Does exhaust placement matter?

[GSTARR]

Two questions:

 

A) Is having your "cooler" air being exhausted going to change temps a significant difference

 

B) Is negative pressure worse only because of dust, or does it also come with higher temps?

 

Ive heard over and over that your top and back fans should be exhausts because hot air rises. However, with my 760t if I fill it out with case fans to try and get airflow, that will leave me with negative pressure.

 

1st world problems I know, but my poor 5820k is starting to show his age and filling the case out with fans is the best thing I can justify buying prior to saving up for a rebuild. Advice?

PositiveAirflow.jpg NegativeAirflow.jpg

[OhioYJ]

Option B (Negative) is likely to perform quite a bit better.

 

Blowing some dust out every now and then is not a big deal.

[Alex Atkin UK]

56 minutes ago, OhioYJ said:

Option B (Negative) is likely to perform quite a bit better.

 

Blowing some dust out every now and then is not a big deal.

Option B is only good for water cooling, if air cooling I'd remove some or all the top fans personally.  Negative pressure will force air in from other ventilated parts of the case which can reduce the push from the intakes.

 

In an ideal situation the fans are doing all the work of directing the airflow to where it needs to be, because the more forward pressure the air has, the more its going to remove heat.

 

Its harder to remove heat with negative pressure as you aren't forcing it into the harder to cool spots effectively, its naturally going to take the easiest path rather than through tighter gaps.

 

In my own experience, less fans actually cool better if those fans are carefully placed.  Exhausting out the top is purely a benefit when you are using water cooling so you already moved the heat to the exhaust location.

[RevGAM]

In order to accurately answer that, it's important to know your setup and see a photo. There is more than one way to set it up, and sometimes negative is best even when you don't have an AIO. I have my case full with positive pressure and it never gets too hot, but some cases and setups do better with negative. 

 

Having a full case of fans can also decrease noise. 

 

Yes with negative you'll have to dust your PC more often. You could, I suppose, build your own filtration box for all your intakes. https://engineering.ucdavis.edu/news/science-action-how-build-corsi-rosenthal-box

 

Also, there are more intricate fan configuration that work with the airflow instead of against it. @TeraSeraph did a great experiment on that. 

[freeagent]

I almost never use my top fans as exhaust, if I even use them. I almost always run a positive pressure config. Meaning more intake than exhaust, as I let the vents release the pressure. Because chances are, you won’t be able to vent the GPU fast enough. The laws of convection don’t apply to computers because they have fans. Fans change everything.

[GSTARR]

1 hour ago, RevGAM said:

In order to accurately answer that, it's important to know your setup and see a photo. There is more than one way to set it up, and sometimes negative is best even when you don't have an AIO. I have my case full with positive pressure and it never gets too hot, but some cases and setups do better with negative. 

 

Having a full case of fans can also decrease noise. 

 

Yes with negative you'll have to dust your PC more often. You could, I suppose, build your own filtration box for all your intakes. https://engineering.ucdavis.edu/news/science-action-how-build-corsi-rosenthal-box

 

Also, there are more intricate fan configuration that work with the airflow instead of against it. @TeraSeraph did a great experiment on that. 

@Alex Atkin UK

 

Thanks for the input guys! I do have an AIO, a 280mm that im currently using as an exhaust up top. I provided pictures of the setup, but didnt think to include that tidbit as he's sitting on the counter after being cleaned

 

It seems though, even without that information, that both of you are leaning towards negative pressure.

 

A) Would your mind change if I added a 360mm radiator in the future (probably not, I think yalls logic would say watercooling justifies more exhaust fans)

 

and B) Is the only solution for the bottom left of the case to get more air to have positive pressure?

[GSTARR]

3 minutes ago, freeagent said:

I almost never use my top fans as exhaust, if I even use them. I almost always run a positive pressure config. Meaning more intake than exhaust, as I let the vents release the pressure. Because chances are, you won’t be able to vent the GPU fast enough. The laws of convection don’t apply to computers because they have fans. Fans change everything.

Could you explain what you mean by vent the gpu?

 

Do you mean supply it with enough new air, instead of drowning it in a current of air that it cant grab?

[Alex Atkin UK]

1 minute ago, GSTARR said:

@Alex Atkin UK

 

It seems though, even without that information, that both of you are leaning towards negative pressure.

 

A) Would your mind change if I added a 360mm radiator in the future (probably not, I think yalls logic would say watercooling justifies more exhaust fans)

 

and B) Is the only solution for the bottom left of the case to get more air to have positive pressure?

Well for cooling the CPU, pulling air directly in through the radiator rather than out will run cooler.  Ideally you have the radiator on the front as an intake but I assume that case doesn't allow it.  I'd always favour positive pressure, just now how you had it in the diagram.

[freeagent]

Just now, GSTARR said:

Could you explain what you mean by vent the gpu?

 

 

The GPU heats up while you are in game right? People do not like noise and from what I see they try to run their systems as quietly as possible. Doesn’t work for high performance systems though. So if you flood the chamber with cooler air, you can at least cool the GPU air before it gets exhausted from the main chamber before it can affect your other components negatively.

[GSTARR]

Just now, Alex Atkin UK said:

Well for cooling the CPU, pulling air directly in through the radiator rather than out will run cooler.  Ideally you have the radiator on the front as an intake but I assume that case doesn't allow it.  I'd always favour positive pressure, just now how you had it in the diagram.

Technically the case does allow it, but years ago I watched jayztwocents and gamers nexus discuss AIO placement and where the air bubble in an AIO ends up, and I believe I decided that putting it in the front leaves the bubble right on the pump. I'll have to put it in again and see where it sits.

 

Thanks for your help!

[GSTARR]

1 minute ago, freeagent said:

The GPU heats up while you are in game right? People do not like noise and from what I see they try to run their systems as quietly as possible. Doesn’t work for high performance systems though. So if you flood the chamber with cooler air, you can at least cool the GPU air before it gets exhausted from the main chamber before it can affect your other components negatively.

I see what you're saying - but I wasnt aware that GPU airflow actually goes out the back. I thought the GPU fans just throw air up into the heatsink, and the slots on the back of the card are just one of the many escape routes...

 

I.E. some of the hot air escapes, and some of the hot air stays in your case

[Alex Atkin UK]

2 minutes ago, GSTARR said:

Technically the case does allow it, but years ago I watched jayztwocents and gamers nexus discuss AIO placement and where the air bubble in an AIO ends up, and I believe I decided that putting it in the front leaves the bubble right on the pump. I'll have to put it in again and see where it sits.

 

Thanks for your help!

If the pump is higher up that the top of the radiator yes, also the recommendation that the pipes should be at the bottom (so the air pocket isnt where the pipes enter the radiator) which can be tricky to reach.

[freeagent]

1 minute ago, GSTARR said:

I see what you're saying - but I wasnt aware that GPU airflow actually goes out the back. I thought the GPU fans just throw air up into the heatsink, and the slots on the back of the card are just one of the many escape routes...

 

I.E. some of the hot air escapes, and some of the hot air stays in your case

It doesn’t, it will spread out to cover all of your components. Good airflow is important for that reason. I don’t game much, but I do run distributed computing like F@H, and WCG. In turn my system will be at full load for extended periods of time. And always highly overclocked because stock sucks.

[Alex Atkin UK]

2 minutes ago, GSTARR said:

I see what you're saying - but I wasnt aware that GPU airflow actually goes out the back. I thought the GPU fans just throw air up into the heatsink, and the slots on the back of the card are just one of the many escape routes...

 

I.E. some of the hot air escapes, and some of the hot air stays in your case

Most GPUs 99% of the airflow goes into the case, the vent on the back is just to allow any minor air leakage to escape, not to actually actively vent out there (except in blower or hybrid cards like the NVIDIA FE models).

[thrasher_565]

3 minutes ago, GSTARR said:

Technically the case does allow it, but years ago I watched jayztwocents and gamers nexus discuss AIO placement and where the air bubble in an AIO ends up, and I believe I decided that putting it in the front leaves the bubble right on the pump. I'll have to put it in again and see where it sits.

 

Thanks for your help!

you want the rad higher then the cpu block so if there a bubble it will sit at the top of the rad then in the cpu block.

tubes up or down dont matter with an aio. on custom loops the thory was one way made it harder to get the bubbles out and was a bit harder to fill the loop but once filled and air bubble out dose not matter. all you need to do is have the res above the pump. and not have the cpu block the highest point.

 

i guess with an aio and an bubble you want tubes down so you can trap the bubble up top in the rad i guess.

[RevGAM]

• If you front-mount the rad with the tubes at the top, make sure they come out of the bottom of the pump block.
• If you front-mount the rad with the tubes at the bottom, make sure they come out of the top of the pump block. This config is supposedly slightly cooler.
• A front-mounted AIO on intake, as counter-intuitive as it seems, will lower the temps more than if it is on exhaust or on top. Is it a significant difference? Yes. Unfortunately, that would limit you to a 240 or 280mm rad, which isn't ideal, so it'd be best to top-mount it.
• Jay did a video where he felt negative pressure is bad. Why? Dust. If you don't mind having to clean dust out more often, then get an appropriate blower tool instead of canned, compressed air. Some cases and setups function better with negative pressure, but I think that more are designed with positive pressure in mind.
• If you want it to be positive but follow the negative plan in your negative airflow jpg, put more powerful fans on intake and weaker ones on exhaust.

How much space is under the case? I can see that it's elevated by the legs. 2"?

Can you replace the glass door with the one from the 730t? That'd give you more airflow.