This message was posted on behalf of Intel Corporation
Hi Inteln2: Thank you very much for contacting the Intel® NUC communities. We will do our best to provide the information you are looking for.
In regard to your inquiry, it is expected to hear the some noises coming from the fan, now if the buzzing sound is really loud, then it could be a problem with the fan, please make sure that there is no dust on the NUC and that is placed on a well ventilated area to avoid this kind of problem. Another option will be to set the fan to “quiet” on the BIOS to reduce the noise.
In reference to the temperature, the processor on the NUC is the Intel® Celeron® Processor J3455, the T-junction of temperature of that processor is 105°C, so if it is running at 55°C it is actually working great.
Any further questions, please let me know.