My computer sits on my desk and imo i would never set a computer on carpet.
Bottom mounted psu on carpet.
When intel designed the atx form factor the power supply fan was designated as the primary case fan.
Determine where the psu is intended to fit.
Hot air rises and cool air you get the point.
Avoid placing case on carpet for bottom mounted psu with fan down never put your computer case on the carpet when you have a bottom mounted psu fan facing downwards.
In my case i get cool air for the intake and the hot air goes out the side of the case.
On a correctly oriented bottom psu it pulls cool air from the bottom and blows out the back.
Once you ve located where the psu will sit check the case for any grills or vents directly beneath this location.
To figure out whether your psu fan needs to point up or down start by looking over your pc case.
The problem of bottom mounted power.
My psu is mounted in the bottom of my case a tj07.
A top mounted psu is like a 2nd exhaust fan but if you want it to run cooler go with a bottom mounted psu.
The carpet will block the airflow to the psu and in worst cases if you have no psu fan filter installed then the small fiber particles from the carpet can get deposited inside.
A bottom mounted psu keeps the psu cooler not the case.
You have to have space under the case though and be careful on high carpet.
Mounting a psu in the top of the case should be ok as long as it vents to the top.
Deciding on whether to mount your psu either facing up or down depends entirely on a few factors namely case design airflow with other fans and the power supply unit itself.
This is typically at the bottom of the case in most modern chassis designs.
Psu s mounted on the top have to draw air from inside the case.