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H150i PRO Push/Pull and Control Questions


marlomiranda
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I am running a 9900k on an Aorus Ultra MB inside a Corsair Crystal 680x Case. I have the 150i Pro set up in front with 6 LL120 fans set up in push pull configuration as intake. Additionally I have 2 LL140 fans on top as intake and 2 LL140 fans on bottom as exhaust and 1 LL140 in rear as exhaust. I have the LL 120s being run by a CoPro and the other 5 fans run by a second CoPro. I felt that I wanted exact control of Push/Pull Fan speed to keep them balanced-reasoning that we wouldn't want either push or pull being stronger. I recently figured out how to set up custom fan curves and all 11 fans are on the same curve based on CPU temp with all fans maxing out at 70C. So far so good but getting ready to start OC and want to make sure I am on the right track. Did some cinebench testing to test my curves and temp on the CPU which maxes out at about 75C-77C running Cinebench 20 in back to back tests. I have left the pump speed alone assuming that the software will bump pump speed if the coolant temp hits around 80C?? That is the great unknown as no research gives me any inside info on when the pump will actually go up and I never hit that kind of temp on my coolant. Would you recommend any changes?
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Your typical coolant temp range will be about +4-7C over your ambient room temperature at idle. Load temps will vary with fan speed, but should be about +8C at max load with a fan speed around 1300 rpm. This means you should not break 40C unless your room temp is near 30C.

 

The Pro has an ultra low "quiet pump mode" of 1100 rpm. This is substantially slower than most other AIO coolers allow you to run. It is meant for quiet desktop work. You will pay a temperature penalty for leaving it there at load. Other H150i owners report an extra 6-8C in addition to normal load swings. I would recommend you set it to balanced (2160 rpm) anytime you need to do something more strenuous for an extended period of time. You are welcome to use the highest Extreme setting as well, but most users report a 0-1C improvement. Flow rate is a problem when it is too low, but there aren't benefits to increasing beyond a certain point.

 

You really should move off of the CPU temp control and back to coolant temperature (H150i Temp). I understand it takes some getting used to, but the fans and flow rate do not cool the CPU. The cold plate on the CPU block physically conducts heat away from the CPU. That is how the CPU is cooled. You don't have any control over that rate of heat transfer. It's all about voltage and materials. Your cooler (air or water) takes that transferred heat and moves it somewhere else. If it does not, then the accumulated heat build up is added back to the CPU. For water cooling, +1C coolant temp equals +1C CPU temp. The same is true in reverse for cooling it down. You can blast your fans at 3000 rpm, but if the coolant only goes down 1C, you only reduced your CPU temp by 1C.

 

As noted above, the typical max load coolant temp delta is only going to be about 8C. Probably less for normal mixed loads. That means the most you can possible reduce the CPU temp with any setting is 8C back to room temp. In reality, you can't get there and a coolant delta of around 3C is about as low as it you can go with a closed system. This means you are generally making small adjustments to the temperature through the fan and pump settings, with the notable exception above.

 

When you run from CPU temp, all those case fans are ramping up and down attempting to respond to something they cannot affect directly. Stage 1 heat conducted in. Stage 2, heat is dumped out. As long as you keep taking out the heat at the same rate it is added, the coolant temp stays the same. If more heat is added than removed, the coolant temp goes up and the fans speed up to keep pace. Slow and steady wins. You can't cool the system by having the fans blast to 1500 rpm for 3 seconds and then slow down.

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There's a discussion of fan curves and temperature in the AIO FAQ linked in my signature. Start with that.

As c-attack said (and as you'll see in the FAQ), you should use the coolant temp for control. The fans don't cool the CPU (not directly) ... they cool the coolant. The coolant cools the CPU. Cooler coolant == cooler CPU. And modern CPUs have wildly varying temperatures - they'll spike 30-40C in a matter if milliseconds when you add load.

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Thank you both, making more sense to me. I have been reading a lot of what both of you write and never could have figured out the CoPro's without what you guys have written about it. Why is Corsair so discrete about putting useful info out there? Without this forum, many of us would be sunk. That said, I just was not really sure I wanted to take fan control directly away from the AIO but have heard tons of negatives with fan balance in push/pull setups. I almost pulled the trigger on a more advanced cooling system but wanted to try this first. Do you think my fan setup makes sense? If not what would you change?
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Don't overthink the push-pull arrangement too much. The advantage of push-pull is the pressure stacks between fans. This makes an otherwise average or poor radiator fan quite good. When running mis-matched blade types or some other unusual circumstance with high fan speeds, you might need to really dial in opposing fan sides on the radiator. However, in my experience with LL and QL fans, this is unnecessary. Both are very compliant with other fans types and each other. You can set them to identical speeds. If one side seems louder to you, drop it by 100 rpm. This can be caused by fan interaction, but with matching fans more likely by a secondary surface like the case grills, etc.

 

However, all of the above is nit-picking. With push-pull, you should be able to them run at 700-1000 rpm and not need more, except for very long duration CPU loads. 1300 rpm should give you a +9C delta for 300W and the 9900K overclock should be a good 75W less than that. This means most of the time you will see a coolant temp rise of 5-8C. This can be quiet and efficient.

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just to add to this. and slightly off the og topic...... re simplifying syncing the 6 fans in push/pull config..

 

using one of these..

 

Carbide 678C 6-port PWM Repeate (click me)

 

you can do this sort of stuff..

 

http://i.imgur.com/lxZv62Wl.png

 

buy using one of the repeater hubs for the 6 fans on the H150i rad you would see them all as one single fan in iCUE. they would all spin at the same speed and react at the same time. so easy to configure... that would cut you down to one commander pro for the other case fans....

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  • 2 weeks later...
Thank you very much, I have the fans all running according to coolant temp now and did some mild OC to 4.9ghz at 1.275 volts. Running Prime 95 and small fft's the CPU temp never goes above 85C. Using Cinebench 20 never goes above 75C. The fans are all running on the same custom curve and I just leave the pump on balanced (2070rpm). Zotty, I appreciate the info on the pwm repeater, I think had I known I would have done that rather than what I did with the 2 CoPro's but as they say, you don't do enough research before you build you learn the hard way!! Thank you all for all your incredible help. I am searching for more answers and trying to get the courage to step out and build my own youtube channel to help simple folks out like myself that just need safe tips on building. It seems like for an average guy with an average budget and knowledge, its pretty hard to find. Its cool to watch all those guys build machines with the latest and greatest but that really is n/a to me. I had to wait until the perfect time to purchase my 9900k (right as the 10900 came out) to save money and I still don't have the GPU I really want. Thanks again guys!! You are all amazing.
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