If your home was built within the last few decades, then the electrical wiring throughout your home should include a ground wire. This is important because having a grounded system offers the maximum in electrical protection. If you're not sure whether your outlets are grounded, here is a simple way to test for ground.
Check the outlet itself to see if it has a ground wire attached to it-but before you do this, be sure to turn the breaker that is feeding the outlet OFF.
With the power off to the outlet, simply remove the cover plate and the two screws securing the outlet to the wall box. Carefully pull the outlet out of the box.
You should see either one or two black wires connected to one side, one or two white wires connected to the other side and a bare or green wire connected to a green-colored screw on the top or bottom of the outlet. If you do not have a green or bare wire connected, then this outlet was wired without a ground.
If you don't feel comfortable pulling the outlet out of the wall box, there is another way to tell if your outlet is grounded-with a tester. In fact, even if your outlet has a ground wire attached, you should still test it with a tester to ensure that everything is wired correctly.
To test for ground, the outlet should be reinstalled into the wall box (if you removed it) and the power should be ON.
If you are using a multitester, set it to read "voltage." If you are using a regular voltage tester, then you don't have to set anything.
Take a look at the front of the outlet. You should see two outlets, each with three holes. One slot should be slightly smaller than the other slot, and below those two you should see a hole that resembles a "U."
The bottom U-shaped hole is the ground slot, the small slot is the hot and the larger slot is the neutral.
Insert one tester probe into the smaller slot and the other probe into the larger slot. Your tester should read "voltage."
Keeping the probe in the small slot, take the other probe and insert it into the U-shaped slot. If you read "voltage," then your outlet is grounded.
Always check both outlets on a duplex receptacle because one can be wired correctly while the other may not be.
If your tester does not read "voltage" when you probe the small slot and the ground slot, then insert one probe into the larger slot and keep the other probe in the ground slot. If you read "voltage" this way, then the hot and neutral wires are reversed. If you again get no voltage reading, then your outlet is NOT grounded.
If the outlet is wired incorrectly it is not grounded, in which case you should avoid using that outlet until it is properly repaired.