Background (the blog part)
Over my past couple of personal builds, as well as some I’ve built for family and friends, I’ve almost exclusively used Asus ROG boards. I’ve found them to be well made, reliable, and I had become very familiar with the ROG UEFI layout. There is also the fact that as someone who does a lot of custom loop liquid cooling, I like to utilize coolant temp sensors if they are available on the motherboard, and almost every ROG board I’ve encountered has them. If you have ever done custom loop cooling and not utilized a coolant temp sensor, I highly recommend it.
Warning – boring and technical liquid cooling stuff follows.
When liquid cooling a PC your system fans are not cooling the CPU, at least, not in a relationship as directly as the fans are affecting the cooling in an air cooled solution. Liquid has a much higher thermal capacity than air, so it removes the heat very efficiently as it flows through your system to the radiator or radiators. Radiators also have a huge surface area to then dissipate the heat from the coolant which then flows back into the system and removes more heat. Much like the fins on an air cooled heatsink, a radiator still needs some airflow across its fins to lower the coolant temp as it flows through the coolant passages.
Without adequate airflow, a radiator will become heatsoaked and will no longer be able to dissipate heat from the coolant. The lower your coolant temp, the more thermal capacity a specific volume of coolant has, and will be able to transfer more heat within the loop. So in a liquid cooled system, your fans are actually dissipating heat from the radiator.
What all that means is that you don’t need your fans to ramp up and down to match your CPU or GPU temps. You want your fan speed to be based on your coolant temp. Having a motherboard that not only has a two pin temperature sensor, but also allows the fans to be controlled from use the readout from that sensor allows this level of control. The way I’ve set it up in all my builds over the last few years is to connect the pump to the motherboard’s CPU header, and then fix the rpm (on my current build, my D5 pump runs at a constant 3000 rpm).
Most motherboards will give you an alarm if they sense a malfunction there, and your pump is the one thing in your system that you want to know immediately if it stops. After that, I just connect my fans to the other motherboard headers, and then go into the UEFI (or the motherboards fan control software) and set fans speeds based on the coolant temp reading from the sensor. Using this method prevents the fans from constantly ramping up and down as your CPU temps rise and fall, but also won’t omit the effect of the GPU in the loop.
We now return you to your regular blog-type programming.
