[SOLVED] Am I getting positive or negative pressure with this set-up?

[MajdiO]

 

[JohnBonhamsGhost]

just list where your fans are located, their orientation, and their curve profile or static RPM settings.

more air coming in = positive pressure
more air being exhausted = negative pressure

 

[Paperdoc]

The truth is you can NOT calculate internal pressure from fan counts and ratings. There are too many other factors. BUT you CAN test for what really IS happening.

This is a smoke tracer test, so you need some small source of smoke - a smouldering incense stick or cigarette. Look over your system and spot where there are small cracks that air can leak through. Get your system running at low load (idle) for starters. Move the smoke source near the cracks and observe which way it flows. Slow movement into the case says small vacuum inside; slow movement away from the case says small positive internal pressure, which is what I would say you want. Fast movement in either direction says the airflow imbalance is large and needs some adjustment.

Repeat the test for different workloads like common office tasks and high-level gaming.

 

[haseeb98ahm]

Use a airflow smoke generator or that scent stick, if smoke is getting trapped inside the case or if you see vortices inside the case it's positive air pressure.
If smoke is getting sucked in for anywhere other than intake fans then it negative air pressure.
If neither then it's neutral air pressure.

 

[Grobe]

Soft toilet paper can be used because it is so light weighted that even the faintest air current can make it move.

Find a spot on the case that let air through, but not located too close a fan outlet. Seems the bottom behind may be a good spot from the pictures.

Suspend the paper and hold it close to the hole in the cabinet while the fans are running. You should be able to see if the paper have a tendency to move away from or towards the hole - unless the fan setup in a rare case result in a perfectly even pressure.

 

[geofelt]

If the front is intake, and the top is exhaust you are likely positive pressure.
But, if the top and rear exhausts are stronger than the front, unfiltered air will leak in from other openings.
Still positive pressure, but you will have lost the air cleaning capability.

 

[Karadjgne]

From the picture, top is exhaust, rear is exhaust, front is intake. But thats next to meaningless as said prior, because fan curves can/will change that. It's not just the amount of fans, but also what they are doing. It's entirely possible to have the front fans over power the exhausts resulting in positive interior pressure, or have the exhausts over power the intakes and have a negative pressure. Either of which can change according to usage, idle, max states, curve settings.

It's generally of very little concern as to which pressure you do have at any given time as long as airflow is sufficient, temps are optimized and balanced and you can live with the results. You could swap the top to intake and see a 5°C drop in cpu temps, at the cost of a 10°C gpu temp rise, which for most is unacceptable.

It's a matter of what actually works for you and your setup, not any specific designation like positive or negative pressure.