Mon Sep 09, 2013 6:01 pm
Of course you are right, in that a 802.3af (or now/soon .3at) system is 'better' in many cases...
If you are trying to come up with a 'cookie-cutter' solution that will work in the widest range of situations.
If you are using .3af gear.
If you need to go a really long distance.
If you have high current draw.
If you need gigabit.
Etc...
But none of that seems to be true here. What stewie01 describes is very simple, and easily accomplished with a RB750UP (or probably even one of the new RB951Ui units), cheaper than could be done with an .3af extender and DC-DC converter.
Given the minimal power requirements of the RB711 series, the voltage drop will also be minimal, and _well_ within the range the gear will tolerate. Combine that with the DC-DC losses (especially from a cheap converter), and any power savings you gain from using 48v on the wire will be negligible (this would obviously not be true for significantly higher-power gear).
As you said, if it isn't broke then don't fix it. Why add unnecessary extra parts and use unmanaged devices; when a simpler, cheaper, and managed solution exists (from the same manufacturer as the device being powered, even)?
--Eric