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View Full Version : Power Supply Poll: Do your fans suck or blow?



Billy T
23-07-2004, 10:39 AM
Hi Team

This thread (http://pressf1.pcworld.co.nz/thread.jsp?forum=1&thread=49409) about power supplies raises an interesting question.

Do your power supply fans suck or blow?

I hadn't given this a moment's thought until now, but my curiosity has been aroused. Logic says they should draw the (cooler) ambient air in, and expel the heated air to maximise the cooling effect. This would seem to be particularly important with high power CPUs and video cards because their heatsinks are only as effective as the temperature gradient between them and the surrounding air.

To blow pre-heated air into the case would be a very strange idea in my opinion.

My fans all suck cool air in.

How about yours?

Cheers

Billy 8-{) ?:|

andrew93
23-07-2004, 10:49 AM
I thought all PSU fans blew air out of the case - I haven't yet seen one that goes the other way. By forcing the hot air out of the back of the PC, the cooler air is usually drawn in through the front and side vents. Check out the accumulated dust inside the case and how it sits on various bits - this will tell you which way the air is moving.

> Do your power supply fans suck or blow?

Just wait for those Austin Powers / school boy humour jokes to flow.....
:D

tweak\'e
23-07-2004, 10:53 AM
virtually all psu's have the air flow going from the case throught the psu to the outside. having the reverse would cook the pc. a psu can handle 40 degree air temp no problems but motherboards, vid cards, hardrives etc don't like being cooled by such high temps.

however i have known techs to reverse psu fans simply to get the (non-standard) psu's to last more than a month on some very shitty pc's.

CYaBro
23-07-2004, 10:55 AM
I'm 99.99% sure that every PSU I've seen the fan blows air out of the PSU.

PaulD
23-07-2004, 10:55 AM
Isn't it part of the overall ATX spec that PSU sucks air from case?

Billy T
23-07-2004, 10:57 AM
LOL :^O

I agree with your technical point too, but there are arguments both ways that only a poll can resolve.

One of my computers uses an old Compaq XT psu adapted to fit a standard PC. It has the biggest and quietest mother of a fan you have ever seen, and it definitely sucks outside air into the box.

Cheers

Billy 8-{)

godfather
23-07-2004, 12:19 PM
All my systems (4) have the fan extracting air from the PC case and blowing it out the back.

These include brand name PCs and custom built. Even the laptop extracts the air from the case to the outside.

Tobas
23-07-2004, 12:43 PM
The power supply generates heat, the fan pulls air over the power supply and blows the warmer air out the back.

Fresh and cooler air is drawn in the front and side vents to replace the warmer air blown out the back.

Pure logic.

beetle
23-07-2004, 12:45 PM
:o

without taking the comp apart (which is not a good beetle idea) how can i tell which way it goes?
i dont think i am techie enuf to open the box yet, but had a thought - ]:)
if i block all vent areas it will cause over heat and cook my comp? = get new comp?
no i wouldnt do that im to honest and patient..... im just waiting for it to die so i can replace it.
:D

and also does that mean you shouldnt have stuff (paper etc) around tower then ? cause overheating?

;)

and really not a good idea to say beetle pull the tower to peices.....it may never survive the activity :D


beetle

andrew93
23-07-2004, 12:50 PM
test the airflow at the back of the PC as you would test the direction of the breeze outside....

godfather
23-07-2004, 12:51 PM
beetle, the power supply is located where the power plug goes in the back of the PC.

If the fan that is close to that socket extracts air from the case you van feel it blowing out on your hand.

Oh - the power must be on and the PC running of course :)

beetle
23-07-2004, 12:54 PM
With a hammer ???? :D

lol slight problem you havent seen my desk lately and the effort to see the back of the pc...lol maybe should tie some little ribbons onto back of case for pretty test.....
my comp desk is not a on wheels type and takes at least 2 people to lift it when empty let alone move it while chocka block of junk and school work.

thanxs anyway.

beetle

beetle
23-07-2004, 01:01 PM
LOL after knocking a few things off the desk i can reach that far, but dont feel a breeze just lots of heat? im taking it thats not a good sign?

and all i can tell you is noise wise it hums....well i think it hums, thats what it sounds like, should get hubby's ears to listen as i cant tell the diff.....

and no air coming out is not good huh? shoould i get someone to check it and clean it then?

how often do people dust their comps?

?:|

beetle

andrew93
23-07-2004, 01:08 PM
sorry beetle - I meant for you to lick your finger and see which side feels cold when you hold it near the fan. No ribbons necessary. :)

beetle
23-07-2004, 01:13 PM
Well i see...... finger pointing time is it??

for me to currently get to the back of my tower box i have to stand on my desk.......... not a good sight to see that one...

and how many things can i dislodge at this point ? oooh lots..... maybe a new post would be what does your comp desk look like?

hmmmm

beetle

Cptn Hotshot
23-07-2004, 01:30 PM
I guess it is relative as to the postion you consider it. If you are looking at it from the point of view of inside the case, I guess it would be blowing it. out However, if you looking at it from outside the case, I guess it it would be sucking it out!

:-)

mikebartnz
23-07-2004, 01:57 PM
To me it would make more sense having the air flow in through the PSU and out through the case vents. That way in a dusty enviroment you could filter the one intake. I have found over the years a few floppy and CD's that have not been used for a long period become so dirty they wouldn't read. I have another case fan so I don't think the heat from the PSU would be a problem. It has more to do with actual air flow.

Cptn Hotshot
23-07-2004, 02:00 PM
.... on second thoughts, if air is being removed from the case, it has to be replaced by something, which is AIR!. So in this situation, the air which is being blown out (or is it sucked out, if you are outside the case?) is being replaced by air being sucked in. :D :D

JJJJJ
23-07-2004, 04:23 PM
I think Billy T is trying to start something. ;\
In all STANDARD cases the fan is sucking hot air out which is replaced by cold air through the vents. That is why the fan is at the top of the case. Warm air rises. If you have a fan at the bottom of your case it is sucking cold air in.

That reminds me of something I was told years ago when I was learning to fly. That big fan blade on the front of the aircraft is blowing air back to keep the pilot cool. If you don't believe that, watch the pilot sweat if his fan stops.
Jack

Elephant
23-07-2004, 04:40 PM
My PSU has two fans both of which remove air from the tower case and expel. Air incoming is from the ambient air in the room where the computer lives.

One fan at the bottom of the PSU and one on the back.

Elephant
23-07-2004, 04:51 PM
> oooh lots..... maybe a new post would be what does
> your comp desk look like?
>
> hmmmm

Errrrkkk. Hurries to remove used beer cans, coffee cups, word docs I haven't looked at in yonks, assorted manuals etc.

All this before taking photo.

Please bear in mind that a clean desk is a sign of nothing much else to do.

Maybe when you get the camera back you could start?

Megaman
23-07-2004, 05:04 PM
i'll refrain from making a comment i'll regret :p

my one blows

Elephant
23-07-2004, 05:43 PM
> To me it would make more sense having the air flow in
> through the PSU and out through the case vents. That
> way in a dusty enviroment you could filter the one
> intake. I have found over the years a few floppy and
> CD's that have not been used for a long period become
> so dirty they wouldn't read. I have another case fan
> so I don't think the heat from the PSU would be a
> problem. It has more to do with actual air flow.

If you really want to know I suggest you go here for a look. The photo looks like the front of a case to me. The photo is linked off my LangaList Newsletter which I get weekly.

http://freetune.com/images/PIC000018.JPG

If you want to know more about LangaList then go here:-
http://langa.com/newsletters/2004/2004-07-22.htm

All well worth a read in my opinion.

The link to the photo mentioned is near the bottom of the LangaList newsletter given.

I'm almost sure I have recommended this newsletter in the past.

Please note that I get the standard edition at no charge and I don't work for them.

TonyF
23-07-2004, 05:49 PM
The answer to the question as posed must be YES.

Elephant
23-07-2004, 06:13 PM
> i'll refrain from making a comment i'll regret :p
>
> my one blows

I will try to make this more clear. :-)

I have ONE power supply unit (PSU).

This has TWO fans!

One fan sucks air into the PSU and the other fan removes air from the PSU. If I am inside the PSU then one sucks and the other blows. I must admit that I can't get inside the PSU to test this right now. If I am inside the case then both suck. If I am outside the case then both blow.

A little like if I want to give people directions on how to get to my place isn't it.

If you leave from JAFA land you come down SH1 and turn right. If you leave from Wellinton you come up SH1 and turn left. It all rather depends on where you are. Whether a fan blows or sucks depends on the way you look at it. If I am inside my case then both fans suck as there is no airflow from the PSU INTO the case. If I am inside the PSU then one sucks and one blows. If I am outside the case then both blow do they not?

All people look at things differently and that's the way it should be. I can look at a glass half full of liquid and describe this as being half EMPTY or half FULL. Either description will be accurate in my opinion.

Growly
23-07-2004, 06:22 PM
Suck, suck, suck, blow, blow, blow, suck.

Billy T
23-07-2004, 06:28 PM
Okay, I'm convinced. :D

Logic said that the fan should suck air out of the case, but I have these two disparate computers in my office that are definitely blowing air into the case, and no, I have not fiddled with them in any way, apart from modifying the Compaq wiring by extending it via cut-offs from an old XT supply so that I could have two plugs instad of Compaq's proprietary single plug arrangement.

If I start trying to work out why both of my supplies suck instead of blow my brain is likely to explode before I can get WFTWE done so thanks to all who contributed.

Cheers

Billy 8-{)

-=JM=-
23-07-2004, 06:46 PM
All depends on what side of the fan you stand on ;-)

Yes, mine blows out hot air to my room, keeping my room warm.

mikebartnz
23-07-2004, 06:48 PM
I have seen one almost as bad as the one in the picture. Why it wasn't cooked I don't know.

mikebartnz
23-07-2004, 08:13 PM
>Yes, mine blows out hot air to my room, keeping my room warm.
Mine doesn't keep my room warm,. :D

Elephant
23-07-2004, 08:36 PM
> >Yes, mine blows out hot air to my room, keeping my
> room warm.
> Mine doesn't keep my room warm,. :D

Well then.

Use an AMD CPU like I do.

BTW my CPU fan blows if I am sitting on the CPU or sucks if I sit on the fan.

Your mileage may vary!

Before anyone asks my CPU reports 40 - 50 degrees celsius as far as I can tell. Inside case is usually 20 -28 degrees.

It all depends on which side of the fan you are doesn't it?

:-)

Elephant
23-07-2004, 08:47 PM
So stand outside the computer and hold a hand close to the psu fan. You should feel a little draught coming from the fan.

If you have rewired something and I have no idea what you are on about then you may have reversed the polarity. In which case the fan will be in reverse. If this is the case then the fan will not cool the PSU.

I guess the question you ought to ask is does the fan on the PSU revolve clockwise or anticlockwise?

Stand at the back of the system unit, or box or hard drive or whatever you want to call it. (see previous threads on this)

Which way does it turn?

mikebartnz
23-07-2004, 08:47 PM
If my room was just a little bigger than my case my AMD might keep me warm. :D
I'm going to be adding some insulation very shortly because I can have the fire roaring 2.5 metres away and still be cold on a day like today.

Elephant
23-07-2004, 08:56 PM
> If my room was just a little bigger than my case my
> AMD might keep me warm. :D
> I'm going to be adding some insulation very shortly
> because I can have the fire roaring 2.5 metres away
> and still be cold on a day like today.

Oh goodness gracious me. I was going to say B****R

Please ensure that you move elsewhere then to a tropical area like Hawaii. That will cure the heat problem.

Unfortunately you will have to put something that will get rid of humidity in your case. Air conditioning perhaps?

:-)

PaulD
23-07-2004, 09:00 PM
"All people look at things differently and that's the way it should be. I can look at a glass half full of liquid and describe this as being half EMPTY or half FULL. Either description will be accurate in my opinion."

If you were an engineer you would describe the glass as being too BIG.

John Grieve
23-07-2004, 09:53 PM
I build the odd machine for gaming friends and I always try to create a virtual wind tunnel in the box which moves air directly from the front of the case using 2 - 3 fans sucking across the motherboard etc (I hand cut my own holes) and being blown straight out by 2 - 3 fans on the back blowing out.

I want the air to move fast across the whole motherboard to help cool not just the CPU and videocard but the new "bridge" chipsets (which nowadays generate substantial heat). I also like to mount fans in front of the hardrives if the case will allow or can be coaxed with a hacksaw :D

If you use the new silent fans you can just about have a normal conversation when your PC is running :D

Big John
23-07-2004, 10:33 PM
Mine sucks air from just over the CPU cooler fins/fan and takes it into the PSU and then blows it out the back of the PSU. It has two fans in it.One that is just above the CPU and one on the outside of the PSU.

This sucks the warm air off the CPU cooler and creates an additioonal draft over it.

If it was the other way around it would just be pushing the warm air from the PSU onto the CPU fan and also the cooler fins. This would defeat the purpose.

Big John
23-07-2004, 10:35 PM
> "All people look at things differently and that's the
> way it should be. I can look at a glass half full of
> liquid and describe this as being half EMPTY or half
> FULL. Either description will be accurate in my
> opinion."

Depends if your an optimist or a persimist.

> If you were an engineer you would describe the glass
> as being too BIG.

Not really. You would say you left room for expansion.

metla
23-07-2004, 11:05 PM
In many small form factor PSU's the fan is located on the outside of the psu but internally casewise,it blows air thru the psu,Rather then how a normal psu works..ie on the outside edge,sucking air through the psu.

As to what the thread stater was i think referring to,A PSU that sucks cold air from outside and blows it over the CPU....I did read somewhere that the original ATX Standard was designed this way,It fell over as the air was warmed as it passed through the psu......I do believe it may have been nearly suiltable for a cpu from many years ago,They didnt exactly need a lot of cooling.

exLL
23-07-2004, 11:21 PM
No matter which way it goes, I hope the fans keep their cool if there is any hot-headedness at the rugby on Saturday. :D

metla
23-07-2004, 11:28 PM
The Boks by 8.

Rob99
23-07-2004, 11:36 PM
> half EMPTY or half FULL

Its impossible to have something half empty, if empty is nothing, how can you have half of that???

Rob

btw. my fan blows, all fans blow, you need a vacume or simmilar to suck

metla
23-07-2004, 11:39 PM
The vacume just depends on what side of the fan your on.....

andrew93
23-07-2004, 11:49 PM
> The Boks by 8.

really?

metla
23-07-2004, 11:53 PM
> > The Boks by 8.
>
> really?



heh?....we wont know until the game is played,and if so it will suck more then any fan can blow......

andrew93
24-07-2004, 12:57 AM
> heh?....we wont know until the game is played,and if
> so it will suck more then any fan can blow......

:^O

lol - and it took 40 or so posts for the school boy humour to come out - but its still funny

good on ya metla and BTW congrats on the recent arrival

:^O

Megaman
24-07-2004, 10:12 AM
Elephent> I ment towards the original statement "Does your PSU suck or blow" :p

stumpey
24-07-2004, 12:01 PM
I note some regferences here to "AMD".

In the early 70's (ie last century - not mine) I had a straightfaced engineer extol the virtues of a new processor (yeahh - mainframe of course) which blew air down instead of up. Made sense because it didn't drag dust etc of the floor. Of course being computer engineers they had to cme up with new acronym - AMD or "Air Movement Device". Only a computer designer could come up with a three letter acronym to replace a three-letter word!! It's true = I saw the circuit diagrams. (AMD1; AMD2 ..... et al)

Megaman
24-07-2004, 06:24 PM
ummm... you realise we're talking about AMD (Advanced Micro Devices) Processors ?:|

Winston001
25-07-2004, 12:45 AM
Is this where I jump in with

" No Marybeth, it's just a figure of speech"

No???......... oh well.....(slinks off to pull the wings off some flies)......