fan direction

cavity · Post by **cavity** » Mon Jan 17, 2005 10:17 pm

i've currently got my bp6 running fairly stable, it only crashes about once a month now. the cpu's have nice big aluminum heatsinks on them because they're overclocked from 400 to 558mhz. i found that a cold air intake over each of the fans will lower the temps by 5c but they pick up lots of dust, and i have to clean them regularily.

so, to the point: can i flip the cpu fans over to make them blow out the top and avoid dust, without causing any cooling problems? I dont want to do it and find they get real hot right away. i just wanted to check if anyone else has ran cpu fans out from the heatsink instead of pointing them down at it.

davd_bob · Post by **davd_bob** » Tue Jan 18, 2005 1:55 am

I've tried both directions for air flow. It seems like the heat sink is also a "dust sink" nomater which direction the airflow is. The only advantage is sometimes the dust can be cleaned without having to remove the fan if air is pulled out of the HS instead of being pushed through it. No real difference other then that in my experience.
Only tried it on 486 and Pentiums that the fan flipped over easily because I never thought about reversing the wiring.(d'oh)

hyperspace · Post by **hyperspace** » Tue Jan 18, 2005 7:23 am

For best cooling, air flow should be pointed into heatsink. Pointing away will not cool the entire heatsink properly. Most of the air will be pulled through the top of the heatsink and the metal closest to the core will not get maximum air flow.

cavity · Post by **cavity** » Tue Jan 18, 2005 3:00 pm

i guess I'll have to make an aircleaner for the intakes then... thanks for saving me trouble of flipping the fans over and back

headseed · Post by **headseed** » Tue Jan 18, 2005 6:48 pm

Some HSFs are made to work with the fan sucking rather than blowing. Alphas (6035, 8045) have a shroud and it forces the air to be pulled up lower on the sink than with out it. Alot of the thermalright sinks work equally well both ways also. Try it and see if it works. If not, try to fashion a shroud around the heatsink, but leaving the bottom open so the air is pulled in low.

It all really depends on the type of heatsink, size of fan, how big the deadspot of airflow is below/above the fan hub, the size and spacing of the fins/pins on the heatsink, etc.

Post by **Derek** » Tue Jan 18, 2005 10:19 pm

cavity wrote:i guess I'll have to make an aircleaner for the intakes then... thanks for saving me trouble of flipping the fans over and back

That is a great idea. I taped cheese cloth over the metal fan grates and replace the cloth whenever it looks like they’ve accumulated a lot of dust. It really works!

~~~^^^mercury^^^~~~ · Tue Jan 18, 2005 11:51 pm

this fan thread has me asking:

on the bx chipset,
should the 486 fan blow into the bx, or
away from the chip.

mine blows into it, and
can't be turned over.
s'pose the wires could be clipped and switched and
soldered and heatshrunk.

~~~^^^mercury^^^~~~

davd_bob · Post by **davd_bob** » Wed Jan 19, 2005 12:10 am

Either way is fine because forced airflow is the result. Blowing into the heat sink is more effective for heat transfer for most HSF combos. Dust is going to collect no matter which way the air flows because...thats the way dust is.

Dave Rave · Post by **Dave Rave** » Wed Jan 19, 2005 12:35 am

I have a nice set of matching Macase cases for my bp6.s
with the fan extract on the back....
and the 'filtered' fan intake on the front.

dust still gets in through all the gaps, but most gets into the filter.
yay for filters

purrkur · Post by **purrkur** » Wed Jan 19, 2005 4:35 am

davd_bob wrote:Only tried it on 486 and Pentiums that the fan flipped over easily because I never thought about reversing the wiring.(d'oh)

Reversing the wiring won't work. The fans run brushless DC motors which need electronics to run. Reversing the wiring will reverse the wiring on the electronics and not the motor. It won't budge that way and if no diode "fuse" is set between ground and 12V then you might fry your fan electronics.

Good thing you never tried

InactiveX · Post by **InactiveX** » Wed Jan 19, 2005 1:28 pm

Dave Rave wrote:I have a nice set of matching Macase cases for my bp6.s

Sounds good. Got any pictures?

Wolfram · Post by **Wolfram** » Sun Jan 23, 2005 8:11 am

Dust filters are nice, but I think you should have a little more airflow into the case than out of it. The overpressure keeps dust from creeping through tiny openings and gaps in the case, so most of the dirt is caught in the filter(s).