PSU fan direction

Hi,

I recently decided to disassembly my dusty PSU and blow all the dust away from it. I came across a problem when re-assemblying it back together. Which way is the fan supposed to be blowing ? Towards the guts of the PSU or out from the PSU ?

Thanks!

 

It depends on your PSU. I think the main objective is to blow air our the back. So For PSUs with the fan at the back of the PC, it should be out. For PSUs with the fan at the bottom of the PSU, inside the PC, it should be sucking air in.

 

Having a positive pressure inside the case is not healthy for the PC. Neither is turbulence inside the case.

In my experience, exhaust fan CFM needs to exceed intake fan CFM. In fact, unless you are employing a RAID array instead of a single hard drive, or are doing some serious overclocking intake fans genuinely are not necessary.

PSU units mounted at the upper rear of the tower should be exhaust fans, as well as the case fan at the rear of the tower. Air intake through the forward ports/underside of the case should be sufficient to keep things cool under normal operating circumstances.

 

I have never seen a PSU fan that did not direct air out the back of the PSU. If it went the other direction, it would pump [potentially a lot of] heat into the case interior and that would not be good.

Ummm, sorry but I disagree with this completely. It is the case's responsibility to provide a sufficient "flow" of cool air through the case. Not the PSU fan. Therefore, you need at least one case fan, preferably two. One in back exhausting heated air, and one in front pulling cool air in. And preferably large fans (120mm or larger) to move massive amounts of air, but at a lower RPM, thus lower (if any) fan noise.

The PSU fans are designed to keep the PSU cool, not the CPU, RAM, motherboard, GPU, or the drive (or drives). Plus, PSU designers have no clue what their PSUs will be running, or how the PSUs will be mounted.

Also, it is essential to note many, if not most PSUs - and especially quality PSUs (and we all buy "quality" PSUs, right?) - all have speed controls for their fans that increase or decrease the PSU's fan speed (and thus noise), depending on the PSU's temperature and work load, and not the CPU or motherboard's temperatures. So you MUST have at least 1 case fan - even with an entry level "office" machine to keep CPU and system temps under control.

I fail to see how running a RAID setup matters. A second (or third) drive adds the same amount of heat because the motors are still spinning - regardless in mirror, stripped, or single configuration. The R/W head armature adds very little heat to the equation. Unless using 10K RPM raptors, one or two extra drives don't really add a lot of heat - compared to other components.

Therefore, it is the number of drives you have that matters, not if they are configured in a RAID array or not. That said, adding a second, or third drive may not require an additional fan if your case is already providing a good flow through the case, except, maybe, a new front fan blowing over the drives themselves, since they tend to be packed into tight quartered drive bays.

Even with PSUs with a fan at the bottom, the PSU still mounts with its exhaust side going out the back of the case. So regardless the PSU's mounting location, and regardless the PSU fan location, air still flows out the back of the PSU, thus out the back of the case.

 

Yeah, that's what I meant. Air out the back. I was trying to stress, that, depending on the position of the fan, it can be blowing air out the back, or sucking in from inside the case; in which case (as you mentioned) resultant air flow will still be out the back.:major

 

I've never had an intake fan in a personal build, and a 120mm exhaust fan and a dual fan PSU has always been sufficient. I've never had any excessive heat issues, and the CPU/GPU are mildly overclocked.

For reference, my case is a 12 year old Obi-Zero, and pulls fresh air into the case via a port in the bottom of the case, and the inner front panel under the bezel is ported. If you put your hand over the intake port, you can feel the air whipping into the case. In fact, it will cool your fingers off.

 

And that's good. But not all cases, computer components, users, ambient environments (room temps), etc. are the same. Or PSUs, for that matter as most only have one fan.

Certainly, not all cases support an intake fan either. But those that do ensure cool air flows through the drive cage, and many cases with front fans have removable, washable air filters - something I require all my cases to have.

That said, I should have worded my response better and I apologize to all, and specifically to the mekanic for that. the mekanic is correct that an "intake" fan (that is, a fan typically mounted in front, drawing cool air in) is not specifically required. The point I was trying to make is the case - NOT the PSU - must provide enough "flow" of cool air through the case to exhaust the heat and provide cool air to heat sensitive components. A front intake facilitates that "flow" much better than air being sucked in from every other crack and crevice via only rear fans.

BTW, more and more cases are supporting "blow-hole" fans - large (up to 240mm) fans on the top of the case. These huge fans are virtually silent, but really keep air flowing.