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power supply overheating?

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Anonymous
a b B Homebuilt system
May 26, 2004 7:32:53 PM

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
Anonymous
a b B Homebuilt system
May 26, 2004 7:32:54 PM

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
Anonymous
a b B Homebuilt system
May 27, 2004 2:41:41 AM

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).
Related resources
Anonymous
a b B Homebuilt system
May 27, 2004 3:15:43 AM

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
>
>
>
Anonymous
a b B Homebuilt system
May 27, 2004 5:38:53 AM

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
May 27, 2004 5:38:54 AM

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
Anonymous
a b B Homebuilt system
May 27, 2004 7:09:11 AM

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.
Anonymous
a b B Homebuilt system
May 27, 2004 2:10:44 PM

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.
Anonymous
a b B Homebuilt system
May 27, 2004 2:10:45 PM

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*
Anonymous
a b B Homebuilt system
May 27, 2004 7:05:52 PM

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.
Anonymous
a b B Homebuilt system
May 27, 2004 8:17:33 PM

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*
Anonymous
a b B Homebuilt system
May 28, 2004 1:52:59 AM

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
Anonymous
a b B Homebuilt system
May 28, 2004 4:33:14 AM

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.
Anonymous
a b B Homebuilt system
May 28, 2004 7:55:27 PM

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
Anonymous
a b B Homebuilt system
May 30, 2004 2:34:28 AM

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.h... (Direct)
Anonymous
a b B Homebuilt system
May 30, 2004 5:33:37 AM

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.h... (Direct)
Anonymous
a b B Homebuilt system
May 30, 2004 5:33:38 AM

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*
Anonymous
a b B Homebuilt system
May 30, 2004 3:48:11 PM

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*
Anonymous
a b B Homebuilt system
May 30, 2004 4:15:43 PM

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 :p 
Anonymous
a b B Homebuilt system
May 30, 2004 5:04:41 PM

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.
Anonymous
a b B Homebuilt system
May 30, 2004 5:04:42 PM

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.
Anonymous
a b B Homebuilt system
May 30, 2004 7:14:36 PM

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*
Anonymous
a b B Homebuilt system
May 30, 2004 9:10:16 PM

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
May 30, 2004 10:32:36 PM

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.
Anonymous
a b B Homebuilt system
May 31, 2004 4:15:17 AM

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 :p 
Anonymous
a b B Homebuilt system
May 31, 2004 4:15:18 AM

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

"w_tom" wrote:
> 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.


No, relevant. A rule of thumb in chemistry is that a reaction
doubles in speed for every 10 degrees F. increase in temperature.
Since many of the thermal mechanisms at work in chemistry
are also those for disk drive wear, I'd say a 5 degree drop in
temperature is worthwhile.

*TimDaniels*
Anonymous
a b B Homebuilt system
May 31, 2004 4:20:01 AM

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

Of course removing obstructions increases fan output to
rated CFM. See the other post about cross sectional area for
details.

Have you assumed that a fan with 50% obstruction is the fan
being posting about? Obviously not. A fan 50% obstructed is
installed wrong - which means all data is now distorted just
like a fan trying to blow into a sealed box. Will that 120
VAC power supply work properly with half the incoming AC
current obstructed? Of course not.

Airflow is the equivalent of a current source - but not an
ideal current source. Airflow is equivalent to current - not
voltage. An ideal fan will maintain CFM just like an ideal
current source. A 'less than idea' fan is more like a real
world current source. It mostly maintains airflow (current)
until obstructions (resistance) become too great. Then CFM
(or current) falls off appreciably. You are unfortunately
trying to make the fan equivalent to a voltage source.

Two fans will double fan CFM if the fans are excessively
obstructed. Do we therefore install two fans in series to
double the airflow? Of course not. We eliminate the
obstruction as the original poster demonstrated with his
cardboard side panel and larger outlet hole. But the
excessively obstructed fan was beyond the scope of numbers
provided for fans and beyond the scope of what Dorothy
posted. Excessive and unacceptable obstruction invalidates
all numbers, data, and concepts. Apparently this was not
understood by some posters here.

Timothy Daniels wrote:
> 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*
Anonymous
a b B Homebuilt system
May 31, 2004 4:20:02 AM

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

"w_tom" wrote:
> Of course removing obstructions increases fan output to
> rated CFM. See the other post about cross sectional area for
> details.
>
> Have you assumed that a fan with 50% obstruction is the fan
> being posting about? Obviously not. A fan 50% obstructed is
> installed wrong...

You're waffling. And you're setting up a straw man, again.

First, the grills and perforated screens covering fans do not
cover 50% of the cross-sectional area and they are not
"installed wrong" as every manufacturer does that. So arguing
against a 50% obstruction - which no one has mentioned - is
a straw man.

Second, you've said that CFM remains constant regardless of
decrease or increase of resistance to air flow. Now you're
backing off and waffling. Just what IS your position?


> Airflow is the equivalent of a current source - but not an
> ideal current source. Airflow is equivalent to current - not
> voltage. An ideal fan will maintain CFM just like an ideal
> current source. A 'less than idea' fan is more like a real
> world current source. It mostly maintains airflow (current)
> until obstructions (resistance) become too great. Then CFM
> (or current) falls off appreciably. You are unfortunately
> trying to make the fan equivalent to a voltage source.


And just where did I equivacate a fan to a voltage source
or to its analogue, a constant pressure differential device?
You're arguing against a straw man, again, as I made no
such claim. In fact, I pointed out that a fan is a combination
of a constant flow device and a constant pressure device,
IOW not an ideal example of either but rather, a real world
device.


> Two fans will double fan CFM if the fans are excessively
> obstructed.


Waffling, again. Define "excessively".

In truth, two fans in series will increase air flow, but
not double it, two fans in parallel will increase air flow,
but not double it.

*TimDaniels*
Anonymous
a b B Homebuilt system
May 31, 2004 1:29:45 PM

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

Now lets put example numbers to your speculations from
chemistry. If the CPU temperature increases, then the CPU
might only last 100 years instead of 200 years. That 5
degrees is totally irrelevant except when other unresolved
hardware problems make it relevant. Again, I cite the Dorothy
post as example. Use numbers such as from datasheets before
making conclusions. Otherwise we get this junk science
conclusion about chemical reactions inside semiconductors.
Manufacturer provides a temperature limit that the CPU works
at just fine. As long as semiconductor stays within those
limits, then all is well. And yes, don't bother citing
electromigration. The "CPU might last 100 years instead..."
sentence includes that concept as well.

If 5 degrees makes a big difference to a system, then the
system has serious hardware problems elsewhere. If 5 degrees
make a big difference to the human, then human needs to first
learn basic semiconductor concepts or read numbers from
manufacturer datasheets. Those 5 degrees created by doubling
the fans is totally irrelevant. But then many also want to
fix computers using the Home Improvement concept of "More
Power". Double the fans (and noise) for an amazing 5 degree
temperature reduction!

Timothy Daniels wrote:
> "w_tom" wrote:
>> 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.
>
> No, relevant. A rule of thumb in chemistry is that a reaction
> doubles in speed for every 10 degrees F. increase in temperature.
> Since many of the thermal mechanisms at work in chemistry
> are also those for disk drive wear, I'd say a 5 degree drop in
> temperature is worthwhile.
>
> *TimDaniels*
Anonymous
a b B Homebuilt system
May 31, 2004 1:42:56 PM

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

Tim - 50% obstruction was provided as an example and not as
what is happening in every case. Clearly all you want to do
is argue. Cut the bullshit with 'waffling' and 'strawmen'.
When you are ready to discuss technical, then it will be
obvious that you first read a manufacturers datasheet. You
are posting numbers using junk science concepts - such as
irrelevant chemical reactions inside a semiconductor.

In the meantime, I never said "CFM remains constant
regardless of decrease or increase of resistance to air
flow." This is the twisted reasoning so common by lawyers and
those who argue subjectively. If I had posted that, then I
would have also said a fan blowing into a closed box would
move 100% of rated CFM. Obviously I posted completely the
opposite - remember? If only you did not read selectively.
Then what I had posted would not have been intentionally
misrepresented. Then 'waffling' and 'strawman' would be
replaced with good technical numbers. Currently your posts,
devoid of numbers, are classic of junk science reasoning
combined with selective reading. Please feel free to cite
manufacturers data sheets and numbers before replying. Use
technical facts rather then a lawyer's subjective terms such
as 'waffling' and 'strawmen'. Demonstrate a technical grasp
before replying. Don't continue posting using 'junk science'
reasoning.

Timothy Daniels wrote:
> "w_tom" wrote:
>> Of course removing obstructions increases fan output to
>> rated CFM. See the other post about cross sectional area for
>> details.
>>
>> Have you assumed that a fan with 50% obstruction is the fan
>> being posting about? Obviously not. A fan 50% obstructed is
>> installed wrong...
>
> You're waffling. And you're setting up a straw man, again.
>
> First, the grills and perforated screens covering fans do not
> cover 50% of the cross-sectional area and they are not
> "installed wrong" as every manufacturer does that. So arguing
> against a 50% obstruction - which no one has mentioned - is
> a straw man.
>
> Second, you've said that CFM remains constant regardless of
> decrease or increase of resistance to air flow. Now you're
> backing off and waffling. Just what IS your position?
>
>> Airflow is the equivalent of a current source - but not an
>> ideal current source. Airflow is equivalent to current - not
>> voltage. An ideal fan will maintain CFM just like an ideal
>> current source. A 'less than idea' fan is more like a real
>> world current source. It mostly maintains airflow (current)
>> until obstructions (resistance) become too great. Then CFM
>> (or current) falls off appreciably. You are unfortunately
>> trying to make the fan equivalent to a voltage source.
>
> And just where did I equivacate a fan to a voltage source
> or to its analogue, a constant pressure differential device?
> You're arguing against a straw man, again, as I made no
> such claim. In fact, I pointed out that a fan is a combination
> of a constant flow device and a constant pressure device,
> IOW not an ideal example of either but rather, a real world
> device.
>
>> Two fans will double fan CFM if the fans are excessively
>> obstructed.
>
> Waffling, again. Define "excessively".
>
> In truth, two fans in series will increase air flow, but
> not double it, two fans in parallel will increase air flow,
> but not double it.
>
> *TimDaniels*
Anonymous
a b B Homebuilt system
May 31, 2004 4:17:22 PM

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

Hi Matt,

> Functionality shouldn't be ugly.

Perhaps not but some of those cases really are :-)

http://www.intel.com/cd/channel/reseller/asmo-na/eng/te...

Most of them look fairly hard to get hold of in the UK as well and I can't
even find the Coolermaster model on their own site.

> Looks like you could just take your side panel to a glass shop to have
> them cut a hole in the plexiglass. And buy a grill and/or an 80mm fan
> to put over the hole. Or take it to somebody who does case
> modifications. Or, if you are so inclined, practice a little with a
> plexiglass cutter (cheap) and some scrap plexiglass and do it yourself.

Well, it is an aluminium side panel, not windowed but, no doubt, there is
some way to get it modified (though it would be easier if Antec sold a
replacement side panel which already achieved this).

> Then you could keep the oh-so-attractive P160. :-)

I've been reading the remainder of this thread and considering issues such
as the potential obstuction created by the dust filter etc. Personally,
there is no difference in temperature in my case whether the dust filter is
present or not (which isn't to suggest that there is no difference in the
quantity of air being moved because I'm sure there is). I've also tried
attaching the case fan to a 'normal' power supply outlet rather than the
'special'/variable fan-only ones provided by the PSU. Again, it makes no
difference to the speed of the fan which was already rotating at around its
maximum 1700RPM anyway.

My current thinking is still to buy an Antec Plus1080-AMG, which is on
Intel's "Thermally Advantaged Tested Chassis List" - at least then neither
company's technical support can use "you aren't using a thermally advantaged
chassis" as a reason to ignore my questions or generally obfuscate the whole
situation. I've got another use for the P160 to house an older machine.

I'm still not sure about the Plus1080-AMG as a case though. I'd feel better
if instead of being on Intel's list or advertising itself as 'thermally
advantaged', it actually conformed to Intel's Chassis Design Guide (version
1.0 or 1.1) which recommends a Chassis Air Guide assembly. At least it has a
side-vent which, I believe, has a good chance of curing the problem.

-dan
Anonymous
a b B Homebuilt system
May 31, 2004 7:14:48 PM

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

"w_tom" wrote:
> Now lets put example numbers to your speculations from
> chemistry. If the CPU temperature increases, then the CPU
> might only last 100 years instead of 200 years. That 5
> degrees is totally irrelevant except when other unresolved
> hardware problems make it relevant. Again, I cite the Dorothy
> post as example. Use numbers such as from datasheets before
> making conclusions. Otherwise we get this junk science
> conclusion about chemical reactions inside semiconductors.


Again, a straw man argument. Who said anything about
semiconductor "wear"? I said "hard drive", which includes
platter bearings and armature bearings. Mechanical wear
is very much influenced by temperature, and I would
consider a 5 degree F. drop in temperature worthwhile.
If you prefer your hard drives hotter than that, go for it!

*TimDaniels*
Anonymous
a b B Homebuilt system
May 31, 2004 7:21:14 PM

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

"w_tom" wrote:
> Tim - 50% obstruction was provided as an example and not as
> what is happening in every case. Clearly all you want to do
> is argue. Cut the bullshit with 'waffling' and 'strawmen'.
> When you are ready to discuss technical, then it will be
> obvious that you first read a manufacturers datasheet. You
> are posting numbers using junk science concepts - such as
> irrelevant chemical reactions inside a semiconductor.


Straw man. I made no such reference to chemical reactions
inside a semiconductor. You're arguing with your own b.s.


> Currently your posts, devoid of numbers, are classic of
> junk science reasoning combined with selective reading.
> Please feel free to cite manufacturers data sheets and numbers
> before replying. Use technical facts rather then a lawyer's
> subjective terms such as 'waffling' and 'strawmen'.
> Demonstrate a technical grasp before replying. Don't
> continue posting using 'junk science' reasoning.


You have claimed in this very thread that putting two fans
in series will not increase air flow. Cite your vaunted
"manufacturer's data sheets and numbers" to prove that.
Let's see where the junk science really is.

*TimDaniels*
Anonymous
a b B Homebuilt system
June 1, 2004 12:46:39 AM

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

Chemical reactions inside disk drives have doubled because
the temperature has risen how many degrees? Yes, higher
temperature can increase mechanical wear. And that disk drive
is rated for something on the order of 50,000 hours even when
run at 100 degrees F. Again numbers. 50,000 hours at eight
hours everyday is something like 17 years. Clearly a disk
drive that fails after 17 years is a disaster? Tim- are you
still worried about all those chemical reactions inside a disk
drive now that we apply numbers to your speculations?

The only strawman I see here is the one who wishes he had a
brain. At least be a tin man. Have enough heart to admit you
don't have sufficient technical knowledge. Admit that massive
chemical reactions have not doubled inside a warmer disk
drive. Posted earlier was criticisms about those who post
without even providing numbers. Your posts provide no numbers.
Only demonstrates proof using junk science - sweeping
conclusions without a single numerical fact. Numbers, Tim.
They have a very important purpose in technical discussions.
Numbers are what characterize Dorothy's post separate from
'computer literates' who know and therefore don't need no
stinkin' numbers.

In the meantime, please provide the empirical equations for
those massive chemical reactions inside a disk drive due to 5
degrees more heat. If chemical reactions are damaging disk
drives, then we all must be informed of that chemistry.

Timothy Daniels wrote:
> "w_tom" wrote:
>> Now lets put example numbers to your speculations from
>> chemistry. If the CPU temperature increases, then the CPU
>> might only last 100 years instead of 200 years. That 5
>> degrees is totally irrelevant except when other unresolved
>> hardware problems make it relevant. Again, I cite the Dorothy
>> post as example. Use numbers such as from datasheets before
>> making conclusions. Otherwise we get this junk science
>> conclusion about chemical reactions inside semiconductors.
>
> Again, a straw man argument. Who said anything about
> semiconductor "wear"? I said "hard drive", which includes
> platter bearings and armature bearings. Mechanical wear
> is very much influenced by temperature, and I would
> consider a 5 degree F. drop in temperature worthwhile.
> If you prefer your hard drives hotter than that, go for it!
>
> *TimDaniels*
Anonymous
a b B Homebuilt system
June 1, 2004 1:12:13 AM

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

"w_tom" wrote:
> Chemical reactions inside disk drives have doubled because
> the temperature has risen how many degrees?...
> Admit that massive chemical reactions have not doubled
> inside a warmer disk drive.


You are so very dependent on jousting with straw men,
aren't you. No one spoke of "chemical reactions" inside
disk drives. No one spoke of "massive chemical reactions",
either. But that the increased kinetic energy of the atoms
and molecules of a medium increase both chemical reactions
and wear rates *is* true, and the mechanisms are much
the same when you consider that much of mechanical
wear occurs at a molecular level.

As for the significance of a 5 degree F. decrease in temperature,
if it makes a difference to your body, why wouldn't make a
difference to a disk drive? When considered on a Kelvin scale,
the operating temperatures of both are similar. Just how much
of a temperature decrease do you need to feel that it is
"significant"?

*TimDaniels*
Anonymous
a b B Homebuilt system
June 1, 2004 6:46:28 AM

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

On Mon, 31 May 2004 15:14:48 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:

>"w_tom" wrote:
>> Now lets put example numbers to your speculations from
>> chemistry. If the CPU temperature increases, then the CPU
>> might only last 100 years instead of 200 years. That 5
>> degrees is totally irrelevant except when other unresolved
>> hardware problems make it relevant. Again, I cite the Dorothy
>> post as example. Use numbers such as from datasheets before
>> making conclusions. Otherwise we get this junk science
>> conclusion about chemical reactions inside semiconductors.
>
>
> Again, a straw man argument. Who said anything about
> semiconductor "wear"? I said "hard drive", which includes
> platter bearings and armature bearings. Mechanical wear
> is very much influenced by temperature, and I would
> consider a 5 degree F. drop in temperature worthwhile.
> If you prefer your hard drives hotter than that, go for it!
>
>*TimDaniels*

While it's certainly true that a hard drive's (maximal) lifespan is
related to temp, unfortunately it seems none of the manufacturers provide
temp vs lifespan projections. Further we're getting into a grey area,
where one persons's idea of acceptible lifespan may not be the same as
another person's, and futher the willingness to go to extra measures to
extend lifespan may also vary.

On the other hand, fan and capacitor manufacturers are sometimes more
forthright about this relationship, that a typical lifespan reduction of
50% can be expected with 10C rise in temp. This will not affect some
people, but often plays a role in failure of video card fans, power supply
sleeve bearing exhaust fans, and video or motherboard power regulation
circuit capacitors (varying per design, space and budget), in addition to
system power supply capacitors.

The issue is not so much whether the temp is dropped by 5C, but what the
maximal temp is that will provide adequate service life... a difficult
thing to determine except in retrospect, comparing aged parts to next-gen
parts, particulary with parts having unlabled or generic components,
unobtainable specs. Of course if the temp is above this acceptible
service life margin, 5C drop is much more significant than if temp is
below that.

As for hard drives, we need specs for manufacturer to make individual
determination of realistic (not MTBF ratings) lifespan projections per
temp before this information can be used to plan a system's service life,
or at least that of the drive itself to implement a rotation schedule,
replacing drives as an informed choice.
Anonymous
a b B Homebuilt system
June 3, 2004 5:07:37 AM

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

Timothy Daniels wrote:

> "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.

Nice analogy, except that fans don't work like that and an easy way to
visualize it is to imagine a very high CFM fan going into a low CFM fan.
The second fan itself becomes a resistance, and not a 'boost', to the high
CFM fan because, for one, it's blades simply can't spin that fast. And even
if they 'free wheel' they'd obviously not be adding anything to the effort.
Indeed, they'd be bleeding off CFM by absorbing the energy needed to blow
the blades faster.

You may protest that that isn't two equal fans but the point is they do not
'add' like your electrical analogy.


>> 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*
>


Fans are rated CFM into free air and CFM per back pressure.

Under ideal conditions, identical fans, and ignoring side effects:

Put two fans in series and you raise the slope of the back pressure curve
(I.E. 0 CFM occurs at a higher pressure) but you do not increase the
'rated' CFM into free air.

Put two fans in parallel and the 0 intercept of the back pressure curve
remains the same (I.E. 0 CFM will be at the same pressure as for 1 fan) but
you double the 'rated' CFM into free air.


When people say that putting fans in series doesn't 'increase' the airflow
they are speaking of the 'rating': What you 'could' get under ideal
conditions (it's where you start with any spec). It can result in increased
airflow if you're working into a high resistance because the ability to
push/pull into/against the resistance has increased (assuming it isn't
screwed up by turbulence, blade beat, and other problems), but that
characteristic is the same as for 1 fan: I.E. you get less than the
'rating' depending on the resistance to the airflow. You simply have a 1x
CFM fan that can handle more pressure.

To put it another way, the airflow resistance is an external influence and
not a characteristic of the fan configuration, be it single or dual. You
spec what the configuration can do (e.g. I get twice the pressure
capability with series fans) and then calculate into the environment.

If you insist on an 'airflow' description, the way to characterize it is
that you "lose less airflow" with series fans, not that you get 'more',
because the free air rating of 1 fan is all you 'can get'.

A better way is to say you double the pressure capability with series fans
and double the airflow with parallel fans because that is the actual
characteristic of the configuration. You can then see what effect the
environment they're placed into has on them.
Anonymous
a b B Homebuilt system
June 3, 2004 5:07:38 AM

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

"David Maynard" wrote:
> Nice analogy, except that fans don't work like that and an easy way to
> visualize it is to imagine a very high CFM fan going into a low CFM fan.
> The second fan itself becomes a resistance, and not a 'boost', to the high
> CFM fan because, for one, it's blades simply can't spin that fast.


That's where fans are non-ideal. Over a span of loads, the fans
speed up when the load (back pressure) is decreased. Beyond
those loads, the fans act differently. You are merely observing that
fans are not ideal pressure differential devices. And, of course,
that is what I have been saying - that fans are a real world combin-
ation of constant pressure differential devices and positive displace-
ment (constant flow) devices.


> You may protest that that isn't two equal fans but the point is they
> do not 'add' like your electrical analogy.


And why not? If the larger fan is turning at the low end of its speed
range so that its flow rate doesn't put the smaller fan outside its normal
speed range, their efforts will indeed be additive - not perfectly
additive - but additive. What you are proposing is a situation in which
only one of the real world devices can approximate a constant pressure
differential device and not both. And what does *that* prove? It only
proves that there are no ideal devices in the real world. Even electrical
devices don't act as ideal devices.


> >> 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*
> >
>
>
> Fans are rated CFM into free air and CFM per back pressure.
>
> Under ideal conditions, identical fans, and ignoring side effects:


Exactly. Fans are given a rating for a given set of conditions.
Their ratings are not isolated parameters of the fans without
reference to their environments, i.e. they are real world devices.
And it also means that they can also interact - one can, in fact,
act as a flow inhibitor for the other for certain ranges of
fan rpms, just as in your example.

And getting back to the original question about whether two
case fans in series can move more than one case fan (with
the implicit condition that the fans are of comparable size),
the answer is still "Yes".

*TimDaniels*
Anonymous
a b B Homebuilt system
June 3, 2004 5:10:11 AM

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

Timothy Daniels wrote:

> "w_tom" wrote:
>
>> Of course removing obstructions increases fan output to
>>rated CFM. See the other post about cross sectional area for
>>details.
>>
>> Have you assumed that a fan with 50% obstruction is the fan
>>being posting about? Obviously not. A fan 50% obstructed is
>>installed wrong...
>
>
> You're waffling. And you're setting up a straw man, again.
>
> First, the grills and perforated screens covering fans do not
> cover 50% of the cross-sectional area and they are not
> "installed wrong" as every manufacturer does that. So arguing
> against a 50% obstruction - which no one has mentioned - is
> a straw man.
>
> Second, you've said that CFM remains constant regardless of
> decrease or increase of resistance to air flow. Now you're
> backing off and waffling. Just what IS your position?
>
>
>
>> Airflow is the equivalent of a current source - but not an
>>ideal current source. Airflow is equivalent to current - not
>>voltage. An ideal fan will maintain CFM just like an ideal
>>current source. A 'less than idea' fan is more like a real
>>world current source. It mostly maintains airflow (current)
>>until obstructions (resistance) become too great. Then CFM
>>(or current) falls off appreciably. You are unfortunately
>>trying to make the fan equivalent to a voltage source.
>
>
>
> And just where did I equivacate a fan to a voltage source
> or to its analogue, a constant pressure differential device?
> You're arguing against a straw man, again, as I made no
> such claim. In fact, I pointed out that a fan is a combination
> of a constant flow device and a constant pressure device,
> IOW not an ideal example of either but rather, a real world
> device.
>
>
>
>> Two fans will double fan CFM if the fans are excessively
>>obstructed.
>
>
>
> Waffling, again. Define "excessively".
>
> In truth, two fans in series will increase air flow, but
> not double it,


> two fans in parallel will increase air flow,
> but not double it.

Of course two in parallel will double it. Why would you think not?
Anonymous
a b B Homebuilt system
June 3, 2004 8:01:43 AM

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

Timothy Daniels wrote:

> "David Maynard" wrote:
>
>>Nice analogy, except that fans don't work like that and an easy way to
>>visualize it is to imagine a very high CFM fan going into a low CFM fan.
>>The second fan itself becomes a resistance, and not a 'boost', to the high
>>CFM fan because, for one, it's blades simply can't spin that fast.
>
> That's where fans are non-ideal.

Fans are not ideal under ANY conditions, not just 'there'.

> Over a span of loads, the fans
> speed up when the load (back pressure) is decreased. Beyond
> those loads, the fans act differently. You are merely observing that
> fans are not ideal pressure differential devices. And, of course,
> that is what I have been saying - that fans are a real world combin-
> ation of constant pressure differential devices and positive displace-
> ment (constant flow) devices.

No, what I'm saying is that your analogy does not represent how fans work.

>>You may protest that that isn't two equal fans but the point is they
>>do not 'add' like your electrical analogy.
>
> And why not?

Because they DON'T is why. Nor are they going to suddenly 'change' and work
that way simply because you find the analogy satisfying.

> If the larger fan is turning at the low end of its speed
> range so that its flow rate doesn't put the smaller fan outside its normal
> speed range, their efforts will indeed be additive - not perfectly
> additive - but additive.

The term "additive" means something; like 1+1=2. There is no term "not
perfectly additive" but if there were it would mean "not additive but some
other kind of relationship." And I explained to you what the other
relationship is: the pressure capability when placed in series.

> What you are proposing is a situation in which
> only one of the real world devices can approximate a constant pressure
> differential device and not both.

I'm saying no such thing. I'm saying your analogy, and insistence on
calling them constant pressure differential devices, is inappropriate and
leads to incorrect 'guesses'.

> And what does *that* prove? It only
> proves that there are no ideal devices in the real world. Even electrical
> devices don't act as ideal devices.

I gave you an extreme case, because it's easy to visualize, to illustrate
that the fans are not additive in the manner you claim.

>>>> 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*
>>>
>>
>>
>>Fans are rated CFM into free air and CFM per back pressure.
>>
>>Under ideal conditions, identical fans, and ignoring side effects:
>
>
>
> Exactly. Fans are given a rating for a given set of conditions.

EVERY rating for ANY thing is for a given set of conditions.

Fans are rated at free air because that is the condition which represents
the fan's ability sans 'other things', which are unknown until the fan is
placed somewhere.

> Their ratings are not isolated parameters of the fans without
> reference to their environments, i.e. they are real world devices.

No kidding? It isn't a rating in an alternate universe? Whod'a thunk it?

> And it also means that they can also interact - one can, in fact,
> act as a flow inhibitor for the other for certain ranges of
> fan rpms, just as in your example.

So? All this hand waving you're doing about generalities doesn't accomplish
anything.

> And getting back to the original question about whether two
> case fans in series can move more than one case fan (with
> the implicit condition that the fans are of comparable size),
> the answer is still "Yes".

I couldn't care less what, you say, "the original question" was, or who you
think you're having a proxy argument with. All I did was tell you how fans
work when placed in series and parallel configurations.

Here

http://www.comairrotron.com/engineering_notes_02.asp

>
> *TimDaniels*
Anonymous
a b B Homebuilt system
June 3, 2004 10:37:44 AM

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

On Thu, 03 Jun 2004 01:10:11 -0500, David Maynard <dNOTmayn@ev1.net>
wrote:


>> two fans in parallel will increase air flow,
>> but not double it.
>
>Of course two in parallel will double it. Why would you think not?

In _free_air_ two parallel fans will have double flow rate, but not if
there is a pressure gradient.
Anonymous
a b B Homebuilt system
June 3, 2004 10:37:45 AM

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

kony wrote:

> On Thu, 03 Jun 2004 01:10:11 -0500, David Maynard <dNOTmayn@ev1.net>
> wrote:
>
>
>
>>>two fans in parallel will increase air flow,
>>> but not double it.
>>
>>Of course two in parallel will double it. Why would you think not?
>
>
> In _free_air_ two parallel fans will have double flow rate, but not if
> there is a pressure gradient.

Two fans in parallel will put out twice what a single fan would into the
same gradient.
Anonymous
a b B Homebuilt system
June 3, 2004 12:55:48 PM

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

On Thu, 03 Jun 2004 03:16:54 -0500, David Maynard <dNOTmayn@ev1.net>
wrote:

>kony wrote:
>
>> On Thu, 03 Jun 2004 01:10:11 -0500, David Maynard <dNOTmayn@ev1.net>
>> wrote:
>>
>>
>>
>>>>two fans in parallel will increase air flow,
>>>> but not double it.
>>>
>>>Of course two in parallel will double it. Why would you think not?
>>
>>
>> In _free_air_ two parallel fans will have double flow rate, but not if
>> there is a pressure gradient.
>
>Two fans in parallel will put out twice what a single fan would into the
>same gradient.

.... but with two fans, it wouldn't be the same gradient, unless there are
other changes beyond simply the addition of second fan.
Anonymous
a b B Homebuilt system
June 3, 2004 12:55:49 PM

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

kony wrote:

> On Thu, 03 Jun 2004 03:16:54 -0500, David Maynard <dNOTmayn@ev1.net>
> wrote:
>
>
>>kony wrote:
>>
>>
>>>On Thu, 03 Jun 2004 01:10:11 -0500, David Maynard <dNOTmayn@ev1.net>
>>>wrote:
>>>
>>>
>>>
>>>
>>>>>two fans in parallel will increase air flow,
>>>>> but not double it.
>>>>
>>>>Of course two in parallel will double it. Why would you think not?
>>>
>>>
>>>In _free_air_ two parallel fans will have double flow rate, but not if
>>>there is a pressure gradient.
>>
>>Two fans in parallel will put out twice what a single fan would into the
>>same gradient.
>
>
> ... but with two fans, it wouldn't be the same gradient, unless there are
> other changes beyond simply the addition of second fan.

And what would it be? Don't know. That's why these things are calculated
with the assumption of "all else being equal" and then when things aren't
equal you put in the numbers for that criteria. Put another way, when
building characteristic equations one likes to change only one variable for
'that' characteristic. If you link them then, invariably (pun), the next
application has one of them different.

However, you should have stuck to your original contention because it was
correct and it was I who misread it.

The doubling of flow for a parallel combination, and pressure handling for
series combination, is only accurate at the end points of max pressure and
max airflow because the fan's airflow/backpressure curve is not linear, and
neither is it when the two are combined.

http://www.comairrotron.com/engineering_notes_02.asp
Anonymous
a b B Homebuilt system
June 3, 2004 1:44:07 PM

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

"David Maynard" blurted:
> I couldn't care less what, you say, "the original question" was,
> or who you think you're having a proxy argument with. All I
> did was tell you how fans work when placed in series and
> parallel configurations.
>
> Here
>
> http://www.comairrotron.com/engineering_notes_02.asp


Thanks. It proves my point that two fans in series flow
more air than a single fan. Here are three paragraphs from
the above web page, titled:

"Series and Parallel Operation"

"Combining fans in series of [sic] parallel can achieve
the desired airflow without greatly increasing the
system package size or fan diameter. Parallel operation
is defined as having two or more fans blowing together
side by side. The performance of two fans in parallel
will result in doubling the volume flow, but only at
free delivery. As figure 4 shows, when a system curve
is overlaid on the parallel performance curves, the
higher the system resistance, the less increase in flow
results with parallel fan operation. Thus, this type of
application should only be used when the fans can operate
in a low impedance near free delivery."

"Series operation can be defined as using multiple fans
in a push-pull arrangement. By staging two fans in series,
the static pressure capability at a give airflow can be
increased, but again, not to double at every flow point,
as Figure 5 displays. In series operation, the best results
are achieved in systems with high impedance."

"In both series and parallel operation, particularly with
multiple fans (5, 6, 7, etc.) certain areas of the combined
performance curve will be unstable and should be avoided.
This instability is unpredictable and is a function of the
fan and motor construction and the operating point. For
multiple fan installations, Comair Rotron strongly recommends
laboratory testing of the system."


As the article points out, choice of the fan size and flow rate is
important to minimize power usage and noise production. It
points out that for high impedance (i.e. air resistance) cases,
the impedance rises at approximately the square of the flow rate
increase, in line with turbulent flow principles of aerodynamics.
This would lead one to seek ways to reduce the impedance before
resorting to a larger fan or fans in parallel. And, of course, one
way to reduce air impedance is to use "round" IDE cables instead
of flat cables in situations using many ATA/ATAPI drives, and to
remove perforated fan grills. Interestingly, in cases having high
impedance, the article says that fans in series are more effective
than fans in parallel.

*TimDaniels*
Anonymous
a b B Homebuilt system
June 3, 2004 11:36:24 PM

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

Timothy Daniels wrote:

> "David Maynard" blurted:
>
>>I couldn't care less what, you say, "the original question" was,
>>or who you think you're having a proxy argument with. All I
>>did was tell you how fans work when placed in series and
>>parallel configurations.
>>
>>Here
>>
>>http://www.comairrotron.com/engineering_notes_02.asp
>
>
>
> Thanks. It proves my point that two fans in series flow
> more air than a single fan.

It is no 'point' to ME nor do I care what your apparent proxy argument with
someone else is.

> Here are three paragraphs from
> the above web page, titled:
>
> "Series and Parallel Operation"
>
> "Combining fans in series of [sic] parallel can achieve
> the desired airflow without greatly increasing the
> system package size or fan diameter. Parallel operation
> is defined as having two or more fans blowing together
> side by side. The performance of two fans in parallel
> will result in doubling the volume flow, but only at
> free delivery. As figure 4 shows, when a system curve
> is overlaid on the parallel performance curves, the
> higher the system resistance, the less increase in flow
> results with parallel fan operation. Thus, this type of
> application should only be used when the fans can operate
> in a low impedance near free delivery."
>
> "Series operation can be defined as using multiple fans
> in a push-pull arrangement. By staging two fans in series,
> the static pressure capability at a give airflow can be
> increased, but again, not to double at every flow point,
> as Figure 5 displays. In series operation, the best results
> are achieved in systems with high impedance."
>
> "In both series and parallel operation, particularly with
> multiple fans (5, 6, 7, etc.) certain areas of the combined
> performance curve will be unstable and should be avoided.
> This instability is unpredictable and is a function of the
> fan and motor construction and the operating point. For
> multiple fan installations, Comair Rotron strongly recommends
> laboratory testing of the system."

I already read it, and the equations. I'm the one who posted the link.


> As the article points out, choice of the fan size and flow rate is
> important to minimize power usage and noise production. It
> points out that for high impedance (i.e. air resistance) cases,
> the impedance rises at approximately the square of the flow rate
> increase, in line with turbulent flow principles of aerodynamics.
> This would lead one to seek ways to reduce the impedance before
> resorting to a larger fan or fans in parallel. And, of course, one
> way to reduce air impedance is to use "round" IDE cables instead
> of flat cables

Better yet, simply run the flat cables flat along the walls like they're
intended.

> in situations using many ATA/ATAPI drives, and to
> remove perforated fan grills. Interestingly, in cases having high
> impedance, the article says that fans in series are more effective
> than fans in parallel.

Well, I tell you what. Why don't you post your fan specs and the air
impedance of your case and we'll crunch the numbers?

>
> *TimDaniels*
Anonymous
a b B Homebuilt system
June 3, 2004 11:36:25 PM

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

"David Maynard" snarled:
> It is no 'point' to ME nor do I care what your apparent proxy argument with
> someone else is.
>
> [..........]
> I already read it, and the equations. I'm the one who posted the link.
>
>
> Well, I tell you what. Why don't you post your fan specs and the air
> impedance of your case and we'll crunch the numbers?


Dear David: I have no quarrel with you or your link, and I
don't care what you think or don't think. My purpose in
posting is to get at truth because many more people read
this newsgroup than you and I. And again, thank you for
the link.

*TimDaniels*
Anonymous
a b B Homebuilt system
June 4, 2004 1:06:01 AM

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

Timothy Daniels wrote:

> "David Maynard" snarled:
>
>>It is no 'point' to ME nor do I care what your apparent proxy argument with
>>someone else is.
>>
>>[..........]
>>I already read it, and the equations. I'm the one who posted the link.
>>
>>
>>Well, I tell you what. Why don't you post your fan specs and the air
>>impedance of your case and we'll crunch the numbers?
>
>
>
> Dear David: I have no quarrel with you or your link, and I
> don't care what you think or don't think.

Good. And thank you for having finally stopped trying to argue with me
about what you think someone else's 'point' was.

> My purpose in
> posting is to get at truth because many more people read
> this newsgroup than you and I. And again, thank you for
> the link.

You're welcome.
!