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Fans connected to H100i v2 have different speeds than the rest


bgunn925
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I have 6 identical case fans (LL120's). 4 are connected directly to a Commander Pro and the other 2 connect to the H100i v2 which then connects to the Commander Pro via a single cable. I am using Link (fully up to date) to control all fans with the same (Quiet) fan curves and all fan control has been disabled in BIOS. The two fans attached to H100i v2 don't seem to follow the fan curves... For example, right now my computer is at 50% load and the CPU Package temp is ~56C. Based on the fan curve, all 6 fans should be at ~1500 RPM -- the 4 fans connected directly to the CLCP are at the correct speed. However, the two fans which connect directly to the H100i v2 are only running at ~970 RPM. By looking at the logos on the fan hubs, these number appear to be accurate as these two fans are clearly spinning at a slower speed. Is there some way to fix this? It is problematic because as my CPU temp rises, the other 4 fans kick up but the 2 fans with the largest contribution to lowering the CPU temps do not, giving me extra noise without the full gain in cooling power. I suppose I can bypass the H100i v2 completely and plug these two fans directly into the CLCP if all else fails.
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The H100i v2 internal fan controller is responsible for the two radiator fans in this configuration. Best guess is even if you "group" all 6 fans into one control scheme, the existing controls for the H100i v2 may override them until you directly instruct it otherwise.

 

Click on the H100i v2 fan speed in the Main panel in the H100i v2 Box. That should bring up the control curve for the radiator fans. It may be possible to copy the other fan curves onto the radiator fans or vice versa, but I am not sure you really want those sets of fans in sync. The radiator fans by default will respond to changes in coolant temperature (h100i v2 Temp). This is how the cooling system actually works and they do not need to respond in real time to changes in CPU temp. Generally steady speeds work just fine for case fans as well, but they have a different purpose and they need more speed if you want to increase your air turnover rate. You only need to do that when the case starts getting hot and most often that is from long duration GPU load, not CPU load. Regardless of what you decide, the CPU end temperature is only affected by changes in the coolant temperature, plus or minus. So if you only have a +6C coolant delta, you can only reduce your CPU temp by 6C at any fan speed. In reality, you might be lucky to a 2-3C reduction at absolute maximum and most people consider that a bad trade for the noise. Radiator fans tend to be louder in comparison to case fans because of the increased resistance the pathway. No reason to run them faster than needed.

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Edit.. beat me to it c-a lol......

 

hi bud.....

 

Firstly... set the H100i v2 to liquid temp for fan control. far more stable than cpu package, Cpu readings will have your fans revving up and down.. as for matching fan curves,, can be tricky as you have one for the fans connected through the Commander and then one for the H100i.

 

i had this very issue due to having my h100i as Push/pull and 2 of the fans running off the commander... took me a while to match rpm's/curves between the push and the pull fans... also the fans on the rad will run a tad slower due to being restricted by the rad's airflow ;)....

Edited by Zotty
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The H100i v2 internal fan controller is responsible for the two radiator fans in this configuration. Best guess is even if you "group" all 6 fans into one control scheme, the existing controls for the H100i v2 may override them until you directly instruct it otherwise.

 

Click on the H100i v2 fan speed in the Main panel in the H100i v2 Box. That should bring up the control curve for the radiator fans. It may be possible to copy the other fan curves onto the radiator fans or vice versa, but I am not sure you really want those sets of fans in sync. The radiator fans by default will respond to changes in coolant temperature (h100i v2 Temp). This is how the cooling system actually works and they do not need to respond in real time to changes in CPU temp. Generally steady speeds work just fine for case fans as well, but they have a different purpose and they need more speed if you want to increase your air turnover rate. You only need to do that when the case starts getting hot and most often that is from long duration GPU load, not CPU load. Regardless of what you decide, the CPU end temperature is only affected by changes in the coolant temperature, plus or minus. So if you only have a +6C coolant delta, you can only reduce your CPU temp by 6C at any fan speed. In reality, you might be lucky to a 2-3C reduction at absolute maximum and most people consider that a bad trade for the noise. Radiator fans tend to be louder in comparison to case fans because of the increased resistance the pathway. No reason to run them faster than needed.

 

Thank you very much for that detailed response, it was extremely enlightening. Adjusting the fan curve for the "H100i v2 Fan" was definitely the missing piece to the puzzle. It's a little weird though, it seems that these two fans are being controlled both by the H100i controller and the CLCP. If I adjust them like I would the other four, I can bring them to a stop. But setting the H100i on Performance sends them to max RPM. The two inputs must be modulating each other in some way -- I'm going to play around with it later.

 

That makes sense regarding which temperature to use for feedback control. Obviously increasing the pump and radiator fan speeds will lower the coolant temperature more quickly, but I agree that's a poor noise tradeoff. I switched everything from CPU Package to the H100i temp and my ears are thanking me. I haven't seen any increase in CPU temps, either, and I've been running some simulations in a vm for about 14 hours now so the load has been pretty constant). Although,I'm not really sure what to do with the other case fans, now -- just leave them on fixed RPM?

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Edit.. beat me to it c-a lol......

 

hi bud.....

 

Firstly... set the H100i v2 to liquid temp for fan control. far more stable than cpu package, Cpu readings will have your fans revving up and down.. as for matching fan curves,, can be tricky as you have one for the fans connected through the Commander and then one for the H100i.

 

i had this very issue due to having my h100i as Push/pull and 2 of the fans running off the commander... took me a while to match rpm's/curves between the push and the pull fans... also the fans on the rad will run a tad slower due to being restricted by the rad's airflow ;)....

 

I wish I would have thought of that sooner; the H100i temp was so much lower than the CPU Package that I didn't think it would be aggressive enough at keeping the CPU temps down. Before switching to LL120's I had seven SP120's synced to the CPU Package and the revving up and down was driving me nuts.

 

I'm planning on doing push/pull but I'm in a 460x with a front mounted radiator and super long ROG Strix GPU and there just isn't enough room to use standard case fans. I'm in the process of finding some black slim fans to use behind the radiator; I'm thinking maybe the easiest approach would be just use fan splitters and force each pair of push/pull fans to operate in sync?

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Although,I'm not really sure what to do with the other case fans, now -- just leave them on fixed RPM?

You can ... it really depends on your system and your cooling needs.

You do want airflow in there. But ... your CPU isn't the biggest generator of heat inside the system, thanks to to the cooler. If you have a air-cooled discrete GPU, that would be it. With the Commander Pro, you've got options ... four temperature sensors that you can place around your system and use as your control variable for fan speeds. For my case fans, my primary control variable is a temp sensor just above my dGPU ... the GPU will warm up other parts of the case, particularly my NVME drive if I don't keep the air flowing. I also have a sensor at the radiator intake, radiator exhaust and the lower part of the case. It does make for an interesting fan curve because the temperature range isn't all that much. I find that, with the number of fans that I have, I really don't need more than 1000RPM out of my case fans - usually less.

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I'm in the process of finding some black slim fans to use behind the radiator; I'm thinking maybe the easiest approach would be just use fan splitters and force each pair of push/pull fans to operate in sync?

 

Don't worry about keeping the fans exactly in sync. It isn't necessary and the airflow is never that smooth to point where it would matter. I actually prefer to run the back side exhaust pair a bit slower than the push intake side. Often the tone is improved with no measurable difference in cooling. Each case environment is unique, so you can play around and see, but don't worry about having all 4 fans locked in step.

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