What safety precautions should I follow when plugging in the HP Z840 Workstation?

Plug the power cord into an AC outlet that is easily accessible, and always disconnect power by unplugging the cord from the AC outlet rather than from the workstation itself. You must use a grounded (earthed) three-pin outlet and must not disable the grounding pin, such as by attaching a two-pin adapter, as the grounding pin is an important safety feature.