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View Full Version : Negative air pressure in the case, how to solve?



leon_123
07-15-2016, 07:49 PM
Hi guys,

I'm having a problem with negative pressure inside my case, how do I change to positive air pressure?

Currently my setup:

- One 200mm fan at the front for intake (rotate at 730RPM, max speed).
- One 140mm fan at the back for exhaust (rotate at 1200RPM, max speed).
- Three 140mm fan at the top for exhaust (Two from H115i AIO cooler config for pull air through the radiator, one from pre-installed case fan rotate at 1200RPM max speed).

My case is Phanteks Enthoo Luxe, here is the supported fan configuration.

http://i.imgur.com/UHE1RKt.jpg

Should I replace 200mm fan at the front with two Phanteks PH-F140SP? Can I get any improvement?

doyll
07-15-2016, 11:43 PM
Simple
Replace the PH-F200SP with the back and top PH-F140SP fans

Problem is you have 4x 140mm fans exhaust and only 1x 200 intake. In ideal conditions with no resistance at all (spinning in open space) the PH-F200SP is rated 110cfm. while the 2x PH-F140SP are rated 82cfm each. That's a potential of 110cfm in and 164cfm out .. and we still have the 2x SP140L rated 49.5cfm with a potential of 99cfm to add giving us a whopping exhaust potential of 263cfm out. 2.6 times as much exhaust potential as intake!

2x PH-F140HP intake is a potential of 110cfm in to 2x SP140L exhaust potential of 99cfm.

Other options are
Add a 3rd intake in back (problem is air behind case is likely already warmed by warm air from GPU).
Remove PSU cover and use bottom intakes.

I think it is a mistake to use H115i on CPU when GPU probably makes twice the heat with almost not natural ability to keep it's heated exhaust separte from cool intake air. But then I think all CLCs are a mistake. :p

A bit of FYI:
If you turn your case over and look, I think you can tape the PSU filter to the 2x vent filter that slides out the front and then be able to slide both out the front. After sliding it out put tape on other side too. I use wrapping tape like on boxes for shipping.
I've done this on a couple of these cases, but can't remember if there was anything stopping PSU filter from sliding farther in. If there was, it was easy to change or I would remember it.
This makes cleaning filters so much easier because we no longer have to move case to access PSU filter. ;)

leon_123
07-16-2016, 12:04 AM
Simple
Replace the PH-F200SP with the back and top PH-F140SP fans

Problem is you have 4x 140mm fans exhaust and only 1x 200 intake. In ideal conditions with no resistance at all (spinning in open space) the PH-F200SP is rated 110cfm. while the 2x PH-F140SP are rated 82cfm each. That's a potential of 110cfm in and 164cfm out .. and we still have the 2x SP140L rated 49.5cfm with a potential of 99cfm to add giving us a whopping exhaust potential of 263cfm out. 2.6 times as much exhaust potential as intake!

2x PH-F140HP intake is a potential of 110cfm in to 2x SP140L exhaust potential of 99cfm.

Other options are
Add a 3rd intake in back (problem is air behind case is likely already warmed by warm air from GPU).
Remove PSU cover and use bottom intakes.

I think it is a mistake to use H115i on CPU when GPU probably makes twice the heat with almost not natural ability to keep it's heated exhaust separte from cool intake air. But then I think all CLCs are a mistake. :p

A bit of FYI:
If you turn your case over and look, I think you can tape the PSU filter to the 2x vent filter that slides out the front and then be able to slide both out the front. After sliding it out put tape on other side too. I use wrapping tape like on boxes for shipping.
I've done this on a couple of these cases, but can't remember if there was anything stopping PSU filter from sliding farther in. If there was, it was easy to change or I would remember it.
This makes cleaning filters so much easier because we no longer have to move case to access PSU filter. ;)

I'm thinking about replace the front 200mm fan with two 140mm fan from Phanteks (PH-F140SP, rated at 82.1CFM each) for intake. The other remain fans keep at original position. Is that a good idea?

Since I install my PSU fan face toward the motherboard, I don't need to worry about cleaning PSU filter at the bottom. :D

I think use bottom intakes in not a good idea because most of dust always gather on the ground.

doyll
07-16-2016, 02:47 AM
No it is not a good idea.

What part of my post about the potential airflow of your case fan setup now and how to improve it don't you understand? I posted the fan airflow rating and explained how you have many times as much exhaust potential as intake potential now. It told you what would happen if you had 2x PH-F140SP in front and only your radiator as exhaust. But your reply gives me the impression you don't understand what I said .. or simply didn't read it. :(

When a case has more exhaust airflow protential then intake air leaks in other places to balance the flow, but the overall case airflow is still less then the intake fan rating because of grills and filters.

I gave you suggestions of how best to improve your case airflow based on years of working with airflow and cooling to get the best performance .. like almost 50 years of experience .. this is combined with many others I know who also have lots of experience.

If you do not what to follow the suggestions that is fine, but please read and learn from what is posted. If you don't understand it, ask questions about how it works. But don't ignore sound advice by asking question about things already explained.

Having PSU draw air from inside case means it is drawing air from under PSU cover only, and therefor drawing air from under the case through the bottom vents.

leon_123
07-16-2016, 03:35 AM
No it is not a good idea.

What part of my post about the potential airflow of your case fan setup now and how to improve it don't you understand? I posted the fan airflow rating and explained how you have many times as much exhaust potential as intake potential now. It told you what would happen if you had 2x PH-F140SP in front and only your radiator as exhaust. But your reply gives me the impression you don't understand what I said .. or simply didn't read it. :(

When a case has more exhaust airflow protential then intake air leaks in other places to balance the flow, but the overall case airflow is still less then the intake fan rating because of grills and filters.

I gave you suggestions of how best to improve your case airflow based on years of working with airflow and cooling to get the best performance .. like almost 50 years of experience .. this is combined with many others I know who also have lots of experience.

If you do not what to follow the suggestions that is fine, but please read and learn from what is posted. If you don't understand it, ask questions about how it works. But don't ignore sound advice by asking question about things already explained.

Having PSU draw air from inside case means it is drawing air from under PSU cover only, and therefor drawing air from under the case through the bottom vents.

Sorry, I understand what you said, but I don't want to repeat so I ask another solution if possible. Just discusssing, I'm not telling that you're wrong, relax bro.

From what I understand, just simply change the position of the PH-F140SP in the back and the top to the front, that's all. So that means in the back there is no fan, in the front there are two fan, at the top there are two fans from the radiator.


2x PH-F140HP intake is a potential of 110cfm in to 2x SP140L exhaust potential of 99cfm.

This make me confuse because above you said 2 x PH-F140SP are rated 82cfm each. So in theory, I will have 164cfm in, not 110cfm in.

Do I understand you correctly?

doyll
07-16-2016, 04:43 AM
You are correct, I wrote the wrong cfm rating. :( It should be 164cfm intake if 2 x PH-F140SP are used in front instead of PH-f200SP rated 110cfm

This is a rating of 164cfm intake to a rating of 99cfm rating for your radiator fans as exhaust.

The paragraph before the sentence you quotes says

Problem is you have 4x 140mm fans exhaust and only 1x 200 intake. In ideal conditions with no resistance at all (spinning in open space) the PH-F200SP is rated 110cfm. while the 2x PH-F140SP are rated 82cfm each. That's a potential of 110cfm in and 164cfm out .. and we still have the 2x SP140L rated 49.5cfm with a potential of 99cfm to add giving us a whopping exhaust potential of 263cfm out. 2.6 times as much exhaust potential as intake! potential as intake!

So instead of questioning my mistake in putting 110cfm instead of 164 in that sentence you ignored the explanation completely and come up with other questions. Better to question what you don't understand and my mistake first. Especially when it was correct a few lines above.. ;)

leon_123
07-16-2016, 05:31 AM
You are correct, I wrote the wrong cfm rating. :( It should be 164cfm intake if 2 x PH-F140SP are used in front instead of PH-f200SP rated 110cfm

This is a rating of 164cfm intake to a rating of 99cfm rating for your radiator fans as exhaust.

The paragraph before the sentence you quotes says


So instead of questioning my mistake in putting 110cfm instead of 164 in that sentence you ignored the explanation completely and come up with other questions. Better to question what you don't understand and my mistake first. Especially when it was correct a few lines above.. ;)

I understand the CFM in is far lower than CFM out, that's why I made this thread to said that I'm in negative air pressure. I just want to clarify what is the best solution, so I don't say anything about your first paragraph, is that ok with you? Not because I don't read, just because I've understand before I made this thread.

I don't know why does you keep blaming me, or you have too much negative thinking? :|

doyll
07-16-2016, 05:42 AM
Something is getting lost in translation here :D
I made a mistake and put '110' when it should have been '164'. The sentence is still correct in saying front in and top out. If you try and use more fans exhaust you will not have enough intake to keep dust out.

Please forget everything you have been told about 'positive pressure' in cases. 'Positvie intake airflow' / 'negative intake airflow' is better way to explain it. This is because the 'pressure' involved is extremely low. Really it's pressure differential .. the difference between air in area where fan is pushing it compared to the air in the area fan is pulling air from. This slight difference in pressure is about as much as standing with your toes in the ocean and walking away from ocean until you are about 2 meters above the surface. It is a pressure differential you cannot even feel .. except for the airflow it causes. This airflow is like a gentle breeze .. enough air moving to cause smoke to drift away from a fire or a candle to flicker.

leon_123
07-16-2016, 05:58 AM
Something is getting lost in translation here :D
I made a mistake and put '110' when it should have been '164'. The sentence is still correct in saying front in and top out. If you try and use more fans exhaust you will not have enough intake to keep dust out.

Please forget everything you have been told about 'positive pressure' in cases. 'Positvie intake airflow' / 'negative intake airflow' is better way to explain it. This is because the 'pressure' involved is extremely low. Really it's pressure differential .. the difference between air in area where fan is pushing it compared to the air in the area fan is pulling air from. This slight difference in pressure is about as much as standing with your toes in the ocean and walking away from ocean until you are about 2 meters above the surface. It is a pressure differential you cannot even feel .. except for the airflow it causes. This airflow is like a gentle breeze .. enough air moving to cause smoke to drift away from a fire or a candle to flicker.

Thanks for spend time to explain for me, and the tip about the filter. :D

I'm from Vietnam, English is not my strength, so maybe I didn't understand you clearly. I'll replace the intake fan to give better air intake since I really hate dust.

doyll
07-16-2016, 06:07 AM
I can understand not liking dust. The language problems we can figure out. You speak English as good as many natives do.

My guess is the 2x PH-F140SP as front intake will give you good enough airflow.

I have a guide to simple way to make cleaning bottom filters easy.
The front part of bottom filters slides out. Most of us have the front of our computers accessible so easy to slide that filter out.
The guide shows how to attach PSU filter so it will slide out with the front part of filter. All that is needed is some tape to put them together. If you would like, I can post it here for you.

leon_123
07-16-2016, 06:15 AM
Thanks, I'm still improving my English at the moment. :p

If you don't mind, please go ahead post it, I would appreciate that.

doyll
07-16-2016, 06:41 AM
Here it is
http://phanteks.com/forum/showthread.php?462-Enthoo-Luxe-Enthoo-Pro-and-Enthoo-Pro-M-filter-modification
Clicking on image a couple times should enlarge it enough to read. Feel free to ask questions.

leon_123
07-20-2016, 07:28 AM
OK, I just got two Phanteks PH-F140SP today, install it at the front to replace preinstalled 200mm fan for intake. Still keeping the 140mm at the back for exhaust. The problem is with three exhaust fans at the top, my plan is to reverse the Phanteks fan for intake, but the 280mm radiator blocking my way to access two screws of the fan. So my option is to turn off that fan completely, minimize exhaust fan at the top to two fan (Corsair SP140L).

Do you think that's a good idea? Or I have to stick with the original plan?

doyll
07-23-2016, 12:27 PM
Trying to run intake and exhaust fans side by side creates a circular airflow. Not a good deal.
Click on image to enlarge
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