So... how important is a front fan in a case?

cyberknight · Post by **cyberknight** » Mon Apr 18, 2005 8:16 pm

http://www.inwin-ru.com/html.dat/in-win ... h=7_41.htm

Interesting... I was looking at the InWin C720T case the other day and I was curious if it had a front fan. I couldn't tell, so I decided just to email them.

Response:
This model cannot support a front case fan. According to AMD's Guide To Cooling, some tests have shown that front cooling fans are actually more likely to re-circulate warm air rather than introduce cool air. Therefore, we don't recommend to put an optional case fan in the front.

They linked this:
http://www.amd.com/us-en/assets/content ... _guide.pdf

Apparently, AMD does state that the front fan is non-essential and can sometimes be detrimental at the very last statement of the pdf.

From my personal experience with my Antec Sonata, I know my HDDs cook if I don't have a front fan, while my case temps aren't affected too much. But then again, we have to consider that the Sonata's front intake is poor to begin with.

So do you guys believe that front fans can actually be worse for some cases? (haha, the pun actually makes sense in the sentence in both meanings) Would you guys ever consider buying a case that did not support a front fan?

Having no front fan would also create negative pressure right? That would mean more dust? Or is that stuff just a myth?

Would you guys consider this case to be a good base for a quiet PC? It does have a CPU duct, vents on the side near the video card, and an extremely unrestricted rear grill. Now the front fan question...

sthayashi · Post by **sthayashi** » Mon Apr 18, 2005 8:49 pm

I completely agree and believe that having no front fan can be better. Here is some very good anecdotal evidence to prove it.

Generally, we (should) recommend a fan in the front only if you're worried about drive temperatures. Since drive temps are generally more critical than CPU temps for most people, some people will just put a fan there anyways.

Negative pressure will not generate more dust necessarily than positive pressure, but you'll see dust near any and all air intakes. On the Sonata, you can actually get the word "Antec" written in dust on the insides of your computer. Fun and nasty at the same time.

Would I ever buy a case with no front fan support? Probably not.
Would I ever buy a case not on SPCR's recommended list? Probably not.

Does this case look pretty good inspite of the lacking front fan mount? I think it does, but I don't consider myself to be a good authority on case design/layout, so take my thoughts with a grain of salt.

Post by **MikeC** » Mon Apr 18, 2005 11:19 pm

That case looks pretty good, imo. The basics are all there. Plus if you're serious abouit quiet, you'll want to suspend your HDDs. With the (seemingly) removable HDD cage, the front bottom area is the perfect place for this, and you can easly mount a fan there with the cage out of the way.

Shadowknight · Post by **Shadowknight** » Tue Apr 19, 2005 6:37 am

On my case, I cut off both the front and back grills. When I have the bezel off and stick my hand into the front fan opening, I can feel the air being pulled through by the back fan. So you're drives do get some cooling by way of the back fan.

StarfishChris · Post by **StarfishChris** » Tue Apr 19, 2005 6:51 am

A front fan shouldn't be necessary if you take steps to block all the intake spots you don't want air to go through. My drives were 45-48°C with a stock Sonata, however I added a PSU duct (shutting off top partition as intake) and taped over several of the drive cage holes to force more air to travel along the drives. Now it's at 37° with no extra noise, similar to the temperature when I added a front fan temporarily.

pedxingx · Post by **pedxingx** » Tue Apr 19, 2005 7:27 am

Plugging up all the holes in the front of the computer except for the fan intake might allow enough air to flow through such that you won't need a front fan. I used saran wrap and tape on my old computer and I had enough air flow to keep my hard disk drives cool.

My other computer has the superlan boy case which is not easy to seal up because of its unusal construction in the front panel which includes a toolkit drawer. However, tt has a three pin fan socket in the front panel. When I play games, I just plug in the front fan because it help keeps my system several degrees celsius cooler. Otherwise I keep the fan unplugged.

Mar. · Post by **Mar.** » Tue Apr 19, 2005 10:24 am

In my SLK3700AMB, a front intake fan lowers drive temps slightly but increases CPU temps by a lot.

vertigo · Post by **vertigo** » Tue Apr 19, 2005 12:43 pm

I am interested to know now why the intake fan increases temps. Certainly if you have an intake fan there will be less air entering the case from other points. If you have positive pressure then the air will actually be exhausting from any other holes.

You would think that hot air cools down when it gets dispersed amongst cooler air. If you have the air exhausting in one place you will have a large pocket of hot air there. Perhaps having one intake aswell results in this air moving towards the front of the case in a stream, not really getting dispersed. If you have the one exhaust but the air enters your pc from various positions the air would enter the case slowly from any position. There wouldn't be a stream of hot air to the entry then.

So perhaps the lesson is that you should not have both a singular exhaust point and input point. If you choose one exhaust, or a second exhaust fan right below the PSU, you should not have one intake, which happens when you have an intake fan. Or if you have an intake you should perhaps not have a concentrated exhaust.

This is all guesswork. I don't really think that there would be a great difference in a negative case if you have an intake fan or not, most of the air would still enter the biggest hole. It could happen that the air would enter at the same speed that an undervolted fan would supply it. In that case there certainly would be no reason to have the fan there.

You might think that hot air rises and so the air that is exhausted should rise away from the pc and not enter at the front, but it has been mentioned here that the effect of cool air displacing hot air is very much less then the force of a fan.

luggage · Post by **luggage** » Tue Apr 19, 2005 1:46 pm

If the CFM of the intake (front) fan is lower than the combined CFM of all the exit fans (Case, PSU, whatever blowholes) it will actually work as an air-brake as compared to no intake fan.

A front fan will, probably, give give a "fan cone" towards the standard HD-cage position tho.

~El~Jefe~ · Post by **~El~Jefe~** » Tue Apr 19, 2005 3:03 pm

I can say with all honesty that a front fan is a wonderful thing. But not in general.

I so am looking forward to positive pressure in my next setup (p180 where are you....)

The recommended seasonics do not do as well when you have a large draw near them, they actually ramp up more. Someone said NO IT DONT. Yes it does, and I have tested this in several systems. A nexus on the back with none in the front, well, that pulls like 1 inch of air per hour

so that will not create a pressure difference. However, a pabst 120 (pick your flavor) will pull a load, and, this creates lots of negative pressure, pulling away the air that is supposed to be exiting the psu back down.

A front nexus and a rear nexus at like 6volts I just know would be a great setup. The only problem is that I have pabst's lying around at the 120 mm size, so I have to wait for a new case and setup to do this. If i put a pabst on the front, that would be noisy for spcr standards. If i didnt, and went nexus, the nexus would be basically (untested but logic says) useless as it isnt pushing , so someone else is pulling.

I cant stress enough how a performance minded (even mildly performance oriented) has different rules for single vs 2x case fans.... the draws are just too strong and create a negative pressure system. (also an Un channeled system, who knows where the air is really flowing with one big fan in the back, air doesnt make turns only turbulence and lines)

Kwiet · Post by **Kwiet** » Tue Apr 19, 2005 5:09 pm

My case is setup with two intake fans at the front sides (two panaflo L1 80mm at 5 volts blowing air straight at the drives) My case is unable to be positive or negative pressure do to the 120mm port in the top of the desktop case. A 92mm fan sucks air off the XP90 and blows straight up out of the case.

I have done testing with the front Panaflos off, case top removed and blocking the 120mm vent with a towel. With the case top removed, I get the coolest temps from my CPU (5C cooler) but my "ambient" temp stays the same and the hard drives are about the same. Shut off those intake fans and the drive temps jump 3-6C, the ambient jumps 2C but the CPU stays the same.

This box is setup as a HTPC and I want to keep the drives cool. That Samsung is always recording something as my wife likes that function. For me, my Cooler Master ATC620 microATX desktop case and what I use it for... I require those 5 volted Panaflo L1 80mm intake fans to keep the drives and burner cool. Take it for what it's worth.

IceWindius · Post by **IceWindius** » Tue Apr 19, 2005 5:44 pm

"Night Wind" pulls enough air through the front intake area after extensively modifying it. My HDDs stay cool as does the rest of the system and I got one less fan making noise, it works good.

intx · Post by **intx** » Thu Apr 21, 2005 5:34 am

sthayashi wrote:I completely agree and believe that having no front fan can be better. Here is some very good anecdotal evidence to prove it.

Generally, we (should) recommend a fan in the front only if you're worried about drive temperatures. Since drive temps are generally more critical than CPU temps for most people, some people will just put a fan there anyways.

Negative pressure will not generate more dust necessarily than positive pressure, but you'll see dust near any and all air intakes. On the Sonata, you can actually get the word "Antec" written in dust on the insides of your computer. Fun and nasty at the same time.

Would I ever buy a case with no front fan support? Probably not.
Would I ever buy a case not on SPCR's recommended list? Probably not.

Does this case look pretty good inspite of the lacking front fan mount? I think it does, but I don't consider myself to be a good authority on case design/layout, so take my thoughts with a grain of salt.

That's an interesting link. However, I wonder if all the tests were performed with holes in the cases where the fans would've been. Having a rear fan, with holes all over the case vs a regular case with a rear fan would make a difference.

Mar. · Post by **Mar.** » Thu Apr 21, 2005 9:00 am

luggage wrote:If the CFM of the intake (front) fan is lower than the combined CFM of all the exit fans (Case, PSU, whatever blowholes) it will actually work as an air-brake as compared to no intake fan.

Aha, I hadn't thought of that.... thanks.

vertigo · Post by **vertigo** » Thu Apr 21, 2005 10:48 am

If the CFM of the intake (front) fan is lower than the combined CFM of all the exit fans (Case, PSU, whatever blowholes) it will actually work as an air-brake as compared to no intake fan.

I would say that typically the front airtake should not draw more air than a slow fan there could produce. Low airflow is the ideal. I just wonder how you stop noise escaping from the front. I suppose the idea is to dampen the drives and buy really slow fans and hope that after removing the fan grills and any obstructions like flat ribbon cables there will be very little noise left over to escape.

Fan noise is useful to mask other noises (like the PSU), but the type of noise is also important I think. For me I don't mind some (soft) fan noise but don't like high-frequency noise.