How should i set up my fans in the 900D

Zaabi · July 23, 2013

So I have 16 fans and 1 corsair 900D.

I read its good to have negative pressure or something like that. So how can I achieve it.

There are 4 fans on each of the bottom of the case.

3 fans behind the hard drive mount.

4 fans on the top.

And the final one at the back.

How should i set them up in terms of intakes and outlets.

Winther · July 23, 2013

You want POSSITIVE pressure inside the case.

If you dont have enything in the buttom of the case, then fans there is just a waste, if you have it full of harddrives then just fil up one side of the basement!

You just want more fans blowing in than out. So I would say three fans in from the frant and 2 out of the top, depending on the system inside though. If its a really big system you might want to use all the fans spots. I might acutally go for intakes at the top and back and exhaust in the front. Or just go with intakes in the front and back and exhaust in the top. depends on your specific layout.

ThatLazyPickle · July 30, 2013

You want POSSITIVE pressure inside the case.

Hey there Winther,

I'm new to the build-field and was just curious as to what Positive pressure is and how it affects the case?

excalibrax · July 30, 2013

Pressure in buildings Positive and NEgative

2nd article

Negative Pressure:

Essentially the building is being put into a vacuum by the exhaust. The outside air is introduced uncontrolled through any cracks within the building structure. Cold drafts in the office, factory and warehouse spaces are then prevalent.

aka air will be sucked in with too many fans being pointed outward adding to dust problems Assuming your water cooling or have fan filters this is what to avoid.

Positive Pressure:

Positive pressures on the other hand need additional exhaust or a way of relieving the pressure. This mainly occurs when buildings are cooled with an outdoor air economizer or have 100% outside air units.

We create positive pressures in a building by installing a fresh air duct to the HVAC system or by properly installing a Heat Recovery Ventilator (HRV). Positive pressure controls ventilation into a building, and keeps air from being pulled in from undesirable locations.

Fresh air pressurizes a building as it's introduced into the return side of the system before the fan. The amount of return air is reduced by the amount of the fresh air. So if 10% fresh air is brought into the system, the fan can only pull 90% of the return air through the return ducting. The supply side still delivers 100% of its airflow. So, supply airflow exceeds return airflow in the building, leaving a positively pressurized building.

The amount of air required to pressurize a building will increase depending on how leaky the building envelope is. For adequate positive building pressure, some building pressurize with as little as 50 cfm of outside air per every 1000 square feet. Some buildings need as much as 300 CFM or more per 1,000 sq.ft.

Exhaust fans create a negative pressure in a building.

As he said you want more fans blowing in than out, Ideally you want mostly fans blowing in, with your outgoing fans placed near high temperature components or in the upper part of the case. This is because hot air rises and you want to remove hot air. So placing fans in the ceiling of the computer case or upper parts remove the naturally rising hot air, and exhaust near hot components increases airflow over them,