[SOLVED] PSU Fan Up or down?

Jun 16, 2020
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Hello. So i own Corsair CV550 Power Supply. And my problem is, it is smaller than normal PSU's. My ventilation hole on the bottom of the case is not that big so my fan only sticks half way. Im scared if it could overheat or something so i rotated the power supply up side down, so now the fan is facing up to the case. My case is Evolveo Nate 2. I have two intake fans. One is Be quiet Pure wings 2 and another is Evolveo fan that comes with case. And i have one exhaust fan also Evolveo fan that comes with the case. I have exactly 8fans in my case. (I mean i literally counted all fans like gpu fans and cpu fans etc.) And i heard about the negative pressure or positive pressure or something like that so im scared that if my PSU fan is facing up it could do something like that.)

My specs: Ryzen 5 2600 (Arctic Freezer 34)
GIGABYTE Triple fan 1660 Super
HyperX 8gb DDR4 3200mhz
GIGABYTE B450M S2H
Kingston A2000 M.2 NVME SSD
Corsair CV550
Evolveo Nate 2

 

Karadjgne

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It's atx standard size, it's not small at all. It won't overheat unless you are trying to push an extreme load above its realistic rating. Just leave it fan down, Corsair engineers wouldn't design something intended to fail.
 

Karadjgne

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It's atx standard size, it's not small at all. It won't overheat unless you are trying to push an extreme load above its realistic rating. Just leave it fan down, Corsair engineers wouldn't design something intended to fail.
 

geofelt

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A psu will work equally well with the fan up or down.

The psu fan only needs to run when the psu is under load and heats up.

Normally, you want the psu intake to draw in outside air and expel the heated air out the back of the psu.
Your case,half of the intake is obstructed by the case. A poor case design.

You could mount either way.
I think I would mount with the intake up top inside the case.
If, for no other reason than to allow the fan to take in a balanced stream of air.
I wonder if airflow oh half of the fan might lead to premature fan problems.
 
Jun 16, 2020
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A psu will work equally well with the fan up or down.

The psu fan only needs to run when the psu is under load and heats up.

Normally, you want the psu intake to draw in outside air and expel the heated air out the back of the psu.
Your case,half of the intake is obstructed by the case. A poor case design.

You could mount either way.
I think I would mount with the intake up top inside the case.
If, for no other reason than to allow the fan to take in a balanced stream of air.
I wonder if airflow oh half of the fan might lead to premature fan problems.
Thanks for your reply. My PSU fan spins at all time, now that im looking at it bacause the fan is facing up so i can see it. Also im going to rotate it because i know the answer from you guys. Thanks!
 
Hello. So i own Corsair CV550 Power Supply. And my problem is, it is smaller than normal PSU's. My ventilation hole on the bottom of the case is not that big so my fan only sticks half way. Im scared if it could overheat or something so i rotated the power supply up side down, so now the fan is facing up to the case. My case is Evolveo Nate 2. I have two intake fans. One is Be quiet Pure wings 2 and another is Evolveo fan that comes with case. And i have one exhaust fan also Evolveo fan that comes with the case. I have exactly 8fans in my case. (I mean i literally counted all fans like gpu fans and cpu fans etc.) And i heard about the negative pressure or positive pressure or something like that so im scared that if my PSU fan is facing up it could do something like that.)

My specs: Ryzen 5 2600 (Arctic Freezer 34)
GIGABYTE Triple fan 1660 Super
HyperX 8gb DDR4 3200mhz
GIGABYTE B450M S2H
Kingston A2000 M.2 NVME SSD
Corsair CV550
Evolveo Nate 2

Seasonic Focus+ has a similar issue.

According to Seasonic documentation, they actually recommend fan FACE UP if running in hybrid (semi-passive fan off mode) Natural heat convection will allow the air to drift upward when the fan isn't running. But the built in fan is strong enough to suck down any air and push it out the back when it runs in active (fan on) mode
 
It's atx standard size, it's not small at all. It won't overheat unless you are trying to push an extreme load above its realistic rating. Just leave it fan down, Corsair engineers wouldn't design something intended to fail.
I disagree with this answer. His airflow is semi blocked which will cause balance problems and uneven cooling. The ATX power supply design isn't the issue. It's the case that is the problem.
 

Karadjgne

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I disagree with the disagreement. The fan creates vacuum, it isn't pushing. You can run a fan partially covered all day long, many cases, if not most, are such with anything from psu to intakes, to exhaust.

Not going to hurt the fan. Flow isn't segmented where you'll only get flow exactly under open areas, you get flow from all the areas as the blades themselves will drag air around as well as expel, and cooling is determined by temp via thermistor. You'll even get equitable amounts of flow since the fan will just spin a few rpm higher according to loads and temps. It's not a set piece of simply off or max.

The CV doesn't have semi/passive modes. It's nothing more than a VS except bumped to Bronze 80+.

The issue with face up in smaller cases is the gpu. The psu sees higher temps (case temps are always higher than ambient) so naturally runs the fan at higher rpm. This can do 1 of 2 things for gpu. Either help it by creating a low pressure area under the gpu, forcing more air draw from intakes, or it can steal air from the gpu. Much depends on loads, strength of gpu fan draw vs psu draw etc. If the fan is too close to the gpu, you'll often end up sucking the gpu exhaust into the psu, which elevates temps inside, forcing the fan to spin faster, which has more draw, pulls more exhaust etc.

It's one of those things that's pretty case by case situational, test out and see what happens with gpu under light, heavy loads etc with the psu up and down.
 
I disagree with the disagreement. The fan creates vacuum, it isn't pushing. You can run a fan partially covered all day long, many cases, if not most, are such with anything from psu to intakes, to exhaust.

Not going to hurt the fan. Flow isn't segmented where you'll only get flow exactly under open areas, you get flow from all the areas as the blades themselves will drag air around as well as expel, and cooling is determined by temp via thermistor. You'll even get equitable amounts of flow since the fan will just spin a few rpm higher according to loads and temps. It's not a set piece of simply off or max.
You keep thinking that.

Your ideas all depend on where the thermistor is. And uneven balance will create uneven flow under the covered sections. We do this intentionally with heat wheel heat exchangers to keep air from mixing on the two sides. Those components under the covered section + a few degrees WILL run hotter if the thermistor is not sitting over them. Or if the thermistor is running over them, the fan will run harder than it needs to. There will also be uneven bearing pressure causing the covered side to pull up. To get similar air flow you have to decrease pressure more.

P1=P0 - .5pvv. The pressure drop makes the fan work a lot harder. Also
F
d = Cd * A * v*v/v0.

A lot of that drag energy get converted to heat and noise.

The force of drag on the fans exponentially increases with velocity increases. If you cut off 30% of the volume space, you need to move 30% more air over the remaining 70%. That's a substantial increase in speed provided you do achieve even flow under the blades.

I'm telling you that inverting the PSU is the best option here.

-Signed
-Aerospace Engineer who does thermal heat exchange simulations.
 
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My personal opinion? Run the PSU with the fan up.

Will running it fan down make it run slightly hotter? Only slightly.

Does the blockage really matter? If you opened up the PSU (PLEASE DO NOT) you will see there's a acetate diverter located right around where the blockage is on the inside of the fan.

Example:


Also my personal opinion? The case design is flawed. There's nothing "wrong" or "unusual" about the size of a CV Series PSU. That case is just "cheap".
 
Reactions: digitalgriffin
Jun 16, 2020
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My personal opinion? Run the PSU with the fan up.

Will running it fan down make it run slightly hotter? Only slightly.

Does the blockage really matter? If you opened up the PSU (PLEASE DO NOT) you will see there's a acetate diverter located right around where the blockage is on the inside of the fan.

Example:


Also my personal opinion? The case design is flawed. There's nothing "wrong" or "unusual" about the size of a CV Series PSU. That case is just "cheap".
Okay thanks guys. I have half of people suggesting that and half of people suggesting that. So i dont know exactly what to do. When my fan is facing down or up its no difference at all the psu is cold even when the fan was down and i touched the side of the psu(where the logo is located) it was cold. So i litteraly dont know what to do. Oh and i asked a guy that has this PC case too and he said that he runs the psu down. And when i told him about this he was like. "Oh, never run a psu fan facing up. It will pull hot air in from the case and the psu will be hotter. Its better to run half fan with cold air rather than full fan with hot air."
 
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Jun 16, 2020
25
0
30
0
I disagree with the disagreement. The fan creates vacuum, it isn't pushing. You can run a fan partially covered all day long, many cases, if not most, are such with anything from psu to intakes, to exhaust.

Not going to hurt the fan. Flow isn't segmented where you'll only get flow exactly under open areas, you get flow from all the areas as the blades themselves will drag air around as well as expel, and cooling is determined by temp via thermistor. You'll even get equitable amounts of flow since the fan will just spin a few rpm higher according to loads and temps. It's not a set piece of simply off or max.

The CV doesn't have semi/passive modes. It's nothing more than a VS except bumped to Bronze 80+.

The issue with face up in smaller cases is the gpu. The psu sees higher temps (case temps are always higher than ambient) so naturally runs the fan at higher rpm. This can do 1 of 2 things for gpu. Either help it by creating a low pressure area under the gpu, forcing more air draw from intakes, or it can steal air from the gpu. Much depends on loads, strength of gpu fan draw vs psu draw etc. If the fan is too close to the gpu, you'll often end up sucking the gpu exhaust into the psu, which elevates temps inside, forcing the fan to spin faster, which has more draw, pulls more exhaust etc.

It's one of those things that's pretty case by case situational, test out and see what happens with gpu under light, heavy loads etc with the psu up and down.
Hello man. Please respond to this comment that i wrote. I really need a clear answer.
 
Jun 16, 2020
25
0
30
0
You keep thinking that.

Your ideas all depend on where the thermistor is. And uneven balance will create uneven flow under the covered sections. We do this intentionally with heat wheel heat exchangers to keep air from mixing on the two sides. Those components under the covered section + a few degrees WILL run hotter if the thermistor is not sitting over them. Or if the thermistor is running over them, the fan will run harder than it needs to. There will also be uneven bearing pressure causing the covered side to pull up. To get similar air flow you have to decrease pressure more.

P1=P0 - .5pvv. The pressure drop makes the fan work a lot harder. Also
F
d = Cd * A * v*v/v0.

A lot of that drag energy get converted to heat and noise.

The force of drag on the fans exponentially increases with velocity increases. If you cut off 30% of the volume space, you need to move 30% more air over the remaining 70%. That's a substantial increase in speed provided you do achieve even flow under the blades.

I'm telling you that inverting the PSU is the best option here.

-Signed
-Aerospace Engineer who does thermal heat exchange simulations.
Please man respond to what i just wrote . I really want a clear answer.
 
"Oh, never run a psu fan facing up. It will pull hot air in from the case and the psu will be hotter. Its better to run half fan with cold air rather than full fan with hot air."
Maybe if the PSU is the only exhaust fan in the PC.... and there's no intake fan?

The PSU is rated to operate upto 50°C. And can put out 100% even as long as temps are < 30°C. If the temps inside your case are anywhere near 40°C, you have other problems.
 
Reactions: digitalgriffin

Karadjgne

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Digital griffin is a Aerospace engineer, one might say a 'rocket scientist', consequently he deals with pretty exacting measurements and very small tolerances, as noted by his formulae.

But it's a psu, and while some aspects are involved that include the need for rocket scientists of several branches, for the most part psus are designed by electrical engineers, like me when I was much younger.

What it boils down to is preference. Your preference and the temps preference. There really is no absolute right or wrong way to install it, you can do either. If fan up affects gpu temps in a negative manner, turn the psu upside down. If fan down gives erratic behavior such as super high speed fan for no real reason, turn it fan up.

It's a CV. It's a budget unit, but Is designed quite well, and shouldn't have any issues lasting long beyond its warranty with your current components. You could definitely do far worse in choice.

As Jon noted, your case is not a brilliant design, really could have used digitalgriffin's input since which ever engineer did actually design it has little concept of what's actually important, and spent far too long on just trying to make it look appealing.
 
Reactions: 3bec
Jun 16, 2020
25
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Digital griffin is a Aerospace engineer, one might say a 'rocket scientist', consequently he deals with pretty exacting measurements and very small tolerances, as noted by his formulae.

But it's a psu, and while some aspects are involved that include the need for rocket scientists of several branches, for the most part psus are designed by electrical engineers, like me when I was much younger.

What it boils down to is preference. Your preference and the temps preference. There really is no absolute right or wrong way to install it, you can do either. If fan up affects gpu temps in a negative manner, turn the psu upside down. If fan down gives erratic behavior such as super high speed fan for no real reason, turn it fan up.

It's a CV. It's a budget unit, but Is designed quite well, and shouldn't have any issues lasting long beyond its warranty with your current components. You could definitely do far worse in choice.

As Jon noted, your case is not a brilliant design, really could have used digitalgriffin's input since which ever engineer did actually design it has little concept of what's actually important, and spent far too long on just trying to make it look appealing.
Thanks man! So im going to let it be the fan down option. If i notice something i will let you know.
 
Jun 16, 2020
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Maybe if the PSU is the only exhaust fan in the PC.... and there's no intake fan?

The PSU is rated to operate upto 50°C. And can put out 100% even as long as temps are < 30°C. If the temps inside your case are anywhere near 40°C, you have other problems.
I have two intake fans. One is Evolveo and second one is Be Quiet. I have one exhaust fan, also Evolveo. So there should be no problem?
 

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