re a question about vac outlet wiring jeh cmkrnl com writes hmmm how are those orange isolated ground outlets often used in computer rooms wired they require two separate grounds one ground goes to the ground pin of the outlet and the other ground wire is connected to the outlet s mounting tabs and thus grounds the box and faceplate screw and metal faceplate if any the box faceplate ground goes to the normal distribution panel ground the outlet ground pin wire is generally connected to an insulated busbar in the distribution panel which is in turn connected to the building entrance main ground by its own wire so the two separate ground systems are connected together at the building s service entrance but one is also connected to every grounded piece of electrical equipment in the whole building while the isolated ground is shared only by the equipment plugged into isolated ground outlets of that panel if someone happens to accidentally short one phase of a v feeder to ground the main building ground is likely to have a lot of noise on it until the breaker trips or the fuse blows while the isolated ground will remain relatively noise free
