P182 - Why ignore the top fan?

mtx · Post by **mtx** » Sun Oct 28, 2007 10:20 pm

I've seen a few people cover up the top fan. Why so?

Was there an article somewhere that pointed out to better airflow without the top fan?

Das_Saunamies · Post by **Das_Saunamies** » Sun Oct 28, 2007 11:25 pm

It just isn't necessary. The hole invites dust(and foreign objects) and an extra fan will add to noise with no justifiable improvement in cooling. It's been discussed on the forums before, can't remember if there's been a proper article or test.

If you've got one, the tests should be easy enough to do, just cover the top hole with a book or leave it open, see what happens in both scenarios.

nick705 · Post by **nick705** » Sun Oct 28, 2007 11:26 pm

It's more a noise thing - for many people, the additional fan doesn't provide much benefit, and the hole in the top provides a direct path to the ears for noise-making components inside the case. Also, if the hole's uncovered but minus the fan, there's a "short-circuit" of air to the rear fan - the CPU might benefit, but not so good for other components in the case.

There's no hard and fast rule though - theory and practice don't always coincide, so it's best to fiddle around until you find the right configuration that suits your particular setup.

/edit: snap.

mtx · Post by **mtx** » Mon Oct 29, 2007 9:01 am

Hmmm....if I'm running a C2D config with a heavily OCed CPU, would it be better to blow air in or out on the top fan or completely leave it sealed off?

Ashex · Post by **Ashex** » Mon Oct 29, 2007 9:03 am

mtx wrote:Hmmm....if I'm running a C2D config with a heavily OCed CPU, would it be better to blow air in or out on the top fan or completely leave it sealed off?

You would want it to pull air out (since heat rises). But the fans on the rear are generally closer then those on the top, so you're better off sealing it.

Luminair · Post by **Luminair** » Mon Oct 29, 2007 12:39 pm

Removing the top output would only increase cooling performance in a misconfigured monster of a setup that I can't even imagine.

People like to get rid of the top vent because it lets noise out.

People can afford to get rid of the top vent because they probably only had one active input anyway, so the one of the two outputs was being poorly utilized. This is why people who add a kama bay, etc, find unexpectedly nice cooling performance increases, while people who block the top output find unexpectedly minor performance decreases. It's because the state they were moving from wasn't optimally configured in the first place.

If you have a bunch of hot parts generating a bunch of hot air that isn't sufficiently removed by one output, then you won't want to cut your potential airflow in half by removing half of your outputs. That is simple to understand!

Ashex · Post by **Ashex** » Mon Oct 29, 2007 1:11 pm

Luminair wrote:Removing the top output would only increase cooling performance in a misconfigured monster of a setup that I can't even imagine.

People like to get rid of the top vent because it lets noise out.

People can afford to get rid of the top vent because they probably only had one active input anyway, so the one of the two outputs was being poorly utilized. This is why people who add a kama bay, etc, find unexpectedly nice cooling performance increases, while people who block the top output find unexpectedly minor performance decreases. It's because the state they were moving from wasn't optimally configured in the first place.

If you have a bunch of hot parts generating a bunch of hot air that isn't sufficiently removed by one output, then you won't want to cut your potential airflow in half by removing half of your outputs. That is simple to understand!

After reading your post, I should probably restate my opinion on the top fan.

I'm kinda bored, so here's what an ideal case would look like in toon town:

For me, the only way a top fan would make sense is in this setup:

But that doesn't always work, since we have cable clutter:

Plus occasionally people don't pay attention to the direction the fans are blowing, and they will both be pulling air out or pushing air in, so that you don't have any flow.

Bluefront · Post by **Bluefront** » Mon Oct 29, 2007 2:27 pm

There are many airflow configurations that could be constructed....the P180 is a good example. The problem with a standard case is that the location of the PSU blocks upward airflow. The answer is simple if you want to use a top vent.....move the PSU backwards about half-way. This can leave a sizable opening for a passive exhaust on the top......like this setup. The rear fan is blowing inward, and the exhaust goes outward through the fanless Zen PSU, and a passive vent setup on the top cover. The HD and the video card are cooled by a lower fan blowing inward.....very quiet setup.

ronrem · Post by **ronrem** » Tue Oct 30, 2007 11:57 am

Where you park the case matters. If it's on the desktop,a lot of soundwaves get aimed above your ears. If it's low....but below a table or desk or ?,that also means a less direct path.

Antecs with a bottom PSU benefit some by having a lot of exhaust near the hot parts. However...Antecs tend to have a front fan,and yet not a whole lot of Air-In square inches. Without having an Antec to chop up...I'd guess that a good plan is no fan in the front...cut away some obstructions to the inlet there...and add some floor intake,probably with a base or feet to give clearance. Then....the deal is what's inside to MAKE heat. Obviously an OC'd Intel Quad is way hotter than a Sempron and a 8800 Vid card is way hotter than an omboard video... Those factors decide your fan RPMs

The Antecs tend to do best with a mid-power rig. A high-heat gamer beast will do better with a bit bigger case and big fans.

thejamppa · Post by **thejamppa** » Tue Oct 30, 2007 1:01 pm

ronrem wrote:
The Antecs tend to do best with a mid-power rig. A high-heat gamer beast will do better with a bit bigger case and big fans.

I like many has noticed that when running hot video card. P-180/P182series is not best gamer case. But with extremely hot components, the top exhaust can be very usefull. But not in silence perspective.

High heat producing beasts need cases with very good ventilation, like antec 900 or upcomming antec 1200 ( or Coolermaster CM 690 with all 7 fans ). But they're hardly a quiet cases. I guess antec gamer series is the exception that strengthen the rule.

Natronomonas · Post by **Natronomonas** » Tue Oct 30, 2007 2:42 pm

My p182 isn't the quietest out, but seems to handle an o/c q6600 and 8800gts ok, running at 100% (just cpu) all the time.

No extra fans, just the two tri-cools on low and an undervolted nexus on the ninja cpu cooler.

I'll probably swap out the tri-cools at some point, they're a bit noisy for my liking but the irritation factor hasn't got overwhelming yet, so they can't be too bad (plus there's the aesthetics, they have that switch on the back that would have to be removed and covered).

So I don't think a 900 or 1200 is really required, except perhaps for bling or whatever it is these days.

ntavlas · Post by **ntavlas** » Tue Oct 30, 2007 3:22 pm

But how about using the top output only? Yes, I know it would be easier for the fan noise to reach ones ears from the top position but lets pretend we don`t care about noise for a moment. Wouldn`t it be more efficient to have a fan blowing in the same direction as convection? Some say convection plays a negligible role but I tend to disagree. Many of us have fans running at 800rpm or less producing lets say 25cfm after factoring in some losses. Even 5cfm (produced by convection) is a nice bonus to that, accounting for 18% of total output airflow (if we assume my crude guesstimate is correct). What do you think?

As for noise, a good fan around 800rpm can be inaudible in many environments, so the top position wouldn`t always be a problem acoustically.

Actually, I have serious indications that convection is important in a system with slow fans. For instance, my psu fan (located above the h/s) seems to evacuate more heat than the case fan, even though it has a ~150rpm deficit.