A5120+rps1600 POE Question

[Nicolausf]

i have HP A5120-48G-PoE+ EI Switch with 2 Interface Slots (JG237A) and A-RPS-1600 (JG136A) Redundant Power System.
I've plugged both AC input and the rps-1600.
In rps-1600 manual i read:
"...
- If using a different AC power source from the PD, when the AC power source to the PD fails, the RPS1600-A can provide DC power supply to the PD, ensuring uninterrupted operation of the PD.

The RPS1600-A adopts a power supply failover mechanism: when the power supply of the PD works properly, both the RPS1600-A and the PD’s power supply can supply power to implement load sharing; when the power supply of the PD fails, only the RPS1600-A works to ensure uninterrupted operation of the PD.
..."

The question is: in switch management i can see only one pse (id 4) with a maximum load of 370w+370w.

How can i advise the switch that is powered by an external psu? 
How can i reach maximum load provided by rps-1600 (of 1400w i understand).

I've read a plenty of manuals (Hp, H3c) but i couldn't find answer.

Many thanks 

Nicola