Case Fan Positions: High RPM vs Low RPM

[MayuraDeSilva]

Hello,

I have the Armaggeddon Hectotron T3X casing and it had 2 fans pre-installed - front intake and rear exhaust.

The front intake fan has higher RPM than the rear exhaust fan. So I believe it was set up for positive pressure. However, the drive bay is right behind the front intake and has a SSD and 2 HDDs installed.

I wanted to try installing another fan to keep the temps low and to get the hot air out quickly. Hence got a Cooler Master JetFlo 120mm. Installed it on top rear mount (with Silent Adapter = 1200RPM) and noticed a drop in CPU temp.

Since the rear exhaust fan had Low RPM, I wanted to try another setup. Replaced it with JetFlo and mounted the Low RPM fan as a side intake.

Now I can still see the drop in CPU temp and further, GPU temps go down quickly after playing games or performing GPU intensive tasks. For example, 63C comes down to 47C within a minute. I didn't see such a drop with the absence of Side Panel fan. And so much air coming out of the rear exhaust fan.

I'm happy with the results, and I just wanna clarify a few things as I'm still getting to know about PC cooling:

1. Do I still has a positive pressure set up? (Front + Rear: High RPM / Side Panel: Low RPM)

2. Does this set up has any disadvantages?

3. Should I have the side intake fan mounted as top (rear) exhaust instead? Or JetFlo is enough to pull out the hot air since it runs on 1200RPM?

Thanks in advance

 

[Gam3r01]

1) Impossible to say without really knowing the CFM of each fan, I would say you do (or close to it). It dosent really matter all that much though.
2) Not really, if you are getting good temps then it works well.
3) Try it, see what works better.

If you remove the adapter it would be a better idea.

 

[geofelt]

If you want a clean pc, you need a positive pressure arrangement.
That means that ALL of the intake air comes from one source and is filtered.
It is not clear to me if your case can accommodate two front intake fans.
If so, I would do that.
If you only have one fan position in front, put the highest rpm fan there and perhaps a single low speed fan in the rear to direct the airflow.

The danger with too much exhaust capability is that it will draw in unfiltered air from nearby openings.

I would concentrate in intake capability.
Whatever comes in will go out someplace, taking the heat from your parts with it.

 

[MayuraDeSilva]

1) Impossible to say without really knowing the CFM of each fan, I would say you do (or close to it). It dosent really matter all that much though.
2) Not really, if you are getting good temps then it works well.
3) Try it, see what works better.

If you remove the adapter it would be a better idea.

Thanks for the quick response, Gam3r01

1. Unfortunately, I don't have CFM for case fans except for JetFlo (Rated: 95 CFM). If it helps, JetFlo is the one moving most air and it's very noticeable. Front intake does less than JetFlo (70% - 80%) and Side intake is the lowest of 'em all. Probably, half of what the front intake does.

2. Awesome!

3. Just did and didn't see any improvements in CPU temps though. JetFlo is already doing its job?

However, since the side fan is removed, I can't see the quick drop in GPU temp after playing a game or running a benchmark now.

Any thoughts?

If you want a clean pc, you need a positive pressure arrangement.
That means that ALL of the intake air comes from one source and is filtered.
It is not clear to me if your case can accommodate two front intake fans.
If so, I would do that.
If you only have one fan position in front, put the highest rpm fan there and perhaps a single low speed fan in the rear to direct the airflow.

The danger with too much exhaust capability is that it will draw in unfiltered air from nearby openings.

I would concentrate in intake capability.
Whatever comes in will go out someplace, taking the heat from your parts with it.

Got it, geofelt I have all the intake fans filtered. Plus, doing my best to keep it clean by cleaning the case, fans and filters biweekly or so.

Unfortunately, my case can't accommodate 2 front fans though.

If you refer to my response to Gam3r01 above, you can get an idea about the air flow of each fan. However, the highest is JetFlo and mounted as rear exhaust. The next one is the front intake fan.

Isn't it best to get the hot air inside the case out fast than pumping more fresh air to mix with hot air inside?

 

[Isokolon]

The side Fan will of course lower the temps of.the GPU as it's usually directly behind it
Also a higher rpm intake is not too uncommon as it has more obstacles (HDDs for example) that block the flow in the way and has to push the air further into the case than a rear exhaust that just.pushes out the already moving air from the cpu cooler.

If your case supports a bottom mount I'd install the fan there.
Typically a rear exhaust is more effective than a top exhaust if you have both possibilities.
Generally I'd just test a few setups and see what gives you the best temps

 

[MayuraDeSilva]

The side Fan will of course lower the temps of.the GPU as it's usually directly behind it
Also a higher rpm intake is not too uncommon as it has more obstacles (HDDs for example) that block the flow in the way and has to push the air further into the case than a rear exhaust that just.pushes out the already moving air from the cpu cooler.

If your case supports a bottom mount I'd install the fan there.
Typically a rear exhaust is more effective than a top exhaust if you have both possibilities.
Generally I'd just test a few setups and see what gives you the best temps

"Also a higher rpm intake is not too uncommon as it has more obstacles (HDDs for example) that block the flow in the way and has to push the air further into the case" ~ Agree Hence I think that's why the higher RPM fan was mounted on front.

I've also mounted the JetFlo as top (rear) exhaust with no rear fan installed, but the CPU temp was 1C - 2C higher than having it mounted as a rear exhaust. So figured I should keep it as a rear exhaust.

Unfortunately, it doesn't have a bottom mount either. Only a bottom filter for PSU and my current PSU has only one exhaust fan.

 

[madmatt30]

As long as you've filtered that side fan I don't see any issue with the way you have it at all.

I'm jot big on side fans simply because you tend to get some vibration on a lot of cases.

 

[MayuraDeSilva]

As long as you've filtered that side fan I don't see any issue with the way you have it at all.

I'm jot big on side fans simply because you tend to get some vibration on a lot of cases.

Great! I'm happy with the current arrangement and nice to see a drop in temps too. Think it will be the optimal set up for now. Still thought of some expert advise

That's a BIG No for me too. Glad the vibration is minimum and keeps it quiet. Probably because it has Low RPM.

 

[geofelt]

If you are having to clean things more than a couple of times a year, you do not have positive pressure cleaning.

You can tell which fans are strongest by the RPM it runs at. Higher is better (at the expense of more noise).

I think side fans tend to disrupt the natural front to back airflow.
I have seen some studies that show side intakes do provide better cooling. But, they will tend to draw in unfiltered air from nearby opwnings.

Try just a single strong intake and no exhaust at all.
I suspect you will still get decent cooling.

What cpu/gpu do you have and how much airflow do you really need?

 

[MayuraDeSilva]

If you are having to clean things more than a couple of times a year, you do not have positive pressure cleaning.

You can tell which fans are strongest by the RPM it runs at. Higher is better (at the expense of more noise).

I think side fans tend to disrupt the natural front to back airflow.
I have seen some studies that show side intakes do provide better cooling. But, they will tend to draw in unfiltered air from nearby opwnings.

Try just a single strong intake and no exhaust at all.
I suspect you will still get decent cooling.

What cpu/gpu do you have and how much airflow do you really need?

It's not that my case and components get covered with dust easily. But I can't stand a thin layer of dust, so tend to clean more often May be, overdoing it? Spending most of the year in hot and humid weather, dust is common though.

The RPMs as follows:

Front Intake: 1200RPM (CFM: N/A)
Side Intake: 800RPM (CFM: N/A)
Rear Exhaust: 1200RPM (CFM: 95)

Specs are:

Intel i3 3210 @ 3.20GHz (Will upgrade to i5 3470 in this or next week)
ASUS P8B75-V
ASUS GeForce GTX 660 DirectCU II OC
G.SKILL RipjawsX 16GB (2x8GB) 1600 DC
Samsung 850 EVO 250GB + Clover 1TB + WD Caviar Blue 1TB
Antec IPA450 450W

My PC temps are normal without the 3rd fan - even under the load too. It's just I'm worried about the longevity of components and hence I wanted to add more cooling to keep it cool.

I've gone through different studies and experiments I could find online, and noticed the optimal number of fans is 3 -4 (Front + Rear + Top (Rear) + Side) and no much difference after that.

Thanks for the suggestion and will try with single intake fan too.

 

[geofelt]

The biggest heat generator will be your GTX660.
It only needs a single 6 pin connector so it does not generate much heat.
Neither does the I3-3210 nor the i5-3470 for that matter.

I would say that if your cpu temperatures are 75c. or less under load and your gpu is in the 80c. range, that is nominal.
On the cpu, consider paying $30 for a cryorig H& cooler.
Not so much for the cooling, but the 120mm fan will be quieter.

 

[MayuraDeSilva]

The biggest heat generator will be your GTX660.
It only needs a single 6 pin connector so it does not generate much heat.
Neither does the I3-3210 nor the i5-3470 for that matter.

I would say that if your cpu temperatures are 75c. or less under load and your gpu is in the 80c. range, that is nominal.
On the cpu, consider paying $30 for a cryorig H& cooler.
Not so much for the cooling, but the 120mm fan will be quieter.

Well... With my current set up, the max. CPU temp is 57C and the GPU temp is 67C under load. It will be fine?

Prior to the addition of new fan, CPU temp was in 60s and GPU temp was in 70s.

As I'm gonna upgrade to i5-3470, I was gonna grab the Cooler Master Hyper 212X. Also I've gotten a new Cooler Master X Dream i117 to spare and it's very quiet compared to the stock cooler too. Thought I'd use it on i5 and see if the temps are alright. Do you think I should still go for CRYORIG H7 or Hyper 212X for CPU?

 

[geofelt]

The main advantage of the H7 or hyper212 is that they use 120mm fans which will be quieter than the 92mm fans on the stock type coolers.
Cooling is better also.

 

[chegalhavara]

Or you can buy a Zalman CNPS 9900 Max for serious air cooling. but it will cost you maybe about 50$.

 

[MayuraDeSilva]

The main advantage of the H7 or hyper212 is that they use 120mm fans which will be quieter than the 92mm fans on the stock type coolers.
Cooling is better also.

Oh... Alright. Then I'll opt into Hyper 212X. Couldn't find H7 around here.

Or you can buy a Zalman CNPS 9900 Max for serious air cooling. but it will cost you maybe about 50$.

Unfortunately, Zalman CNPS 9900 is not available to purchase around here too.

 

[madmatt30]

Just be careful on cooler height mate , while it looks like a 212 will fit there are no specs for that case & very little reviews
The 212 is a fairly hefty 157mm deep.

The deepcool gammaxx 300 & s40 are good options if they're available -less than 145mm & don't require a custom backplate fitting so are very very quick to fit.

Have an s40 on a 3470 here.
Under prime testing it has NEVER seen above 55c.

 

[MayuraDeSilva]

Just be careful on cooler height mate , while it looks like a 212 will fit there are no specs for that case & very little reviews
The 212 is a fairly hefty 157mm deep.

The deepcool gammaxx 300 & s40 are good options if they're available -less than 145mm & don't require a custom backplate fitting so are very very quick to fit.

Have an s40 on a 3470 here.
Under prime testing it has NEVER seen above 55c.

You're right - that crossed my mind when I go through the reviews of 212X too Then I measured the width of the case and it's 18.2 cm. From CPU to other side of the casing it has a room of 16.5 cm. So I think the 212X will fit in.

Thanks for the suggestions too, mate. I'll see if I can find DEEPCOOL GAMMAXX 300 or S40 around here. If not, still 212X would be fine, isn't it?