fan settings

  • Thread starter Thread starter Jim
  • Start date Start date
J

Jim

I've got an Antec case with a 120mm fan in the back for exhaust. I've just
added a front "intake" fan. Both fans are identical and have 3 speed
settings. Is it OK to set both to high, or should one fan be set faster
than the other for better airflow?
 
Set both fan speeds at low. You'll get plenty
of air circulation and less fan noise.

--
Carey Frisch
Microsoft MVP
Windows - Shell/User

---------------------------------------------------------------------------­-----

:

I've got an Antec case with a 120mm fan in the back for exhaust. I've just
added a front "intake" fan. Both fans are identical and have 3 speed
settings. Is it OK to set both to high, or should one fan be set faster
than the other for better airflow?
 
I've got an Antec case with a 120mm fan in the back for exhaust. I've
just added a front "intake" fan. Both fans are identical and have 3
speed settings. Is it OK to set both to high, or should one fan be
set faster than the other for better airflow?
Click to expand...


The exhaust fan can only exhaust as fast as air can get in. The intake
fan can only intake as fast as air can get out. If the potential
exhaust rate is higher than the potential intake rate (for all avenues
of intake and exhaust) you will have negative pressure inside the case
which promotes the collection of dust. If the potential intake rate is
higher than the potential exhaust rate, you will have positive pressure
inside the case which promotes the movement of dust to reduce its
collection.

In general, you want a higher potential intake rate than the potential
exhaust rate. Also, in general, you won't be able to measure either.
The airflow rate spec for fans is their FREE flow rate; i.e., without
any restrictions, like a grill or against a case that can disturb linear
airflow into the intake side of the fan.

Get Speedfan or a temperature monitor utility included for your
motherboard. Then test it yourself. The run through the 9 combinations
of speeds for the fans and monitor the resultant temperature (wait 10 to
15 minutes for temperatures to somewhat stabilize).

Front=low, Rear=low
Front=low, Rear=medium
Front=low, Rear=high

Front=medium, Rear=low
Front=medium, Rear=medium
Front=medium, Rear=high

Front=high, Rear=low
Front=high, Rear=medium
Front=high, Rear=high

While this lets you determine which combination gives you the coolest
temperature, having the coolest temperature may not be necessary if
another combo is quieter and gives a temperature within spec for the
CPU. You'll probably get the coolest temperature with both fans at high
but also the most noise.

With Speedfan, and if the fans have 3 leads (power, ground, and sense),
you can control the fan speeds to give you a reasonable temperature and
to up fan speeds when temperatures exceed your configured thresholds.
That way, the fans would be quiet most of the time but probably will
speed up when you play a game (but the game is probably far more noisy
than when you are writing e-mails so the game drowns out some of the
increased fan noise). Most fans can have their speed control by
changing their duty cycle but I don't know about your 3-speed fans. I'm
guessing they simply add another inline resistor and are basically
12-volt fans, and probably can be duty-cycle controlled by Speedfan.
 
Depends on the internal layout of the hardware in the PC. Too fast, and
there will be low air movement areas downstream from the air flow. Too
slow, air movement may be inadequate for adequate cooling.

The offset speed front vs. back depends on the obstacles and, of those
obstacles, if some need more cooling on the downwind side.
Dave
 
Vanguard said:
in message



The exhaust fan can only exhaust as fast as air can get in. The intake
fan can only intake as fast as air can get out. If the potential
exhaust rate is higher than the potential intake rate (for all avenues
of intake and exhaust) you will have negative pressure inside the case
which promotes the collection of dust. If the potential intake rate is
higher than the potential exhaust rate, you will have positive pressure
inside the case which promotes the movement of dust to reduce its
collection.

In general, you want a higher potential intake rate than the potential
exhaust rate. Also, in general, you won't be able to measure either.
The airflow rate spec for fans is their FREE flow rate; i.e., without
any restrictions, like a grill or against a case that can disturb linear
airflow into the intake side of the fan.

Get Speedfan or a temperature monitor utility included for your
motherboard. Then test it yourself. The run through the 9 combinations
of speeds for the fans and monitor the resultant temperature (wait 10 to
15 minutes for temperatures to somewhat stabilize).

Front=low, Rear=low
Front=low, Rear=medium
Front=low, Rear=high

Front=medium, Rear=low
Front=medium, Rear=medium
Front=medium, Rear=high

Front=high, Rear=low
Front=high, Rear=medium
Front=high, Rear=high

While this lets you determine which combination gives you the coolest
temperature, having the coolest temperature may not be necessary if
another combo is quieter and gives a temperature within spec for the
CPU. You'll probably get the coolest temperature with both fans at high
but also the most noise.

With Speedfan, and if the fans have 3 leads (power, ground, and sense),
you can control the fan speeds to give you a reasonable temperature and
to up fan speeds when temperatures exceed your configured thresholds.
That way, the fans would be quiet most of the time but probably will
speed up when you play a game (but the game is probably far more noisy
than when you are writing e-mails so the game drowns out some of the
increased fan noise). Most fans can have their speed control by
changing their duty cycle but I don't know about your 3-speed fans. I'm
guessing they simply add another inline resistor and are basically
12-volt fans, and probably can be duty-cycle controlled by Speedfan.
Click to expand...

All this work for a computer case that is unsealed, full of holes and
openings? The only important thing is to insure that the differential
favors air intake versus air exhaust, the degree of the differential
being the convectional cooling that is desired or required whereby the
Laws of Thermodynamics takes over at the heatsink/fan to ventilating air
level. It's the airflow...not the fan speed...that is important.
 
Ghostrider said:
All this work for a computer case that is unsealed, full of holes and
openings? The only important thing is to insure that the differential
favors air intake versus air exhaust, the degree of the differential
being the convectional cooling that is desired or required whereby the
Laws of Thermodynamics takes over at the heatsink/fan to ventilating
air
level. It's the airflow...not the fan speed...that is important.
Click to expand...

And the OP can measure the effect of changing airflow by monitoring the
resultant temperature(s). It is NOT required that the case, CPU,
memory, disk, and other areas be ran at room temperature. They just
need to be within operating environmental spec. I've seen lots of users
giggle at having their CPUs run at 40C when their host would run just as
well at 55 to 60C. The OP doesn't need to make more noise with
high-flow fans running at max speed when slower and quieter is
sufficient.

The OP already added the front 120mm fan, so "all this work" is already
done and in the past. Now the OP needs to figure out how to achieve
sufficient cooling at minimal noise. Speedfan, or any other temperature
monitoring utility, will help.
 
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