Fan orientation in a case.

Simon Belmont · 8 Jul 2018 at 09:22

I have 2 140mm in front as intake. 2 on top as outflow and 1 in the back as out flow.

Or should I do 2 front intake, 2 on top as intake and 1 in back as outflow?

Not sure which would be the best? I thought having more air going in would help with dust and positive pressure?

Thanks

LuckyBenski · 8 Jul 2018 at 09:30

More in than out is good, but location and direction are important too. If you can adjust speeds, you could have the exhaust fans run slower. Are they all 140mm?

Pocah · 8 Jul 2018 at 09:48

Diminishing returns and Positive is best! Two basic rules.
Positive air pressure simply means more in that out and the reason you do this is keep duet out of the nasty little crevices in the PC.
Diminishing returns is simply that one "out" at the back and one "in" at the front is best and anything else adds a reduced effect. The more you add, the less of a difference each new fan makes.
These days most systems seem to have two fans at the front and one at the rear. The only real time it needs more than that is if you for some specific reason want to run the fans at low RPM or for show! I have put seven fans in a PC for show before now.
So if you start with two at the front as intake and one at the back as out, and you want to maintain positive pressure then it's not a good idea to have the two on the top. You could have the two on the top as intake but honestly I don't think they would achieve much. Better to have smooth flow through the case rather than a ton of turbulence. You could have course crank the front fans up a little and let the back and top ones run more slowly. In that way you can maintain the positive pressure.

Simon Belmont · 8 Jul 2018 at 10:03

LuckyBenski said:
More in than out is good, but location and direction are important too. If you can adjust speeds, you could have the exhaust fans run slower. Are they all 140mm?

The 2 140s are front intake.

Simon Belmont · 8 Jul 2018 at 10:05

Pocah said:
Diminishing returns and Positive is best! Two basic rules.
Positive air pressure simply means more in that out and the reason you do this is keep duet out of the nasty little crevices in the PC.
Diminishing returns is simply that one "out" at the back and one "in" at the front is best and anything else adds a reduced effect. The more you add, the less of a difference each new fan makes.
These days most systems seem to have two fans at the front and one at the rear. The only real time it needs more than that is if you for some specific reason want to run the fans at low RPM or for show! I have put seven fans in a PC for show before now.
So if you start with two at the front as intake and one at the back as out, and you want to maintain positive pressure then it's not a good idea to have the two on the top. You could have the two on the top as intake but honestly I don't think they would achieve much. Better to have smooth flow through the case rather than a ton of turbulence. You could have course crank the front fans up a little and let the back and top ones run more slowly. In that way you can maintain the positive pressure.

So Basically you’re saying have the two on top as outflow but at a slower speed? Or the top as intake slower?

doyll · 8 Jul 2018 at 10:24

Simon Belmont said:
I have 2 140mm in front as intake. 2 on top as outflow and 1 in the back as out flow.

Or should I do 2 front intake, 2 on top as intake and 1 in back as outflow?

Not sure which would be the best? I thought having more air going in would help with dust and positive pressure?

Thanks

A case can only flow as much air in as it flow out .. or .. a case can only flow as much air out as it flows in. It is not physically possible for case to have more air flowing in than out. Airflow is fluid dynamics. Think of your case as a rectangular tank of water and room as a bigger tank. You might find this link to basic guide to case airflow and how to set it up in this of interest
https://forums.overclockers.co.uk/t...-my-temp-sensor.18564223/#post-26159770irflow and how it works.

It would help to know what case, motherboard, cooler and GPU you have. Also all fans are not created equal. Some of very good while some are almost worthless.

Pocah · 8 Jul 2018 at 10:37

Simon Belmont said:
So Basically you’re saying have the two on top as outflow but at a slower speed? Or the top as intake slower?

Personally I think the top would best as "out", but you may have to increse the RPM of the front fans and reduce the RPM of the "out" fans a little if you want to maintain positive pressure. A good way to test pressure is to buy some incense sticks. Hold the sticks close to a hole or vent you want to test ( away from a fan ). If smoke is drawn in, so will dust!

Bugbait · 8 Jul 2018 at 11:14

Or instead of incense sticks, just use strips of toilet or tissue paper

. That's how I tested my case and fan configuration.

Simon Belmont · 8 Jul 2018 at 11:58

I have a fractal design meshify c

Installed 5 Corsair LL RGB fans. 2 140 and 3 120's

I did 2 140's as intake and 2 top and 1 back as outtake. Will have the outtake fans at a slow speed. I'm going full air. going to sell my AIO and I bought a be quiet dark rock 4 but won't be here until tomorrow if you are wondering why I have a Intel stock cooler.

doyll · 8 Jul 2018 at 13:28

Using top exhaust the front one is pulling out the cool air coming in front fans up and out before it can reach CPU cooler, as well as drawing the heated exhaust coming off of GPU up and warming the cool air going to CPU cooler .. and every degree warmer the air into cooler is translated into basically a degree hotter component is. As explained in link I posted before, remove all PCIe back slot covers to increase rear venting, 2x 140mm front and 1x 120mm intakes with top 140mm fan speed controlled to sync with CPU cooler airflow needs and bottom 120mm speed controlled to supply GPU cooler airflow needs. Lower front can be speed controlled to sync with CPU, GPU or motherboard heat / airflow needs. With good intake fans you don't even need exhaust fans. The airflow the intakes push into case continues to flow on back and out of case. If it did not there would be no airflow .. back to the air in = air out / what flows in must flow out.

Pocah · 9 Jul 2018 at 07:54

I think it will be fine with the front as intakes and the back as out. I can understand why you have the two top fans, they look great! I would leave then as-is just slow them down a little. So thats's front as intakes and back and top as out.
In passing, I can't see if you have an M.2 plugged in anyplace but the bottom slot is best!! Don't put one under the heat cover at the top because it's sat in a dead-spot and the "heat-thing" just makes it worse (That's not a theory, I actually tested it).
I usually just run the fans according to which processor develops the most heat and that's normally the GPU. It may not work for everyone but it works for me.

Simon Belmont · 9 Jul 2018 at 17:57

Pocah said:
I think it will be fine with the front as intakes and the back as out. I can understand why you have the two top fans, they look great! I would leave then as-is just slow them down a little. So thats's front as intakes and back and top as out.
In passing, I can't see if you have an M.2 plugged in anyplace but the bottom slot is best!! Don't put one under the heat cover at the top because it's sat in a dead-spot and the "heat-thing" just makes it worse (That's not a theory, I actually tested it).
I usually just run the fans according to which processor develops the most heat and that's normally the GPU. It may not work for everyone but it works for me.

Cheers mate. I thought putting the 2 big 140mm in front would help with cooler air over the GPU. I just put a GTX 1080 founders edition in there this morning. I ran Heaven for 20 mins and it does get to 82c, but it is the founder's edition card they all get hot, but it didn't go higher then 82c so there wasn't any throttling. I also tried the 2 top fans as intake and the temps were the same.

LuckyBenski · 9 Jul 2018 at 18:04

Simon Belmont said:
Cheers mate. I thought putting the 2 big 140mm in front would help with cooler air over the GPU. I just put a GTX 1080 founders edition in there this morning. I ran Heaven for 20 mins and it does get to 82c, but it is the founder's edition card they all get hot, but it didn't go higher then 82c so there wasn't any throttling. I also tried the 2 top fans as intake and the temps were the same.

You will find you get marginally better performance if you keep the card cooler, as GPU Boost 3.0 boosts the clock higher progressively down to 32°C. Might be so small you never notice though.

Simon Belmont · 9 Jul 2018 at 18:38

LuckyBenski said:
You will find you get marginally better performance if you keep the card cooler, as GPU Boost 3.0 boosts the clock higher progressively down to 32°C. Might be so small you never notice though.

I found the 1080 founder's card to be slightly cooler than the Giagbyte G1. Temps and noise are good so far.