Case Fan Questions

[Baldy]

As a tinkerer and hobbist builder of multiple systems over the past 10
years, I guess I've developed "old school" habits when it comes to
providing proper air flow through a case to provide optimum cooling.

In short, this usually involves air entering at or around the front of
the case, flowing over the HDD,RAM, and other components, and exiting
the back of the case. Most newer systems have at least one fan at the
front sucking air in and at least one fan at the rear pushing air out.
This is all in addition to the usual CPU fan and most likely includes
a VGA and northbridge chip fan.

Now here is where a question or two comes up. Many new cases include a
side window fan. If this side window is NOT DUCTED towards the CPU,
should this fan blow out or suck in? (For those of you without the
dirty minds, that would be "intake or exhaust".)

Now, lets throw one monkey wrench into the equation. Lets assume that
this side window fan is ducted/directed right onto the CPU. The
typical CPU fan itself almost always blows air down and through the
associated heatsink material. Should this DUCTED fan blow out or suck
in?

Next, enter the latest generation of PSU, typically with the 120mm
single fan that ends up positioned directly over the CPU. I'm still
shaking my head over this one, namely that these new products do not
exhaust the hot PSU air out the back but rather blow it down onto the
CPU. Can someone explain the reasoning for this apparent backward
step?

Enquiring minds want to know.

Baldy

 

[Rod Speed]

As a tinkerer and hobbist builder of multiple systems over the past
10 years, I guess I've developed "old school" habits when it comes to
providing proper air flow through a case to provide optimum cooling.

No such animal. Its just adequate cooling.

In short, this usually involves air entering at or around the front
of the case, flowing over the HDD,RAM, and other components,
and exiting the back of the case. Most newer systems have at
least one fan at the front sucking air in and at least one fan at
the rear pushing air out.

That isnt true unless you mean the systems you have assembled.

This is all in addition to the usual CPU fan and most
likely includes a VGA and northbridge chip fan.

Most dont include a northbridge chip fan either.

Now here is where a question or two comes up. Many new
cases include a side window fan. If this side window is NOT
DUCTED towards the CPU, should this fan blow out or suck in?

There isnt any point in a side window except to
get outside air over the cpu heatsink and fan.

(For those of you without the dirty minds, that would be "intake or exhaust".)

Now, lets throw one monkey wrench into the equation. Lets assume
that this side window fan is ducted/directed right onto the CPU.

As it should be. Thats the whole point of it.

The typical CPU fan itself almost always blows air down and through the
associated heatsink material. Should this DUCTED fan blow out or suck in?

There isnt necessarily a fan, and it should blow in if there is one,
because the whole point is to get the lowest temperature air,
from outside the case, directly onto the cpu heatsink and fan.

Next, enter the latest generation of PSU, typically with the 120mm
single fan that ends up positioned directly over the CPU. I'm still
shaking my head over this one, namely that these new products do not
exhaust the hot PSU air out the back but rather blow it down onto the CPU.

Thats not the latest, that was in fact the earliest arrangement
seen with ATX supplys that got binned because it makes no sense.

Can someone explain the reasoning for this apparent backward step?

That step hasnt happened.

Enquiring minds want to know.

Well they cant, so there.

 

[Shep©]

As a tinkerer and hobbist builder of multiple systems over the past 10
years, I guess I've developed "old school" habits when it comes to
providing proper air flow through a case to provide optimum cooling.

In short, this usually involves air entering at or around the front of
the case, flowing over the HDD,RAM, and other components, and exiting
the back of the case. Most newer systems have at least one fan at the
front sucking air in and at least one fan at the rear pushing air out.
This is all in addition to the usual CPU fan and most likely includes
a VGA and northbridge chip fan.

Now here is where a question or two comes up. Many new cases include a
side window fan. If this side window is NOT DUCTED towards the CPU,
should this fan blow out or suck in? (For those of you without the
dirty minds, that would be "intake or exhaust".)

Now, lets throw one monkey wrench into the equation. Lets assume that
this side window fan is ducted/directed right onto the CPU. The
typical CPU fan itself almost always blows air down and through the
associated heatsink material. Should this DUCTED fan blow out or suck
in?

Next, enter the latest generation of PSU, typically with the 120mm
single fan that ends up positioned directly over the CPU. I'm still
shaking my head over this one, namely that these new products do not
exhaust the hot PSU air out the back but rather blow it down onto the
CPU. Can someone explain the reasoning for this apparent backward
step?

Enquiring minds want to know.

Baldy

Stick to what you know.You are right.It's merely fashion and as the
great Oscar said,"Fashion is so ugly they have to change it every 6
months"

 

[Noozer]

In short, this usually involves air entering at or around the front of
Makes perfect sense, even with todays systems.

You want to keep the case with positive pressure so blowing it is good.

The original ATX spec called for the PSU to suck outside air in, then blow
it over the CPU (P2 at the time). I don't think I've seen a PSU that still
works that way for a long time now. Most suck from inside the case and blow
out the back. I'd reverse any fan that wasing sucking out case air these
days, with one small exception...

I've seen several cases now that come with a 120mm (or larger) fan on top of
the case, blowing hot air out of the case. If I had one of those, I'd
install the PSU upside down, so the 120mm PSU fan was blowing upwards,
towards the case top fan. I might even turn the rear fan so it sucks into
the case. It all depends on how big that top fan was and how much air it
moved.

 

[kony]

As a tinkerer and hobbist builder of multiple systems over the past 10
years, I guess I've developed "old school" habits when it comes to
providing proper air flow through a case to provide optimum cooling.

There's nothing inherantly different today, just cases with
more provisions for mounting larger fans, sometimes too many
fans for a flash factor instead of a need, and higher heat
parts in the case.

In short, this usually involves air entering at or around the front of
the case, flowing over the HDD,RAM, and other components, and exiting
the back of the case. Most newer systems have at least one fan at the
front sucking air in and at least one fan at the rear pushing air out.
This is all in addition to the usual CPU fan and most likely includes
a VGA and northbridge chip fan.

Whether the case needs the front fan can depend on the
particular case, and parts in it. Any case meant to hold
semi-modern parts should have the rear exhaust fan towards
the middle-upper area of the rear case wall in addition to
the PSU exhaust.

VGA and northbridge depends on the particular chips used,
some have low enough thermal density (or every good passive
heatsinks) such that a fan isn't necessary. On some boards
there is another fan nearby so a passive heatsink could
still be used, but if designing this yourself you will need
to check the temps to be sure it's cool enough.

Now here is where a question or two comes up. Many new cases include a
side window fan.

Many of them shouldn't, often it is better to block that fan
hole entirely, it can even do more harm than good. However,
IF you had a very strong case exhaust and a poor CPU
heatsink, it might help compensate some for the poor
heatsink, though a better heatsink is the preferred
solution. Having the front case fan is another way to
offset the problems caused by the side fan, to keep more
airflow through the drive rack in the front, but continually
adding fans will add noise, it isn't always necessary to do
so.

Essentially, a case should have provisions to remove the
maximum heat the parts in it could produce, but your chosen
parts may not produce that level of heat, and so you may
(almost always can) choose lower noise, lower fan wear
(reducing fan RPM), and lower dust accumulation from a more
conservative airflow rate.

If the side duct is lower it can instead help to cool SLI'd
video cards, and since this configuration is typical with
gamers that would be expected to put more of a load (and
resultant heat) on their video cards, and since these cards
tend to cost quite a lot, a fan devoted to helping to cool
them may be far more of a benefit than detriment.

If this side window is NOT DUCTED towards the CPU,
should this fan blow out or suck in? (For those of you without the
dirty minds, that would be "intake or exhaust".)

It should never blow out. If it were ducted, if that duct
were well placed over the CPU 'sink, AND if you had an
aftermarket CPU 'sink that had a less common upside down fan
orientation such that the fan sucked air out of the heatsink
rather than blowing into it, THEN it would tend to be better
to have the side fan blowing out. It is an unusual enough
situation that most often a "no" answer is correct.

Try the case without the fan though, and check temps...
change like that (beyond the more typical front intake and
mid-high rear exhaust, only) are meant to address problems
you may not have, and have their own detractions.

Now, lets throw one monkey wrench into the equation. Lets assume that
this side window fan is ducted/directed right onto the CPU. The
typical CPU fan itself almost always blows air down and through the
associated heatsink material. Should this DUCTED fan blow out or suck
in?

Suck in, except you still shouldn't have the fan or duct at
all unless it's really necessary. Being able to drop CPU
temp a few degrees is not essential, especially when it is
expected to similarly increase temps of other areas.

Remember that cases are designed to sell, by perceived
features, more than because they actually do a good job.
Most cases are rather poor and while some of this can be
excused because they were trying to reduce EMI escape, in
other cases they just didn't put much thought into the
design or tried to target a tradeoff from users that weren't
setting up airflow properly (thus a lot of passive holes
everywhere, not just in the bottom front) instead of an
optimal design towards a configuration tailored to the
expected parts in the system.

Next, enter the latest generation of PSU, typically with the 120mm
single fan that ends up positioned directly over the CPU. I'm still
shaking my head over this one, namely that these new products do not
exhaust the hot PSU air out the back but rather blow it down onto the
CPU. Can someone explain the reasoning for this apparent backward
step?

They don't, that 120mm fan is an intake for the PSU, which
flows through PSU and exhausts out the rear of the PSU.
The benefit to the 120mm fan is that it can more more air at
lower RPM, so it's quieter. The detraction is that a 120mm
fan takes up a lot of room in a PSU and limits the
remaining space available for the rest of the components...
more of a problem with higher wattage units, say above 400W,
(and/or systems needing a lot of power) than lower wattage.

 

[Baldy]

On Mon, 12 Feb 2007 11:24:34 +1100, "Rod Speed"

There isnt any point in a side window except to
get outside air over the cpu heatsink and fan.


Thats not the latest, that was in fact the earliest arrangement
seen with ATX supplys that got binned because it makes no sense.

Thanks for your replies and to all the others that also replied.
You've helped confirm that I am indeed not going crazy in spite of
what seems to be happening from the quality control end of
manufacturers. I usually end up putting together systems for my
friends (and friends of friends) who tend to buy their own hardware or
the majority of it and then leave the assembly and details of getting
the OS installed and running to me.

In the past six months, I have been presented with two new cases, each
with a side window and fan. In each case, the fan was installed by the
factory with the air flow blowing out. When I saw the first one, I
thought it was just a random mistake and I simply corrected it. Now,
when I saw the second one, I started to second-guess myself thinking
maybe there was some new design principle that I had missed about
exhausting hot air over the importance of bringing in fresh air for
the CPU.

Last week I was presented with a RaidMax PSU that has the 120m single
fan over the CPU and it blows hot air down onto the CPU. This is where
I was shaking my head and I then read over a multitude of product
reviews from users on the web. Surprisingly many commented about the
fact that they also noticed the fan blowing hot air onto the CPU.

Apparently this earliest incarnation of backward air flow in the ATX
PSUs is either still in production or there are several shit loads of
them all over the US still unsold. Then again, I'm thinking that just
like most industries, once they are set up for production in one
manner, it takes an act of God to get anything changed on the
production line. In other words, little "Jun Ling" working on the
assembly line for 20 cents per hour is still installing the fans
backwards because that's how he was taught a year or two ago.

One final comment: I think the bulk of computer products have gotten
significantly better over the years not only in design but in quality
control. The sole exception is the manufacture of power supplies. I
know there will be those that will comment about how technically
proficient the new designs are and I will agree with that but I am
specifically addressing the quality control of assembly and the
tendency of using less than high quality materials. This applies to
all those major brands names and not just the generics.

You can no longer go solely on a brand-name; for instance the Antec
Basiq line of PSUs has a warranty of only one year and from experience
I've seen them fail just about right on schedule, namely one day out
of warranty. The Rosewill brand, one that I used to consider as a
cheap, generic has the Preformer line with a 3 year warranty.

Compare the design, manufacture, and quality of mainboards with PSUs
yet each sells in the same approximate price range. We continue to see
PSU failure rates much greater than any other component.

OK, that's my 2 cents.

Baldy

 

[Rod Speed]

Thanks for your replies and to all the others that also replied.
You've helped confirm that I am indeed not going crazy in spite of
what seems to be happening from the quality control end of
manufacturers. I usually end up putting together systems for my
friends (and friends of friends) who tend to buy their own hardware or
the majority of it and then leave the assembly and details of getting
the OS installed and running to me.

In the past six months, I have been presented with two new cases, each
with a side window and fan. In each case, the fan was installed by the
factory with the air flow blowing out. When I saw the first one, I
thought it was just a random mistake and I simply corrected it. Now,
when I saw the second one, I started to second-guess myself thinking
maybe there was some new design principle that I had missed about
exhausting hot air over the importance of bringing in fresh air for the CPU.

Looks like the case 'designer' hasnt got a clue. Not that unusual with the low end cases.

Last week I was presented with a RaidMax PSU that has the 120m single
fan over the CPU and it blows hot air down onto the CPU. This is where
I was shaking my head and I then read over a multitude of product
reviews from users on the web. Surprisingly many commented about the
fact that they also noticed the fan blowing hot air onto the CPU.

You should check that with the power supply out of the case, because
if you have too much fan horsepower blowing out of the case and not
enough inlet capacity, you can see the airflow thru the power supply
reversing because its overpowered by the other fans.

Apparently this earliest incarnation of backward air flow in the ATX
PSUs is either still in production or there are several shit loads of
them all over the US still unsold. Then again, I'm thinking that just
like most industries, once they are set up for production in one
manner, it takes an act of God to get anything changed on the
production line. In other words, little "Jun Ling" working on the
assembly line for 20 cents per hour is still installing the fans
backwards because that's how he was taught a year or two ago.

Trouble with that theory is that it was a lot longer ago than that now.

One final comment: I think the bulk of computer products have gotten
significantly better over the years not only in design but in quality control.

Yeah, even the stupidest 'designer' does improve over time usually.

The sole exception is the manufacture of power supplies.

Cant agree with that. Round IDE cables are an obscenity in my opinion.

And then there's the flashy stuff, lighted fans etc.

I know there will be those that will comment about how technically
proficient the new designs are and I will agree with that but I am
specifically addressing the quality control of assembly and the
tendency of using less than high quality materials. This applies
to all those major brands names and not just the generics.

Yes, we have certainly seen a much higher failure rate of power
supplies than we should have. Not completely clear what the
failure rate would have been without the bad electrolyte fiasco tho.
Likely it still would have been unacceptable, particularly with
power supplys that kill whats powered from them when they die.

You can no longer go solely on a brand-name; for instance the Antec
Basiq line of PSUs has a warranty of only one year and from experience
I've seen them fail just about right on schedule, namely one day out
of warranty. The Rosewill brand, one that I used to consider as a
cheap, generic has the Preformer line with a 3 year warranty.

Yeah, and we have seen motherboard warrantys improving like that too.

Compare the design, manufacture, and quality of mainboards with PSUs
yet each sells in the same approximate price range. We continue to see
PSU failure rates much greater than any other component.
Indeed.

OK, that's my 2 cents.

We've binned 1 and 2 cent coins in my country |-(