H100i pro coolant temps

How hot can my coolant get and still be safe? Long gaming sessions bring it to 39c. That normal?

Yes, most often people will see warmer coolant temps when gaming then a straight max CPU test. This is not a reduction in efficiency or a greater CPU load, but indicative of a rise in case temperature from the GPU heat warming the entire case. Here are some general rules.

 

Your H100i Temp or coolant temperature is the measure of how much heat in the system. It is second stage of cooling management. The first is the more familiar CPU temperature. That is determined by voltage and CPU physical design. More voltage, more heat, but no matter what to connect to the CPU, the heat created at the pins must pass through through the CPU and then through the cold plate on whatever cooler is mounted. All of this is conductive and there is no setting to alter the rate, other than reducing voltage. The cooler is second stage. It collects the heat from the cold plate and transports it somewhere else (the radiator), where the fans then help disperse it.

 

The relationship between coolant temperature and CPU temps is this:

 

a) Coolant temperature is the minimum possible CPU temperature when the Vcore is at 0.0 volts. You won't ever be at 0 volts except when shutdown, so in practical terms you will always see idle CPU temps just a bit above the coolant temp even when using C-states, EIST, and other power saving features. Turn all those off and the difference will increase.

 

b) +1C coolant temp = +1C CPU temp. Every time you add 1C to the coolant temperature, you raise that basis/lowest possible CPU temp by 1C as well. A typical 100% CPU load for the 8700K is going to be +4-6C, depending on CPU settings. That is not a lot in comparison to the voltage part of the the total CPU temp (typically +30-50C). Fans help reduce coolant temperature, not the +30C from the voltage. So even with maximum fan speed, you likely can only reduce your CPU temp by a few degrees. While this seems detrimental, it is not. An air tower is bound by the same rules, but has a much smaller capacity to hold heat. It will suffer a greater penalty when faced with the same load. In your case, the "penalty" is the coolant temperature rise and that is small.

 

c) Typically most people see coolant temp rises of +4-6C for CPU only loads or general mixed use. Gaming or other max GPU loads often give the appearance of more. Some people will see as much as +10C while gaming with large watt GPUs, although it has nothing to do with CPU load or efficiency. When you heat up the case with the GPU waste heat, you raise the local environment temperature. Only 3-4C of the gaming temp might be from load. The rest is because you raise the case temp by +6C and that's the final rule....

 

d) Minimum coolant temperature is case ambient temp in that specific location. Not surprising, you can't make the liquid in the cooler colder than the room or case temp. Most people will see coolant temps of +4-7C above their room temp and pretty much exactly what the local case temp is at the radiator mount location. Some place are worse than others. I think this is where we need to look at things for you.

 

 

The greatest reductions you can make in terms of CPU temp is going to be to curb the voltage on the 8700K. There a lots of overclock guides out there and even if you are not going to increase the frequency, there are settings on most boards you need to check to ensure the boards isn't piling on voltage enthusiastically. Voltage is the still the largest factor in your end CPU temperature.