power supply overheating?

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

Hi,

This question began with my attempts to find out why the CPU fan in my new
homebuilt PC was rotating so fast (5000+ RPM) and, as a result, causing so
much noise. I have one of the newish Intel P4 3E (Prescott/90nm)
processors - the core temperature of which seems to vary between 60 and 65
Celsius (with the Intel supplied heatsink/fan). Initially assuming that the
reason for the high fan speed was the high CPU temperature, I emailed Intel
product support who claimed that the cause was probably a failure to
maintain the internal chassis temperature at or below 38 Celcius (and that
this *chassis temperature* was what the CPU fan was responding to).

As part of this ongoing investigation, I've noticed that the case of my
power supply (an Antec TruePower 430) gets very warm - between 43 and 50
Celsius (depending on load). I can imagine that a large block of metal
emanating heat at 50 degress might make it difficult to maintain an internal
temperature of 38 Celsius! But... does this indicate a fault with the PSU?
What should the approxiate temperature be? (For instance, this review
http://www.anandtech.com/showdoc.html?i=1774&p=8 at AnandTech measures the
temperature *inside* the unit after 30 minutes at 33.7C)

As a comparison, I have another computer with a lower spec Antec TruePower
380 PSU. The temperature of its case holds rock steady at about 40C
irrespective of usage or apparent load - this is in contrast to mine which
fluctuates without really stabilising (at about 10 degrees higher).

It seems to me that I am rather stuck in a cycle between various
manufacturers/vendors claiming that there equipment is not to blame and I
definitely need some independent advice. The actual cooling system is two
120mm Antec case fans (one intake, one exhaust) in an Antec Performance One
P160 aluminium chassis. There are also the usual number of other fans in the
system - on the graphics card (ATI Radeon 9800 Pro) and North Bridge
(Gigabyte GA-8KNXP Rev 2.0 motherboard) etc.

-dan

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

Ignore the power supply chassis temperature. The Intel
response was correct. With two 120 mm fans, you are moving so
much air that the internal chassis *AIR* temperature should be
under 38 degrees. Is that same air also moving in the
vicinity of CPU? No ribbon cables obstructing airflow? Air
temperature - irregardless of PSU chassis temperature - is
only important.

Measure air temperature - not power supply temperature - as
the Intel rep suggested. Don't speculate about something
irrelevant as power supply chassis.

Furthermore, Prescott runs so hot that newer Intel designs
were scrapped - due to heat dissipation problems. The new
Intel CPUs will be multiple chips to radiate more heat. At 60
some degrees, you are still more than 20 degrees below max
temperature. That is significant so that your system works
just fine in a 100+ degree F room.

Dan Brill wrote:
> This question began with my attempts to find out why the CPU fan
> in my new homebuilt PC was rotating so fast (5000+ RPM) and, as
> a result, causing so much noise. I have one of the newish Intel
> P4 3E (Prescott/90nm) processors - the core temperature of which
> seems to vary between 60 and 65 Celsius (with the Intel supplied
> heatsink/fan). Initially assuming that the reason for the high
> fan speed was the high CPU temperature, I emailed Intel product
> support who claimed that the cause was probably a failure to
> maintain the internal chassis temperature at or below 38
> Celcius (and that this *chassis temperature* was what the CPU fan
> was responding to).
>
> As part of this ongoing investigation, I've noticed that the case
> of my power supply (an Antec TruePower 430) gets very warm -
> between 43 and 50 Celsius (depending on load). I can imagine that
> a large block of metal emanating heat at 50 degress might make it
> difficult to maintain an internal temperature of 38 Celsius! But...
> does this indicate a fault with the PSU? What should the
> approxiate temperature be? (For instance, this review
> http://www.anandtech.com/showdoc.html?i=1774&p=8 at AnandTech
> measures the temperature *inside* the unit after 30 minutes at
> 33.7C)
>
> As a comparison, I have another computer with a lower spec Antec TruePower
> 380 PSU. The temperature of its case holds rock steady at about 40C
> irrespective of usage or apparent load - this is in contrast to mine which
> fluctuates without really stabilising (at about 10 degrees higher).
>
> It seems to me that I am rather stuck in a cycle between various
> manufacturers/vendors claiming that there equipment is not to blame and I
> definitely need some independent advice. The actual cooling system is two
> 120mm Antec case fans (one intake, one exhaust) in an Antec Performance One
> P160 aluminium chassis. There are also the usual number of other fans in the
> system - on the graphics card (ATI Radeon 9800 Pro) and North Bridge
> (Gigabyte GA-8KNXP Rev 2.0 motherboard) etc.
>
> -dan

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

On Wed, 26 May 2004 15:32:53 GMT, "Dan Brill" <news@mangoed.com> wrote:

>Hi,
>
>This question began with my attempts to find out why the CPU fan in my new
>homebuilt PC was rotating so fast (5000+ RPM) and, as a result, causing so
>much noise.

Max RPM of a fan is dictated by the design of the fan, or rather, the
resistor value used in the fan circuit, generally same circuit is used but
different value for one or two resistos is the determination of fan speed.
This is not a user-changeabe parameter, BUT the user can change the fan
(and heatsink if necessary) to one with more efficient thermal dissipation
and lower noise. In other words, a high-end aftermarket heatsink with a
800-92 x 25 mm fan on top, running at sub-3000 RPM.

Likely your motherboard also fan RPM control, but that fansink which it
controls, is the ultimate determination of resulting noise level per CPU
temp.

>I have one of the newish Intel P4 3E (Prescott/90nm)
>processors - the core temperature of which seems to vary between 60 and 65
>Celsius (with the Intel supplied heatsink/fan). Initially assuming that the
>reason for the high fan speed was the high CPU temperature, I emailed Intel
>product support who claimed that the cause was probably a failure to
>maintain the internal chassis temperature at or below 38 Celcius (and that
>this *chassis temperature* was what the CPU fan was responding to).

It's difficult to build a system that is so poorly ventilated that the
chassis air temp is 38C. I mean, VERY difficult, you might have to take
extra measures to block all fan exhaust to achieve that temp. Even the
temp monitoring chip itself, which is it's own source of heat and always
reads higher than ambient temp, seldom gets much higher than 38C.

>As part of this ongoing investigation, I've noticed that the case of my
>power supply (an Antec TruePower 430) gets very warm - between 43 and 50
>Celsius (depending on load). I can imagine that a large block of metal
>emanating heat at 50 degress might make it difficult to maintain an internal
>temperature of 38 Celsius! But... does this indicate a fault with the PSU?

The PSU is hot because it is creating (converting) so much power, and
isn't 100% efficient so the "waste" heat is being produced. That is not a
sign of a power supply fault but rather a sign of a (relatively) highly
loaded power supply, that the system it's powering is using a lot of
current. Any modern power supply has exhaust fan, the heat created is
being removed from the system by this path rather than heating up the
chassis except in rare cases where generic manufacturers use a bottom
intake fan on PSU that has substantially higher airflow than the
exit/exhaust fan on PSU... it is possible to "cause" this but it's not a
situation seem in any decent name-brand like Antec unless your case had an
overly restrictive stamped-in-metal grill guard behind the power supply
fan...more often seen with OEMs like Compaq in the past years but it's
easy enough to see for yourself by airflow rate out of power supply.


>What should the approxiate temperature be? (For instance, this review
>http://www.anandtech.com/showdoc.html?i=1774&p=8 at AnandTech measures the
>temperature *inside* the unit after 30 minutes at 33.7C)

It is a meaningless test, since it varies based on degree of load as
mentioned previously, and actually the higher the temp from same load, the
better... that means the regulator to 'sink junction is more efficiently
transferring heat, and to a lesser extent, that the heatsink is smaller
and heat more concentrated, inherant in any PSU using a 2nd bottom-mounted
fan due to heatsink clearance issues. In other words, the temp may be
more of an indication that your system uses a lot of power more than
anything else, and that you need good quality heatsinks and as much
chassis cooling as reasonably possible if you'd like to minimize temps,
which isn't so necessary as keeping on eye on temps of sensitive parts of
the system, for example the CPU stability, HDD temp, and capacitor, fan
temp as they affect lifespan of those components as well.

If you want PSU to run cooler then you might focus on improving chassis
air intake, either increasing air passage size or installing fan in
addition to increasing air passage, but this may not be enough to achieve
significantly lower CPU temp without a heatsink swap. By significant, I
mean a dozen degrees or so.

>
>As a comparison, I have another computer with a lower spec Antec TruePower
>380 PSU. The temperature of its case holds rock steady at about 40C
>irrespective of usage or apparent load - this is in contrast to mine which
>fluctuates without really stabilising (at about 10 degrees higher).

How did you measure case temp? Keep in mind what I wrote previously about
the temp shown by motherboard bios or software usually being reported from
a thermal sensor in a chip, typically eing higher than actual chassis air
temp or having an artificial numerical offset that is a guesstimation, not
accurate across different systems that that used to determine the offset.


>It seems to me that I am rather stuck in a cycle between various
>manufacturers/vendors claiming that there equipment is not to blame and I
>definitely need some independent advice. The actual cooling system is two
>120mm Antec case fans (one intake, one exhaust) in an Antec Performance One
>P160 aluminium chassis. There are also the usual number of other fans in the
>system - on the graphics card (ATI Radeon 9800 Pro) and North Bridge
>(Gigabyte GA-8KNXP Rev 2.0 motherboard) etc.
>

Your 120mm fans certainly have the potential to move sufficient air, but
for two things...

1) Make sure case bezel is unobstructed enough... any case bezel WILL
decrease airflow, but it's the case designer (or user's will to modify
that bezel) that determines the tradeoff between a sleek front without
large hole, and how much noise escapes from the front.

2) Stamped-in-metal fan grills on case walls... Every system I own has
these cut out. Typically there will be at least a 50% improvement in
airflow by just getting rid of (cutting them out with metalwork tools)
these stamped guards, give or take a little when adding a chrome grill
guard(s) in their place.... which I would do for a 120mm fan because the
larger area increases chance of wires, fingers, pets, etc, getting
damaged.

One thing not mentioned often enough, is that on smaller or newer cases
(often with thinner metal) a large percentage of chassis structural
integrity may be lost by cutting out a 120mm hole! This can be quite
significant with a rear fan because the rest of the width of the rear may
be a snap-in I/O shield, removable motherboard tray, etc, such that
there's little uncut metal left. In such cases you must assess the
resulting integrity and plan accordingly... sometimes it's beneficial to
only cut out part of that stamped-in grill, or cut slits and fold the
metal backwards, so it's not blocking the fan anymore but still providing
rigidity.

Folding can be less asthetically pleasing though, it is difficult to get
professional looking results compared to using a fairly rigid fan and a
couple of beefy chrome grills with screws mounted though the metal instead
of a plastic slip-in fan mount.... each case must be assessed
individually, there is not one solution that applies to all of them plus
your willingness and ability to work with metal also makes a difference.
In some situations the easiest fix for an already-built system is to add a
(left) side-panel fan, since the side panel can be removed and modified
without disassembly of rest of system. Perhaps your case has such a fan,
but again the air passage to that fan is mostly obstructed. Cutting out
that area or a larger area and larger fan will help lower chassis temp,
but be mindful of potential changes in HDD bay airflow.

Bottom line is as w_tom suggested, Intel's Prescott runs quite hot, for
optimal temps you have to take extra measures compared to most users (of
different CPU).

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

The problem is that the Prescott CPU's put out over 100 WATTS of heat! And
Intel has not wanted to admit to the world that their latest products are
the cause of the overheating problems. Short of replacing the Prescott with
a much cooler and just as fast Northwood., you're looking at putting in a
high capacity cooling unit on the CPU, and installing the maximum number of
case fans that your case allows.

--
DaveW



"Dan Brill" <news@mangoed.com> wrote in message
news:FM2tc.5334372$iA2.623847@news.easynews.com...
> Hi,
>
> This question began with my attempts to find out why the CPU fan in my new
> homebuilt PC was rotating so fast (5000+ RPM) and, as a result, causing so
> much noise. I have one of the newish Intel P4 3E (Prescott/90nm)
> processors - the core temperature of which seems to vary between 60 and 65
> Celsius (with the Intel supplied heatsink/fan). Initially assuming that
the
> reason for the high fan speed was the high CPU temperature, I emailed
Intel
> product support who claimed that the cause was probably a failure to
> maintain the internal chassis temperature at or below 38 Celcius (and that
> this *chassis temperature* was what the CPU fan was responding to).
>
> As part of this ongoing investigation, I've noticed that the case of my
> power supply (an Antec TruePower 430) gets very warm - between 43 and 50
> Celsius (depending on load). I can imagine that a large block of metal
> emanating heat at 50 degress might make it difficult to maintain an
internal
> temperature of 38 Celsius! But... does this indicate a fault with the PSU?
> What should the approxiate temperature be? (For instance, this review
> http://www.anandtech.com/showdoc.html?i=1774&p=8 at AnandTech measures the
> temperature *inside* the unit after 30 minutes at 33.7C)
>
> As a comparison, I have another computer with a lower spec Antec TruePower
> 380 PSU. The temperature of its case holds rock steady at about 40C
> irrespective of usage or apparent load - this is in contrast to mine which
> fluctuates without really stabilising (at about 10 degrees higher).
>
> It seems to me that I am rather stuck in a cycle between various
> manufacturers/vendors claiming that there equipment is not to blame and I
> definitely need some independent advice. The actual cooling system is two
> 120mm Antec case fans (one intake, one exhaust) in an Antec Performance
One
> P160 aluminium chassis. There are also the usual number of other fans in
the
> system - on the graphics card (ATI Radeon 9800 Pro) and North Bridge
> (Gigabyte GA-8KNXP Rev 2.0 motherboard) etc.
>
> -dan
>
>
>

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

Hi, thanks for the responses (to all three of you).

Just to be precise - the thermal guideline for this processor is 89.0 watts
and the thermal spec is 69.1 Celsius. The Intel tech support guy wrote:

"This processor's maximum temperature is 69.1 degrees Celsius"

From which, it seems like the CPU is running only a few degrees below
maximum (not much!).

One point I forgot to mention is that if I open the side of the case, the
air temperature *immediately* drops by ten degrees (say from 45C to 35C)
which had led me to believe that it might be a heat dissipation issue. There
are no ribbon cables obstructing airflow and the 120mm exhaust fan is only 2
or 3 inches away from the processor. As to measuring points, I have one
probe mounted on the CPU fan hub and (prior to moving it to check the PSU
temperature) another in the air about an inch vertically from the first. The
temperature of the second probe was generally a degree or so cooler than
that of this first (but still in the mid-40s). I'm pretty new to this so if
someone could let me know where the appropriate points would be, I'd be
grateful.

The max RPM of this fan is 6000 (again according to Intel) but it is not the
speed which worries me (or even the surrounding temperatures) - it was that
the fan makes a hell of a lot of noise whenever it exceeds 4000RPM (which is
almost all of the time, at 5000RPM it sounds rather like a jet aircraft
taking-off). I have be looking at all this from the perspective of
preventing the fan from reaching those speeds but maybe I am looking in the
wrong direction!

I can't easily install more fans (there are only two 120mm mounts) but I
could buy an aftermarket heatsink and fan. I believe, however, that this
will void my warranty - shouldn't the Intel supplied one at least be up to
the job? If I was overclocking it would be a different matter but...

Also, with this motherboard (Gigabyte GA-8KNXP) there is a riser card
(DSP2), with its own fan, very close to the CPU and apparently this prevents
the fitting of many third-party cooling solutions. Since the card is
specifically intended to regulate the power provided to Prescott CPUs I
would be loathe to remove it (and have been specifically recommended
elsewhere not to do so).

All three of you seem to think I should lay off the power supply angle which
is fair enough (though its behaviour still, to me, seems odd compared to
the, if anything, more heavily loaded Antec TruePower 380 I have in another
computer).

Finally, it has been brought to my attention that this case (Antec
Performance One P160) may not be 'thermally advantaged' - unfortunately it
certainly isn't advertised as such. It is fairly newly released, aluminium,
and expensive - so I'm potentially quite unhappy about this. However, before
I shell out another $150, I want to explore all other avenues.
Unfortunately, if there is nothing 'wrong' with any of the components (and
therefore nothing to return/replace), then this might be my only real
option. That and I'm really begining to wish I'd bought a Northwood for
around the same price!

Cheers,

-dan

 

[Lou]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

"Dan Brill" <news@mangoed.com> wrote in message
news:NEbtc.16302788$Of.2719310@news.easynews.com...
> Hi, thanks for the responses (to all three of you).
>
> Just to be precise - the thermal guideline for this processor is 89.0
watts
> and the thermal spec is 69.1 Celsius. The Intel tech support guy wrote:
>
> "This processor's maximum temperature is 69.1 degrees Celsius"
>
> From which, it seems like the CPU is running only a few degrees below
> maximum (not much!).
>
> One point I forgot to mention is that if I open the side of the case, the
> air temperature *immediately* drops by ten degrees (say from 45C to 35C)
> which had led me to believe that it might be a heat dissipation issue.
There
> are no ribbon cables obstructing airflow and the 120mm exhaust fan is only
2
> or 3 inches away from the processor. As to measuring points, I have one
> probe mounted on the CPU fan hub and (prior to moving it to check the PSU
> temperature) another in the air about an inch vertically from the first.
The
> temperature of the second probe was generally a degree or so cooler than
> that of this first (but still in the mid-40s). I'm pretty new to this so
if
> someone could let me know where the appropriate points would be, I'd be
> grateful.
>
> The max RPM of this fan is 6000 (again according to Intel) but it is not
the
> speed which worries me (or even the surrounding temperatures) - it was
that
> the fan makes a hell of a lot of noise whenever it exceeds 4000RPM (which
is
> almost all of the time, at 5000RPM it sounds rather like a jet aircraft
> taking-off). I have be looking at all this from the perspective of
> preventing the fan from reaching those speeds but maybe I am looking in
the
> wrong direction!
>
> I can't easily install more fans (there are only two 120mm mounts) but I
> could buy an aftermarket heatsink and fan. I believe, however, that this
> will void my warranty - shouldn't the Intel supplied one at least be up to
> the job? If I was overclocking it would be a different matter but...
>
> Also, with this motherboard (Gigabyte GA-8KNXP) there is a riser card
> (DSP2), with its own fan, very close to the CPU and apparently this
prevents
> the fitting of many third-party cooling solutions. Since the card is
> specifically intended to regulate the power provided to Prescott CPUs I
> would be loathe to remove it (and have been specifically recommended
> elsewhere not to do so).
>
> All three of you seem to think I should lay off the power supply angle
which
> is fair enough (though its behaviour still, to me, seems odd compared to
> the, if anything, more heavily loaded Antec TruePower 380 I have in
another
> computer).
>
> Finally, it has been brought to my attention that this case (Antec
> Performance One P160) may not be 'thermally advantaged' - unfortunately it
> certainly isn't advertised as such. It is fairly newly released,
aluminium,
> and expensive - so I'm potentially quite unhappy about this. However,
before
> I shell out another $150, I want to explore all other avenues.
> Unfortunately, if there is nothing 'wrong' with any of the components (and
> therefore nothing to return/replace), then this might be my only real
> option. That and I'm really begining to wish I'd bought a Northwood for
> around the same price!
>
> Cheers,
>
> -dan
>
>
>

I have the Antec P-160 also, but with an Athlon 64 3400 and the Zalman
70000A-cu hsf ,Coolmax 400w PS with 120mm fan (on low speed), only 1 case
fan placed in the back for exhaust and running on 5 volts for low speed, ATI
9800 pro with Zalman HSF at 7 volts, no other fans in the PC ,DVD and DVD R
and two HDD's. My case temp under load measured behind the top DVD drive is
about 37c max. My CPU under load is about 50c and 40c at idle. I could run
my fans faster for more cooling, but I wanted to build a quiet PC and
compromise temp for low noise (although I think its still cool enough).

My PC is very quiet with this setup and because I removed the front filter
and I cut out the grill the air flow is very good and that allows me to run
the fans slow and quiet. Also my HDD's are very quiet Samsung SpinPoint
mounted on Sorbathane rubber so they are nearly silent and even though I can
just about see them through the front case slots, I don't hear them.
I have read that the Intel P4 3E can run hot, but I think you also have an
airflow problem.
I would try a better CPU hsf that you can run quiet or even try a larger fan
using a fan adaptor on your stock CPU hs.
http://www.svc.com/fanad80to60.html .
Also try taking the front filter out for more air flow.
More info on making PC's quiet and air flow here
http://www.silentpcreview.com/

Lou

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

On Thu, 27 May 2004 01:38:53 GMT, "Dan Brill" <news@mangoed.com> wrote:

<snip>

>One point I forgot to mention is that if I open the side of the case, the
>air temperature *immediately* drops by ten degrees (say from 45C to 35C)
>which had led me to believe that it might be a heat dissipation issue. There
>are no ribbon cables obstructing airflow and the 120mm exhaust fan is only 2
>or 3 inches away from the processor. As to measuring points, I have one
>probe mounted on the CPU fan hub and (prior to moving it to check the PSU
>temperature) another in the air about an inch vertically from the first. The
>temperature of the second probe was generally a degree or so cooler than
>that of this first (but still in the mid-40s). I'm pretty new to this so if
>someone could let me know where the appropriate points would be, I'd be
>grateful.

It seems pretty clear from this that your fan grills are a large part of
the problem. Two 120mm fans "can" result in a LOWER temp with the cover
on than with it off, due to reducing amount of air recycled though
heatsink by moving air in different path.

>
>The max RPM of this fan is 6000 (again according to Intel) but it is not the
>speed which worries me (or even the surrounding temperatures) - it was that
>the fan makes a hell of a lot of noise whenever it exceeds 4000RPM (which is
>almost all of the time, at 5000RPM it sounds rather like a jet aircraft
>taking-off). I have be looking at all this from the perspective of
>preventing the fan from reaching those speeds but maybe I am looking in the
>wrong direction!
>
>I can't easily install more fans (there are only two 120mm mounts) but I
>could buy an aftermarket heatsink and fan. I believe, however, that this
>will void my warranty - shouldn't the Intel supplied one at least be up to
>the job? If I was overclocking it would be a different matter but...

Well, Intel didn't make any claim that it would run at low noise, right?
So, it's running cool enough to be stable, but their (as always) marginal
fan design is the problem. Frankly it has amazed me for years that they
can make great CPUs (not to discount AMD's products, but in the larger
picture...) yet have failed to understand the simple fan... it's not even
an issue of cost really, since a standard larger fan could only be a few
cents more expensive if not cheaper than their proprietary design.

Perhaps you will have to void your warranty... I still have a few brand
new P3 1GHz heatsinks lying around because I wouldn't use them, even a $6
volcano 5 heatsink with a voltage-reduced fan was a better alternative,
but that was then and this is now... your CPU needs a higher-end cooler
and/or chassis changes. It would likely help to remove heatsink, scrape
off TIM with a credit card and lap it, use heatsink compound instead, but
again the warranty is voided.


>Also, with this motherboard (Gigabyte GA-8KNXP) there is a riser card
>(DSP2), with its own fan, very close to the CPU and apparently this prevents
>the fitting of many third-party cooling solutions. Since the card is
>specifically intended to regulate the power provided to Prescott CPUs I
>would be loathe to remove it (and have been specifically recommended
>elsewhere not to do so).

WITH that 2nd VRM, it's a great motherboard for supporting a Prescott, but
without it merely average. There is still a bit of clearance, you can
find a good 'sink that fits if you pay attention to measurements, but it's
really not THAT close unless I'm misjudging how tall (thick) the VRM card
is with the fan on it.


>All three of you seem to think I should lay off the power supply angle which
>is fair enough (though its behaviour still, to me, seems odd compared to
>the, if anything, more heavily loaded Antec TruePower 380 I have in another
>computer).

The power supply's heat is directly removed, and you have two of the
largest fans any "PC" case can support without extreme (excessive)
measures. If anything the primary problem with the power supply would
seem to be that your case has inadequate airflow because of the fan
grills. That is, when a lot of the heat off the CPU is expelled though
the power supply, it'll certainly run hotter. It simply means you need
the case fans to be more effective.


>
>Finally, it has been brought to my attention that this case (Antec
>Performance One P160) may not be 'thermally advantaged' - unfortunately it
>certainly isn't advertised as such. It is fairly newly released, aluminium,
>and expensive - so I'm potentially quite unhappy about this. However, before
>I shell out another $150, I want to explore all other avenues.

Frankly, after cutting out the fan grills it'll have superior cooling to
most cases at any price. If the two 120mm fans are being throttled back
too much then you might also use a fan controller to choose a higher RPM,
or if they're thermally controlled fans then either replace the fans or
short their thermal sensor which will result in full-speed operation,
which is also noisey so it'd make a fan speed controller even more
important. The HDD rack in your case is convenient, but also reduces
airflow more than the traditional longitudinal arrangement. That cannot
be easily overcome but it can be the area of greatest restriction instead
of only one of many, so overall airflow rate can be be higher with that
bay than it is at present.

>Unfortunately, if there is nothing 'wrong' with any of the components (and
>therefore nothing to return/replace), then this might be my only real
>option. That and I'm really begining to wish I'd bought a Northwood for
>around the same price!


Replacing heatsink is the easiest solution.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

On Wed, 26 May 2004 23:43:19 -0700, "Lou" <no-spam@sonic.net> wrote:

<snip>

>My PC is very quiet with this setup and because I removed the front filter
>and I cut out the grill the air flow is very good and that allows me to run
>the fans slow and quiet.


NOW it's starting to make sense why a pair of 120mm fans can't keep his
rig cool enough... the filter

I have a shedload of fans and every combination of fan and filter that
I've tried (of any density even slightly high enough to stop dust, be more
than a decoration) cuts airflow by well over 50%.

Right now I'm building a system that has filter area over 300% greater
than the intake area of the fans, and still I expect significant airflow
reduction from their use. Unfortunately with the OP's system, having the
two exhaust fans and the intake filtered, the filter isn't even going to
be optimal, with a greater exhaust than intake potential all the cracks
(and drives) will have negative pressure and air will flow in though them,
somewhat defeating the purpose of a filter since it's quite easy to blow
out many areas of a pc that isn't filtered, but the small cracks and
drives are the harder parts to clean.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

"kony" wrote:
> "Lou" <no-spam@sonic.net> wrote:
>
> <snip>
>
> >My PC is very quiet with this setup and because I removed
> >the front filter and I cut out the grill the air flow is very good
> >and that allows me to run the fans slow and quiet.
>
>
> NOW it's starting to make sense why a pair of 120mm fans
> can't keep his rig cool enough... the filter
>
> I have a shedload of fans and every combination of fan and
> filter that I've tried (of any density even slightly high enough
> to stop dust, be more than a decoration) cuts airflow by well
> over 50%.
>
> Right now I'm building a system that has filter area over 300%
> greater than the intake area of the fans, and still I expect
> significant airflow reduction from their use. Unfortunately with
> the OP's system, having the two exhaust fans and the intake
> filtered, the filter isn't even going to be optimal, with a greater
> exhaust than intake potential all the cracks (and drives) will have
> negative pressure and air will flow in though them, somewhat
> defeating the purpose of a filter since it's quite easy to blow
> out many areas of a pc that isn't filtered, but the small cracks
> and drives are the harder parts to clean.


Yeah, but....
You better blow out the system frequently without having a
filter and with all that air flowing through the case. The reason
I distrust those humongous heatsinks with all the narrowly
spaced fins is that dust gets in between the fins and blankets
their surface, reducing their capacity to conduct heat to the
passing air.

*TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

To put numbers to what Matt has posted. The three
parameters that define case internal air temperature are watts
consumed (which is less than what power supply is rated at),
incoming air temperature, and CFM. For example, if you have a
122 mm fan blowing in and another blowing out, then your CFM
is the CFM rating for one fan. That CFM number is provide by
the fan's manufacturer. CFM is the volume of air moved
through chassis. However if both 122 mm fans blow in, then
fans cannot move rated volume of air. Resulting insufficient
CFM means higher internal temperature.

Even worse, too much air means major dust problems. No
computer in a standard room environment should have dust
problems. Excessive dust buildup occurs when chassis moves
too much air - has too many high CFM fans. Most cases move
more than enough air with one 80 mm fan.

Hang and read a thermometer inside the case. That is the
'less than 38 degree C' that Intel cited. That temperature
would only be excessive if insufficient CFM are pushed through
case or if room temperature is too high.

Further note. That entire system must work just fine even
when room temperature is over 100 degree F. IOW measure CPU
temperature when room is at 70 degree F. That CPU temperature
must be 20 or more degrees C less than the maximum rated
temperature for the CPU. If not, then system will not work in
a 100 degree F room; therefore system is defective.

Therein defines how hot a CPU can run. It must remain below
manufacturer's maximum rated temperature even when room is 100
degree F. That means a CPU needs only run at 20 or more
degrees below maximum operating temperature (from Intel
datasheet) when room temperature is 70 degree F.

Matt wrote:
> Matt wrote:
>> Presumably you have one 120mm blowing in and the other blowing
>> out. Please verify.
>
> I mean to say that you _should_ have the lower front fan blowing
> in and the upper rear fan blowing out. If they both blow in or
> both blow out, they fight each other and you get poor air flow
> and poor heat removal.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

"w_tom" wrote:
> ...For example, if you have a
> 122 mm fan blowing in and another blowing out, then your CFM
> is the CFM rating for one fan. That CFM number is provide by
> the fan's manufacturer. CFM is the volume of air moved
> through chassis. However if both 122 mm fans blow in, then
> fans cannot move rated volume of air.


You assume that the volume of air per minute (CFM) is
independent of the resistance and internal pressure of the
case. If it were, two fans in series (i.e. in-line) would
provide the same CFM as a single fan, as you state.
But the one blowing in raises the pressure inside the case,
easing the load for the exhaust fan, and the exhaust fan
lowers the pressure, easing the load on the intake fan.
IOW, they help each other. And if there were no internal
resistance to the air flow, it wouldn't matter *how* much
voltage one supplied to a fan - it would always produce
the same air flow - which is not the case. The conclusion,
therefore, is that air flow is a function of the speed and the
size of the fan, and it varies with the amount of electrical
power supplied to the fan, and fans can help each other
increase air flow even when arranged in series.

*TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

In article <FM2tc.5334372$iA2.623847@news.easynews.com>, Dan Brill says...
>
>Hi,
>
>This question began with my attempts to find out why the CPU fan in my new
>homebuilt PC was rotating so fast (5000+ RPM) and, as a result, causing so
>much noise. I have one of the newish Intel P4 3E (Prescott/90nm)
>processors - the core temperature of which seems to vary between 60 and 65
>Celsius (with the Intel supplied heatsink/fan). Initially assuming that the
>reason for the high fan speed was the high CPU temperature, I emailed Intel
>product support who claimed that the cause was probably a failure to
>maintain the internal chassis temperature at or below 38 Celcius (and that
>this *chassis temperature* was what the CPU fan was responding to).
>
>As part of this ongoing investigation, I've noticed that the case of my
>power supply (an Antec TruePower 430) gets very warm - between 43 and 50
>Celsius (depending on load). I can imagine that a large block of metal
>emanating heat at 50 degress might make it difficult to maintain an internal
>temperature of 38 Celsius! But... does this indicate a fault with the PSU?
>What should the approxiate temperature be? (For instance, this review
>http://www.anandtech.com/showdoc.html?i=1774&p=8 at AnandTech measures the
>temperature *inside* the unit after 30 minutes at 33.7C)
>
>As a comparison, I have another computer with a lower spec Antec TruePower
>380 PSU. The temperature of its case holds rock steady at about 40C
>irrespective of usage or apparent load - this is in contrast to mine which
>fluctuates without really stabilising (at about 10 degrees higher).
>
>It seems to me that I am rather stuck in a cycle between various
>manufacturers/vendors claiming that there equipment is not to blame and I
>definitely need some independent advice. The actual cooling system is two
>120mm Antec case fans (one intake, one exhaust) in an Antec Performance One
>P160 aluminium chassis. There are also the usual number of other fans in the
>system - on the graphics card (ATI Radeon 9800 Pro) and North Bridge
>(Gigabyte GA-8KNXP Rev 2.0 motherboard) etc.
>
>-dan
>
>
>
Are your 120 case fans connected to the "fan only" connectors on the TruePower?
If so this may be causing your fans to run slower. I use the same PS on a
SuperLanboy and switched the fans to the regular non-thermally controlled
connections.

Ed

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

On Thu, 27 May 2004 20:25:35 GMT, Matt <matt@themattfella.zzzz.com> wrote:

>w_tom wrote:
>> To put numbers to what Matt has posted. The three
>> parameters that define case internal air temperature are watts
>> consumed (which is less than what power supply is rated at),
>> incoming air temperature, and CFM. For example, if you have a
>> 122 mm fan blowing in and another blowing out, then your CFM
>> is the CFM rating for one fan. That CFM number is provide by
>> the fan's manufacturer. CFM is the volume of air moved
>> through chassis. However if both 122 mm fans blow in, then
>> fans cannot move rated volume of air. Resulting insufficient
>> CFM means higher internal temperature.
>
>I expect he has both case fans blowing out, so that they are fighting
>the PSU fans, which are also blowing out, so that there is reduced or
>even reversed flow through the PSU.
>
>Dan, I believe your problem will be solved by making the lower-front fan
>blow in instead of out. Maybe you can even just removed it to reduce
>noise and still have enough air flow.

If the fans were pre-installed it's doubtful that the front fan is blowing
out. I suppose the factory might've accidentally installed one backwards
but odds are certainly against it.

I can simply look at the front of that case and see where the problem
lies, with the relatively small intake area, having a filter behind it,
and futher the more obstructive drive bay arrangement, the case is likely
restructing intake below what is seen with an unfiltered, unobstructed
80mm fan... and if the case is sealed enough, few if any aux air ports or
gaps, etc, then the rear fan is pretty much irrelevant, constrained by the
intake flow rate.

The quick and easy way to see if this is true would be to remove the front
bezel and filter, leaving side panels on the case, checking temp
difference running in that state. Also while the front bezel is off it
might be a good opportunity to take a nibbler and cut out the front fan
grill, if it's overly constrictive.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

kony wrote:
> It's difficult to build a system that is so poorly ventilated that the
> chassis air temp is 38C. I mean, VERY difficult, you might have to
> take extra measures to block all fan exhaust to achieve that temp.
> Even the temp monitoring chip itself, which is it's own source of
> heat and always reads higher than ambient temp, seldom gets much
> higher than 38C.

Depends on the positioning of the thermistor that is monitoring the case
temp. My case temp regularly gets over 38°C (On a hot day, 25°C ambient or
hotter) but then again the thermistor is positioned right in the exhaust
air-flow from my graphics card. My case has plenty of ventilation.
--
~misfit~


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.691 / Virus Database: 452 - Release Date: 26/05/2004

 

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Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

Some notes...

Filters, even large ones are not suitable for PC cases
o Typical "fan filters" have a resistance of 15-25Pa when clean
---- when dirty this figure can rise to 45-60Pa
o Even a 120mm fan at 12V, shifting 55cfm (typical) is not enough
---- you will lose 50% of your airflow when clean, 75-90% when dirty
o Clean regarding small "fan filters" is a *very* short period of time

Put simply, PC fans are typical Axial fans - not Radial/Blower fans.
o Axial fans produce typically 0.1-0.25" of H2O pressure at 0cfm
---- at *0cfm* they will depress a column of water 0.1-0.25"
o Radial/Blower fans will typically produce 1-2.5" of H2O pressure at 0cfm
---- an order of magnitude larger, and overcoming filter resistance

The only way to make a PC work with filters to attack on 3 fronts:
o Extremely larger filter
---- this is unlikely to be practical on a typical PC case
o Change it often & use the lowest filtering grade
---- typically it's the white polyester media, designed to stop fan blade dusting
o High pressure fans
---- this means large fans of large DEPTH (38mm deep) & high airflow
---- this also necessitates an increase in noise generally
---- admittedly you could try a 24V Comair Rotron 172x55mm at 12V

So a few simple things to check:
o Verify the 120mm fans are running on 12V
---- as someone points out, they may be on the PSU voltage-varied fan feed
o Remove the filter
---- then verify the temperatures from the existing known baseline
o Enlarge the front intake port
---- most of the resistance in a PC comprises 2 areas
---- 1) the punched case grill -- a mere 45-55% free air
---- 2) the intake plastic cut-out -- many PCs have a tiny 3x1" cutout

Regarding 2) above...
o One single miserly 80mm exhaust fan is around 4,800mm^2
o Most PC cut-outs are barely 1,500mm^2

Excellent that you have an exhaust fan directly behind the CPU cooler,
that will reduce the tendency of the CPU cooler to recirculate its own heat.
Most coolers recirculate 40-50% of their air = more rpm/noise to compensate,
and particularly since they can't compensate, more elevated temperatures.

However, all this fails UNLESS the PC can get cool air in fast enough.

At the lowest level, 300cfm will cool 1500W of heat in electronic apps.
That figure is a EBM-Papst rule-of-thumb which must then be adjusted for
enclosure static resistance - and so *realised* cfm in your application matters.

Serial mounted fans (exhaust 120mm, intake 120mm) will not elevate the
cfm beyond that of a single fan - but it will assist the static pressure created,
and so increase the cfm realised within your enclosure. That is still limited by
the case inlet c/sectional area, and the intake & exhaust fan fingerguard grills.

Considering you have about 75cfm of exhaust air, enough to cool around 400W
of internal heat, you should see better temperatures than you are seeing. Thus in
reality your 75cfm of *spec'd* exhaust air is reduced to enclosure resistance, or
potentially fan speed control by the PSU (often overlooked).

Yes the Prescott kicks out a lot of heat, but a 120mm fan stuck behind a CPU
is going to yawn at it - IF you can get the cool air into the enclosure. You may
also want to verify you have no air inlet short-circuits - ie, the exhaust fan can
exhaust air not from the CPU area, but from other empty case fan holes above
it or omitted drive-bay blanking plates or such like.

Clearly there is an airflow static resistance problem since you get quite marked
drop in temperature with a case side removed - which will essentially *stop*
airflow to the 120mm exhaust fan being pulled over the components.
--
Dorothy Bradbury
www.stores.ebay.co.uk/panaflofan for fans, books & other items
http://homepage.ntlworld.com/dorothy.bradbury/panaflo.htm (Direct)

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

Everyone who offered Dan advise should have no problem with
what Dorothy has just posted. This is how a repair person is
suppose to think. Facts supported by numbers. There is
nothing posted by Dorothy that is too complicated for any high
school science graduate. IOW if one repairs computers and
does not understand what she has posted, then one has no
business advising others on fan and heat solutions. Again,
Dorothy did not post anything complicated. She demonstrated
how easily computers can be cooled even with one fan.

IOW when someone foolishly recommends four or six fans for
cooling, well Dorothy's numbers demonstrate why the word
foolish applies.

Dorothy Bradbury wrote:
> Some notes...
>
> Filters, even large ones are not suitable for PC cases
> o Typical "fan filters" have a resistance of 15-25Pa when clean
> ---- when dirty this figure can rise to 45-60Pa
> o Even a 120mm fan at 12V, shifting 55cfm (typical) is not enough
> ---- you will lose 50% of your airflow when clean, 75-90% when dirty
> o Clean regarding small "fan filters" is a *very* short period of time
>
> Put simply, PC fans are typical Axial fans - not Radial/Blower fans.
> o Axial fans produce typically 0.1-0.25" of H2O pressure at 0cfm
> ---- at *0cfm* they will depress a column of water 0.1-0.25"
> o Radial/Blower fans will typically produce 1-2.5" of H2O pressure at 0cfm
> ---- an order of magnitude larger, and overcoming filter resistance
>
> The only way to make a PC work with filters to attack on 3 fronts:
> o Extremely larger filter
> ---- this is unlikely to be practical on a typical PC case
> o Change it often & use the lowest filtering grade
> ---- typically it's the white polyester media, designed to stop fan blade dusting
> o High pressure fans
> ---- this means large fans of large DEPTH (38mm deep) & high airflow
> ---- this also necessitates an increase in noise generally
> ---- admittedly you could try a 24V Comair Rotron 172x55mm at 12V
>
> So a few simple things to check:
> o Verify the 120mm fans are running on 12V
> ---- as someone points out, they may be on the PSU voltage-varied fan feed
> o Remove the filter
> ---- then verify the temperatures from the existing known baseline
> o Enlarge the front intake port
> ---- most of the resistance in a PC comprises 2 areas
> ---- 1) the punched case grill -- a mere 45-55% free air
> ---- 2) the intake plastic cut-out -- many PCs have a tiny 3x1" cutout
>
> Regarding 2) above...
> o One single miserly 80mm exhaust fan is around 4,800mm^2
> o Most PC cut-outs are barely 1,500mm^2
>
> Excellent that you have an exhaust fan directly behind the CPU cooler,
> that will reduce the tendency of the CPU cooler to recirculate its own heat.
> Most coolers recirculate 40-50% of their air = more rpm/noise to compensate,
> and particularly since they can't compensate, more elevated temperatures.
>
> However, all this fails UNLESS the PC can get cool air in fast enough.
>
> At the lowest level, 300cfm will cool 1500W of heat in electronic apps.
> That figure is a EBM-Papst rule-of-thumb which must then be adjusted for
> enclosure static resistance - and so *realised* cfm in your application matters.
>
> Serial mounted fans (exhaust 120mm, intake 120mm) will not elevate the
> cfm beyond that of a single fan - but it will assist the static pressure created,
> and so increase the cfm realised within your enclosure. That is still limited by
> the case inlet c/sectional area, and the intake & exhaust fan fingerguard grills.
>
> Considering you have about 75cfm of exhaust air, enough to cool around 400W
> of internal heat, you should see better temperatures than you are seeing. Thus in
> reality your 75cfm of *spec'd* exhaust air is reduced to enclosure resistance, or
> potentially fan speed control by the PSU (often overlooked).
>
> Yes the Prescott kicks out a lot of heat, but a 120mm fan stuck behind a CPU
> is going to yawn at it - IF you can get the cool air into the enclosure. You may
> also want to verify you have no air inlet short-circuits - ie, the exhaust fan can
> exhaust air not from the CPU area, but from other empty case fan holes above
> it or omitted drive-bay blanking plates or such like.
>
> Clearly there is an airflow static resistance problem since you get quite marked
> drop in temperature with a case side removed - which will essentially *stop*
> airflow to the 120mm exhaust fan being pulled over the components.
> --
> Dorothy Bradbury
> www.stores.ebay.co.uk/panaflofan for fans, books & other items
> http://homepage.ntlworld.com/dorothy.bradbury/panaflo.htm (Direct)

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

"w_tom" wrote:
> Everyone who offered Dan advise should have no problem with
> what Dorothy has just posted....
> Dorothy did not post anything complicated. She demonstrated
> how easily computers can be cooled even with one fan.


Dorothy's quite well informed, but I wonder about her statement:

"Serial mounted fans (exhaust 120mm, intake 120mm) will
not elevate the cfm beyond that of a single fan - but it will
assist the static pressure created, and so increase the cfm
realised within your enclosure."

That sounds self-contradictory. Serially mounted fans won't increase
the CFM beyond that of a single fan - but they will? Hmmmm....

*TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

Dorothy has posted accurately. Due to some airflow
resistance, the CFM of one fan may be trivially decreased.
Better fan manufacturers even have charts for this. But flow
through each fan still remains about same CFM. One fan or one
million fans in series makes no difference. They all still
move the same CFM. That CFM only slightly decreased by
airflow resistance.

Having said this, if airflow resistance is created by a
closed box (infinite resistance), then yes a 30 CFM fan is now
outputting 0 CFM. But the primary reasons for putting an
incoming and outgoing fan in series 1) is backup so that if
one fan fails, the other still maintains airflow, and 2)
creates turbulence so that interior hot spots (ie created by a
ribbon cable) are less likely to exist. IOW Dorothy has
posted accurately.

Do two fans in series double the airflow? Double the CFM?
Of course not. Obviously not. And yet some would even 'feel'
that is so.

Timothy Daniels wrote:
> Dorothy's quite well informed, but I wonder about her statement:
>
> "Serial mounted fans (exhaust 120mm, intake 120mm) will
> not elevate the cfm beyond that of a single fan - but it will
> assist the static pressure created, and so increase the cfm
> realised within your enclosure."
>
> That sounds self-contradictory. Serially mounted fans won't
> increase the CFM beyond that of a single fan - but they will?
> Hmmmm....
>
> *TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

> Dorothy has posted accurately. Due to some airflow
> resistance, the CFM of one fan may be trivially decreased.
> Better fan manufacturers even have charts for this. But flow
> through each fan still remains about same CFM. One fan or one
> million fans in series makes no difference. They all still
> move the same CFM. That CFM only slightly decreased by
> airflow resistance.

Only slightly? I hope so. Right now I've got a 2-fan system (both
120mm). The intake fan has an aluminum mesh dust filter. I opted for
the aluminum fitler in hopes that the flow resistance would be
negligabele. Your post gives me a little more confidence in that area.

Of course, even if the 2-fan system is very even in terms of
CFM-in/CFM-out, I sitll have a 2-fan PSU exhausting air, and an exhaust
fan located beneath my GPU. Which is why I'm planning on adding a 3rd
80mm fan... somewhere. Hopefully I will be supplying more than enough
air into the case, and let the exhausts do whatever they can.

> Having said this, if airflow resistance is created by a
> closed box (infinite resistance), then yes a 30 CFM fan is now
> outputting 0 CFM. But the primary reasons for putting an
> incoming and outgoing fan in series 1) is backup so that if
> one fan fails, the other still maintains airflow, and 2)
> creates turbulence so that interior hot spots (ie created by a
> ribbon cable) are less likely to exist. IOW Dorothy has
> posted accurately.

Interesting. I would think that one intake and one exhaust fan, located
on either side of the case, would be MORE likely to create hotspots,
because they would create a tunnel effect. As in, the air flows along a
specific path and right out of the case again. What would create
turbulence is 1) internal fans moving air "sideways" or 2) objects in
the direct path of the airflow, forcing it to move around the case more.

Of course, this is all conjecture until I tie little ribbons to the
inside of my case and "see" my airflow

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

On Sun, 30 May 2004 01:33:37 -0400, w_tom <w_tom1@hotmail.com> wrote:


> IOW when someone foolishly recommends four or six fans for
>cooling, well Dorothy's numbers demonstrate why the word
>foolish applies.
>

Not necessarily true.

If considering her post, then the part about filtering alone is evidence
that given an enclosure that cannot accept one or more monster-sized fans,
it may become a necessity to have 3 or more fans, and with a modern
high-end system, potentially MUCH more than 3. Although more and more
cases accept 120mm fans these days, the majority do not, typically 80mm or
a few more fortunate to have 92mm.

On the other hand, a differt very good reason to have multiple fans is the
noise level per same airflow rate. Very low RPM fans can be nearly if not
completely inaudible, but it'll obviously require more fans to move same
amount of air. This arrangement may be the most optimal since the
multiple fans build in a partial redundancy, that if a system were
engineered beyond environmetal and component cooling needs, it would likey
continue to function until failed fan can be replaced, if one were to
fail, which is also going ot happen at longer intervals due to the lower
RPM.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

If intent is to install six fans of very low noise and
therefore low CFM; then yes, that is a good reason for many
fans. But that is not the cited example of 'more fans'.
Again, solution is about first doing numbers which is what
Dorothy demonstrated.

In my example, more fans for lower noise is not the case.
The recommendation for many fans all of standard CFM is too
often recommended because they 'feel' that one fan is not
enough. They have the classic Home Improvement solution -
"More Power" - as a solution to CPU problems. The point
remains, fans should be selected for reasons as Dorothy has
provided. Notice the character of her post. Extensive use of
numbers. Those who recommend more fans as a solution to CPU
crashes typically do so without citing any numbers. They
don't need no fancy numbers. They just know. They never
learned any numbers. They just know. Experience without
numbers makes them their own worst enemy.

That being the point. Many will recommend more fans only
because a CPU crashes or because they think a CPU is hot.
They don't do as Dorothy has just demonstrated - first provide
and study the numbers.

kony wrote:
> On Sun, 30 May 2004 01:33:37 -0400, w_tom <w_tom1@hotmail.com> wrote:
>> IOW when someone foolishly recommends four or six fans for
>> cooling, well Dorothy's numbers demonstrate why the word
>> foolish applies.
>
> Not necessarily true.
>
> If considering her post, then the part about filtering alone is
> evidence that given an enclosure that cannot accept one or more
> monster-sized fans, it may become a necessity to have 3 or more
> fans, and with a modern high-end system, potentially MUCH more
> than 3. Although more and more cases accept 120mm fans these
> days, the majority do not, typically 80mm or a few more
> fortunate to have 92mm.
>
> On the other hand, a differt very good reason to have multiple
> fans is the noise level per same airflow rate. Very low RPM
> fans can be nearly if not completely inaudible, but it'll
> obviously require more fans to move same amount of air. This
> arrangement may be the most optimal since the multiple fans
> build in a partial redundancy, that if a system were engineered
> beyond environmetal and component cooling needs, it would likey
> continue to function until failed fan can be replaced, if one
> were to fail, which is also going ot happen at longer intervals
> due to the lower RPM.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

"w_tom" blurted out loud:
> ...Due to some airflow resistance, the CFM of one fan may
> be trivially decreased. Better fan manufacturers even have
> charts for this. But flow through each fan still remains about
> same CFM. One fan or one million fans in series makes no
> difference. They all still move the same CFM. That CFM
> only slightly decreased by airflow resistance....


Numerous people have posted that airflow increased
when they removed or cut away the grill or the perforated
blade guard that covered their fans. Doing so obviously
reduced the resistance to airflow and thus the back pressur,
allowing more air to flow. Adding a fan in series *also*
reduces the back pressure and results in an increase of
air flow. The effect is very analogous to reducing a
resistance in an electrical circuit while keeping the voltage
across the resistance the same - the current increases as a
result, just as airflow increases with the fan. And electrically,
one can do what two fans in series do by applying twice the
voltage across the resistance - which doubles the current.
If fans were ideal fixed pressure differential devices, putting
two in series would do the same thing - it would double the
air flow.


> Do two fans in series double the airflow? Double the CFM?
> Of course not. Obviously not.


Obviously not. And no one claimed that two fan in series
*would* double the airflow over that of one fan. And
that is because a fan is a combination of a fixed CFM device
and a fixed pressure differential device. In other words,
it's a real world device, not an ideal device, and two fans
in series aid each other whether they are in series or in
parallel, but not to the extent of doubling airflow. What
they *do* do in increasing air velocity is to reduce the angle
of incidence of the air as it meets the leading edge of the
fan blades, reduce the turbulence produced by the blades
as they pass through the air, thus reducing the noise. Would
the amount of noise be cut in half? Of course not. But I
would expect a reduction of maybe a couple dB.

*TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

=|[ w_tom's ]|= wrote:

> Do two fans in series double the airflow? Double the CFM?
> Of course not. Obviously not. And yet some would even 'feel'
> that is so.
>
I have put two fans on top of each other, during practical experimentation
and especialy when both are run at lower voltage, they CAN move
significantly more air than either does alone. It all depends on the
details of the implementation, as does the accuracy of the theoretical
formula some are taught to rely on too eagerly.

Theorise how you will, but testing and observation routinely deviate from
the normalised math.

--
' gathering moss,
android

 

[Nomad]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

Just a couple of things regarding cooling I thought I would throw in.
In my case I found that going for the round drive data cables rather
than the flat ones helped. I also threw in one of those PCI slot fans
that are designed similar to a furnace fan. The PCI slot fan is not
thermally controlled but it is quiet enough for my purposes. I am also
running a dual fan power supply, the Intel supplied CPU fan on my P4
3.0, a fan on my sound card and one case fan. Current temps after
running three hours with five apps going, proc. zone 34C, zone 1 30C,
zone 2 31C. All of this is with 2GB of DDR 400 PC3200.
The meek shall NOT inherit the earth.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt,alt.comp.hardware.pc-homebuilt (More info?)

That aluminum screen is a major obstruction. Look at the
cross sectional inlet area that fan needs. Now you have put a
screen that has cut that cross sectional area by maybe as much
as one half. So now you have done the simplistic equivalent
of half a closed ended box. Therefore you have reduced CFM.
Obstructing the fan was beyond scope of this discussion.

Why are you installing the aluminum screen? When the
standard computer user has dust problems, it is usually from
moving too much air through the case (or the room is a
construction site). Solve dust problems by only moving
sufficient air - not using so many fans.

Only slight resistance in airflow means the incoming hole and
outgoing hole are same as the cross sectional area demanded by
fan. Usually this is understood by default.

In the meantime, why are you adding so much more airflow?
If I remember the ballpark number, the second fan only adds,
at best, maybe 5 degree decrease in case temperature.
Irrelevant. If that temperature decrease is important, then
you have a serious design problem elsewhere in the machine.

Where is this hot spot creating so much worry? Without
understanding what is and is not a significant hot spot
problem, then a proper airflow design cannot be developed.

David Besack wrote:
> Only slightly? I hope so. Right now I've got a 2-fan system
> (both 120mm). The intake fan has an aluminum mesh dust filter.
> I opted for the aluminum fitler in hopes that the flow resistance
> would be negligabele. Your post gives me a little more confidence
> in that area.
>
> Of course, even if the 2-fan system is very even in terms of
> CFM-in/CFM-out, I sitll have a 2-fan PSU exhausting air, and
> an exhaust fan located beneath my GPU. Which is why I'm planning
> on adding a 3rd 80mm fan... somewhere. Hopefully I will be
> supplying more than enough air into the case, and let the
> exhausts do whatever they can.
> ...
>
> Interesting. I would think that one intake and one exhaust fan,
> located on either side of the case, would be MORE likely to
> create hotspots, because they would create a tunnel effect. As
> in, the air flows along a specific path and right out of the case
> again. What would create turbulence is 1) internal fans moving
> air "sideways" or 2) objects in the direct path of the airflow,
> forcing it to move around the case more.
>
> Of course, this is all conjecture until I tie little ribbons to the
> inside of my case and "see" my airflow