Difference between intake and output fans?

[Toastey]

This may be a stupid question, but what makes an intake fan an intake fan, and what makes an output fan an output fan? Are all case fans the same and can they all be converted from intake to output, and vice versa, or are all case fans designated to either being an intake or an output fan?

 

[derekullo]

Intake fans blow applying positive pressure.

Output fans suck applying negative pressure.

A fan can be either depending on its orientation.

For the most part fan blades are symmetrical, in order to keep them balanced which stops them from flying apart, leading to similar output and intake pressure values.

 

[jwcrellin]

Most cases have intake fan(s) at the front and exhaust fan(s) at the rear/top so as to not fight thermodynamics. Depending how well made your case is made and where it has dust screens installed may determine where to place fans as well.

 

[boju]

Its the fan curve which determins air flow direction, concave and convex.

 

[jwcrellin]

Its the fan curve which determins air flow direction, concave and convex.

Yeah, most fans blow out the side with the bracing. Took me a while to realize that.

 

[boju]

Yeah, most fans blow out the side with the bracing. Took me a while to realize that.

Yeah that's a great way of putting it.

For the op just to follow on, the convex side of the fan is intake -> ( and concave (the inner fan) is output -> )

You could revert any fan to face the same way if the wires could reach and out of harms way. The bracing jwcrellin mentioned is where the motor and wires originate from so to reverse an intake fan would mean the wires would be outside the case

Can see here all intake/exhaust fans are all facing convex