My corsair h100i is always running at max

Some notes on the H100i (I've used many of them, mostly with 6-core SB-E builds)...

The stock fans are way too loud at even moderate speed. I replace them all with Nanoxia
Deep Silence 120s (ie. I use 4 in push pull), with an Akasa 5-way PWM splitter so all 4
fans run at the same speed (power is provided using a SATA connector link, so it does not
rely on power from any mbd fan header).

As Michael says, ensure the 4pin cable is correctly linked to the CPU fan header on the mbd,
but note that if you decide to use the Corsair Link software to control the unit remember you
will not be able to use whatever package the mbd vendor provides to control general mbd
functions, eg. AI Suite for ASUS boards. Apps that read sensors are usually incompatible. The
solution is to not bother with the Corsair Link sw at all (ie. don't use the USB link cable), and
control the whole system using the mbd vendor's app, eg. in my case with an ASUS P9X79 WS
I use AI Suite II to control the fans cooling the H100i. Works nicely. It means of course the
H100i's variable LED colour function will not work, but that's just unnecessary bling IMO.

Think carefully how you want airflow to behave in your case. Depends very much on the GPU(s)
installed, how they vent hot air, etc. Getting the fan intake vs. exhaust issue wrong for the
H100i can have a big impact on internal temps, affecting other components, especially the mbd
chipset. If you're not sure, try testing both options under typical intended usage scenarios,
see which is best. I set the fans on the H100i as intakes as that also helps cool the mbd, though
a separate small fan is also used to cool the heatsink next to the ATX power socket.

As implied above, using a water cooler means the mbd chipset area around the CPU socket
is not being hit with any partial airflow from an air cooled CPU heatsink, so you need to be
sure the mbd chipset is also cooled sufficiently, eg. via a dedicated fan or fans. Numerous small
models are available, though remember that really small fans tend to make a higher pitched
whiney noise; a larger fan at slower speed will sound better.

Ian.