Kunsy's questions

I have a PTZ Security Camera that requires PoE+ (PoE class 4, IEEE802.3at). It requires 30 watt. I have an existing switch that only provides standard PoE/PSE 802.3af at a max of 15.4 watts. My question is whether I can us a PoE Injector such as the Veracity Outsource Plus POE+ injector in line to power my camera? In my proposed configuration, the Ethernet cable would come out of the existing standard POE Switch (15 watt max), through the POE plus injector and on to the camera. Would this cause too much wattage in the line since the switch that is upstream of the POE injector is POE also? Thank you!