Too many fans?

[Pablosammy]

Hi all,

I'm moving back to air cooling, and wanted to run the above set up by you. I had a load of 140mm Noctuas from past builds and thought I might as well max out the cooling space, but I'm a bit worried it'll be self defeating.

That's a 3090 FE and a Noctua D15, which both dwarf the case.

There's two Noctua A14s at the front set as intake - one is directed underneath the GPU to feed the two fans, and the other is aimed at the CPU cooler. I'm hoping the exhaust from the GPU won't affect the CPU cooler too much.

The exhaust are 3 P14s. My main worry was about the top two exhaust fans. The left one doesn't look like it'll be doing much, and the right one could end up just exhausting cold air from the intake that could have gone through the cooler. Would you set the right one as intake? Or just not have them at all?

Obviously I'll experiment a bit when it's up and running, but there's a lot of variables so I thought it would be better to draw on experience!

 

[Pablosammy]

Cheers guys, make sense. I'll give it a go and see what works.

The other question I had was around recirculating flow. I've stuffed some foam in between the intake fans so it doesn't just draw it's own supply back to the suction.

If I lose the right top exhaust, it's it wise to block that vent with something, or is it better just to let the airflow do what it needs to do? Or again, is it just a case of test it and see?

 

[Pablosammy]

I flipped the front top exhaust to be a supply, and unfortunately it set up some horrible resonance with the cooler and sounded awful at anything over idle speed, so that's one idea out of the window. Putting a filter on the top reduced the noise a touch, but it was still unpleasant.

I've now removed both fans and fitted the solid roof to the case, and I've seen very little change in temps under load suggesting the roof fans were helping as much as they were hindering. The rear exhaust seems to be blowing much more efficiently than before, so I suspect the top fans were just messing with the airflow - although the rear one was removing heat, it was limiting the rear fan's effect.

In a full stress test, the CPU did get rather toasty. I suppose that's the effect of having a 350W heater sat just below it.

Thanks for the tips.

 

[Pablosammy]

thats interesting...have you got those rubber mounts installed to the case fans?

Yeah, all fans on rubber mounts. I checked they were installed correctly, but it wasn't the problem. There is a similar resonance at the rear exhaust, albeit a lot quieter, so the cooler seems like the common factor. I'd not come across anything like this before, but I couldn't eliminate it.

 

[Pablosammy]

I would try top vents open with no no fan .. assuming that is easy to try. It may lower temps a little.
I would remove the 3 unused PCIe back slot covers to increase rear venting around gpu to see it that helps.
Can you fit a 3rd front intake in? That would give you about 50% more case airflow and help push GPU & CPU heated exhaust on back and out rear vent and PCIe open slots much better, thus moving cooler air into both CPU and GPU coolers.
What speeds do front intakes run relative to CPU cooler fans and/or GPU cooler fans?
Below is link to simple guide of how I setup case airflow and optimize it, including how to monitor airflow temp into coolers vs room.
https://forums.overclockers.co.uk/t...-i-put-my-temp-sensor.18564223/#post-26159770

Cheers for that, I'll have a read. No room for a 3rd intake unless I drop to 120mm fans, and I run the front fans a fair bit faster than the rest to try and create a bit of positive pressure.

 

[Pablosammy]

Turn all your fans off except the rear exhaust, then set it to different levels and see what noises it makes.
I find some cases have unusual grilles on this mount, which doesn't always work with particular fans. One way to reduce this is to mount the fan on the outside (may require slight case mod for cable routing), ideally on rubber pins, and affix a second grille (Silverstone do good cheap ones, but rip out the plastic mesh first) over that fan's exhaust. It would also give you a touch more space between the CPU cooler and take it out of the airflow of the fan above, so should reduce the resonance too.

I don't really want to fit external fans for aesthetic reasons. I think you're right about the grill being part the issue, but the grill itself isn't vibrating.

I must admit, I'm tempted to get a Meshify S2 - I'm not particularly sold by this case (Bequiet Pure Base 500). I'll continue to play and see if I can get a setup I'm happy with.

 

[Pablosammy]

for the resonance try dropping or raising the rpm on the fans bit by bit. it You should be able to pick up the point where it quietens down. Just set your fan curve with a step that passes that rpm

It's odd, there's no particular resonant frequency, the noise is proportional to the fan speed. Maybe it isn't strictly resonance, but there is some interaction going on. More playing required.

 

[Pablosammy]

I think to be honest you're worrying a bit too much so long as you've got some forward->back->up airflow moving through the case thats all that matters really. I've no idea about resonance I've never heard of such a thing.

How are you finding the temperatures? I'm finding the 3090 dumps an awful lot of heat in the case no surprises there with the collosal power consumption and its totally overwhelmed my previous case fans/airflow setup the heat rising saturates the CPU and temperatures go through the roof I swapped out the air cooler with a liquid cooled AIO originally top mounted but that was no better due to the same heat so had to front fit the rad and swap the fans around to pull air in rather than exhaust it and that seems to have fixed it its gone from to 45/85c to 35/65c, much better. (Only trouble is had to ghetto mod the case to fit it in the front but oh well.)

The GPU temps are fine, it's quite efficient at removing it's own heat, but as you say it does warm the rest of the case fairly well! The GPU controls itself at 68 degrees under load whatever I do with airflow, the fan speed is the only thing that changes. Currently it maxes at 50%. I do have a mild undervolt though.

I've got my airflow fairly sorted now so it's staying relatively quiet and the CPU is okay, but as soon as a waterblock is released I'm going to do a custom loop.