How to achieve positive pressure with my setup

Jared485 · Aug 9, 2015

I have the Corsair 380t, which only has a 120mm rear exhaust fan, and on the front either: 2 120mm, 1 140mm, 1 200mm fans. I have a itx x99 motherboard with the i7-5820k which is overclocked.

So i got the H100i for the CPU, i have that exhausting in push on the right side of the case.

I currently have the stock front fan (140mm) as intake and the rear 120mm along with the 2 120mm radiator fans all in exhaust. this is creating negative pressure and this case has lots and lots of holes to pull air and dust through.

I've got the gigabyte windforce 980 oc, which doesnt exhaust out the back the heat just disapates which really doesnt help, all that heat is going into the case, all more reason to get more poitive pressure to get cool air in. Even though the GPU intakes from the side by the time it cools the GPU thats just more hot air and doesnt help as an intake.

So im trying to figure out how to create posistive pressure to help temp and dust control.

Im thinking the first step would be to get 2 120mm fans for the front intake. But that still doesnt do it. Once i have those ill have 2 120mm intakes in the front and 3 120mm exhausts at the side and rear, (2 of which are cooling a radiator, so itd be nice to have plenty of cool air in the case to push through those).

So id like to hear what youve all got to say and your reccomendations on how to setup my fans...

KKAW · Aug 9, 2015

Jared485 :

I have the Corsair 380t, which only has a 120mm rear exhaust fan, and on the front either: 2 120mm, 1 140mm, 1 200mm fans. I have a itx x99 motherboard with the i7-5820k which is overclocked.

So i got the H100i for the CPU, i have that exhausting in push on the right side of the case.

I currently have the stock front fan (140mm) as intake and the rear 120mm along with the 2 120mm radiator fans all in exhaust. this is creating negative pressure and this case has lots and lots of holes to pull air and dust through.

I've got the gigabyte windforce 980 oc, which doesnt exhaust out the back the heat just disapates which really doesnt help, all that heat is going into the case, all more reason to get more poitive pressure to get cool air in. Even though the GPU intakes from the side by the time it cools the GPU thats just more hot air and doesnt help as an intake.

So im trying to figure out how to create posistive pressure to help temp and dust control.

Im thinking the first step would be to get 2 120mm fans for the front intake. But that still doesnt do it. Once i have those ill have 2 120mm intakes in the front and 3 120mm exhausts at the side and rear, (2 of which are cooling a radiator, so itd be nice to have plenty of cool air in the case to push through those).

So id like to hear what youve all got to say and your reccomendations on how to setup my fans...

So currently you have...
Front Intake: 140mm
Rear Exhaust: 120mm
Side (Radiator) Intake: 120mm + 120mm

?

Jared485 · Aug 9, 2015

KKAW :

Jared485 :

So currently you have...
Front Intake: 140mm
Rear Exhaust: 120mm
Side (Radiator) Intake: 120mm + 120mm

?

yes but i beleive changing the front 140 to 2 120mm is a no brainer to start with

Jared485 · Aug 9, 2015

KKAW :

Jared485 :

So currently you have...
Front Intake: 140mm
Rear Exhaust: 120mm
Side (Radiator) Intake: 120mm + 120mm

?

and the 2 120mm radiator fans are exhaust

KKAW · Aug 9, 2015

Jared485 :

KKAW :

Jared485 :

So currently you have...
Front Intake: 140mm
Rear Exhaust: 120mm
Side (Radiator) Intake: 120mm + 120mm

?

and the 2 120mm radiator fans are exhaust

My recommendation:
Front Intake: 200mm

Make the front intake run at max speed.

The 3 other fans should run at medium speeds.

Jared485 · Aug 9, 2015

KKAW :

Jared485 :

KKAW :

and the 2 120mm radiator fans are exhaust

My recommendation:
Front Intake: 200mm

Make the front intake run at max speed.

The 3 other fans should run at medium speeds.

a 200mm at max speed would be really loud wouldnt it?

KKAW · Aug 9, 2015

Jared485 :

KKAW :

Jared485 :

My recommendation:
Front Intake: 200mm

Make the front intake run at max speed.

The 3 other fans should run at medium speeds.

a 200mm at max speed would be really loud wouldnt it?

Not at all, the bigger the fan is the more quiet it is because it can move the same amount of air for a lower speed. I run my 200mm fans at max speed and i can barely hear it from a 80cm distance.

Jared485 · Aug 9, 2015

wouldnt 2 120mm fans move more air than a 200, even at lower rpms.

KKAW · Aug 9, 2015

Jared485 :

It really depends on how good your 120mm fans are, however if your 120mm fans are rated to have 90 CFM or more then a slightly louder 2x120mm will perform better.

Jared485 · Aug 9, 2015

KKAW :

ok so even if i get those for the fron those are my only intake and have 3 other exhaust.. im still have negative presure

Dogsnake · Aug 9, 2015

To create an internal positive pressure you need to bring slightly more air in than is being exhausted. Basic and you seem to understand this. Some of the issues with your setup (conditions maybe not issues) are that you water radiator is using internal heated case air to cool. If I read the description right you have the radiator fan blowing our the side of the case. The internal air is being heated by the exhaust from the video card. Also the internal air is being heated by the heat from the VRM's and other devices on the MB and in the system. I would suggest the following possible changes:
1. Reverse the air flow at the radiator so that you will be using cooler external air to cool the water system. This added air pressure/flow will help create the positive case condition you say you want.
2. If you do #1 then you will need to increase both the current supplied air (front fans) and removed air (rear and or top). Since now the internal air will be heated even more by the video card, radiator and other components (MB, memory, drives...). This heated air needs to be removed and cool air flow brought in to cool everything but the radiator.
3. Create a negative pressure flow by again reversing the radiator air flow (use exterior cool air exhausted into the case) and increase both the current air supply and the current air removal. This is my preferred method.
You have the basic goals of providing cool air to the radiator; getting rid of the heated air from the radiator; supplying enough cool air flow to permit the video card and other system items to cool and finally to get rid the heated air from all of these sources. Cool air comes from outside the case, it gets heated as it flows across heated components. The heated air must be removed and replaced with new cool air. Positive case pressure does not maximize this. A negative pressure does. As to dust, well clean your system twice a year and you should be fine. Sorry to be so long winded.

InvalidError · Aug 9, 2015

There is only so much a 140mm or a pair of 120mm fans can do against 3x120mm exhaust fans, especially if they have to suck air through dust filters. Crank the speed on the intake fans up, lower the exhaust fan speeds and if you are lucky, you will find a sweet spot where you can have temperatures close to what you are looking for without wishing you were deaf.

KKAW · Aug 9, 2015

Jared485 :

If you make the front intakes max speed and the exhaust's on medium speeds you will have more or less a neutral pressure, depending on the exact airflow of the different fans this may vary.

Jared485 · Aug 9, 2015

InvalidError :

Thanks for the advice. Would it be a good idea to change the rear 120mm into intake so that the only exhaust would be my 2 120mm on the radiator? That way thered be lots of cool air, and the radiator would be having cool air pushed through it as well

KKAW · Aug 9, 2015

Jared485 :

Not the best idea because hot air flows upwards and the front intake and the back intake will cause a bit of turbulence, however you can give it a shot and see if it work's for that case.

Jared485 · Aug 9, 2015

Dogsnake :

To create an internal positive pressure you need to bring slightly more air in than is being exhausted. Basic and you seem to understand this. Some of the issues with your setup (conditions maybe not issues) are that you water radiator is using internal heated case air to cool. If I read the description right you have the radiator fan blowing our the side of the case. The internal air is being heated by the exhaust from the video card. Also the internal air is being heated by the heat from the VRM's and other devices on the MB and in the system. I would suggest the following possible changes:
1. Reverse the air flow at the radiator so that you will be using cooler external air to cool the water system. This added air pressure/flow will help create the positive case condition you say you want.
2. If you do #1 then you will need to increase both the current supplied air (front fans) and removed air (rear and or top). Since now the internal air will be heated even more by the video card, radiator and other components (MB, memory, drives...). This heated air needs to be removed and cool air flow brought in to cool everything but the radiator.
3. Create a negative pressure flow by again reversing the radiator air flow (use exterior cool air exhausted into the case) and increase both the current air supply and the current air removal. This is my preferred method.
You have the basic goals of providing cool air to the radiator; getting rid of the heated air from the radiator; supplying enough cool air flow to permit the video card and other system items to cool and finally to get rid the heated air from all of these sources. Cool air comes from outside the case, it gets heated as it flows across heated components. The heated air must be removed and replaced with new cool air. Positive case pressure does not maximize this. A negative pressure does. As to dust, well clean your system twice a year and you should be fine. Sorry to be so long winded.

Sorry i seemed to have had skipped over your post. Thanks for the in-depth reply.

So youre saying if i have the H100i intaking cool air and blowing some warm air into the case, along with the graphics card blowing warm air into the case. Having 2 120mm intake on front and 1 120mm fan in the rear would be what you suggest. Because i have no bottom or top fans.

InvalidError · Aug 9, 2015

Jared485 :

If you wanted positive pressure to mitigate dust ingress, putting an intake fan in a filter-less location would defeat that purpose. As others mentioned, hot air rises, so putting an intake fan at the top might hinder airflow in some spots instead of assisting it.

Jared485 · Aug 9, 2015

InvalidError :

i dont have any top fan mounting spots on the corsair 380t. And i would put a filter on all intake fan there arent already filtered.

Dogsnake · Aug 10, 2015

OK so from a check of your case you have Front: 2 x 120mm or 1 x 140mm/200mm and Rear: 1 x 120mm available. The side is taken by the water radiator. If you want to go by some approximate numbers, you would check the cfm of 2 of your chosen 120's vrs the cfm of 1 140. I would run the rear 120 full speed as it is your only exhaust. So if you use 2x120 in the front at full speed and 1x120 at the rear you will have created a very positive case pressure. Even if you leave the radiator blowing out of the case you most likely will still be internal positive as the 2x120 front will bring more air in than the 1x120 and the radiator fans remove. This is the config. I would try first. The condition to keep an eye on are all your temps. Your setup is just not removing the internal heated air very fast and you will be using this warmed air to cool the radiator. Given the very small size of your case and the limited fan slots you may just have to do many trials. You say you overclock so load up your stress test and temp monitor. Run the system full out for an hour and see if the temps on the video card, cpu and MB sensors are acceptable. Remember the ambient temp. is critical. Using the system in a warm room is very different then in a room with cool air. If you o.c. the video card I would try it at default settings as it is a major source of heat in the case. Please keep in mind that the "job" of the case air flow is to bring enough cool air in so that the components can transfer their heat to that air. Then to get rid of the heat be exhausting the heated air to the outside. Using already heated air for the radiator inhibits the ability to cool the cpu. My guess is you will find 1x120 rear exhaust; radiator bringing outside air in (blow into case) and 2x120 front (bringing air in) will give the best balance of cooling. This will also give you the positive pressure condition you wanted.

How to achieve positive pressure with my setup

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