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Which fans/pump to use – 2xgpu 1xcpu lownoise?

post #1 of 6
Thread Starter 
I am planning to put together a watercooled desktop ‘soon’. I’m using the Mountain Mods Ascension case (I have a spare one from a previous build) and plan to bolt radiators to the back, so space is not an issue. I would rather go with extra radiators, with slower, quieter fans rather than a maximally efficient loud loop. I would like a single loop system, with 2xGTX1080 (factory overclock only) 6900X CPU (moderate overclock, 3.8-4.0 GHz), 2x Nemesis GTX 4x120 radiators, 1x Nemesis GTX 3x120 radiator (radiator overkill = slower fans). Ideally, I want the system to be low-noise, with the fans hitting around 25 dB total (lower is better, but this might be the realistic floor), and single loop, with the ideal loop as reservoir->pump->CPU->4x120 radiator->gpu1->gpu2->7x120 radiator (4x+3x)->reservoir. The minimum flowrate should be a reasonable 1 GPM. I have some ideal choices for fans and a pump, but might have to go with second choice if they can’t handle it:

First up, what pump should I use?
Ideally, I’d want to use a single MCP655 pump, tuned to around 70% power for noise control. Unfortunately, with 2 GPUs, a CPU, and 3 mid-restriction radiators, I’m not sure a single pump’s going to cut it and get 1GPM at this restriction level. The MCP50x has the power, but not necessarily the flow rate, and seems a bit loud. The MCP35x2 or EX-XTOP Revo Dual D5 are definitely options, but 1) seem like overkill and 2) have PWM speed management, which means I really have no control over the pump noise, when compared to a pump I can dial in manually and leave alone (trust in my motherboard to make everything nice is not a happy option). Can I get away with a single MCP655? What if I don’t use the Revo dual top and instead put two 655’s in series (reservoir->pump->pump->cpu) both tuned to 50-75%? Would that work, or am I really not getting much extra there? If I absolutely have to, I know I can split this into two loops with a 655 on each, but I’d really rather not. I’d also much rather have larger, quieter pumps (D5) than small, noisy ones (50x).

Next up: fans
There are 15 case slot fans (6 front going in, 6 back going out, 3 top going out) and 22 radiator push-pull fans (11 slots, going into the case). This leaves the case at positive pressure (6in, 11radblockedin, 9 out), but that’s fine with me because 1)I hate cleaning dust and 2) the case fans/pressure don’t matter too much, as the real cooling is done via the external bolted-on radiators, which aren’t going to care about internal case temperature as long as there’s airflow. 3) Did I mention dust?
Ideally, I’d like the 37(!) fans to hit about 25 dB total or lower (which isn’t happening, but hey, I can dream).

The fans I’m eyeing for this are:
22x Noctua P12 w/ULN @ 1.21 pressure, 900 RPM, 37 CFM, 12.6 dB in push pull on radiators
15x Noctua S12 2/LN @ 0.73 pressure, 900 RPM, 49 CFM, 11 dB on case (with a filter over the front 6 for dust control)
This gives be about 28 dB total noise 10*Log10(22*10^1.26+15*10^1.1)=27.7ish which is pretty close to my goal.

I’m not sure if 900 RPM is enough for the radiators to cool 2 high-end GPUs and an mid-overclocked CPU though, even with the overprovisioning on surface area: If I have to, I can upgrade to:
22x Noctua F12 w/LN @ 1.83 pressure, 1200 RPM, 44 CFM, 19 dB in push pull on radiators
15x Noctua S12 2/LN @ 1.19 pressure, 1200 RPM, 63 CFM, 18 dB on case (with a filter over the front 6 for dust control)
Unfortunately, this will give me a bit over 34 dB of noise, or about 4-5 times as loud  Can I get away with the quieter fans?

As an aside, are there any good filters I could put on the input fan side of the radiators to help with dust control without excessively restricting airflow? Although I’d love to say I’ll be cleaning out the radiator fans every few months, in reality, I’ll probably be lucky to get around to it once a year, and dust happens. There don’t seem to be many filters designed to fit on top of radiator fans, sadly. I could cut some pantyhose/Swiffer filter to fit, but this might halve airflow, which might be an issue if I’m using the 900RPM fans? Ideas?

Thanks for the advice!
Zithras

Summary:
1)cpu, 2xgpu, 11x120 rad, can I use 1 MCP655 pump for 1 GPM? If not, what (quiet) pump(s)?
2)900 RPM push/pull @0.73 pressure okay for 11x120 radiators, or do I need up upgrade to much louder 1200RPM fans?
3) Any dust filters I could use with the radiators?
post #2 of 6
Thread Starter 
Update: most of the questions answered. I will use 2x655 Vario pumps with an EK Dual top, DCIMFlex radiator shields, single loop, with an inline flow monitor. Here is the remaining question:

I have a loop with 2 GTX1080 cards (factory overclock only) and 1 6900K processor (moderate overclock to 3.8-4.0Ghz). I am cooling it a 1 GPM with 11x120mm radiators (HardwareLabs Nemesis GTX 2x4 + 1x3) with fans in a push-pull setup, giving me a loop TDP of about 750W to dissipate.

I want to run 22x Noctua P12 fans in ULN mode (1.21 pressure, 37CFM, 900RPM 12.6DDB ea) to cool this. They will likely have DCIMFlex radiator shrouds over them (20% efficiency loss).
Will these fans be enough for this loop?

If I have to, I can upgrade to NF-F12s (1.83 pressure, 1200 RPM, 44 CFM, 19dB) but this is a last resort, as it will make the computer about 4x as loud, and I want a build as quiet as possible.

No, I don't want PWM fans or GentleTyphoon-15 1850 RPM fans.

Thanks for the help!
Zithras
post #3 of 6
22 fans is way overkill. You could probably cool 3 of these computers with what you have.

Push and pull isn't necessary and won't make enough difference to justify 11 more fans. Put one set of fans on it and you will be fine.
Edited by mtrapuzz - 7/11/16 at 4:29pm
post #4 of 6
You don't need that much cooling.

figure each 120x120 worth of radiator can cool 100 watts. With your radiator space, you could cool in excess of 1000 watts.

considering your cooling 2x1080's and a 6900k, your only cooling around 500watts. The lowest speed fans you can find will work just fine. I'd probably only rock the 2 480's and call it a day.
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post #5 of 6
For what it's worth, I have a single 140x4x80mm radiator with 8 high pressure bgears fans at full RPM, yes rather audible, BUT, the radiator and everything is actually outside (protected from rain/snow, but otherwise exposed to outside air quite readily) so it is silent to me since I don't hear it anymore in my room, and all the heat is dumped outside and not in an enclosed space where it will build up or make someone uncomfortable. With a ~700 watt load (820 on kill-a-watt, minus fans/pump and psu inefficiency), my coolant has gone up by only 6C after about 10 minutes and seems to have leveled off. Using furmark and unlocked GPU power to absolutely obliterate my GTX 980 (350 watt power draw!) and non-AVX prime95 28.9 on my 4.7GHz 5960x (package temperature reporting 90C at its highest) to produce the power draw. This is not a realistic scenario; your gaming power draw and heat dump will probably be an order of magnitude below this.

So with a decent radiator/fan setup, you should minimize coolant temperature increase under load (which is the point of radiator). You can probably maintain low noise easy enough if you are doing such modest/no overclock, depending on what sort of realistic load you are going to put it under. Could do what I do and have an external radiator with a long coolant tube, or you may need multiple radiators with low rpm fans. But really IMO, a single triple radiator will be more than enough for your target system IMO.

On-die temperatures comes down to the quality of the block used as well as choice of coolant. My on-die temperatures could be a little better if I used all distilled water, but I use a winter-ready mix of alcohol and water.
Edited by ssateneth - 7/11/16 at 5:13pm
post #6 of 6
Thread Starter 
Thank you for the replies, and for the advice; question answered - I'll definitely be going with the lower speed fans!
I might try starting with 11 for decreased noise and then swap to 22 if unhappy with the results. I totally realize the radiator area is overkill for what I'm using, but it let's me go really light on the fan noise, which is the idea here, and I have the space on the case to do it.
I'll be using distilled water, a killcoil, and a couple drops of PTNuke. Waterblock on the CPU will be the Supremacy EVO x99 (same as the standard one, but without all the extra backplates, because I can't use them anyways). TIM will be
GPU waterblocks still haven't come out, but I'll either use the EK blocks or the stock ASUS, depending on which has lower restriction probably.
TIM will be Prolimatech PK-3 - last build used IndigoExtreme, and really, unless you're in an OC competition or something, it's annoying to use and a bit overrated.
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