USB-C PD for an industrial Cisco IR829 router

I bought a second hand Cisco IR829 in a thrift store for 25€ without a power supply. On the bottom it says that it runs on 12-24 volts and draws 6 amps max. I soldered a 20 volts USB-C PD trigger board to the P4 connector of an old ATX power supply and added a heatshrink. It can at most deliver 3.25 amps. With my power meter it measures 15 Watts idle, which is around 0.