802.3af v 802.3at - Is 30W enough no matter how you get there?

[RumorConsumer]

Hello!

Meraki support told me that as long as my APs are powering they are receiving enough power. This turns out to be untrue for many models as @PhilipDAth has written in another post.

Oddly, the AR42 pulling 106.9mbit in this image is using an adapter from Cisco that can output 30W. Images:

The power adapter looks like this:

The voltage/amperage math gets us to 30W. Why would this power adapter not provide 802.3at? I swapped it for a PoE+ adapter which does supply at but really this should do it, no? I have also seen a number of adapters with wildly different voltages and amperes where the math works but the ratio is much higher. Any problems there? 

Thanks.

[PhilipDAth]

I don't know the answer.

My guess - power supplies are often not dumb power supplies any more.  Often they include a communication protocol.  My guess is the AP asks the AP what it is capable off.  It is expecting to talk to a Meraki power supply.  It doesn't know how to talk to this one, and so instead assumes a safer power budget (802.3af).

[RumorConsumer]

That makes sense. This one is considerably lighter and chintzier feeling than the other one I’m now using. Check out this sample. The MathWorks but this wouldn’t even give POE+ to a MR 30 H.

[BlakeRichardson]

I would avoid using non Meraki power supplies for two reasons.

1. You wont get support

2. If you manage to fry the device it's not covered by warranty.