How Ground Wires Can Help Protect Your Home's Electrical System
Grounding is a critical element in household wiring systems. This safety feature helps protect you and your home from electrical mishaps by running part of the electrical load into the ground. If your wiring system experiences a breakdown, short circuit, or another issue, for example, grounding provides an alternate path that directs the electrical current away from your home and back to the earth itself, reducing the risk of fire or electrical shock. It's essentially a backup system that's generally only used in case of an emergency.
To determine if your home is grounded, start by checking out the outlets throughout the rooms. Do they have two holes or three? If a receptacle has three openings, the outlet is likely grounded. However, some older homes feature only two-slot receptacles, which may or may not be grounded. In either case, you can use a voltage tester tool ($5, The Home Depot) to determine whether the outlet is grounded. If you discover that your electrical system is not grounded, strongly consider adding this safety feature to your home. Our handy guide below will introduce you to different types of grounding, plus offers tips on how to ground 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 (either 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
Your electrical system can be grounded through rods or plates, and the best choice for you might depend on the type of terrain around your home and the local building codes.
A copper ground rod is driven at least 8 feet into the ground. Its top might be visible, or it might 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. Alternatively, a ground wire might 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.
Grounding with a Cold-Water Pipe
The service panel ground wire might 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, which is typically 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.
For a simpler solution, install ground fault circuit interrupter (GFCI) receptacles ($16, The Home Depot). These offer protection similar to grounding. Installed correctly, a single GFCI can protect all the receptacles on a circuit.