The specifications https://mikrotik.com/product/netpower_16p seem to be contradictory:
Max power consumption: 316W
Max total out: 2.8 A (24V) & 1.4 A (48V)
so max output power (even asuming voltages at high end of range: 30V and 57V) is about 164W.
In my opinion the 5.5/2.1 DC jacks were a poor choice, a terminal block would be better for high currents. Then 6A at 24V and 3A at 48V would give 288W total, close to real max specs (but still a bit less than needed for all ports at max load).
Also, beware:
both 24V and 48V DC input jacks are the same size, too easy to swap by mistake (48V applied where 24V was expected, possibly letting magic smoke out).
both share a common negative ground, not compatible with standard telecom power (negative 48V DC, positive ground) often used for licensed radio links etc. It is necessary to use an isolated DC/DC converter.
I really don’t understand why Mikrotik is not making (more) dual neg48 devices. For devices like 16P or bigger switches, those have very high chances of getting installed in such an environment. Is tehre anyone that installed 16p in a dual neg48 power setup?
That document is as confusing as all the other places. I did not find any clear mention about the type of POE that can be used when only the low voltage input port is connected. Is this device able to supply 802.3af when it is powered via the 18-30V port only?
You can give power-out only what you power-in, if you power it with 18V you will be giving out 18V as “Low”. If you power it with 30V, you will be giving out 30V as “low” if you have 48V, you need to connect it to corresponding PEXT and then you will have “High” option available. This gives you unprecedented flexibility with your setups.
It is obvious that device is too small to have any power adapter/conventor build-in and also it uses same PoE implementation that MikroTik has since the beggining of CRS112-8P.
Is “high” standing for 802.3af and “low” for passive POE?
And it really depends on your “flexibility” needs. As far as my needs, I always have to invent something to power these devices, in order to make them work as they should be (redundant as far as power, telco environment). I really don’t see the point of not offering true power redundancy for these devices, for all the low/high options available on them.