fan rpm query

weeder

http://www2.hardwareversand.de/articledetail.jsp?aid=30976&agid=42 looking at one of these to go into a htpc where space is an issue so but obviously want as quiet a possible.

this fan was recommended to me by someone anyway but i see theres several versions and i was told to go for the 800rpm one as its the quietest but im wondering is that really the way to go?

like would there be anything wrong with going for the fastest one and setting it down to 800 rpm or am i missing somthing here?

at the moment ive taken an old dell fan and mounted it to the sidepanel and its giving desirable temps but it has to sit on the outside of the case(ugly) so even if the 800rpm model could cool better id be happy, dont know the specs on the dell fan mind you.

dwighet

weeder wrote: »

http://www2.hardwareversand.de/articledetail.jsp?aid=30976&agid=42 looking at one of these to go into a htpc where space is an issue so but obviously want as quiet a possible.

this fan was recommended to me by someone anyway but i see theres several versions and i was told to go for the 800rpm one as its the quietest but im wondering is that really the way to go?

like would there be anything wrong with going for the fastest one and setting it down to 800 rpm or am i missing somthing here?

at the moment ive taken an old dell fan and mounted it to the sidepanel and its giving desirable temps but it has to sit on the outside of the case(ugly) so even if the 800rpm model could cool better id be happy, dont know the specs on the dell fan mind you.

If noise isnt an issue I`d say go for the 1900 rpm fan...I have a 2000 rpm slipstream on my sythe gfx cooler and there not too noisy

Serephucus

I wouldn't bother TBH. You could, but... why? Might as well just get the 800RPM model.

Download Speedfan, and see what the Dell fan is running at RPM-wise. If it's a 2000RPM fan, and your temps are just about acceptable, then you'll need something faster than 800 anyway.

weeder

no good, its one of those thermally controlled fans with no rpm sensor, and i cant find specs online for it anywhere.

Serephucus

Weird. PWM fans should still be able to be monitored. If you have a look in your BIOS, it's usually under something like PC Health Status, it'll show temperatures, and if your lucky, RPM for any connected fans.

weeder

its an old propietary dell yoke.


there is a thermistor in the fan and the yellow wire sends temp data back to the dell motherboard which changes fan speed accordingly. Of course the user never got his hands on this info.


EDIT: just googled 4W022 which i found is dells part number(wasnt on the fan that i seen) and it brought me to a jmc/datech fan which isnt the same fan but the same dell part, apparently its 82cfm at 4000rpm, fan couldnt be running anywhere near that by the sound off it. but again its a slightly different fan. the model on it is 33610KL-04w-b66 which google turns up nohing for but i got a few hits on the cfm rating with 04w-b66 for slightly differnt fans, but im guessing unless i can find out the true rpm im pissing against the wind on finding the cfm


edit 2: model number is actually 3610 not 33610 so im getting a few hits now.

Serephucus

Right, so it's probably crap... Hmmm...

Right, I can't think of any other way to test this, so try to stop the fan blades with your finger. If you can do it, and it just feels like you're brushing the fan to a stop, it's under 1000RPM. If it is a little choppy, it's about 1500, and if it hurts, then it's about 2000.

Sorry, can't think of anything else. When I was testing my case components for sound, I'd stop each component when the computer was running to hear the difference in noise. Not wanting to damage anything, I was using something softer than a pencil.

weeder

NMB 3610KL-04W-B40. DC 12V 0.28A. 2850 RPM. 47.6 CFM. 3-Inch / 2-Wire / 2-Pin.

well the "finger test" tells me its between a grand and 1500, the noise test tells me its nowhere near 2850. so maybe the 800 will be grand, but what im curious about is why schythe offers multiple versions based on rpm when you could just get the 1900 one and jack it down with speedfan? im building a new box at the moment anyways so somthing tells me ill end up getting 800 and 1900 when there only a fiver anyway

Serephucus

Well if you go by CFM, the Dell fan is ~48, the 800RPM Slipstream is ~41, so odds are you'll be fine with it. There's a 1200RPM/70CFM if that helps you.

whizbang

CFM is quoted at full speed. If your not looking for full speed (quiet) then the airflow figures can be drastically off. and its not linear. 10% less speed can be 50% less airflow. Worst culprits are high speed fans (>2000)
however speed = noise. no way around that.
basically lo speed fans have a better flow at reduced speeds than hi speed fans..
often the wattage/current rating is a better indicator of air shifting power..

whizbang

also: the yellow wire is fan speed. If you need to know the speed, put a finger on the fan so you hear it without slowing it: use the pc microphone and a media player with oscilloscope visualisation!