3 Questions - Case Fan Setup and AIO Water Cooling

Hey,

Just got a new case (Fractal Design Define S - through the Hexus competition!), and had three questions.

1) For the case fan setup, I want to go for positive pressure - mainly to avoid dust build - so I am thinking of 3 x intakes (FD Venturi HF-14 fans running at 7V, 78.5 CFM each) and then a single exhaust (FD Dynamic GP-14 running at 12V, 68.4 CFM). There are plenty of holes for air to escape out of (e.g. vented PCI slots), so will this be OK?

2) The PSU is designed to be mounted with the fan sucking cool area directly from under the case. There is a dust filter underneath, but I was thinking it would be better to flip it around and have it suck air from inside instead (there will be plenty of fresh air from the 2 x intakes).

3) At the moment, I am using a Zalman CPU cooler, which has a nasty whine when it ramps up. Quiet running is a priority, so I'm wondering if I should switch out for a low end AIO? I do want to overclock the CPU (target 4.33 GHz), if that makes a difference.

PC spec is the desktop in my sig (old machine!) - any advice appreciated!

Cheers,

Su

Come on Hexites, you must have something for me?! :p

All in ones aren't noted for being particularly quiet so you're probably best off swapping to a different air cooler.

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Originally Posted by Sumanji

Hey,

Just got a new case (Fractal Design Define S - through the Hexus competition!), and had three questions.

1) For the case fan setup, I want to go for positive pressure - mainly to avoid dust build - so I am thinking of 3 x intakes (FD Venturi HF-14 fans running at 7V, 78.5 CFM each) and then a single exhaust (FD Dynamic GP-14 running at 12V, 68.4 CFM). There are plenty of holes for air to escape out of (e.g. vented PCI slots), so will this be OK?

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I can't see how push vs pull makes any difference to dust build up. Dust is in the air - for the same volume of air movement you surely get the same amount of dust. Only way to prevent dust is filters and regular cleaning.

However, that sounds OK, presuming the exhaust is near local hotspots (ie in line with CPU cooler.

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2) The PSU is designed to be mounted with the fan sucking cool area directly from under the case. There is a dust filter underneath, but I was thinking it would be better to flip it around and have it suck air from inside instead (there will be plenty of fresh air from the 2 x intakes).

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Always better for the PSU to take cooler air from outside rather than internal air, helps with efficiency and fan speed etc.

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3) At the moment, I am using a Zalman CPU cooler, which has a nasty whine when it ramps up. Quiet running is a priority, so I'm wondering if I should switch out for a low end AIO? I do want to overclock the CPU (target 4.33 GHz), if that makes a difference.

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Just change the fan on the CPU cooler! :p See what the temps are like on the overclock first with the existing set up, then only if they're too high consider using the money on a better tower cooler - AIO maybe, if going for high voltage as well, but I've never had a problem with a good tower cooler and considered airflow (particularly case exhaust in line with tower).

I am using a R4 (very similar case) and have previously run it with the two original fans on the front and a Noctua 140mm on the back - the dust filters do their job very well and no temperature improvements what-so-ever.

Now running original fans one front intake/one rear exhaust (Turned down to low setting on rear speed controller) with an overclocked 5820K@4.4Ghz on a D15 temps max out at 69oC but more usually 65oC - This is with fan profile set to Silent i.e. CPU fans running silently at around 600rpm. No PSU airflow as I'm using an Corsair AX760 where the fan doesn't switch on until around 400W load so silent.

I agree with the other posts get yourself another fan (or two) for the cooler and Enjoy The Silence...

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Originally Posted by kalniel

I can't see how push vs pull makes any difference to dust build up. Dust is in the air - for the same volume of air movement you surely get the same amount of dust.

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In a positive pressure setup, you have more intakes than exhausts (e.g. the 3 in, 1 out that I'm suggesting). Since cases aren't airtight, this means that any airflow through case gaps (e.g. vented PCI slots) will be outward due to the forced pressure differential. Assuming all your intake fans are behind dust filters, this should minimise the build up of dust inside the case.

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Always better for the PSU to take cooler air from outside rather than internal air, helps with efficiency and fan speed etc.

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Yeah I get this, but I guess it's the dust-o-phobic in me that wants to avoid sucking in crap from underneath the case :p

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Just change the fan on the CPU cooler! :p See what the temps are like on the overclock first with the existing set up, then only if they're too high consider using the money on a better tower cooler - AIO maybe, if going for high voltage as well, but I've never had a problem with a good tower cooler and considered airflow (particularly case exhaust in line with tower).

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Changing the fan would the easiest option, but not such a simple task on the Zalman cooler I'm using unfortunately... I've been reading good things about the Cooler Master 212 though, and it seems I can pick one up for just $20, so may give that a shot. The AIO I'm looking at is $90, so that's a huge delta, especially with such an old system.

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Originally Posted by Gronich26

This is with fan profile set to Silent i.e. CPU fans running silently at around 600rpm. No PSU airflow as I'm using an Corsair AX760 where the fan doesn't switch on until around 400W load so silent.

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Nice, 600rpm = bliss! Planning to run all fans at <7V, so hopefully I can replicate your noise results! :)

Cheers,

Su

Ok a few things for you.

You're correct about positive pressure reducing dust, IF the intakes are filtered, although there is more than just that.
kalniel is correct in that the amount of air flow will effect the dust levels, then more air that gets pulled through the more dust is getting pulled in regardless of the setup.
And there is a minor issue in that all the dust is being focused into just the filters on the intake fans any other filtered vents/fans is just going to hinder overall air flow. (not much but it does depend on the filters and vents.)

Which zalman cooler have you got? any 92mm fan (or smaller) based cooler will get a bit "whiny" when the fan ramps up.

You also need to consider air flow path through the case for fan layout and positions within the case.
This can also have a major effect on noise.

Environment is also another major factor in terms of noise, cooling and dust.
eg A pc on the floor under your desk will generally sound less noisy than if it was on top of your desk, this is simply because it's farther away from and the sound will have a less direct path to, your ears.
However it will tend to pick up more dust as dust settles on the floor and gets stirred up as you move around the room.
Pets and carpet also tend to create higher levels if air born particulates.

For bottom mounted psu's dust isn't generally a major issue esp with a fliter, although standing a case on carpet isn't great for bottom mounted psu's.
Standing you pc on a chunk of wood or something else that lifts it off the floor can have a major impact on dust levels.
That said, there is generally no harm in having the psu upside down and pulling air from inside the case.
Yes the air will be a bit warmer, but not overly so especially from lower down inside the case.
Remember your two main heat sources are the cpu and gpu, the heat from these tend to rise and pool in the top of the case.
This is in part why bottom mounted psu case design is more popular these days, you're removing the psu from a major heat build up area and having exhaust fans/vents in the top of the case help get the warm air from the cpu and gpu out of the case as quickly as possible.
It's also why in a bottom mounted psu layout case a negative pressure setup tends to give better cooling results as you're pulling the warm air out of the case more quickly giving it less time to transfer that heat into the case and other components.
Although top mounted vents allow sound to escape more easily esp with fans on them, so have greater potential of becoming a noise issue, with that case you've got the option of covering the vents to reduce noise or leaving them open for added cooling/ventilation.

Noise, airflow and dust are things that are a fairly complex combination of multiple factors and environment is often a major factor in that, this means any advice can only ever be general not specific.
Depending on what it is you're trying to do and to what level you're trying to chase things too, often the best answer is to experiment for yourself, try it one way see how well it works, then try it another and see what effect it has.
For something like dust you'd probably have to run your pc in one setup for a month or so in each setup to get a solid idea as to how well it's working.

My guess is you're planning 3 fans at the front as intake and the one on the rear as exhaust? or are you thinking fans in the top as intake?

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Originally Posted by Sumanji

For the case fan setup, I want to go for positive pressure - mainly to avoid dust build

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You won't ever avoid it. Just reduce it.
Better to clean the case out regularly. I like a monthly clean-out, but I'm funny like that.

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Originally Posted by Sumanji

There are plenty of holes for air to escape out of (e.g. vented PCI slots), so will this be OK?

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Depends on how the airflow runs in your case and where these holes are. If you have any particular dead zones, the dust will pack into these.

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Originally Posted by Sumanji

The PSU is designed to be mounted with the fan sucking cool area directly from under the case. There is a dust filter underneath, but I was thinking it would be better to flip it around and have it suck air from inside instead

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There is a whole argument about not drawing warmer air in, regardless of how cool your system is and how good your PSU is.
I prefer to focus on what a PIG these things are to clean out and remember that drawing air from inside the case will also draw in more dust. If the PSU intake on your case has a dust filter, why not take advantage of that and just give it a quick clean occasionally, while placing the case in a lower dust location?

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Originally Posted by Sumanji

At the moment, I am using a Zalman CPU cooler, which has a nasty whine when it ramps up. Quiet running is a priority, so I'm wondering if I should switch out for a low end AIO?

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Is that the cooler itself, or the fans making that noise?
If the latter, change the fans. If the former, just compare user reviews and pick whichever one sounds quietest, I guess. I personally like the Corsair AIO ones and Noctua for air coolers.

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Originally Posted by kalniel

I can't see how push vs pull makes any difference to dust build up.

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Push traps more dust between fan and rad due to the turbulence. The air spirals out of the fan and then bounces back and forth against itself as it finds its way to a straighter route through the rad fins.
Pull will pull air in a straight line through the rad and then spin it round through the fan to billow out the exhaust, so trapping less dust.
Plenty of test videos online, where a month of Push traps about 4-5 times as much dust as Pull. Linus did a nice one, IIRC...

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Originally Posted by Sumanji

Since cases aren't airtight, this means that any airflow through case gaps (e.g. vented PCI slots) will be outward due to the forced pressure differential.

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I find having those few exhausts working with the general airflow paths works better than bouncing the air around until it finds an escape route, as that's often like having baffles in a silencer.

1/ That will be fine as long as all your intakes are filtered and your passive exhaust and fan will be fine to make positive air pressure.

2/ I'd honestly just recommend having your psu facing down unless you are putting it on carpet, but if there is sufficient gap under the pc just face it down because although there will be a lot of fresh air coming into the case from the front presumably if you are using a gpu it will most likely be putting out hot air right next to the intake for the psu which isn't great.

3/If you want silence I'd honestly recommend an air cooler, but if you plan to overclock or just want the cpu running super cool just for ease of mind I'd say get one of those new nzxt aios (x31, x41, x61) which have a variable speed pump which will be essential for quiet operation as the pump will also turn down when the pc is idling or doing small tasks. But if you want an air cooler go for any noctua cooler they have one for every need whether you need your cpu to be super cool to overclock with or if you just need silence and have no intention to overclock. It's honestly down to your own needs :D

Hey guys,

Thanks for all your replies. I ended up going with the original case fan arrangement (3 in, one out), stuck the PSU the normal way (sucking air from underneath) and just sticking with the current Zalman cooler.

The problem I ran into was the noise! Even at 7V (~900rpm) the Venturi intakes were hellishly loud - although moving a tonne of air, to be fair. Temperatures were pretty great as you can imagine, but quiet running is a priority so I needed to take action!

I just installed an NZXT Grid+ fan controller, and I have to say it's a really great piece of kit. At idle temps I have all the intake fans running at 20% (just over 500rpm). I also hooked up the CPU fan to the Grid+ rather than have it PWM controlled via the motherboard... at idle the fan now runs at 450pm, rather than the PWM minimum of 1300rpm.

Absolute bliss* - temperatures are pretty great as well, so it's a job well done :)

Cheers,

Su


*Except now the vibration of my secondary HDD is very audible... SSD time?! :D