Is it considered a good practice to use the chassis as a return path to a DC Power Supply?
I have been given a rack mounted device that switches 480 volt power on/off remotely. The remote feature is handle via a Raspberry Pi which is powered via 120v to 5v power supply (http://www.mini-box.com/OpenUPS).
I was surprised to find that the return pin on the 5v power supply is tied directly to the chassis and the GND on the Pi is also tied to ground and they are using the chassis as the conductor for the return path. There is only a positive 5v wire going between the power supply and the Pi. Is this considered good practice?