PSU and case airflow issues....your thoughts please.

[Darth Joules]

I'm going to get a 400W+ PSU, the majority of makes have two fans.
The common layout being one fan at the back and one fan on the bottom
(over the mobo).

I'm a little concerned about the impact on case airflow that such a
layout would cause, especially as my midi-tower case already has two
80mm exhuast fans one above the other right below the PSU bay. Won't
the fan on the bottom of the PSU suck precisious cooling air away from
the CPU heatsink fan? Which is why I'm thinking about getting a
Globalwin PSU which has one fan at the back and one at the front, thus
avoiding this problem.

Also, I've been thinking about mounting two 80mm fans into the side of
my case (because I overclock) a bit like the Thermaltake and Cheiftech
cases. Rather than mounting them straight onto the side panel, I was
thinking of mounting them onto a Thermaltake Duct Mod (or make my own)
and then attach them to the side panel. Therefore the fans will be at
a 45 degree angle inside the case facing towards the back. One aimed
at the CPU heatsink fan and the other at the AGP slot (my GPU has the
Artic Cooling IceQ). My thinking is that this will help keep air
moving from the front to the back more easily in the "push-pull"
configuration.

What do you all think?


Cheers,

Darth Joules

 

[w_tom]

Sucking or blowing (airflow direction) is irrelevant.
Equations for PSU and chassis cooling involve airflow - cubic
feet per minute; not direction. Does not matter whether
sucking is at CPU fan heatsink or someplace else inside
case. Even airflow over heatsink created by PSU is
irrelevant to CPU cooling since fan provides airflow on that
CPU heatsink. CFM of that heatsink fan is also irrelevant.

Parameters of consequence are 1) 'degree C per watt' of that
CPU heatsink assembly (which inferior assemblies forget to
provide) and 2) CFMs removed from chassis by PSU. Airflow
from one standard 80 mm fan is typically sufficient for
chassis cooling. Some use two, slower fans that combine to
move same CFMs with less noise.

Airflow over other chips (that can be so gentle as to not
even be felt by a hand) is a third concern. For example, a
dead (hot) spot created by a ribbon cable draped over video
processor. Every chip requires only a minimal airflow.
Airflow that cannot even be felt by hand is still necessary
for chip cooling.

 

[kony]

I'm going to get a 400W+ PSU, the majority of makes have two fans.
The common layout being one fan at the back and one fan on the bottom
(over the mobo).

I'm a little concerned about the impact on case airflow that such a
layout would cause, especially as my midi-tower case already has two
80mm exhuast fans one above the other right below the PSU bay. Won't
the fan on the bottom of the PSU suck precisious cooling air away from
the CPU heatsink fan?

What it will do, is provide a more direct removal of heated air
exhausted from the heatsink. The downside of such a PSU design is
that the heatsinks must be shorter, and overall this reduces the
remaining space inside the power supply... not so significant on a
lower wattage unit, but moreso on 400W & up.

Which is why I'm thinking about getting a
Globalwin PSU which has one fan at the back and one at the front, thus
avoiding this problem.

It's not really a problem. If you find your heatsink isn't doing well
enough, odds are it's the heatsink itself.

Also, I've been thinking about mounting two 80mm fans into the side of
my case (because I overclock) a bit like the Thermaltake and Cheiftech
cases. Rather than mounting them straight onto the side panel, I was
thinking of mounting them onto a Thermaltake Duct Mod (or make my own)
and then attach them to the side panel. Therefore the fans will be at
a 45 degree angle inside the case facing towards the back. One aimed
at the CPU heatsink fan and the other at the AGP slot (my GPU has the
Artic Cooling IceQ). My thinking is that this will help keep air
moving from the front to the back more easily in the "push-pull"
configuration.

What do you all think?

Probably a waste of time, "normally" a good heatsink, a case with a
couple of rear exhaust fans and a fair amount of air intake passage
through the front, will eliminate the need for the side-panel fans.
If your video card has a poor 'sink or heavily overclocked, you might
first try removing the PCI slot case cover under it, which will help.
For more extreme o'c it might be beneficial to add a fan dedicated to
video cooling, but it may be best to first get a better heatsink on
the video card.

Then again, only you know what level of overclocking you'll be trying.
Adding multiple low-RPM fans is a proven way to get a higher
airflow/noise ratio, but you've made no mention of the hard drives,
how your cooling plans will affect them.

Frankly, I wouldn't bother with the 45' angle on the fans, nor get the
Globalwin PSU. Beyond that, have fun with it... you probably don't
"need" all those changes but it's easier to overplan cooling then
reduce fan speed if possible, than build a whole box up only to later
need disassemble it to rework the chassis for increased airflow.

 

[ElJerid]

I'm going to get a 400W+ PSU, the majority of makes have two fans.
The common layout being one fan at the back and one fan on the bottom
(over the mobo).

I'm a little concerned about the impact on case airflow that such a
layout would cause, especially as my midi-tower case already has two
80mm exhuast fans one above the other right below the PSU bay. Won't
the fan on the bottom of the PSU suck precisious cooling air away from
the CPU heatsink fan? Which is why I'm thinking about getting a
Globalwin PSU which has one fan at the back and one at the front, thus
avoiding this problem.

Also, I've been thinking about mounting two 80mm fans into the side of
my case (because I overclock) a bit like the Thermaltake and Cheiftech
cases. Rather than mounting them straight onto the side panel, I was
thinking of mounting them onto a Thermaltake Duct Mod (or make my own)
and then attach them to the side panel. Therefore the fans will be at
a 45 degree angle inside the case facing towards the back. One aimed
at the CPU heatsink fan and the other at the AGP slot (my GPU has the
Artic Cooling IceQ). My thinking is that this will help keep air
moving from the front to the back more easily in the "push-pull"
configuration.

What do you all think?

Globally, you could consider a PC cooling as one main circuit with a lot of
subcircuits. The main circuit comes from the front bottom air intake (with
it's fans) of your case and goes to the top rear exhaust fans. Somewhere
between, you have a series of subcircuits like the coolers for cpu, VGA
card, chipset. If the main airflow is insufficient and thus too hot, you
will never be able to achieve efficient cooling for the subcircuits. This
seems basic, but is oftenly forgotten when mounting systems.
Practically, if at one side you have 2 fans at the front bottom of your
case, and at the other side one case output fan plus 2 PSU fans, there is
plenty of airflow in the case. Before reaching the fans of the essential
parts of the PC (CPU, chipset, vga), the flow temp will have been increased
by a few degrees only by the hard disk(s). The "subsystems" will take their
air from this flowe and their hot air will be sucked by the top fans. It's
more important to create a CONTINUOUS air flow in the case than adding fans
everywhere that blow in all directions and create random local pressure
differences and unefficient turbulences.
Don't confuse efficiency and cosmetics.

 

[Spajky®]

Globally, you could consider a PC cooling as one main circuit with a lot of
subcircuits. The main circuit comes from the front bottom air intake (with
it's fans) of your case and goes to the top rear exhaust fans. Somewhere
between, you have a series of subcircuits like the coolers for cpu, VGA
card, chipset. If the main airflow is insufficient and thus too hot, you
will never be able to achieve efficient cooling for the subcircuits. This
seems basic, but is oftenly forgotten when mounting systems.
Practically, if at one side you have 2 fans at the front bottom of your
case, and at the other side one case output fan plus 2 PSU fans, there is
plenty of airflow in the case. Before reaching the fans of the essential
parts of the PC (CPU, chipset, vga), the flow temp will have been increased
by a few degrees only by the hard disk(s). The "subsystems" will take their
air from this flowe and their hot air will be sucked by the top fans. It's
more important to create a CONTINUOUS air flow in the case than adding fans
everywhere that blow in all directions and create random local pressure
differences and unefficient turbulences.
Don't confuse efficiency and cosmetics.

finally someone that understands stuff properlly & just not suggests
just adding fans....
I have made myself a very good air flow thru the case (latelly
even enhanced it further + mounting a 2fan PSU made from few broken
ones). So I have totally silent machine with vibration isolated fans
on 5V running ALL of them (6x) & a positive air presure inside Desktop
case, the temperatures are actually lower than before!!! (I still have
to update my site, lazy me...).
It took me quite a lot of time in a few "champain" enhancing
tries thru last 3y; it is not easy to do it properly & avoiding bad
turbulencies, underpresurized spots etc.
2-fan PSUs usually have side intake fan thinner than exhaust
one & its air flow its lower than the other ones. If having more fans
I recommend like this in tower case (also for silent operation):
- intake (lower front) 7V
-side in/or upper case one @5V blowing-in/sucking out
- back one @ 5V sucking out
-intakePsu @ 5V sucking into Psu
-exaustPsu @ 7V (if not thermocontrolled already)
- CPU one & GPU one @ 7V (trying also if better with sucking instead
of blowing onto ...

.... but not exagerating with numbers of them, trying to make best
ventilation & air flow in the case with less possible fans & noise ...

IMHO this could not be the rule, just because any individual inside
case mounting is unique & sometimes just adding an additional PCI card
can screw thing up with fluid air flow! .... (not mentioning of bad
managed cables!)

But Generally, IMHO 2-fan Psu are better than single fan ones ...
.... covering some unnecesarry holes, adding some air cardboard "flaps"
or partial ducts cah help also ...

-- Regards, SPAJKY ®
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##

 

[S]

finally someone that understands stuff properlly & just not suggests
just adding fans....
I have made myself a very good air flow thru the case (latelly
even enhanced it further + mounting a 2fan PSU made from few broken
ones). So I have totally silent machine with vibration isolated fans
on 5V running ALL of them (6x) & a positive air presure inside Desktop
case, the temperatures are actually lower than before!!! (I still have
to update my site, lazy me...).
It took me quite a lot of time in a few "champain" enhancing
tries thru last 3y; it is not easy to do it properly & avoiding bad
turbulencies, underpresurized spots etc.
2-fan PSUs usually have side intake fan thinner than exhaust
one & its air flow its lower than the other ones. If having more fans
I recommend like this in tower case (also for silent operation):
- intake (lower front) 7V
-side in/or upper case one @5V blowing-in/sucking out
- back one @ 5V sucking out
-intakePsu @ 5V sucking into Psu
-exaustPsu @ 7V (if not thermocontrolled already)
- CPU one & GPU one @ 7V (trying also if better with sucking instead
of blowing onto ...

.... but not exagerating with numbers of them, trying to make best
ventilation & air flow in the case with less possible fans & noise ...

IMHO this could not be the rule, just because any individual inside
case mounting is unique & sometimes just adding an additional PCI card
can screw thing up with fluid air flow! .... (not mentioning of bad
managed cables!)

But Generally, IMHO 2-fan Psu are better than single fan ones ...
.... covering some unnecesarry holes, adding some air cardboard "flaps"
or partial ducts cah help also ...

-- Regards, SPAJKY ®

Good to hear your approach. I also built a box with a slightly
positive air pressure and it has worked out very well for me.
It was well worth the effort.

I wanted a machine designed to run 24/7 so I bought a HUGE file
server case from Antec and modded it so that it has three panaflo
fans -- two 120mm intake and one 92mm exhaust. One intake is low
at the front and the other is on the side blowing at the mobo.
Both intake fans have disposable 1/2" air conditioner media
filters that only have to be changed once every three or four
months. Both 120s are attached to the chassis so there is no
hassle in opening it up.

I use a Rheo Bus to control the fans and maintain positive
pressure. All three of the Panaflows are throttled way back so
it is very quiet. After three years at 24/7 it is still clean
as a whistle inside.

Another benefit to the 'fan overkill -- Rheo Bus' route is that
when I moved a few months ago one of the 120mm intake fans
failed on me and I was to busy to buy/replace it right away
-- so I just disconnected it, sealed the hole with contac
paper and re-tuned the Rheo Bus to compensate. I still had my
filtration, positive air pressure and plenty of cooling --
just louder. I ran it that way for a month and a half before
I could replace all three fans.

The case is so big that ALL drives, whether 3.5" or 5.25", are
installed with empty bays between them -- which also helps
keep everything cooler and makes the box easier to work on.

While it took a little more planning and futzing around
initially, it has worked out really well for me. Anyone building
a box to be run long and hard should consider this approach.
I never have to clean the crud out of my cpu sink or vacuume my
case -- even though it runs around the clock.

I kinda think that if the overall design of the cooling is RIGHT,
the PSU probably won't have much effect either way. I just
ordered a PC Power & Cooling SILENCER 400 ATX as it is both heavy
duty and quiet.

Regards,
/S

 

[Spajky®]

Good to hear your approach. I also built a box with a slightly
positive air pressure and it has worked out very well for me.
It was well worth the effort.

yeah, long term is surely worth the effort ...

I wanted a machine designed to run 24/7

mine runs approx. 16h/day

I use a Rheo Bus to control the fans

Befor with mine ex-schematics (on my site) for fans, I was using
SpeedFan; now not needed any more

I still had my
filtration,
I never have to clean the crud out of my cpu sink or vacuume my
case

I use lady stockings/2layer filter ; now I clean/blow the dust
only once a year (well the micro dust still penetrates a bit...)


-- Regards, SPAJKY ®
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##

 

[Darth Joules]

I use lady stockings/2layer filter ; now I clean/blow the dust
only once a year (well the micro dust still penetrates a bit...)

Decent fan filters are a real pain to find. The only choice here in
the UK are Akasa fan filters and aluminum mesh filters (which are
washable) from KustomPC.co.uk.

So you strech an old piece of nylon (or silk?) stocking over your
regular fan filter? Is stocking material permiable enough not to
restrict airflow into a fan? So would combining an Akasa fan filter
with such material be a wise idea?



Darth Joules

 

[Spajky®]

So you strech an old piece of nylon (or silk?) stocking over your
regular fan filter?

yes,
I had no filter before

Is stocking material permiable enough not to
restrict airflow into a fan?

no problems at all (they are made that you see woman legs thru it )
no problems with 2,3 layers of that ... (the problem is fixing that
stuff, I used paper sellotape & fixed it across cardboard support with
moskito net ...)

So would combining an Akasa fan filter
with such material be a wise idea?

if the Akasa filter is dense enough, you do not need extra filter
anymore...

-- Regards, SPAJKY ®
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##

 

[DaveinOlyWa]

Darth Jouleswrote:

I'm a little concerned about the impact on case airflow that such a
layout would cause, especially as my midi-tower case already has two
80mm exhuast fans one above the other right below the PSU bay. Won't
the fan on the bottom of the PSU suck precisious cooling air away from
the CPU heatsink fan?

you are right about air being drawn away from the cpu. but i think we
need to keep in mind that "cooling" fan is a poorly labeled component
of most pc's.

a better term would be exhaust fan. and that is what is on your cpu,
an exhaust fan. so anything that helps it exhaust will help your
cpu.

i also would strongly recommend adding additional case fans.

just keep in mind a simple rule.

air goes in from front and low. air goes out high in the rear .
remember this and you should do fine.

 

[Darth Joules]

if the Akasa filter is dense enough, you do not need extra filter
anymore...

They're actually quite porus as with most cheap fan filters. They
only stop big lumps of fluff and dust.


Darth

 

[kony]

They're actually quite porus as with most cheap fan filters. They
only stop big lumps of fluff and dust.


Darth

On the one hand, that's bad, but on the other, a very fine filter will
get clogged pretty quickly and very significantly cuts down on
airflow. Typically a filter fine enough to trap small particles
reduces airflow by over 70%... you need ~3X as many fans as with no
filter, and potentially around 1.5X as many as with a courser filter.
Not all cases can accomodate the extra fans without massive rework.

Preplanning a case airflow can make that easy enough, but not everyone
is wanting to carve up a case THAT much, and it's not too bad to open
and clean out a system every now and then, may be as easy/easier than
the extra case mods.

One cost-effective filter medium is that used for furnace filters.
Not the el-cleapo $1 filters with the spiderweb-look, but those with
the finer white, accordian folded pleats. You can get a lot of
filters out of one of those, and they can end up costing about $0.75
per sq. ft.

 

[kony]

On 2 Feb 2004 23:48:28 -0500,

you are right about air being drawn away from the cpu. but i think we
need to keep in mind that "cooling" fan is a poorly labeled component
of most pc's.

a better term would be exhaust fan. and that is what is on your cpu,
an exhaust fan. so anything that helps it exhaust will help your
cpu.

i also would strongly recommend adding additional case fans.

just keep in mind a simple rule.

air goes in from front and low. air goes out high in the rear .
remember this and you should do fine.

It really doesn't matter that much these days. The greatest effect on
cpu cooling isn't the fan anymore, it's the efficiency of the bottom
of the 'sink, how well it gets the heat energy transferred to the
fins. Playing around with different case airflow configurations I
seldom find a CPU temp rise linear with ambient case temp (actual case
temp, not the chipset case temp sensor) which indicates the removal of
heat isn't so significant as once thought, as least not on components
such as the CPU which ARE designed to tolerate heat.

 

[w_tom]

Some fear heat; install five fans where one would do just
fine. Then they have a dust problem. Of course! Moving too
much air through the chassis. Equations make is woefully
obvious. One standard CFM 80 mm fan is sufficient to move
enough air. That makes a computer work just fine in a 100
degree F room - within normal temperature range for a properly
built system.

Simply don't move excessive air through a computer and dust
problems disappear. Simply locate that single fan in a
chassis construction where hot spots don't exist. Put a
heatsink fan assembly on the CPU. It does not matter whether
air blows or sucks. Heatsinks only care about airflow -
positive pressure is irrelevant hype.

That's it. No rocket science. No fancy filters except if
the computer is working on a dusty factory floor. If not on
the factory floor, then no reason for massive filters AND no
reason for so many fans. Too many fans are reason for dust
problems. One 80 mm fan moves more than enough air into and
therefore out of computer chassis. One fan or two placed in
series (to move equivalent CFM of one fan) eliminates the dust
problem created by a "More AIR" mindset.

 

[S]

Some fear heat; install five fans where one would do just
fine. Then they have a dust problem. Of course! Moving too
much air through the chassis. Equations make is woefully
obvious. One standard CFM 80 mm fan is sufficient to move
enough air. That makes a computer work just fine in a 100
degree F room - within normal temperature range for a properly
built system.

Simply don't move excessive air through a computer and dust
problems disappear. Simply locate that single fan in a
chassis construction where hot spots don't exist. Put a
heatsink fan assembly on the CPU. It does not matter whether
air blows or sucks. Heatsinks only care about airflow -
positive pressure is irrelevant hype.

That's it. No rocket science. No fancy filters except if
the computer is working on a dusty factory floor. If not on
the factory floor, then no reason for massive filters AND no
reason for so many fans. Too many fans are reason for dust
problems. One 80 mm fan moves more than enough air into and
therefore out of computer chassis. One fan or two placed in
series (to move equivalent CFM of one fan) eliminates the dust
problem created by a "More AIR" mindset.

More air is not the issue here.

At least two of the previous posters noted that they ran with a
REDUCED air flow AND filters. Have you ever run an off the shelf
box (with the negative pressure designed into it) for three months,
24/7, and then pulled the cpu fan and looked at the dustbunnies in
the sink? I have.

LESS DIRT is the issue. An unfiltered box with negative air
pressure will run incrementally less cool every successive day it
runs. Asside from the dust slowly coating everything and reducing
the cooling of each part, dust is also sucked through ALL holes in
the case -- including the cd burner and floppy drive. Any dust that
makes it through the case unscathed then has one last chance to
deposit itself inside your power supply on its way out, which is
already the hottest part of your computer, even on the day you
bought it.

There are quite a few situations/environments which are not as
demanding as a 'factory floor' which require better
filtering/cooling.

Regards,
/S

 

[DaveinOlyWa]

the more cooling you have the better period...

who gives a rats ass about how clean the pc is?

it doesnt matter what you do with it, you will still have dust
inside.

if the dust bothers you, (let it build up enough and it will) get a
can of air and clean the thing...