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Hydro H75 Installation


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I recently bought a new PC from Chillblast that uses a Corsair Hydro H75 cooler.

The PC has an Asus Z170-A Motherboard.


I was unhappy with the noise from the cooling system. It was making what I can only describe as a growling noise that increases in frequency whenever the CPU load increases. The frequency varies constantly even when the CPU load only changes slightly. This makes the noise seem even more irritating.


I contacted Chillblast support but they were not at all helpful so I ended up doing some investigation myself. I would like confirmation from Hydro H75 experts that my cooling system and fans are configured correctly:-


At first I thought the noise was coming from the pump. The 3 pin pump connector is plugged into the CPU FAN socket on the Motherboard rather than the WATER PUMP socket.

The BIOS is configured with the CPU FAN in DC mode and with the default temp/speed profile. This means the pump speed will vary according to the CPU temp. It will run at 60% of full speed until the CPU temperature crosses the default threshold. After that it will ramp up to full speed as the CPU temp increases. I have read elsewhere that it is better if the pump runs at full speed all the time regardless of CPU temperature.


So my first set of questions are: Which socket should the pump be connected to on an Asus Z170-A MoBo? If it's the CPU FAN, then what speed/temp profile should be selected in the BIOS? Did Chillblast configure my system correctly?


After further investigation, I realised that the noise was actually coming not from the pump but from the two 120mm fans that sandwich the radiator on the rear of the case.

These fans are connected to CASE FAN 1 and CASE FAN 2 sockets on the Motherboard. The speed is linked to the CPU temperature. They have 4 pin connectors which indicates they are PWM controllable. However, the BIOS was actually configured for DC operation. In DC mode, the minimum low temperature fan speed is 60% of the maximum. This could explain why the fans were so noisy. In PWM mode, the fans can run at lower speeds at low temperatures.

After I reconfigured the BIOS fan mode to PWM for both fans, the noise level came down dramatically.

I also increased the delay before the fan speed ramps up after the CPU temp threshold is crossed. It was set to 0. I increased it to 12 sec. This reduces the variation in fan speed.


So my second set of questions are: What is the correct fan mode for the H75? Should it be set for DC or PWM? Also, what temp/speed profile should be configured in the BIOS for the Asus Z170-A? What is the best setting for the delay before the fan speed ramps up after the CPU temp threshold is crossed? Have Chillblast configured my system correctly here too?

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It sounds like you have done most of the legwork already.


1. Yes, the pump should receive 12v all all times. The Water_Pump header should provide this automatically, but you can double check that is set to DC mode and 100% (or Full Speed). That should also immunize it from sporadic changes AI Suite sometimes applies. it is possible to power the pump from a the PSU directly on another CHA header also set to Full Speed, but the water pump header is the logical choice.


2. Yes, the fans are 4 pin PWM. The BIOS is supposed to detect this automatically, but it does sometimes goof or someone may have overridden the choice when setting up your PC. Either way, set what ever header they are on to PWM. As you have seen, this dramatically expands the control range on Asus motherboards with BIOS only control.


My first choice would be to put both of these on the CPU & OPT header at the top of the board. However, I am guessing the H75 is in the rear slot and someone took the shortest run to the CHA_1 header just below. There are some pros and cons to this. The CPU header (and its twin OPT) have smaller delay intervals and the BIOS is programmed to control them in different ways. it always assumes you have a CPU cooler on the CPU_FAN. That header cannot be shut down. The delays are not essential and 12 sec is fine for water cooling where the fans cool the water, not the CPU directly. Just to make the choice complicated, both myself and other have noticed a change in behavior with radiator fans on the CHA_FAN header during the last six months. Fan delays programmed into AI Suite are now ignored completely. I do not know if this is a BIOS issue, Windows 10, or what. Those are the two commonalities and Asus denied any changes were made. Regardless, leaving the radiator fans on CHA_FAN might ignore your programmed delay. I haven't become irked enough to test the other headers, but it is not a problem with chassis fans set to VRM temperature.


You will need to tinker a little with fan speed to see what is an acceptable noise to performance ratio for you. Generally, the cooling efficiency diminishes as the speeds get fast. You do not get double the cooling at 2000 rpm vs 1000. 2000 rpm will remove more heat from the water than 1000, but usually double the noise for 2-4C less in CPU temp is a bad trade. You might consider setting 1500 rpm with the highest CPU temps you see in normal loads (gaming, etc), saving the 2000 rpm speed for a temp you consider "out of bounds". This will provide an audible warning if things are getting hot.


3. I am guessing you also have AI Suite installed. That's fine. However, AI Suite will override your BIOS Q-Fan control settings, except for anything set to Full Speed. So do set the pump to max in the BIOS, and then worry about the fan control from AI Suite. The pump should appear grayed out after tuning and inaccessible.

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As suggested by c-attack, I would definitely connect the pump to the pump header and the cpu fans to the cpu_fan and opt headers. If you are using AI Suite Fan Xpert, you will be able to set the fans up to run at the best combination of performance vs noise. You will also be able to control any case fans that you have installed. This is how I have my H110i GT connected and for much of the time, the cooler fans run at about 600 rpm and below 40 degrees the case fans don't run at all.
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Thanks for the advice. Most helpful.

It makes a refreshing change to get information from people who know what they are talking about.


I wasn't aware of the AI Suite software. I've just installed it today.


Chillblast clearly did not bother to tune the cooling system before my PC was shipped. They didn't test the Akasa card reader either. That didn't work at all. It needed to be hot plugged into the MoBo USB connector to get the driver to install. It also needed a firmware update.

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