PSU sitting outside the case: benefits and risks/drawbacks??

[Rafael Mestdag]

After my PSU had been presenting high temps(during games mainly), I decided to put it just outside my case with the under vent pulling fresh air from the outside and exausting it without the grid of little holes that's there and the PSU is mounted.

What are the benefits of this? What are the drawbacks? I've read on another forum a guy saying that this allows the PSU more output due to the lower temperature it deals with. Is this true?

 

[ARICH5]

grounding may be an issue. when the psu is screwed to the case chassis it acts as a "ground" for static discharge. if its outside of the case it is not grounded to the rest of the case contents allowing for a higher chance of static electricity being an issue.

 

[USAFRet]

Your PSU has "high temps"? How are you measuring this?

The PSU, in the case, should draw air from the outside, and blow it out the back.
Assuming the case has the required vent holes in the PSU mounting location...as most do.


"this allows the PSU more output due to the lower temperature it deals with."
No, this is false, except at the higher ranges of temperature and power draw.

If the PC only needs 200 watts, that's what the PSU would output. Assuming a non-crappy PSU.

 

[Rafael Mestdag]

grounding may be an issue. when the psu is screwed to the case chassis it acts as a "ground" for static discharge. if its outside of the case it is not grounded to the rest of the case contents allowing for a higher chance of static electricity being an issue.

I think that's not gonna be an issue for me, since I screwed one corner of the PSU to the chassis, so it doesn't fall on the ground.

 

[Rafael Mestdag]

Your PSU has "high temps"? How are you measuring this?

The PSU, in the case, should draw air from the outside, and blow it out the back.
Assuming the case has the required vent holes in the PSU mounting location...as most do.


"this allows the PSU more output due to the lower temperature it deals with."
No, this is false, except at the higher ranges of temperature and power draw.

If the PC only needs 200 watts, that's what the PSU would output. Assuming a non-crappy PSU.

But I've read that PSU's are rated as having a certain efficiency, like 80% power output against 20% turning into heat. All I know for a fact is that the air coming out the back of the PSU used to be hot all the time, and now it's at most, warm during gaming, and cold while idling.

Not to mention, that on the Mafia II benchmark, using the same configuration, I got 2FPS extra after putting the PSU outside the case.

 

[USAFRet]

But I've read that PSU's are rated as having a certain efficiency, like 80% power output against 20% turning into heat. All I know for a fact is that the air coming out the back of the PSU used to be hot all the time, and now it's at most, warm during gaming, and cold while idling.

Not to mention, that on the Mafia II benchmark, using the same configuration, I got 2FPS extra after putting the PSU outside the case.

Sort of, but not really.
A reasonable quality PSU, within or above the needed wattage, will run just fine inside the case.
That is what they are designed for.

A properly mounted PSU drawing air from the outside, should be pretty much the same temp as if it was outside the case.
Assuming your airflow in the case does not suck.

2FPS difference? That is almost certainly something else.
The only way mounting the PSU outside the case could affect that is....
If the GPU or CPU was already near its temperature limit
And if the airflow int he case sucked
And if the PSU was mounted incorrectly.

Your PSU wasn't magically delivering a higher output, nor would that have made an FPS difference if it was.

 

[Rafael Mestdag]

But I've read that PSU's are rated as having a certain efficiency, like 80% power output against 20% turning into heat. All I know for a fact is that the air coming out the back of the PSU used to be hot all the time, and now it's at most, warm during gaming, and cold while idling.

Not to mention, that on the Mafia II benchmark, using the same configuration, I got 2FPS extra after putting the PSU outside the case.

Sort of, but not really.
A reasonable quality PSU, within or above the needed wattage, will run just fine inside the case.
That is what they are designed for.

A properly mounted PSU drawing air from the outside, should be pretty much the same temp as if it was outside the case.
Assuming your airflow in the case does not suck.

2FPS difference? That is almost certainly something else.
The only way mounting the PSU outside the case could affect that is....
If the GPU or CPU was already near its temperature limit
And if the airflow int he case sucked
And if the PSU was mounted incorrectly.

Your PSU wasn't magically delivering a higher output, nor would that have made an FPS difference if it was.

Actually my case is one of the older ATX ones, where the PSU is mounted on the top of it, pulling air from the inside of the case(hot air) to push it outside(also hot). Now, if anything else, my PSU is pulling fresh, cold air from the ambient(cold, fresh air) and letting it out(also, colder, fresher air), thus probably augmenting its power output efficiency, providing the components with more power. So, the 2 extra FPS are probably not magic, they're most likely a fact. I may be wrong though.

 

[InvalidError]

grounding may be an issue. when the psu is screwed to the case chassis it acts as a "ground" for static discharge.

Nearly half the pins on the 24 pins ATX connector are also ground pins, as are half the pins on every other power connector. Even if the PSU is not mechanically attached to the case (and in the electrical code, electrical grounds cannot share screws with structural or mechanical components anyway), the case is still grounded to the PSU via the motherboard's tray studs, the add-in boards' rear bracket and peripherals' metal enclosures. That's more than enough grounding to easily handle static discharge and most electrical faults.

 

[USAFRet]

Actually my case is one of the older ATX ones, where the PSU is mounted on the top of it, pulling air from the inside of the case(hot air) to push it outside(also hot). Now, if anything else, my PSU is pulling fresh, cold air from the ambient(cold, fresh air) and letting it out(also, colder, fresher air), thus probably augmenting its power output efficiency, providing the components with more power. So, the 2 extra FPS are probably not magic, they're most likely a fact. I may be wrong though.

Sounds like you need a new case.

(but the PSU is not affecting your FPS)

 

[Rafael Mestdag]

Actually my case is one of the older ATX ones, where the PSU is mounted on the top of it, pulling air from the inside of the case(hot air) to push it outside(also hot). Now, if anything else, my PSU is pulling fresh, cold air from the ambient(cold, fresh air) and letting it out(also, colder, fresher air), thus probably augmenting its power output efficiency, providing the components with more power. So, the 2 extra FPS are probably not magic, they're most likely a fact. I may be wrong though.

Sounds like you need a new case.

(but the PSU is not affecting your FPS)

Actually, my main worry was that a previous PSU of the same brand and model simply died while I was playing a game and no more than 6 or 8 months after being bought. I know I should've at least picked up a different, better PSU but it was easier to get the same model, and besides I supposed that lightning wouldn't strike twice in the same place.

Moreover, my dad has an identical PSU on his PC, an i5 4th gen with a GTX 750 and 16GB DDR3 plus 2 HDD's of 1TB each. He's had that same pc with that same PSU for at least 6 or 7 months and never had an issue. His case is of the more modern type where the PSU is mounted on the bottom of the case pulling air from under the case. Truth be told, 3 days ago, when I decided to go check his PSU's temperature through my palm, it was quite hotter than it should be. Turns out the filter under the fan was completely dirty.

 

[InvalidError]

His case is of the more modern type where the PSU is mounted on the bottom of the case pulling air from under the case. Truth be told, 3 days ago, when I decided to go check his PSU's temperature through my palm, it was quite hotter than it should be. Turns out the filter under the fan was completely dirty.

And that's why I personally hate cases with bottom intakes. I much prefer those where the PSU is still mounted at the bottom but draws air from inside the case, like the original Antec 300. That way, you've only got the front's intake air filters which are more difficult to forget and more difficult to clog to worry about. Also, since there is far more dust lying on the ground than in the air, the bottom filter clogs up much faster than the front ones.

My current PC is in an Antec 300v2 and I did run into Asus anti-surge issues caused by a clogged PSU air filter making the PSU overheat. That never would have happened in a case where the PSU draws from inside the case.