One hAP ac³ is the central router powered directly with the included 24V power brick and all other devices are powered with GESP+POE-IN injectors and their included 24V power bricks. I'm looking into adding one more wAP R ac (or ax) to the network and a new central router RB5009UG+S+IN or perhaps its outdoor version RB5009UPr+S+OUT . The outdoor version provides PoE-out, but after checking my devices compatibility I am unsure if that will work fine:
wAP R ac / ax, and LHGGM support real 802.3af/at PoE at full range of voltages
hAP ac³ supports only passive PoE up to 28V
RB5009UPr+S+OUT provides only 802.3af/at PoE, no voltage conversion, and comes with a 48V PSU
I thought to use the "real" PoE only for wAP R ac and LHGGM, but disable PoE output on ports towards hAP ac³ and use my old passive GESP+POE-IN injectors and power bricks.
Is it possible to safely disable PoE on some outputs so that a passive injector can be used? Or can maybe the ports configured for passive PoE output and hAP ac³ could survive 48V?
Also GESP+POE-IN has surge protection and some of my cabling is outdoors (shielded and grounded), are outputs of RB5009UPr+S+OUT protected as well?
In theory the 802.3af/at/bt protocols are called "active" because there is a negotiation between the PSE (power supply equipment) and the PD (powered device).
BUT BEFORE that there is a resistance check, "low voltage" (passive) 24V or so PoE needs a resistance of around 3 KOhm while "high voltage" (active or passive) 48 V or so needs a resistance of around 26 kOhm.
Still in theory if the PSE doesn't measure a suffcient resistance it won't power the port.
Relying on the router software settings (possible "forced-on" on a port because of some reason) is not (IMHO) a good idea, things can go wrong.
BUT there are converters from 48V 802.3/af/at to 24V that are (IMHO) safe in the sense that their failure mode is that of stopping providing the 24V in output or failing to negotiate with the PSE the 48V in.
About grounding/shielding it is a whole world of possible issues, it has to be seen with a scheme with some more details, whether it is appropriate to ground a cable (on one side) or not and if the use of surge suppressors or similar is recommended/needed.
Yes you can disable the PoE on any port and then use a 24v injector.
You can also use a 48V AF/AT to 24V passive PoE converter like the RBGPOE-CON-HP or the Ubiquiti INS-3AF-I-G.
And there also exists an interesting device "CRS418-8P-8G-2S+RM" (also with WiFi as "CRS418-8P-8G-2S+5axQ2axQ-RM") which can output a mix of 802.3AF/AT (48v) and passive (24v).