The CNC equipment is properly grounded through a "green wire" (not shown) and through the conduits and raceways, to the ground bus/neutral bus junction at the service entrance panel, and from there to the grounding electrode(s) located outside the building. Grounding connections are also made from the neutral-ground bond at the service entrance panel to a metal water pipe and to the building steel. The left of the figure shows a supplemental grounding electrode installed at the CNC machine and connected to the machine cabinet, as originally configured at McAfee Tool & Die. This arrangement is permitted under the NEC, which is concerned mainly about safety, but it is not recommended under IEEE Std. 142 (The Green Book), Grounding of Industrial and Commercial Power Systems, and IEEE Std. 1100 (The Emerald Book), Powering and Grounding of Sensitive Electronic Equipment