If you have enough clearance underneath the case (I have a Rosewill Blackhawk case and the legs give it a 1" clearance) then go ahead and mount it with the fan pointing down. That's really the point as it's supposed to suck cooler air from under the case and throw it out the back. If the clearance is small and your case rests on a carpet or something, flip it with the fan pointing up. Both ways are fine, but common sense will tell you which way will cool the PSU better.

Edit: just looked at the case you bought. I see only tiny legs on the bottom, looks like there is almost no clearance. If your computer is going to rest on a carpet/rug, I would suggest you point the fan up.

Edit2: If you want to mount it with the fan towards the bottom, you can always purchase taller feet. Here for example

I think I'll just mount it facing upwards then, once I extend the 12v auxiliary cable. I never place my computer on carpet, but the total lack of clearance it has even on a flat surface can't be good. Also, the air temperature shouldn't be too much of an issue.

Absolutely mount it facing downwards. It sucks cool air from under the case. The air should be cooler than the one inside the case.

Even if u mount it facing upwards,the air in the lower part of the case it's cooler,then the air in the upper part,where usualy the power supply is mounted.

Isn't there only one possible orientation to mount the power supply, owing to the position of the screws?

Jorpho wrote:

Isn't there only one possible orientation to mount the power supply, owing to the position of the screws?

No. Most (I'd say 99%)of cases have holes that allow you to mount it either way.

Mine allows it to go both ways. I mounted it upwards because there's virtually no breathing room on the bottom, and the dust filter I've noticed does a great job of collecting pet hair. 😜