[SOLVED] PSU airflow help

[Muckster]

I posted a detailed question about my PSU over in the PSU section, but I'm not getting informed answers and I think maybe it's more of a cooling question. Would anyone mind taking a look?

[SOLVED] - PSU case placement help and other noob questions

Two questions. Long post, but I think answers will be quick and easy... I'm hoping for some help deciding which way to mount my PSU. Here's my build: https://pcpartpicker.com/user/pshopper/saved/#view=cjTmgs Case: Silvestone GD05 (sort of an oversize HTPC, horizontally oriented)...

forums.tomshardware.com

I'm not certain if the PSU fan is exhaust or intake, and I'm totally willing to add another vent to my case (by drilling holes) if it makes sense in terms of air flow design. I'm just not sure.

 

[PC Tailor]

I answered a very similar question here: https://forums.tomshardware.com/threads/which-fans-face-in-and-which-ones-out.3486919/ - I've posted an extract in the quote below.

Your case hopefully should have an air filter at this location - where the fan draws cool air from underneath the case (which is why it is best placed on a hard surface as opposed to carpet where it will just suck up dust). It will then typically exhaust the warm air at a right angle out the back of the case as shown in the bottom left of the picture above.

Or as shown here:

If your case does not have this air filter and it just opaque metal, then the PSU fan can face upwards into the case - just this isn't ideal.

 

[Muckster]

I answered a very similar question here: https://forums.tomshardware.com/threads/which-fans-face-in-and-which-ones-out.3486919/ - I've posted an extract in the quote below.

Thank you for the reply.

What you say makes total sense IF the fan on the PSU is an intake fan.

PSU fan is on the "top". If it's actually an exhaust fan, then mounting it upside down with the fan facing down doesnt' seem to make sense to me.

I've looked at many old forum posts and answers about fan direction aren't consistent. I guess I need to figure out a way to plug it in and try it, but this PSU's fan doesn't really engage unless it heats up. I guess I could plug it in and blow a space heater on it and wait until the fan triggers...


For the record, here's the PSU
PSU: PRIME Ultra Titanium 650 W 80+
https://seasonic.com/prime-ultra-titanium
(select 650 model, #SSR-650TR )

 

[PC Tailor]

You'll find the PSU you have linked and most reputable PSUs are intake fans on the largest face of the PSU.
I don't come across many PSUs in the UK where the fan is an exhaust fan unless they are cheap (usually unbranded) units that don't have an exhaust vent / grill either.

If it is facing down as an exhaust, this is still optimal as otherwise you are pumping hot air back into the case - and in many cases, this will be pumping hot air directly towards your GPU and CPU. The standoffs on the case allow air to be pushed outside of the case.

Obviously the normal situation is that the PSU fan is an intake, where it sucks cool air from below the case, then extracts immediately out of the case at a right angle.
The Seasonic Prime will also only start fan usage at 40% loads - if you did want to verify yourself, placing a light tissue over the fan will show which direction the air is moving.

However I will also add that your PSU does operate on a hybrid fan mode - which means it can benefit from facing upwards in the case. Because the fan will not start until higher loads are reached.
This is because at low loads, the heat will just rise directly up and then exhaust through your case fans.

However if you find that your often using your computer under heavy loads most of the time, you may still likely benefit more from placing it face down as a cool air intake. You can find details on seasonic psu placements here: https://seasonic.com/how-to-position-your-power-supply

The facing into the case only really applies to the hybrid fan control models though. So from my point of view, if the majority of the time you use your system, the hybrid fan mode has the fan not rotating, I would place the PSU fan facing INTO the case. If however (like myself) that the majority of the time you are using your system, it is under load from gaming or editing for example, then I would have it still act as an intake from the bottom.

 

[Muckster]

You'll find the PSU you have linked and most reputable PSUs are intake fans on the largest face of the PSU.
I don't come across many PSUs in the UK where the fan is an exhaust fan unless they are cheap (usually unbranded) units that don't have an exhaust vent / grill either.

Thanks for the reply.

If it is facing down as an exhaust, this is still optimal as otherwise you are pumping hot air back into the case - and in many cases, this will be pumping hot air directly towards your GPU and CPU. The standoffs on the case allow air to be pushed outside of the case.

This case is located inside a wall unit in a sort of cubby hole. Above and below this "cubby hole" are a ton of air holes, but the case itself intakes from the sides. IF the PSU fan is an exhaust fan and it's blowing the heat DOWN, I'm not sure that's the best thing because hot air rises and might well just go back into the case intakes. Not only that, but the PSU is sealed on all side except the back (where it plugs in) and the "top" where the fan is. If it's blowing the heat out the bottom, then most of the air it's sucking in will be draw in from outside the back of the case. But that's where all the hot air from the case itself is being expelled, hopefully to travel upward and away. I'd rather the PSU isn't primarily drawing hot air FROM the back of the case and pushing it UNDER the case only to have it cycle through all over again.

Obviously the normal situation is that the PSU fan is an intake, where it sucks cool air from below the case, then extracts immediately out of the case at a right angle.

That makes total sense, IF the fan is an intake. Cool air below the case would be sucked into the PSU and then OUT the back of the case where the hot air is staged to go up and away. Again, because the PSU is sealed on all sides except the back and side with the fan, this airflow movement is primarily a movement from outside the case into the PSU and back out the back of the case with little disturbance or effect to airflow going on INSIDE the case.

The Seasonic Prime will also only start fan usage at 40% loads - if you did want to verify yourself, placing a light tissue over the fan will show which direction the air is moving.

I've tried plugging it in outside the case all by itself. I tried blowing a space heater on it for a couple minutes thinking the heat would trigger the fan, but no luck and I got nervous about heating it up too much so I stopped. I'm not sure how to simulate the load to get the fan to trigger. Any ideas how to get the fan going so I can see the direction?

However I will also add that your PSU does operate on a hybrid fan mode - which means it can benefit from facing upwards in the case. Because the fan will not start until higher loads are reached.
This is because at low loads, the heat will just rise directly up and then exhaust through your case fans.

Exactly! I didn't mention this before in hopes of not over complicating the issue, but I'd really like to try that mode, but it's not recommended if the PSU fan is facing downward. Given the cubby hole location I'm concerned about cooling and fan noise.

However if you find that your often using your computer under heavy loads most of the time, you may still likely benefit more from placing it face down as a cool air intake. You can find details on seasonic psu placements here: https://seasonic.com/how-to-position-your-power-supply

The facing into the case only really applies to the hybrid fan control models though. So from my point of view, if the majority of the time you use your system, the hybrid fan mode has the fan not rotating, I would place the PSU fan facing INTO the case. If however (like myself) that the majority of the time you are using your system, it is under load from gaming or editing for example, then I would have it still act as an intake from the bottom.

Ug. It really all depends on if it's intake or exhaust.

I have that same link in my OP in the other forum section. There I explain how the seasonic instructions are somewhat conflicting given my case design. The instructions I got with my "PRIME" PSU are slightly different and no where do they state if the fan is intake or exhaust. This is a high end PSU with the special hybrid mode you describe.

 

[PC Tailor]

IF the PSU fan is an exhaust fan and it's blowing the heat DOWN, I'm not sure that's the best thing because hot air rises and might well just go back into the case intakes.

Makes sense, yet the same could be said about having it facing up, because it will end up putting heat directly into your case.

I've tried plugging it in outside the case all by itself. I tried blowing a space heater on it for a couple minutes thinking the heat would trigger the fan, but no luck and I got nervous about heating it up too much so I stopped. I'm not sure how to simulate the load to get the fan to trigger. Any ideas how to get the fan going so I can see the direction?

but I'd really like to try that mode, but it's not recommended if the PSU fan is facing downward. Given the cubby hole location I'm concerned about cooling and fan noise.

The Seasonic prime is not heat based - it is load based. The hybrid design is that it expects most systems to not really go above 40% load a good amount of the time - so you have to simulate load, not heat. And yes, because otherwise at idle, the heat generated won't have an optimum route to escape from.

But again, based on Seasonic's instructions and the reputation of Seasonic - you can almost guarantee the PSU you have linked is an intake fan, not an exhaust. And as I said, I rarely come across PSUs that are the adverse where I am. You may also find a small arrow or indication on the fan or PSU shell that might identify what direction it follows.

Ug. It really all depends on if it's intake or exhaust.

Either way, you won't cause catastrophy if you have it facing into the case, it just isn't ideal - but with hybrid mode, you get more benefit out of it than most PSUs that run all the time. The best thing to do, is set it up, see what temperatures you are getting, and adjust accordingly.

 

[Muckster]

Thanks for hanging with me... this is really stalling my build!

Makes sense, yet the same could be said about having it facing up, because it will end up putting heat directly into your case.

Good point, but there actually are two rectangular sized vents (1.5cm x 8cm) above the PSU. They are in the side walls right in the corner above the PSU. (Please check out image of case back where this is pretty easy to see). However, there is no vent in the top of the case above the PSU.

I went over this in the other thread so sorry if I'm being redundant, but Seasonic's first preference for the location of the PSU is with fan up "if and only if" EITHER of the following conditions are met

1. There's at least 5cms of space between the top of the PSU and case (top) wall.

2. There's a top vent above where the PSU is mounted inside the case.

Well, in my case (literally), there's 4.5cm of space above and while there's no "top" vent, there are those corner vents just above the PSU on the sides.

So I basically meet most of the either or criteria but not 100% of either.

Now, the other option would be for me to simply make my own vent right above the PSU. I'd just take the lid of the cased off and drill a bunch of tiny holes. My only fear is that I'd mess up the airflow pattern as designed by Silverstone for this case. There are three 120mm intake fans (all on sides of case) from the factory, and I'm adding two 80mm rear exhaust fans to the back. I expect a little positive pressure inside the case. My concern would be that by creating my own top vent, I might be inviting hot air to come in form above when PSU fan isn't on. To be clear, even when the PSU is mounted with fan side up, there's still a vent on the bottom of the case but it's not sealed off. There's maybe... 5 mm gap between the bottom of the PSU and the inside bottom floor of the case where the vent is, so outside air could still be pulled from the bottom of the case as well.

The Seasonic prime is not heat based - it is load based. The hybrid design is that it expects most systems to not really go above 40% load a good amount of the time - so you have to simulate load, not heat. And yes, because otherwise at idle, the heat generated won't have an optimum route to escape from.

Short of installing everything and running a taxing game (or some sort of software to stress the GPU), I'm not sure how to bring that load up. There's just gotta be an easier way to know fan direction BEFORE I install everything...

But again, based on Seasonic's instructions and the reputation of Seasonic - you can almost guarantee the PSU you have linked is an intake fan, not an exhaust. And as I said, I rarely come across PSUs that are the adverse where I am. You may also find a small arrow or indication on the fan or PSU shell that might identify what direction it follows.

No arrows anywhere. I checked thoroughly. I believe you about the norm, but this is a high end PSU with that special hybrid function designed to have the fan facing up so I'm just not sure.

Either way, you won't cause catastrophy if you have it facing into the case, it just isn't ideal - but with hybrid mode, you get more benefit out of it than most PSUs that run all the time. The best thing to do, is set it up, see what temperatures you are getting, and adjust accordingly.

I don't see much other choice... I guess I can always flip the PSU later after the build is finished and tested. Now that you've heard my long story, what's your final answer guess? Face fan up or face fan down?

And finally, if you have any patience left for me, let me ask this totally noob question.....

Mobo is Micro-ATX. PSU is ATX / Intel ATX 12v form factor.

Mobo: ASRock - B450M PRO4 Micro ATX AM4
http://asrock.pc.cdn.bitgravity.com/Manual/H170M-ITXac.pdf

In terms of power being received bythe mainboard itself, there are two interfaces located on adjacent edges of the mobo. (2x5) ATX12v1 AND the (2x12) ATXPWR1. I think I ONLY need the (2x12) ATXPWR1, right? I just leave the ATX12v1 unused, right?

Then, back at the PSU..:

I'm using the modular cable and connecting to BOTH interfaces (2x5 and 2x9) in the M/B slot section (bottom right of image), right? Then this goes out ONLY to the mobo ATXPWR1 (2x12)? Right?

 

[PC Tailor]

You case has a bottom mounted PSU filter, so I would be putting the fan face down to intake air.

I believe you about the norm, but this is a high end PSU with that special hybrid function designed to have the fan facing up so I'm just not sure.

It is exactly this reason why this is an intake fan, as I said, the only time I personally come across it as an exhaust (which is very rare) is in poor cheap quality model PSUs here. There is practically no doubt that this is an intake fan.

Based on the picture in the manual you posted (If i am reading your request correctly):

https://imgur.com/a/l3IihAK

View: https://imgur.com/a/l3IihAK


5 = ATX Power Connector - ATX PWR1
17 = ATX Power Connector - ATX12V1

You need BOTH. The ATX PWR1 is your motherboard 24pin power connector. The ATX12V1 is your CPU power.
You'll find your modular cables should only fit in one type of port. So you shouldn't be able to accidentally connect to the wrong port on the PSU.

Left most ports are for CPU power and PCIe power only.
Top right are your peripherals (HDD, SSD, Fans etc)
Bottom right is your main MB power.

 

[Muckster]

You case has a bottom mounted PSU filter, so I would be putting the fan face down to intake air.



It is exactly this reason why this is an intake fan, as I said, the only time I personally come across it as an exhaust (which is very rare) is in poor cheap quality model PSUs here. There is practically no doubt that this is an intake fan.

Okay, thanks so much for this help! I'm gonna go with the assumption it's an intake fan and so I will mount it fan side facing down in the case. When fan activates, it will pull air up from the bottom of the case and exhaust it primarily to the rear where all the hot air is already pooling.

Also, just looking at the slant of the blades on the fan of the PSU and assuming it spins in the typical direction fans do, then it would be an intake fan.

Based on the picture in the manual you posted (If i am reading your request correctly):

https://imgur.com/a/l3IihAK

View: https://imgur.com/a/l3IihAK


5 = ATX Power Connector - ATX PWR1
17 = ATX Power Connector - ATX12V1

You need BOTH. The ATX PWR1 is your motherboard 24pin power connector. The ATX12V1 is your CPU power.
You'll find your modular cables should only fit in one type of port. So you shouldn't be able to accidentally connect to the wrong port on the PSU.

Left most ports are for CPU power and PCIe power only.
Top right are your peripherals (HDD, SSD, Fans etc)
Bottom right is your main MB power.

Okay, I think I understand. Let me say it back to you to be sure.

The cable plugging into the M/B section of the PSU (shown in image of PSU, bottom right section) is forked so that there's a 2x9 interface and a 2x5 interface. BOTH of these go into the PSU and at the opposite end where it goes to the mobo, I'm plugging into the ATXPWR1 interface, shown as #5 on the mob diagram. Sorry for such a spoon feed. Power just isn't the part of the install I want to mess up.

Then, for the CPU power, looking again to the PSU back... I can use any of the four interfaces located in the CPU/ PCI-E section (lower left). On the mobo side, this will go to the ATX12v1 interface, #17 on the diagram.

Finally, for my graphics card, I need, going INTO the card, a 6 pin and a 8 pin. This is best done using two different cables. Starting again from the CPU/ PCI-E section of the PSU (lower left on image), I will still have 3 out of four interfaces left (after CPU power already took one). One 2x5 cable goes into the PSU, then goes to the six pin receiver on the graphics card. Then, I plug another 2x5 cable into the back of the PSU in the same section and bring that over to the graphics card in the 8 pin location. In this way, three out of the four 2x5 interfaces in the CPU/PCI-E section will be used. So far as I understand, it doesn't matter which three out of the four 2x5 interfaces I use from this section.

Does this sound right?

 

[PC Tailor]

This sounds right from how I'm reading it - just a note though:

BOTH of these go into the PSU

I can't say for certain which cable is which from the MB section on your PSU, purely because I can't see your modular cables - but I would expect this to simply be your ATXPWR1 24 pin.

Just remember this from your PSU guide:

2. Mainboard connection:
a. DO NOT force the connectors into place; the connectors are “keyed” so they can only fit one way. Make sure the connectors lock in their place securely.
b. Connect the power supply end of the 24/20-Pin convertible connector to the appropriate receptor on the power supply unit.
c. Connect the mainboard end of the 24/20-Pin convertible connector to the mainboard. Depending on the mainboard, you may need to either attach or detach the 4-Pin module of the 24/20-Pin connector.
d. Connect the + 12 V 4-Pin connector and the EPS + 12 V connector, if applicable.
e. If your system requires dual EPS + 12 V connectors, please connect the 8-Pin end of the second CPU 8-Pin connector into the appropriate 8-Pin receptor on the power supply unit. Then connect the mainboard end of this 8-Pin connector to the mainboard.

Then as you are well aware, your onboard headers and MB connections are page 24 of your MB manual. Both of these together should make this clear.

Also just remember:
the connectors are “keyed” so they can only fit one way. So you can't plug the wrong modular cables into the PSU ports.
You will find the connections on your motherboard are also keyed, so you theoretically can't plug a standard PCIe cable into a CPU slot and vice versa unless you do it by brute force.

 

[Muckster]

This sounds right from how I'm reading it - just a note though:


I can't say for certain which cable is which from the MB section on your PSU, purely because I can't see your modular cables - but I would expect this to simply be your ATXPWR1 24 pin.

The cable is 24 pin on one side 2x12 going into the ATXPWR1 interface on the mobo. This is pretty obvious. On the other side of the cable, it splits to form a 2x5 connector and a 2x9 connector. These were obviously made to fit the only two interfaces in the M/B section of the PSU. I wasn't sure if I should plug in one or both, but I think it's both. Afterall, I can't supply 24 pins with only one 18 pin connector (I know some are blanks). I'm guessing it needed to pull from two different ports on the PSU for best power just like how the prefered method to supply a GPU is with two cables and two interfaces on the PSU instead of trying to draw it all from one interface on the PSU.

Just remember this from your PSU guide:


Then as you are well aware, your onboard headers and MB connections are page 24 of your MB manual. Both of these together should make this clear.

Also just remember:
the connectors are “keyed” so they can only fit one way. So you can't plug the wrong modular cables into the PSU ports.
You will find the connections on your motherboard are also keyed, so you theoretically can't plug a standard PCIe cable into a CPU slot and vice versa unless you do it by brute force.

Thank you for that. I've actually build many PCs but it's been a while. Normally I don't beg for all this spoon feeding, but this PSU issues has really taken away from the time I allocated today to get this build done. Thanks to you I think I'm back on track.

 

[PC Tailor]

On the other side of the cable, it splits to form a 2x5 connector and a 2x9 connector. These were obviously made to fit the only two interfaces in the M/B section of the PSU. I wasn't sure if I should plug in one or both, but I think it's both.

Yes in which case if it is one cable leading to a split connection on the PSU end, then connect both.

Thank you for that. I've actually build many PCs but it's been a while.

Completely understandable my friend - there are never judgements here. We all need advice at different points in time - and that's what this community is for!
Hope I have been a help in some way regardless!

 

[Muckster]

Completely understandable my friend - there are never judgements here. We all need advise at different points in time - and that's what this community is for!
Hope I have been a help in some way regardless!

So true. Forums here are great and I'm so grateful for the help and patience from people like you.

I think I'm good from here. I will do a test on that PSU to confirm it's an intake fan, but that might be late today or tomorrow. I even sent an email to Seasonic about it, but I was told it would take 48hrs to hear back. Anyway, I'll post back for the definitive answer on the fan direction here on this thread for anyone looking for closure on the issue.

Anyway, I'm good until the next obstacle. Thanks for all your help.

 

[Muckster]

Got the build together by day's end, but have yet to troubleshoot and do software. Thanks again for your help. Oh and I heard from Seasonic. You were right about it being intake:

Thank you for contacting Seasonic support.

It is an intake fan which will suck in air and exhaust it out the back of the PSU where the power switch is located.

If you have any other questions or concerns, please let us know anytime.

Have a nice day!