Verify Positive Pressure?

[thewind32]

Hi all, is there a way to determine whether a setup is running under positive pressure conditions, other than observing dust accumulation over an extended period of time?

 

My case is a cm storm enforcer, with a front intake of supposedly 110cfm, filtered with demciflex filter which is said to reduce the airflow by 20%, which brings it down to 88cfm.

There's only 1 exhaust (rear), a xigmatek clf-f1252 rated at 68.33cfm.

 

On paper, the intake cfm > exhaust cfm, which would give me a positive pressure setup. But I'm not sure how accurate these cfm ratings are, especially since the 2 fans are from different manufacturers who may have different methods for measuring the cfm.

 

The interior is pretty tidy in terms of cables, so airflow should not be affected too much, but there's a gigabyte gtx770 and a cm hyper 212x. Do I have to take bulky components possibly affecting airflow into consideration when calculating cfm?

 

Thanks!

[0ld_Chicken]

I like to place strips of lightweight paper or thin plastic around every passive vent (holes in the case with no fan) like empty optical drive slots or something like that. When you are in positive pressure the strips will Try to blow away, negative and they'll suck to the case opening. I run benchmarks while i do it so that way you can tell if it goes under negative at high load as well as idle

Hi all, is there a way to determine whether a setup is running under positive pressure conditions,

Snip

Thanks!

Also when you make a new post you can follow it to get notifications when someone comments. Some people forget to quote

Also

Welcome to ltt

[thewind32]

I like to place strips of lightweight paper or thin plastic around every passive vent (holes in the case with no fan) like empty optical drive slots or something like that. When you are in positive pressure the strips will Try to blow away, negative and they'll suck to the case opening. I run benchmarks while i do it so that way you can tell if it goes under negative at high load as well as idle

Also when you make a new post you can follow it to get notifications when someone comments. Some people forget to quote

Also

Welcome to ltt

 

Thanks. I've done the paper method before but looks like I used paper that was too heavy :mellow:, since I did not see any movement. Following your advice, I used a small piece of 1-ply tissue on the top fan grill, and yep they are twitching away to a small extent. That's enough right? I'm assuming a small positive pressure yields the same results as a large positive pressure.

 

Regarding the load vs idle comparison, that only applies if the case fans are controllable right? I'm running both the intake and exhaust directly off the psu via molex. In this case, they would be running at 100% rpm all the time, while only the fan on the 212x is automated via speedfan. Thus, there will not be any difference in terms of pressure whether my system is under load or not. Do let me know if I'm misunderstand anything.

[0ld_Chicken]

Thanks. I've done the paper method before but looks like I used paper that was too heavy :mellow:, since I did not see any movement. Following your advice, I used a small piece of 1-ply tissue on the top fan grill, and yep they are twitching away to a small extent. That's enough right? I'm assuming a small positive pressure yields the same results as a large positive pressure.

 

Regarding the load vs idle comparison, that only applies if the case fans are controllable right? I'm running both the intake and exhaust directly off the psu via molex. In this case, they would be running at 100% rpm all the time, while only the fan on the 212x is automated via speedfan. Thus, there will not be any difference in terms of pressure whether my system is under load or not. Do let me know if I'm misunderstand anything.

 

Yeah I think if your getting movement on the top fan grill i think you're in the positive.

 

and yeah the idle vs load would really probably only matter if they are controlled.  technically the 212x might contribute to the exhaust air when running at high speeds if it is pointing towards the exhaust fan.  I have 2-2600 rpm fans on my 212 evo right now (just trying things out) and if they are running at even 1900rpm, I can turn my back fan off and it'll keep spinning.  If you're using the stock 212x fan you'll probably be positive pressure all the time.

 

I would probably remove a pci slot cover and or a optical drive cover and try those too.  But I also like messing with my airflow way too much hahah

[thewind32]

I would probably remove a pci slot cover and or a optical drive cover and try those too.  But I also like messing with my airflow way too much hahah

 

By this you mean perform the paper test at those locations right?

 

And yea, I'm running one stock 212x fan only.

[0ld_Chicken]

By this you mean perform the paper test at those locations right?

And yea, I'm running one stock 212x fan only.

Yeah, ye old paper test. I'm sure you'll be good with such a simple fan setup. Your parts are staying cool enough right?

[thewind32]

Yes the rig is cool enough, at least considering the climate we have here in Singapore. Not overclocking either. Might do so in the next build but not anytime soon.

 

Thanks for your help, guess I should mark this as solved?

[0ld_Chicken]

Yes the rig is cool enough, at least considering the climate we have here in Singapore. Not overclocking either. Might do so in the next build but not anytime soon.

Thanks for your help, guess I should mark this as solved?

Sure thing! Smoke is also a great indicator of airflow. Long term smoke exposure is bad but I'm sure a very brief small amount would do no harm. Especially if you are pretty sure that you have positive pressure

[thewind32]

Sure thing! Smoke is also a great indicator of airflow. Long term smoke exposure is bad but I'm sure a very brief small amount would do no harm. Especially if you are pretty sure that you have positive pressure

 

Alright, will keep that in mind the next time I modify the airflow setup.