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Case fans question...



 
 
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  #1  
Old June 21st 04, 08:54 PM
Travis King
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Posts: n/a
Default Case fans question...

I have three questions regarding case fans even though I know that this is
an Asus newsgroup. Should the back case fan blow in air or blow out air?
Should the case fan in the side panel blow in air or blow out air? Should
the case fan on the top blow in or blow out? Help would be appreciated.
Thanks.


  #2  
Old June 21st 04, 09:21 PM
Paul
external usenet poster
 
Posts: n/a
Default

In article 72HBc.70875$Hg2.61444@attbi_s04, "Travis King"
wrote:

I have three questions regarding case fans even though I know that this is
an Asus newsgroup. Should the back case fan blow in air or blow out air?
Should the case fan in the side panel blow in air or blow out air? Should
the case fan on the top blow in or blow out? Help would be appreciated.
Thanks.


(Pg.26 has a section on the computer case)
http://www.amd.com/us-en/assets/cont...docs/23794.pdf

Case air 40C
Case air to room air difference less than 7C difference.
Air from lower front to upper back.
Power supply fan doesn't count as a fan (too slow).

Fans not associated with back to front, should do whatever is
best for the whole case. A CPU (side) fan should exhaust, to carry
the CPU air away from the case, and avoid mixing with the rest of the
case air. The assumption is, the CPU fan is responsible for
getting the heat transferred from the CPU heatsink to the air, and
any other fans can be used to carry the hot air away.

The analysis of using fans from multiple directions, blowing in and
out, is really complicated, and you have to be careful not to create
unintentional dead zones in the case, due to spoiling the simple
front to back airflow. For example, too many fans blowing in, from
all directions, might leave the disk drives in a dead zone. If the
back fan is stronger than the front fan, there will be negative
pressure around holes next to the disk drives, and help carry cool air
from front inlet vents, past the disks. If the front fan was much
stronger than the back fan, warm air could end up blowing out the front
of the case, heating the disk drives as it leaves.

The disks deserve the most attention, as they have the most to lose.
Anything else that overheats, will just crash, until it cools
off again.

And I'm still waiting for a credible theory as to what config
doesn't cause dust to build up :-)

Paul
  #3  
Old June 21st 04, 09:22 PM
Silvertip
external usenet poster
 
Posts: n/a
Default

Front and side fans should pull the cooler air IN to the case. Back and top
fans should pull the hot air OUT of the case. If you don't have a front
case fan, then try to have the side panel fan approximately twice the cfm of
the other two combined. You want the input and output to be as close to
equal as possible.
Silvertip
"Travis King" wrote in message
news:72HBc.70875$Hg2.61444@attbi_s04...
I have three questions regarding case fans even though I know that this is
an Asus newsgroup. Should the back case fan blow in air or blow out air?
Should the case fan in the side panel blow in air or blow out air? Should
the case fan on the top blow in or blow out? Help would be appreciated.
Thanks.




  #4  
Old June 23rd 04, 07:00 PM
Matt
external usenet poster
 
Posts: n/a
Default


"Silvertip" wrote in message
ink.net...
Front and side fans should pull the cooler air IN to the case. Back and

top
fans should pull the hot air OUT of the case. If you don't have a front
case fan, then try to have the side panel fan approximately twice the cfm

of
the other two combined. You want the input and output to be as close to
equal as possible.


I like having a slight positive case pressure. I use intake filters on the
fans in front and this keeps dirt out of the optical drives. I use a single
80mm exhaust fan at the top/rear of the case. I also use a filtered intake
80mm fan at the rear of the case that is ducted to the cpu HSF so that the
cpu gets room temp air instead of heated air. Using Digital Doc, I have
found that this keeps everything the coolest.


  #5  
Old June 24th 04, 03:13 AM
Rusty
external usenet poster
 
Posts: n/a
Default

Case air flow is dependent on case design, motherboard layout in the case,
position of additional pci/apg cards, type of cooling on the cpu and video
card (fan, heatsink, water cooled), wire location, and wire configuration.
In general you want air to flow in at the bottom front of the case and out
the upper back of the case. Having said that, the blow hole in the top of
the case would move hot air out using natural convection forces (hot air
rises). Seeing that the fans in the back of the case are elevated in
comparison to the front of the case hot air would naturally exit the upper
back of the case, therefore the fans in the back of the case should exhaust
out hot air (blow air out of the case).

The issue of the side case fan blowing air into or out of the case depends
on the location of the fan. If the side case fan is located relatively
close to the cpu then the side case fan should blow air into the case. If
the side case fan is located above the cpu and relatively close to the power
supply it should blow air out of the case. In most of the cases I have seen
the side panel case fan is located relatively close to the cpu and therefore
should blow into the case providing cool fresh air to the cpu fan.

In relationship to a positive or negative pressure in the case, my
experience and testing lead me to believe that a positive case pressure is
better for two reasons. One, the positive pressure will prevent dust from
entering into the CD drives and covering the laser lens. Two, a positive
pressure keeps the heat build up around the power supply from entering into
the case around the cpu. A positive pressure means that you will have
higher cubic feet per minute fans blowing into the case than out of the
case.

The best way to setup case cooling is to use a fan contoller or manually
adjustable high speed variable fans (thermaltake smart fans, evermax fans)
especially at the front intake area of the case and buy a cheap
indoor/outdoor thermometer to monitor the temperature, adjust the fan speed
and watch the case temperature at various spots (esp around the cpu and hard
drives). Remember that more case fans does not lead to better cooling,
proper air flow though the case leads to better cooling. It also helps to
remove those stupid built in hole drilled case grills with a demel or tin
snips and use a wire grill in its place (if necessary).

If you think that this is long, you should see an engineering paper or
article discribing the effects of fan placement within a PC case. It is
very complicated and unpredictable. Try it, monitor it, and see if it works
for you.


"Travis King" wrote in message
news:72HBc.70875$Hg2.61444@attbi_s04...
I have three questions regarding case fans even though I know that this is
an Asus newsgroup. Should the back case fan blow in air or blow out air?
Should the case fan in the side panel blow in air or blow out air? Should
the case fan on the top blow in or blow out? Help would be appreciated.
Thanks.




  #6  
Old June 24th 04, 04:14 AM
Travis King
external usenet poster
 
Posts: n/a
Default

My computer has a case temperature sensor on the front of although I don't
know how good it is, and is also doesn't to Celsius; it does Fereignheit.
Keep in mind that my room doesn't have air-conditioning - it's running at
84.2. My room is in the basement. (I'm the 16-year old son.) I have the
Aspire X-Dreamer II case.
http://www.newegg.com/app/ViewProduc...144-026&depa=0
FYI: My case came with the side panel fan and the top fan. Both of these
have the holes cut out already with alien grills. I also bought an aluminum
case fan with blue LEDs. I'm a little disappointed in it because it doesn't
have as much air flow as the rest of my fans do. I've also upgraded the PSU
to a 400w PSU with 2 fans. (I know the PSU fans to play much of a role)
I've got an Asus A7V333 motherboard, AMD Athlon XP 2400+ CPU, Kingston
PC-3000 DDR RAM, NVIDIA GeForce3 Ti200 128MB DDR TV Out, 200GB of total disk
space (2 WD's), etc. etc. My system is not water-cooled.
"Rusty" wrote in message
...
Case air flow is dependent on case design, motherboard layout in the case,
position of additional pci/apg cards, type of cooling on the cpu and video
card (fan, heatsink, water cooled), wire location, and wire configuration.
In general you want air to flow in at the bottom front of the case and out
the upper back of the case. Having said that, the blow hole in the top of
the case would move hot air out using natural convection forces (hot air
rises). Seeing that the fans in the back of the case are elevated in
comparison to the front of the case hot air would naturally exit the upper
back of the case, therefore the fans in the back of the case should

exhaust
out hot air (blow air out of the case).

The issue of the side case fan blowing air into or out of the case depends
on the location of the fan. If the side case fan is located relatively
close to the cpu then the side case fan should blow air into the case. If
the side case fan is located above the cpu and relatively close to the

power
supply it should blow air out of the case. In most of the cases I have

seen
the side panel case fan is located relatively close to the cpu and

therefore
should blow into the case providing cool fresh air to the cpu fan.

In relationship to a positive or negative pressure in the case, my
experience and testing lead me to believe that a positive case pressure is
better for two reasons. One, the positive pressure will prevent dust from
entering into the CD drives and covering the laser lens. Two, a positive
pressure keeps the heat build up around the power supply from entering

into
the case around the cpu. A positive pressure means that you will have
higher cubic feet per minute fans blowing into the case than out of the
case.

The best way to setup case cooling is to use a fan contoller or manually
adjustable high speed variable fans (thermaltake smart fans, evermax fans)
especially at the front intake area of the case and buy a cheap
indoor/outdoor thermometer to monitor the temperature, adjust the fan

speed
and watch the case temperature at various spots (esp around the cpu and

hard
drives). Remember that more case fans does not lead to better cooling,
proper air flow though the case leads to better cooling. It also helps to
remove those stupid built in hole drilled case grills with a demel or tin
snips and use a wire grill in its place (if necessary).

If you think that this is long, you should see an engineering paper or
article discribing the effects of fan placement within a PC case. It is
very complicated and unpredictable. Try it, monitor it, and see if it

works
for you.


"Travis King" wrote in message
news:72HBc.70875$Hg2.61444@attbi_s04...
I have three questions regarding case fans even though I know that this

is
an Asus newsgroup. Should the back case fan blow in air or blow out

air?
Should the case fan in the side panel blow in air or blow out air?

Should
the case fan on the top blow in or blow out? Help would be appreciated.
Thanks.






  #7  
Old June 25th 04, 03:52 AM
Rusty
external usenet poster
 
Posts: n/a
Default

After looking at the case, I would recommend that you place the highest air
flow fans in the lower front of the case you will have to remove the front
plastic covering. From the pictures it looks as if it has three plastic
hole snaps. If they are snaps, just slightly squeeze and push on the snaps
at the same time. You may have to use a screw driver to pry on it a little.
If it has screws just use a screw driver and remove the three screws from
each side.

Look at the amperage or wattage printed on the circular center of the fan
the highest amperage or wattage fan usually has the highest air flow. If
you look on the side of the fan there are general arrows which show the air
flow direction. If they don't have arrows the fan will move air from the
open side to the cage or fan support side.

Place the two front fans to move air into the case.
Place the side panel fan to move air into the case.
Have the two back fans move air out of the case.
Place the top blow hole fan to move air out of the case.

I believe that the temperature monitor on the front of the case can be set
to read °C by changing the jumpers on the LED from the back side of the
case. Check your case manual to see if this can be done. If not, the
formula to convert to °C is
(°F-32)/1.8 = *°C

I live in the south and this time of year with AC on the temperature inside
the house runs about 80°F. I have found that for ever 1°C (2°F) increase in
the room temperature there is generally a 2°C (4°F) increase in the cpu
temperature. Check it out for your self, you can use the ASUS probe
software to monitor the cpu temperature and the built in case thermal senor
and compare the two at different room temperatures. Makes for a interesting
experment.

I believe that this will be the best air flow for your case. A good heat
sink (copper) would help lower the cpu temperature along with some artic 5
paste. Thermalright, Swiftech, and Thermaltake make some excellent cpu heat
sink products. (SLK900, MCX462, Volcano 12) Excellent case and system. Had
a GF3 Ti200 and recently bought a Evga GF 5900 SE made a big difference.
Excellent setup.

Abit NF7-S v2.0
AMD 1700+ at 1700Mhz from the default of 1467Mhz (core 680 version A)
FSB 170 Muliplier 10.0 default of FSB 133 Muliplier 11.0
Micron DDR 2100 at 170Mhz 3 3 3 11
Seagate 40 ATA100 (29°C)
cpu voltage 1.675v 31° C idle / 41°C load thermaltake slient boost with a
vantec volcano fan and reostat (4500rpm)
room temp 24.6°C (77°F)
room temp = 27°C (80°F) 34°C idle / 44°C load

I have two thermaltake smart fans and 2 sunon 0.14 amp fans on the front
intake.
One side case led intake fan 30cfm.
One top blow led exhaust fan 32cfm fan
Two back pctoys led exhaust fans both adjustable at approximately 42cfm.
Use a thermaltake 420w power supply with temperature controled fans.
The thermaltake power supply unit (PSU) fans gererally operate at 1300 -
1500 rpm.
The measured case temperature is generally about 1 - 1.5 °C above room temp.
My case is a modified design from an older power max case.
I used a old power max case because of the slotted vent across the top of
the case (hard to find).

hope this helps.

"Travis King" wrote in message
newsGrCc.82034$Hg2.44819@attbi_s04...
My computer has a case temperature sensor on the front of although I don't
know how good it is, and is also doesn't to Celsius; it does Fereignheit.
Keep in mind that my room doesn't have air-conditioning - it's running at
84.2. My room is in the basement. (I'm the 16-year old son.) I have the
Aspire X-Dreamer II case.

http://www.newegg.com/app/ViewProduc...144-026&depa=0
FYI: My case came with the side panel fan and the top fan. Both of these
have the holes cut out already with alien grills. I also bought an

aluminum
case fan with blue LEDs. I'm a little disappointed in it because it

doesn't
have as much air flow as the rest of my fans do. I've also upgraded the

PSU
to a 400w PSU with 2 fans. (I know the PSU fans to play much of a role)
I've got an Asus A7V333 motherboard, AMD Athlon XP 2400+ CPU, Kingston
PC-3000 DDR RAM, NVIDIA GeForce3 Ti200 128MB DDR TV Out, 200GB of total

disk
space (2 WD's), etc. etc. My system is not water-cooled.
"Rusty" wrote in message
...
Case air flow is dependent on case design, motherboard layout in the

case,
position of additional pci/apg cards, type of cooling on the cpu and

video
card (fan, heatsink, water cooled), wire location, and wire

configuration.
In general you want air to flow in at the bottom front of the case and

out
the upper back of the case. Having said that, the blow hole in the top

of
the case would move hot air out using natural convection forces (hot air
rises). Seeing that the fans in the back of the case are elevated in
comparison to the front of the case hot air would naturally exit the

upper
back of the case, therefore the fans in the back of the case should

exhaust
out hot air (blow air out of the case).

The issue of the side case fan blowing air into or out of the case

depends
on the location of the fan. If the side case fan is located relatively
close to the cpu then the side case fan should blow air into the case.

If
the side case fan is located above the cpu and relatively close to the

power
supply it should blow air out of the case. In most of the cases I have

seen
the side panel case fan is located relatively close to the cpu and

therefore
should blow into the case providing cool fresh air to the cpu fan.

In relationship to a positive or negative pressure in the case, my
experience and testing lead me to believe that a positive case pressure

is
better for two reasons. One, the positive pressure will prevent dust

from
entering into the CD drives and covering the laser lens. Two, a

positive
pressure keeps the heat build up around the power supply from entering

into
the case around the cpu. A positive pressure means that you will have
higher cubic feet per minute fans blowing into the case than out of the
case.

The best way to setup case cooling is to use a fan contoller or manually
adjustable high speed variable fans (thermaltake smart fans, evermax

fans)
especially at the front intake area of the case and buy a cheap
indoor/outdoor thermometer to monitor the temperature, adjust the fan

speed
and watch the case temperature at various spots (esp around the cpu and

hard
drives). Remember that more case fans does not lead to better cooling,
proper air flow though the case leads to better cooling. It also helps

to
remove those stupid built in hole drilled case grills with a demel or

tin
snips and use a wire grill in its place (if necessary).

If you think that this is long, you should see an engineering paper or
article discribing the effects of fan placement within a PC case. It is
very complicated and unpredictable. Try it, monitor it, and see if it

works
for you.


"Travis King" wrote in message
news:72HBc.70875$Hg2.61444@attbi_s04...
I have three questions regarding case fans even though I know that

this
is
an Asus newsgroup. Should the back case fan blow in air or blow out

air?
Should the case fan in the side panel blow in air or blow out air?

Should
the case fan on the top blow in or blow out? Help would be

appreciated.
Thanks.








  #8  
Old June 27th 04, 03:11 AM
John Smith
external usenet poster
 
Posts: n/a
Default

"Travis King" wrote in message news:72HBc.70875$Hg2.61444@attbi_s04...
I have three questions regarding case fans even though I know that this is
an Asus newsgroup. Should the back case fan blow in air or blow out air?
Should the case fan in the side panel blow in air or blow out air? Should
the case fan on the top blow in or blow out? Help would be appreciated.
Thanks.


I have a Lian Li case with 2 multi-speed intake fans on the front of
the case near the bottom. 1 exhaust fan on the back and 1 exhaust fan
on the top. And since my computer is under a large desk, I have a
desktop fan behind my computer to stop any build up of hot air from
the power unit.

By the way, don't be tempted to put your finger in to a Pentium
3.06Ghz cooling fan to see if it is spinning. It'll take your finger
off.
  #9  
Old June 27th 04, 06:52 PM
Jay T. Blocksom
external usenet poster
 
Posts: n/a
Default

On Mon, 21 Jun 2004 19:54:43 GMT, in alt.comp.periphs.mainboard.asus,
"Travis King" wrote:

I have three questions regarding case fans even though I know that this is
an Asus newsgroup. Should the back case fan blow in air or blow out air?
Should the case fan in the side panel blow in air or blow out air? Should
the case fan on the top blow in or blow out? Help would be appreciated.
Thanks.


Do you want the "conventional approach" answer, the "in a perfect world"
answer, or the *true* answer?

Taking the last one first:

There are a lot of wrong ways to cool a computer; but there is no one "right"
way. Too much depends on the specifics of the particular case, the equipment
(including the fans themselves) housed in that case, and the conditions under
which it will be used.

Ideally ("perfect world"), you would not need *any* fans, nor any case vents,
to keep the internal system components adequately cool for reliable operation
and long life. The case would in fact be hermetically sealed, thus best
protecting those internal components from such environmental hazards as dust,
moisture, corrosive pollutants in the atmosphere, etc.

But we don't live in a perfect world; so the next-best thing to that is to
have the minimum number/size/etc. of fans needed to accomplish the following
goals:

1. A constant and adequate intake supply of fresh, clean, ambient-temperature
air -- emphasis on "clean", which strongly implies proper filtration.

2. Efficient evacuation of air warmed by convection/radiation from the
heat-producing components (note that "efficient" does *NOT* necessarily mean
"more is better").

3. An unrestricted and more-or-less even distribution of airflow throughout
the case, especially around the most heat-producing components, with no "dead
spots" where the air is permitted to stagnate.

4. Positive internal pressure maintained in the case at all times, so as to
not suck in dirty air through misc. unfiltered vents and gaps.

5. Silent or near-silent operation.

Now, this might seem like a simple and straight-forward list; but in practice,
it is actually rather difficult to fully accomplish all of these goals
simultaneously. The old original IBM PC and PC/AT case/fan designs did in
fact directly violate several of these principles; yet, because it was Big
Blue who did it, for a long time most everybody mindlessly copied them and
hence repeated the same mistakes. More recently, it has become fashionable
(especially in the "I think I know everything" youth market) to stick as many
fans in/on a case as the designer can manage to cram in; but typically, little
thought is given to what is really being accomplished (besides making lots of
racket) with all this monkey motion.

A reasonable compromise, given a typical "tower style" case, is to place one
large-capacity (or sometimes two medium-capacity) intake fan(s) as low on the
front panel as feasible, behind a good high-efficiency (meaning it will trap a
high percentage of the very smallest particles) washable/replacable-element
filter. Then use the fan(s) built into the power supply unit (mounted at the
top-rear of the case) to forcibly exhaust the now-heated air (as you probably
know, the warmest air will naturally migrate to the top of any enclosed
vessel), plus a small fan mounted directly on the CPU's heat sink to ensure
that air does not stagnate around this most critical (and high heat-producing)
item. If the case, fans, and various heat sinks scattered throughout the box
are *properly* designed (which inescapably implies recognition of the *whole*
system design), this should be all you *really* need. If you need to add
still more fans in various other locations, it is a tacit admission that
something is not right with the basic thermal design of the system.

Further notes: The addition of "extra" fans may in fact be counterproductive,
depending on the specific system/case design. It is quite possible to create
am "opposing forces cancel" situation, where two fans are effectively trying
to blow air into the same area from different directions; this can cause the
actual airflow through the subject area to *decrease* (with a concomitant
localized increase in both pressure and temperature). Secondly, all other
things being equal, more fans == more noise, every time. Some thoughtlessly
"hot rodded" systems with a half-dozen or more case fans sound like a freakin'
jetliner on take-off. Think long and hard before adding more fans than you
*really* need, if you want to be able to live with the system long-term.
Also, the faster you spin a fan, the more air it will move -- but also, the
more noise it will make. As a general rule, a larger fan spinning slower will
move more air than a smaller fan spinning faster, and be MUCH quieter while
doing it. Hence, I prefer *one* good 120mm intake fan at the lower front, as
opposed to two 80mm or 60mm fans. Similarly, most power supply units use two
smallish (80mm or 60mm) fans, one on the bottom of the PSU case, one at the
rear; but other PSUs, such as some from Fortron Source, use a single 120mm fan
on the bottom, then simply allow the air to be exhausted through a highly
ventilated rear panel. This latter approach should always produce more
airflow per unit of noise, and probably better overall cooling as well (tho'
this latter issue is somewhat dependant on the specific supply designs).
Finally, in order to maintain a slight positive internal pressure, you MUST
blow more air into the case than you're sucking out of it. The benefits to
doing it this way are manifold, especially in the less-than-pristine
environments (like under your desk) that most systems tend to be used in.

--

Jay T. Blocksom
--------------------------------
Appropriate Technology, Inc.
usenet01[at]appropriate-tech.net


"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
-- Benjamin Franklin, Historical Review of Pennsylvania, 1759.

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