Rear Exhaust Fan Direction

Tyrven · Post by **Tyrven** » Sun Feb 26, 2006 11:32 pm

This is peculiar. I just ordered a new Lian Li PC-V1000 case. The rear 120mm fan in the upper compartment is facing inward.

Normally, I would expect the rear fan to face outward, as an exhaust. Further, the PC-V1000 ships with an exhaust cover in order to dampen the outbound noise, which would seem to confirm a typical fan direction.

The only justification I can think of for the inverse fan would be the fact that there are no other case fans in the upper compartment of the case and the front panel is perforated; facing it toward that front panel may provide better airflow.

My suspicion, though, is that this case was improperly assembled.

My question for you: is there any benefit to the current setup? Is there any reason not to reverse it (so that it's pushing outward)?

If anyone owns this particular case (or related PC-V1x00 models) I'm curious how yours is setup as well.

nici · Post by **nici** » Mon Feb 27, 2006 6:33 am

Im pretty shure it should be blowing outwards and the perforated front works as intake...

btw. you might want to add "... in lian-li v1000" or something to the title and maybe you would get more atttention from actual lian-li owners and not just silly me

TomZ · Post by **TomZ** » Mon Feb 27, 2006 8:59 am

I have a PC-V1100B, and my chassis fan also blows inward. That is how it is supposed to be on those cases.

For fun, I did an experiment and reversed the direction to blow outward, and I noted a ~5-10C increase in CPU temperatures, so I put it back the way it shipped - blowing inward.

You may want to try a similar experiement, since it is so easy to do.

Tyrven · Post by **Tyrven** » Mon Feb 27, 2006 5:52 pm

TomZ: Thank you. That's really interesting. I think I'll try reversing it when I replace the ADDA fan with a quieter option (I'll probably go with the GlobalWin 120 -- if CoolerGuys gets them back in stock, that is).

cpemma · Post by **cpemma** » Tue Feb 28, 2006 10:40 am

See the animation here for how the flow is designed to go.

Tyrven · Post by **Tyrven** » Tue Feb 28, 2006 2:56 pm

Huh - I guess it's relying on that optional 120mm PCI cooler to help pull the air from the front bezel and up from the CPU. That's curious. I don't have that fan installed and, quite frankly, hadn't intended on it because it looks next to impossible to replace with a quieter fan. Of course, if I picked up a fan controller I could stop it down a bit; the Addas have enough airflow that I could probably get away with that.

Anyway, that's really interesting. I've seen that animation before but the relevence of it never really hit until I got my chassis.

TomZ · Post by **TomZ** » Tue Feb 28, 2006 3:04 pm

Since the front and rear fans both blow in, even without the PCI/VGA fan, there will probably be airflow out through that area.

I think the PCI/VGA fan in this case is useless. I tried it installed and not installed, and didn't notice any difference in GPU temperature. I think the issue is that the fan CFM is too low to really be helpful. I also agree with you that the fan would be hard to replace with a quieter one, although I was thinking the fan was already pretty quiet.

I had another thought - I wonder if a fan blowing in is quieter than a fan blowing out, from the perspective of the outside of the case?

Tyrven · Post by **Tyrven** » Tue Feb 28, 2006 4:22 pm

That seems logical to me; it would put most of the air turbulance noise inside the case where it would be buffered by the metal. Of course, it might also relate to more vibration -- but I can't imagine it being more than the vibration from the fan itself (depending on how its mounted).

That's good to hear that the PCI cooler is pretty quiet - I should try out just for kicks. My PCIE card has an Artic Cooler style device built into it, which intakes air from the top of the chassis, blows it across the card and then out the back. It's quiet and seems to work pretty well.

teejay · Post by **teejay** » Wed Mar 01, 2006 12:28 am

It appears you have the "plus" version of this case, which comes with a altered airflow pattern and the slot blowing fan. I think they released that version of the case since in the original setup too much hot & stagnant air remained in the top of the case. With an arctic cooling VGA cooler you can probably keep the fan blowing inwards easily. You could also try blocking all front vents in the upper section of the case to see if you can prevent noise "leaking" out the front.

A fan blowing in could reduce turbulence noise, since most turbulance noise is generated by obstructions on the intake side of fans.