I am an owner of a CRS328-24P-4S+RM for a couple of months now and I'm overly satisfied by the device apart from one thing.. the fan noise.
I understand that a device which can dish out as much as 450 Watts of power in such a small form factor, has correspondingly large cooling needs, but I feel that the currently utilized fan-curve scheme is a bit of an overkill.
The fan turning on would be one thing, but the constant spin up and down in RPM is really really REALLY driving me crazy, especially with their already annoying high-pitch whine.
According to the answer support has given to another user on this forum:
Yes, this device has 2 fans, you cannot control them. Fan speed depends on CPU and SFP temperatures. At full speed, they are louder than ambient noise.
When CPU/SFP or PoE controller reach 40C fans will start. When the controller returns 60C temperature, fans will start spin at full load at 6000rpm.
I had made a suggestion about 1.5 months ago, but it has largely remained ignored. So now I'm formally requesting it in the appropriate forum.
Please give us the ability, for every device that possesses PWM-controlled fan(s), to define our own fan curve within RouterOS (via Winbox/CLI/Webfig/etc) with the usage of Temperature/RPM value pairings.
Yes, do include hard-coded fail safes, to prevent the device from becoming a 360EUR firework, if you must.. but we should damn be allowed to run the device at 55-60°C if we so desire.
Please don't force my hand in voiding the warranty and resistor-modding the fans.. have some mercy on our ears..
EDIT: I would also like to mention that one of my S+85DLC03D modules runs at an idle of 54°C for months on a passively cooled RB4011iGS+5HacQ2HnD without a single problem (besides the problematic v6.45.2 RouterOS release, that is).