I have unifi ac mesh with custom image build with openwrt , I use cat5e cable with this device and the distance between unifi and my patch pane (24v) , over 80 m
With this installation I have problem , when I enable the dual radio , radio0 (5ghz) and radio1 (2.4ghz)
The device didnt work and its turn off . So I have Cisco switch with 48v Poe port i use it to power the unifi the device work perfectly with it without any problem .
They comply with 802.3af which means you can go by the standards without looking at exact voltages. The PoE bus in most Cisco boxes is 52 volts-- this allows for some losses in the port circuitry to provide a nominal 48 volt output.