply with quote

Dagger wrote:

Laughing I had to slide the HD back just so i could put 1 of the fans in the front. But i should get at least 2 more, so i can shove on more on the front and the other back on the side to plug up that hole. And that cold drafty window also does horrible things like keep this room 10 degrees colder than the rest of the house.


but that's why you keep your computer running... electricity = heat... its like having a low wattage electric heater... why, if that window wasn't so drafty your room might be too hot Razz

Honestly though, why is the window drafty? Is the window just really old and therefore not very efficent at all? Or, is there air escaping between the window frame and the wall?

Oftentimes the area around the window frame is not sealed very well (especially in old construction) and if you were to pry the molding off from around the window, buy a can of expaning foam (make sure you get the type that is made for around windows and doors... the other type could cause the window frame to stress due to expansion), seal the area, and replace the molding... could make a HUGE difference... Shocked You do realize that even the best insulated houses can be very costly to heat and cool if the many. many areas where outside air infiltrates are not sealed, caulked, or otherwise plugged? Wink

Alternatively, if the window is only single pane (or old-style double pane and one of the panes is busted) you could buy the plastic sheet stuff they sell at home improvement stores and cover the entire window with that... made a big difference with the single-pane windows in the apartment I used to rent... best solution for an inefficient window is to replace it if possible though Confused




and that concludes this edition of DIY's "How to Insulate and Seal Your Home" Razz
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PostPosted: Fri Dec 03, 2004 9:28 am    Post subject: Reply with quote

Yeah it's old '60's contruction with an aluminum frame, single pane front with a turn handle, then another pane set back about an inch and a half with a slide portion. I'll try to draw what it looks like.

__________|__^^^_____ (The arrows indicate opening direction)
|_________|___<<<____| (The slider part)

It's all mounted on drywall that's chicken wire reinforced. (Found that out when we fixed up the bathroom to install a shower) Found the cause for my high temps i believe. My BOINC cli is running a Seti and CPDN WU at the same time, even though the one says it is paused, it's still running. Take that and add F@H to that, you get some high temps. I just find that wierd seeing as how i have the preempting set to no.
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PostPosted: Fri Dec 03, 2004 10:29 am    Post subject: Reply with quote

Keeping a pc cool is imho not a matter of just throwing in as much fans as possible, but getting a good airflow through the case. Obviously you won't get a good airflow through the case if you let fans on all sides suck in or blow out. See your pc as a sort of a (leaky) pipe. Air should flow in one direction, one way in, one way out. Having fans blow in all directions won't make air flow through the pipe.
Now, you can't suck in air at the back or else it'll just suck hot air from the power supply back in. And hot air rises, so if you put a fan on top then make it blow out.
So that leads to the commonly used setup to have fans suck in at the front, and blow out at the back/top/side near cpu. This way the air gets nicely moved over the mobo and cpu, and never gets recycled.
Basically what Sir Latch said, just with more words. Mr. Green

Then, imo it isn't of much use to put a fan on boths sides of the pipe, sucking on one end and blowing on the other. I mean, they're both doing the same. Having only one fan at one end will still move the same amount of air through the pipe. So imo you can better move the fan from one end to the other so they'll both be blowing in the same direction next to each other. This way you'll move more air through the case with the same amount of fans (and noise). Offcourse this doesn't work if you have a seriously leaky case.
So if the above suck/blow setup works right for ya, you can try having either only fans sucking in at the front, or only having fans blowing out at the back/top. It's a matter of trying out different setups and see which one works best.

For example, my pc is a XP 2800+ running at max overclock. I only have two low-cfm, throttled down, 8cm fans blowing out at the back, and a quiet power supply that doesnt move much air on its own. My temps are 49C for the cpu and 27C for the system while folding
(plus it's dead-silent, my refrigator makes more noise).

(Another tip, take the fan off the cpu-heatsink and clean the heatsink with the vacuum-cleaner. The dust in there can make a few degrees difference.)


Sir Latch wrote:
ball bearings are the only good choice


Not if you want quiet fans. Smile


Dare I mention it..
You can find tons of info on cooling your pc with minimum fans on the site of a rivalling team: SPCR
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PostPosted: Fri Dec 03, 2004 10:42 am    Post subject: Reply with quote

one instance of folding and i'm running at 60/40, that's with 2 blowing in, Front and side, and the PSU blowing it out.. I'll see what i can do to fix it.
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PostPosted: Fri Dec 03, 2004 5:12 pm    Post subject: Reply with quote

I agree with most everything that's been said - smooth airflow is the key. A few ideas:

Using a good CPU heatsink and fan, and using good thermal paste (not pads)

Keeping flat IDE cables tucked away, out of the airflow

I think it helps to have that additional exhaust fan in the back. The PSU will be a little cooler and more efficient if it doesn't have to exhaust all the CPU's heat as well as its own.

Whatever works.

Frank
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PostPosted: Fri Dec 03, 2004 7:54 pm    Post subject: Reply with quote

The King of Swamp Castle wrote:
Keeping a pc cool is imho not a matter of just throwing in as much fans as possible, but getting a good airflow through the case. Obviously you won't get a good airflow through the case if you let fans on all sides suck in or blow out. See your pc as a sort of a (leaky) pipe. Air should flow in one direction, one way in, one way out. Having fans blow in all directions won't make air flow through the pipe.
Now, you can't suck in air at the back or else it'll just suck hot air from the power supply back in. And hot air rises, so if you put a fan on top then make it blow out.
So that leads to the commonly used setup to have fans suck in at the front, and blow out at the back/top/side near cpu. This way the air gets nicely moved over the mobo and cpu, and never gets recycled.
Basically what Sir Latch said, just with more words. Mr. Green

I was thinking that Razz

The King of Swamp Castle wrote:
Then, imo it isn't of much use to put a fan on boths sides of the pipe, sucking on one end and blowing on the other. I mean, they're both doing the same. Having only one fan at one end will still move the same amount of air through the pipe. So imo you can better move the fan from one end to the other so they'll both be blowing in the same direction next to each other. This way you'll move more air through the case with the same amount of fans (and noise). Offcourse this doesn't work if you have a seriously leaky case.

I find most cases tend to have rather serious leaks. Laughing

The King of Swamp Castle wrote:
So if the above suck/blow setup works right for ya, you can try having either only fans sucking in at the front, or only having fans blowing out at the back/top. It's a matter of trying out different setups and see which one works best.

The problem is it really is, IMO, best to have at least on fan blowing out near the CPU... under your instructions this would mean you should have both blowing out in the rear (none in the front)... this imbalance will cause air to seep into the case wherever possible along with a rather large amount of dust (which is not conducive to cooling)... even if you have a well-sealed case air is going to come in unflitered (filter it without the assistance of a fan blowing through the filter and you generally won't have enough suction) through the front of the case. Razz

The King of Swamp Castle wrote:

For example, my pc is a XP 2800+ running at max overclock. I only have two low-cfm, throttled down, 8cm fans blowing out at the back, and a quiet power supply that doesnt move much air on its own. My temps are 49C for the cpu and 27C for the system while folding
(plus it's dead-silent, my refrigator makes more noise).

Have you noticed a lot of dust bunnies in your computer? Of course, it depends on how well your house is sealed from the outside but we know Dagger (due to the drafty window) is really not sealed so well. Razz

The King of Swamp Castle wrote:

(Another tip, take the fan off the cpu-heatsink and clean the heatsink with the vacuum-cleaner. The dust in there can make a few degrees difference.)

*agree* Cool

The King of Swamp Castle wrote:
Sir Latch wrote:
ball bearings are the only good choice


Not if you want quiet fans. Smile

I am referring to the fact that they are much less prone to failure than sleeve bearings...but please enlighten me on what is quieter... sleeve bearings or something else? Confused

The King of Swamp Castle wrote:

Dare I mention it..
You can find tons of info on cooling your pc with minimum fans on the site of a rivalling team: SPCR

As a matter of fact in one of their articles the author (of the article) states, very similarly to my own statement, that 2-In 2-Out seems best with the only caveat being that they be run at 50% normal speed. The article is here... scroll down about halfway to "My Conclusions." Very Happy
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PostPosted: Fri Dec 03, 2004 7:55 pm    Post subject: Reply with quote

Frank the Historian wrote:

Keeping flat IDE cables tucked away, out of the airflow


Or you can buy the cables that are round Wink
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PostPosted: Fri Dec 03, 2004 8:19 pm    Post subject: Reply with quote

Had a triple heat extract going, but it didn't turn out to well, got up 63C on the chip, so i shut er down, moved the bottom most fan back on the side blowing in on the northbridge and just under the heatsink. BTW there is hardly any dust as this is a new system that i had just built last month.
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PostPosted: Sat Dec 04, 2004 12:12 am    Post subject: Reply with quote

You really only need 1 fan (click for specs):


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PostPosted: Sat Dec 04, 2004 12:13 am    Post subject: Reply with quote

jonnyv wrote:
You really only need 1 fan:



#Rofl
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PostPosted: Sat Dec 04, 2004 6:10 am    Post subject: Reply with quote

Sir Latch wrote:
The problem is it really is, IMO, best to have at least on fan blowing out near the CPU... under your instructions this would mean you should have both blowing out in the rear (none in the front)... this imbalance will cause air to seep into the case wherever possible along with a rather large amount of dust (which is not conducive to cooling)... even if you have a well-sealed case air is going to come in unflitered (filter it without the assistance of a fan blowing through the filter and you generally won't have enough suction) through the front of the case. Razz

Him again wrote:
Have you noticed a lot of dust bunnies in your computer? Of course, it depends on how well your house is sealed from the outside but we know Dagger (due to the drafty window) is really not sealed so well. Razz


I didn't instruct, I just suggested. Wink
Yes, but filters obstruct the airflow again, therefore you need more/faster fans which makes it more noisy. Whatever your priorities. I just want my pc to be both cool and dead-quiet. Every few months I go through it with the vacuum cleaner. The amount of dust it collects isn't really that much (considering the work i'm doing on my house and I have 2 cats running around).
You will find many debates over using filters and positive/negative pressure on the spcr forum (search for posts of a guy named 'bluefront'). There isn't really one "right" solution, there are just pros and cons.

Him wrote:
Me wrote:
Him wrote:
ball bearings are the only good choice


Not if you want quiet fans. Smile

I am referring to the fact that they are much less prone to failure than sleeve bearings...but please enlighten me on what is quieter... sleeve bearings or something else? Confused


Well, the general opinion I picked up over there is that ball bearings last longer, but they tend make slightly more noise. But the difference is very little I think. Perhaps the bearing can ratlle more if it has a cheap construction, or it has a more 'scrapy' sound when it rotates. You have to understand that I run fans at only half speed. At that speed there is hardly any sound from the air or the motor. Any oddity in the sound is audible then. And there are more reasons why some fans make more noise then others. I've tried many brands, cheapos, expensive ones. I got a box full of them. Many so-called silent fans are whiny bastards (don't buy Zalmans!). If sleevebearings won't last as long, then too bad. I rather buy a new fan every 2 years then hear it rattle. Smile
Spcr has a forum dedicated to fans. Smile Atm what are considered the quietest fans are Panaflos and Nexus. Panaflo uses an alternative to sleevebearing, which is supposed to be both quiet and longer lasting. (I use nexus and am very pleased with them)

Him wrote:
As a matter of fact in one of their articles the author (of the article) states, very similarly to my own statement, that 2-In 2-Out seems best with the only caveat being that they be run at 50% normal speed. The article is here... scroll down about halfway to "My Conclusions." Very Happy


Isn't that article mainly about getting the quietest setup? If you open the pdf sheet you'll see that they are trying different setups but they only measure noise and no temps.


This is starting to sound like spcr


and I just ran away from there.

So I'm gonna shut up now. If you want to talk about fans, go over there.

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