this post was submitted on 12 Apr 2024
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Hi! I currently have this build using the GT502 case.

I just recently got 3 more case fans. Previously it was set up like this:

I think that for some reason the temps got worse and the PC much louder. It might just be buyer's remorse but I got more fans so that they could use less RPM and be quieter, but I feel like the complete opposite has happened.

Can I change anything about this layout to optimise airflow? I was thinking of maybe switching the side panel fans to exhaust? That might starve the CPU cooler, though...

Maybe I'm just imagining things and I just need to perform exact tests to figure it out. What do you use for testing airflow effectiveness?

UPDATE:
The issue was weirder than I would've thought. The bottom 3 fans are controlled by one motherboard channel using a PWM splitter cable. The rear and side panel fans are the same - one channel for all 3. Previously I had just the rear exhaust plugged in to a single channel but now it's plugged into the splitter.

Apparently the order of the fans in the splitter is VERY important. I changed it so that the rear fan is the first in the splitter and that instantly fixed the issue. ¯\_(ツ)_/¯

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[–] [email protected] 0 points 7 months ago* (last edited 7 months ago) (1 children)

Try this setup:

  • Bottom - Two intake fans
  • Side - Two intake fans
  • Rear - One exhaust fan
  • Top - One exhaust fan

Tl;dr:

With your current setup, aim for slight positive pressure by setting your exhaust fans at a higher speed than the four intake fans (e.g., exhaust - 900 rpm, intake - 800 rpm). This may give you the best balance in noise, cooling, and airflow.

Advantages of this new setup:

  • Reduces noise since you can set all fans to a comfortable speed
  • Optimises airflow to achieve either neutral pressure (ideal) or slightly higher positive pressure to reduce dust
  • Exhausts hot air at a rate that does not allow the air in the case to heat up

Explanation:

Mount the top exhaust fan as far left as possible (over the top left corner of the motherboard). The ideal airflow pattern in any system, not just computers, is to get air in at the same rate as you get air out. The ideal is neutral airflow where there is no pressure buildup in a case - air leaves as quickly as it comes in. The next preferable pattern is positive pressure - simply because it helps to reduce dust - where a slightly higher volume of air is brought in than exhausted.

With your current setup, you have too much positive pressure, which is very bad for cooling. You're introducing an unnecessary volume of air that's bouncing around in that case. The reason your temps get worse is because, while in theory it sounds like shoving more air into the case would be great for cooling, but the problem is that air isn't leaving the case fast enough! So what happens? You're shoving so much air into that case at such a fast rate, and it has nowhere to go! Sure you've got one exhaust fan that's trying to pull some air out of the case, and I guess you have some breathing holes at the top, but there's nothing up there to direct that air, so air will partially get pushed out of there slowly, but it also is forced everywhere in the computer and gets pushed in all the cracks and crevices in that case (e.g., between the glass and the case). In other words - the air in the case is somewhat trapped and it actually gets hotter since it has nowhere to go! This is why your temps are worse by adding those three intake fans. You need to get the hot air out at the same rate it is coming in, and exhaust fans will do that for you.

Key: The air coming in should leave the case at the same rate. A compromise, where the only benefit is to help reduce dust, is to have the air leave the case at a slightly lower rate than it came in.

You only need one rear and one exhaust fan. You'll see other builds with three fans mounted on the top, but that is extremely wasteful and misguided. Those extra fans end up exhausting cool intake air before it even has a chance to blow over the motherboard.

Set your exhaust fans slightly higher than the speed of your four intake fans to help balance them out. It is two exhaust vs four intake, so you can try something like this: intakes at 800 rpm, exhaust at 900 rpm. Of course, set up appropriate fan curves when you're introducing load to the CPU and GPU so they ramp up appropriately.

As for optimization, your definition of noise may be different from others. Introduce sustained load to your PC, and then while you have that load, play around with your fan settings to figure out what you're comfortable with and set the fan curves appropriately so that they gradually ramp and stay at consistent speeds.

[–] [email protected] 0 points 7 months ago (2 children)

Wow, thank you for such a great explanation!

I will probably first try switching the side panel fans to exhaust, just because it's much easier and might help level out the pressure. If that doesn't work, I'll definitely try your proposed layout!

[–] [email protected] 0 points 7 months ago

Late to the party, but if you do turn your bottom fans around, remember to keep the desk/floor/whatever your PC is on clean. We can all pretend to actually clean the bottom filters regularly, but we know that's not true and the filter will turn into a wall in a few weeks. Also why my only intakes are on the front where the filter is just magnetic.

[–] [email protected] 0 points 7 months ago* (last edited 7 months ago)

I don't recommend you do that. You need cool intake air to reach your motherboard and CPU. If you switch those three side fans to exahaust, there is no more cool air reaching your CPU and motherboard. The only air that will reach the CPU is the hot air from the GPU.

[–] [email protected] 0 points 7 months ago

The easiest hack for testing airflow is to burn an incense stick and see where the smoke goes.

[–] [email protected] 0 points 7 months ago* (last edited 7 months ago) (1 children)

Is the top mesh or solid? I can't tell.

If mesh you shouldn't be having any problems with rear exhaust and the rest intake.... I'd just tune the rear exhaust to match the cpu fan and run the rest on a much, much less aggressive ramp up.

If solid, leave bottom 3 intake, rear exhaust, side two exhaust. This leaves the air pressure net balanced but keeps air flowing consistently up through the case.

[–] [email protected] 0 points 7 months ago* (last edited 7 months ago)

The top is mesh. That's why I did so many intake fans - to let the pressure naturally out of the top.

I still might experiment with switching the side panel to exhaust. That's what I wanted to do in the first place but every build I saw used it as an intake and I was scared that would starve the CPU fan.

I did seem to get the noise down a bit by modifying the curves and making the ramp up smoother.

[–] [email protected] 0 points 7 months ago (2 children)

I'd make the back and bottoms intake and exhaust on the side with that config.

Or intake on the side and exhaust in the back and bottoms.

Or mouth the side ones on top as exhaust if possible.

[–] [email protected] 0 points 7 months ago

Back intake means your are fighting the airflow from the CPU cooler unless you switch that one around, too, and pretty much reverse the whole airflow in the case.

Don't think that makes too much sense. Cases these days seem to follow a "front in, back/top out" airflow philosophy anyway.

[–] [email protected] 0 points 7 months ago* (last edited 7 months ago)

Wouldn't a back intake make the CPU cooler useless? I would need to switch the CPU fan to the other side which I'm not sure there is enough space for.

Exhaust in the bottom seems like it would do the same thing - starve the GPU fans of fresh air.

Top exhaust, though, might be better. 🤔