Picture an outlet—does it have two holes or three? If it has three, the outlet is likely grounded, meaning part of the electrical load runs into the ground. This safety feature helps protect you (and your home) from electrical mishaps. This section introduces you to different types of grounding, plus offers tips for grounding your own home.
Understanding The House Ground
Ground wires for individual branch circuits (or metal sheathing that acts as a ground) lead back to the neutral or ground bus bar of the service panel. The service panel itself must be connected to the earth so that the entire electrical system is safely grounded.
Usually a service panel is grounded by a thick wire—bare copper or green insulated—leading to a ground rod or to a cold-water pipe. Follow the ground wire from the service panel to find how it is attached to the earth.
Types of Grounding
A copper ground rod is driven at least 8 feet into the ground. Its top may be visible, or it may be sunk a few inches beneath the ground. The service panel ground wire must be firmly attached to the ground rod, either with a special toothed clamp or by welding. Recent building codes often call for two or more ground rods for added security.
In rocky areas, where it is difficult to drive a ground rod 8 feet down, a grounding plate may be used. This thick piece of metal is buried underneath a footing or foundation. Or a ground wire may connect to a metal reinforcing rod embedded in a house's concrete foundation.
If you have any doubts about your home's grounding—and especially if a receptacle analyzer shows that the receptacles are not grounded—have a professional electrician inspect your home.
The service panel ground wire may lead to a cold-water pipe, which is connected to supply pipes that lead deep underground. The connection must be firmly clamped. Hot-water pipes are not acceptable for grounds because they run only to the water heater, not into the earth.
Because municipal water pipes are buried, a firm connection to a cold-water pipe forms an effective ground.
How to Ground an Ungrounded House
If your home's receptacles have only two holes or if a receptacle analyzer indicates they are ungrounded, don't panic—people have lived with ungrounded homes for decades. However, grounding considerably improves a home's safety and is worth adding.
If you want to ground an entire system, you have to call in a pro to rewire the entire home—an expensive job. If you want to ground only one receptacle, you can ask an electrician to run an individual ground wire from the receptacle to a cold-water pipe.
Here's a simpler solution: Install ground fault circuit interrupter (GFCI) receptacles. These offer protection similar to grounding. Installed correctly, a single GFCI can protect all the receptacles on a circuit.