When I add an additional fan to a case, should it blow in or out?
If it blows out, does it stand the chance of lowering the internal pressure
of the case enough to cause the PS fan to not move enough past it's own
components? Basically "competing" with the PS fan, doesn't seem too prudent
since that thing really needs air flow.
If it blows in, do I need to position it as far from the PS as possible?
(PS fan blows out of course).
"Thomas G. Marshall" <tgm2tothe10thpower@replacetextwithnumber.hotmail. com>
wrote in message news:URX9i.7158$UD4.5546@trndny07...
>
> When I add an additional fan to a case, should it blow in or out?
>
> If it blows out, does it stand the chance of lowering the internal
pressure
> of the case enough to cause the PS fan to not move enough past it's own
> components? Basically "competing" with the PS fan, doesn't seem too
prudent
> since that thing really needs air flow.
>
> If it blows in, do I need to position it as far from the PS as possible?
> (PS fan blows out of course).
>
> Are in-blowing fans problematic?
>
> Thanks
>
>
Try to suck in at the front and blow out at the back. In most towers this
will mean that colder air flows in over the hard drives first, across the
motherboard and then out through the back into nobody's face!
"John A" <nospam@yahoo.co.uk> wrote in message
news:466850db$0$8755$ed2619ec@ptn-nntp-reader02.plus.net...
>
> "Thomas G. Marshall"
> <tgm2tothe10thpower@replacetextwithnumber.hotmail. com>
> wrote in message news:URX9i.7158$UD4.5546@trndny07...
>>
>> When I add an additional fan to a case, should it blow in or out?
>>
>> If it blows out, does it stand the chance of lowering the internal
> pressure
>> of the case enough to cause the PS fan to not move enough past it's own
>> components? Basically "competing" with the PS fan, doesn't seem too
> prudent
>> since that thing really needs air flow.
>>
>> If it blows in, do I need to position it as far from the PS as possible?
>> (PS fan blows out of course).
>>
>> Are in-blowing fans problematic?
>>
>> Thanks
>>
>>
>
> Try to suck in at the front and blow out at the back. In most towers this
> will mean that colder air flows in over the hard drives first, across the
> motherboard and then out through the back into nobody's face!
>
>
"Thomas G. Marshall" <tgm2tothe10thpower@replacetextwithnumber.hotmail. com>
wrote in message news:URX9i.7158$UD4.5546@trndny07...
>
> When I add an additional fan to a case, should it blow in or out?
>
> If it blows out, does it stand the chance of lowering the internal
> pressure of the case enough to cause the PS fan to not move enough past
> it's own components? Basically "competing" with the PS fan, doesn't seem
> too prudent since that thing really needs air flow.
>
> If it blows in, do I need to position it as far from the PS as possible?
> (PS fan blows out of course).
>
> Are in-blowing fans problematic?
If you have just 1 case fan, I would make it an exhaust at the rear. If you
have more than one case fan, I would make a balance of intake and exhausts
(1 extra exhaust for an odd number). Suck air in low and blow out high as
heat rises. Advice from someone was to suck air in at the front and out of
the rear - reasonable advice, but personally, I have removed the bottom 3
PCI slots and have a fan sucking cold air in there, over my GFX and an
exhaust near the CPU. This causes a nice 'draft' round the hot bits and
general air movement in the case to help the hard drives (which have plenty
of space round them).
Fans mounted on the Front of the case blow inwards; fans mounted on the Rear
of the case blow outwards (like on the PSU).
--
---------------------
DaveW
"Thomas G. Marshall" <tgm2tothe10thpower@replacetextwithnumber.hotmail. com>
wrote in message news:URX9i.7158$UD4.5546@trndny07...
>
> When I add an additional fan to a case, should it blow in or out?
>
> If it blows out, does it stand the chance of lowering the internal
> pressure of the case enough to cause the PS fan to not move enough past
> it's own components? Basically "competing" with the PS fan, doesn't seem
> too prudent since that thing really needs air flow.
>
> If it blows in, do I need to position it as far from the PS as possible?
> (PS fan blows out of course).
>
> Are in-blowing fans problematic?
>
> Thanks
>
In comp.sys.ibm.pc.hardware.misc Thomas G. Marshall <tgm2tothe10thpower@replacetextwithnumber.hotmail. com> wrote:
> When I add an additional fan to a case, should it blow in or out?
> If it blows out, does it stand the chance of lowering the internal pressure
> of the case enough to cause the PS fan to not move enough past it's own
> components? Basically "competing" with the PS fan, doesn't seem too prudent
> since that thing really needs air flow.
> If it blows in, do I need to position it as far from the PS as possible?
> (PS fan blows out of course).
> Are in-blowing fans problematic?
The problem is not in or out. It is the path the air takes. The
only thing I found to be working well in two days of measuring
is blow in on the front bottom and maybe middle in addition.
Blow out on the back top and PSU and maybe middle in addition.
Every ting else lead to higher temperatures in some places.
Wort is if you create a mircocirculation, e.g. blow-in right
under the PSU. No fan is better than that, since it essentially
neutralizes the PSU fan.
On Thu, 7 Jun 2007 21:09:55 +0100, "GT"
<ContactGT_remove_@hotmail.com> wrote:
>If you have just 1 case fan, I would make it an exhaust at the rear. If you
>have more than one case fan, I would make a balance of intake and exhausts
>(1 extra exhaust for an odd number). Suck air in low and blow out high as
>heat rises. Advice from someone was to suck air in at the front and out of
>the rear - reasonable advice, but personally, I have removed the bottom 3
>PCI slots and have a fan sucking cold air in there, over my GFX and an
>exhaust near the CPU. This causes a nice 'draft' round the hot bits and
>general air movement in the case to help the hard drives (which have plenty
>of space round them).
>
That does not help the hard drives, it reduces the airflow
past them. If you flipped that fan around the other way so
it was an exhaust that would benefit the HDDs. Same can be
said for side panel intake holes or fans blowing it, they
decrease the front intake rate which flows through (any
typical) HDD bay. That doesn't necessarily mean the drives
are too hot one way opposed to the other but one way will
require higher RPM fans and more noise to achieve same temp
(but the video card can need the air more, if running hot).
On Thu, 07 Jun 2007 18:09:56 GMT, "Thomas G. Marshall"
<tgm2tothe10thpower@replacetextwithnumber.hotmail. com>
wrote:
>
>When I add an additional fan to a case, should it blow in or out?
>
Depends on what your case is like, where you're putting the
fan, and why are you adding an additional fan. Presumably
you feel it needs more airflow as something is too hot?
Focus on what that overheating thing is, where the placement
and orientation will benefit that part while not negatively
impacting the existing airflow/path through the system.
Sometimes, another fan isn't even necesssary as the problem
is a poorly designed case that uses fan grills stamped out
of the metal wall which impede airflow too much, or if the
case is fairly well sealed and practically all intake is
through the front bezel, some bezels don't have large enough
intake area (holes/slits/etc).
>If it blows out, does it stand the chance of lowering the internal pressure
>of the case enough to cause the PS fan to not move enough past it's own
>components?
Yes, with each exhaust fan you add to an otherwise unaltered
case, you will reduce the exhaust rate out of the PSU.
However, most decent PSU these days have a fan control with
thermal sensing so if it were running hotter it would ramp
up the fan speed which again improves PSU exhaust rate.
Problem is, some PSU are better than others at a good and
appropriate fan control circuit that increases fan speed
proportionally, instead of either getting too fast too soon
(at too low a temp, creating excessive noise unnecessarily)
or not fast enough soon enough (PSU always runs hotter than
what would be best for long life).
>Basically "competing" with the PS fan, doesn't seem too prudent
>since that thing really needs air flow.
>
True, BUT there's enough margin built in that normally it is
still better to have the first added fan in a case as an
exhaust fan. IF merely having this first chassis fan is a
problem, the solution is not to reverse it's airflow, it is
to improve the air intake areas, since with ample (infinite)
air intake area the added fan would have no effect on the
PSU and practically speaking there is a middle ground far
from an infinite intake area but still sufficient.
Also, with the larger intake area, this too would result in
higher exhaust rate out of the PSU, and with more airflow in
the system you can use a slower additional fan which also
mitigates the effect on the PSU.
>If it blows in, do I need to position it as far from the PS as possible?
>(PS fan blows out of course).
On average, this will have the best effect on other parts.
It is typically placed in front of the HDD rack as any other
placement would decrease the passive air intake through the
rack.
In other cases/system-configurations, there might be a
particular hot spot where you must place a fan, like in the
side panel across from a high-end video card. In that
situation, ideally you would add that fan there and also add
a second fan in front of the HDD rack so you preserve the
intake there as well.
>
>Are in-blowing fans problematic?
Yes, no, maybe. It is easier to design or redesign a system
where all intake is passive and exhaust is fans. That
doesn't make it hard to do it another way, but it can be a
lot of work to carve up a case to make other methods work
well. Above all when you significantly change airflow be
sure you have again checked all parts' temps.
"kony" <spam@spam.com> wrote in message
news:eoeh63h4ngot7trgjkqseg71r0b2t4k7da@4ax.com...
> On Thu, 7 Jun 2007 21:09:55 +0100, "GT"
> <ContactGT_remove_@hotmail.com> wrote:
>
>
>>If you have just 1 case fan, I would make it an exhaust at the rear. If
>>you
>>have more than one case fan, I would make a balance of intake and exhausts
>>(1 extra exhaust for an odd number). Suck air in low and blow out high as
>>heat rises. Advice from someone was to suck air in at the front and out of
>>the rear - reasonable advice, but personally, I have removed the bottom 3
>>PCI slots and have a fan sucking cold air in there, over my GFX and an
>>exhaust near the CPU. This causes a nice 'draft' round the hot bits and
>>general air movement in the case to help the hard drives (which have
>>plenty
>>of space round them).
>>
>
> That does not help the hard drives, it reduces the airflow
> past them. If you flipped that fan around the other way so
> it was an exhaust that would benefit the HDDs. Same can be
> said for side panel intake holes or fans blowing it, they
> decrease the front intake rate which flows through (any
> typical) HDD bay. That doesn't necessarily mean the drives
> are too hot one way opposed to the other but one way will
> require higher RPM fans and more noise to achieve same temp
> (but the video card can need the air more, if running hot).
True, but my GFX card is a 7600 passive, so needs the airflow. I have
designed the airflow so that it comes in and passes over the GFX card,
swirls round the drives before being sucked out through the exhaust at the
other side of the CPU. I have the fan directed across/over the GFX heatsink
and pointing in the direction of the HDs, rather than pointing onto the GFX
and dispersing round it.
kony said something like:
> On Thu, 07 Jun 2007 18:09:56 GMT, "Thomas G. Marshall"
....[rip]...
>> Basically "competing" with the PS fan, doesn't seem too prudent
>> since that thing really needs air flow.
>
> True, BUT there's enough margin built in that normally it is
> still better to have the first added fan in a case as an
> exhaust fan. IF merely having this first chassis fan is a
> problem, the solution is not to reverse it's airflow, it is
> to improve the air intake areas, since with ample (infinite)
> air intake area the added fan would have no effect on the
> PSU and practically speaking there is a middle ground far
> from an infinite intake area but still sufficient.
This is where it gets confusing.
If I add an additional exhaust fan in the rear, then if I were to open up
one particular part of the front to better breathe through it, the other
parts of the front would be experiencing less air flow.
....[rip]...
--
"Realtor" and "realty" are pronounced "reel'-tor" and
"reel'-tee", *not* "reel'-a-tor" and "reel'-i-tee" !!!!
If you pronounce them with the extra syllable, you will
sound like a complete idiot.
System Fans: Blowz-in or Blows-out? 
Linear Mode
