CPU usage would start the hair dryer at about 30%. As I said, Windows simply installing an update in the background would spike the fans to full RPM. I returned that NUCi7 under its warranty and so far, with the replacement, underclocking the CPU (80% in Windows 10 power management) and turning off hardware acceleration in Chrome and Firefox seems to keep things quiet for the minor computing I do.
If this one starts to overheat, I don't think I'll bother replacing it again. I'll probably invest $200 in a fanless case and experiment with that.
Thank you for weighing in. I don't think replacing the fan with the same fan will fix the problem. The NUC is telling it to spin at 6000 rpm and the fans are functioning fine, they are just amazingly loud at 6000 rpm. The disappointing part of this is that simply watching a YouTube video spikes the heat and thus kicks the fans to full helicopter.
What is needed is a fan that is quality enough to be silent at 6000 rpm or a better heat sink setup that keeps temperatures in check.
So far my solution of underclocking the CPU (80%) in Windows 10 Power Settings and disabling turbo boost and hardware acceleration in Chrome and Firefox has been working, but I don't like that I have to restrict my CPU like that just to keep the thing quiet.
Try fanless case for NUC, it works really nice, my cat loves it (but it's extra cost :/)
if u will set in BIOS:
fan speed to minimum
thermal threshold to maximum
and then u will save settings, it kills NUC instantly!
NUC will never ever boot again, even if u will try to reset CMOS with intel's procedure...
NUC just powers up, you can hear fan working, there is blank screen, it tryes to reboot once again and it stays in such weird stance until u power it off...
I experienced it once, and I didn't try it again on new NUC…
Just a warning before trying such test...
btw. some nice eng. in lab should test it and fix it (if wasn't just my bad luck on single piece of NUC).