The 220R and 420R can accommodate one or two power supplies.

Each power supply provides up to 380 watts.

All system configurations will operate with only one power supply installed.

The second power supply will provide redundancy, allowing the system
to continue operating should one of the power supplies fail.

It is recommended to have each AC input connected to a different circuit 
for redundancy.

Please NOTE that the 2nd power supply is an option.