AC Power System Grounding

1. Install the insulated equipment grounding conductor (sized the same as the supply conductors) in the same conduit as the supply conductors from the main or source panel to the dedicated MICROS panel.
2. Terminate this equipment grounding conductor on the ground bus in the main panel.
3. At the MICROS-equipment panel, install a ground bus that is electrically isolated from the panel frame, and then terminate the feeder equipment grounding conductor on this bus bar.
4. Use the metallic feeder conduit as the equipment grounding system for grounding the AC power panel frame, metallic conduit system, and metallic junction boxes.

For each branch circuit from the dedicated power panel to the device receptacles, include a full size (same as supply conductors) insulated equipment grounding conductor installed in the same conduit as the supply conductors. Ensure the conduit is dedicated to MICROS equipment. Terminate this isolated grounding conductor on the isolated ground bus bar in the panel and on the equipment grounding terminal of a NEMA IG5-15 isolated grounding type receptacle.

In order to maintain isolation of the equipment grounding conductor from the conduit system, use an isolated ground receptacle. This type of receptacle (usually identified by an orange face) provides an insulating barrier between the equipment grounding terminal and the receptacle mounting strap. Terminate all branch circuits from the MICROS power panels with isolated ground receptacles.

Standard receptacles bond the equipment grounding terminal (green screw) to the receptacle mounting strap and metallic conduit when the receptacle is mounted to the box. This defeats the purpose of the isolated grounding system. Do not install an equipment bonding jumper from the receptacle grounding terminal to the outlet box. (NEC Article 250-74, Exception 4 permits the installation of the isolated ground receptacles and isolated equipment grounding conductors specified in this section.)

If a duplex receptacle is installed and only one socket is used, disconnect the unused socket to prevent the temptation of using the outlet for equipment that produces extraneous ground currents (e.g., floor buffers, blenders, vacuum cleaners, etc.). The correct isolated ground receptacle types are listed below.