Electrical Grounding Options

With a typical electrical outlet, the circuit ground is connected to the screw that attaches the cover plate as well as the screws that attach the outlet to the electrical box in which it is mounted. If conduit is used (pipe that contains the wire) ground is also connected to this.

With an Isolated Ground Outlet, the circuit ground that goes to the third pin on the connector is wired only to the ground wire that runs to the main electrical panel. The cover plate and mounting screws are connected together and to the conduit, but not to the circuit ground. This creates a much cleaner ground. It is often used for sensitive computer, audio and medical equipment.

When an Isolated Ground is not used it is also common (and legal) for the conduit to be used for the ground connection. Since the conduit is made up of a number of pieces of pipe that run back to the main electrical box, it does represent a complete connection and will function as a safety ground when needed.

Because the pipes are only connected by screws, there is not a good enough connection to the panel for audio or sensitive computer equipment. In this case a separate wire is used to connect the outlet ground to the main electrical box. This is better than just using the conduit ground, though still not as good as a Isolated Ground.

 
A typical electrical circuit in a building will have a number of outlets in different locations. It is easiest (and cheapest) to run wire from the main electrical box to the first outlet, from there to the second, and on to the last.

At each outlet the wires are connected using wire nuts close to the outlets. This means that ground for the last outlet has gone through a number of connections before getting to the outlet. Each piece of wire and nut/screw connection increases the resistance and effects the impedance of the ground run. A fairly easy solution is to run a separate ground wire from each outlet to the main electrical box. This is often referred to as Home Run Ground. If this is used with an Isolated Ground Circuit the system noise can be greatly reduced.