According to some other posts Intel might have a QA problem regarding the quality of the fans used for their NUCs.
Either you can RMA the unit to have it replaced or you can invest in a fanless chassis made for the NUC to properly solve the noise issue (by making the NUC completely fanless).
I use a Akasa Newton X for my D54250WYK along with 2x8GB RAM Kingston HyperX and 1TB Samsung 850 Pro SSD:
This looks like a great solution, though its a bit out of my price range right now. I am assuming that it will be safe to use a 2.5" HDD in that type of chassis? I was planning to get the 2TB drive by Samsung/Seagate eventually.
Also, would the RMA process go through Intel? I originally bought it at Microcenter just this past weekend.
Sure thing... these numbers are very approx but measured through Psensor in an up2date Ubuntu 14.10, the box itself sits ontop of my desktop next to my monitor. There is no additional fan(s) currently in the room and the room temperature is +22C.
Within this box except for the NUC itself there is also 2x8GB Kingston HyperX and one Samsung 850 Pro 1TB SSD.
There are several temp sensors, currently writing this in chrome with hexchat running in the background (in total 132 tasks according to htop with approx 1-2% cpu on all 4 cores (well this nuc has 2 cores but thanks to HT it shows as 4)):
Physical id 0 +37
Core 0 +36C
Core 1 +36C
SYSTIN +123C (I dunno what this actually shows)
PECI Agent 0 +37C
PECI Agent 1 +0C
cpu usage 6%
After playing a 1080p HD-clip at youtube in fullscreen for 3 minutes (Måns Zelmerlöw - Heroes (Official Video) - YouTube) the CPU temps are between +40-45C.
Going for Left 4 Dead 2 in windowed mode (but fullscreen that is 1680 resoltion) the temps are between +45-65C (average +50-55C).