Things You'll Need
Neon lamp voltage tester
Non contact voltage tester
Green insulated wire or grounding cable of the proper gauge
Wire stripper /cutter
Green grounding screws
Long nose pliers
You can check to see if a metal box is grounded by touching one lead of the voltage tester to the hot lug and the other to the metal box. If the lamp illuminates, the box is either properly grounded or is shorted to the white grounding (neutral) wire.
All the ground wires in the circuit panel attach to either the neutral bus bar or the grounded bus bar, depending on the type of circuit panel, the original electrician, local codes and other factors. Simply follow the convention you see inside the panel.
If you are updating old wiring by installing grounds, consider running new cable that includes a ground wire.
Multiple boxes on the same circuit can all be grounded by connecting the boxes and the receptacles in them with ground wires or cables. Then run one wire or cable back to the circuit panel.
Old wiring methods sometimes grounded a circuit or device by attaching the ground wire to a water pipe. While this worked, modern codes require a single ground point at the circuit panel. Except in rare cases, follow this practice and make all ground connections in the circuit panel.
Plastic boxes will never have a ground wire attached to them, as they do not conduct electricity. If you have a plastic box, attach the ground wires directly to each other and to the receptacle ground lug.
Doing electrical work on your own may expose you to dangerous electrical current. Always turn off the power before beginning, verify the power is off by testing and do not turn the power on until you are ready to test.
Although this installation is easy enough for a beginner to accomplish safely, if you are unsure or do not feel confident in your ability, hire a licensed electrician to do the work.
Always use tools designed specifically for electrical work when working on your homes wiring.
Providing a path for stray electrical current to follow is an important safety feature. Modern wiring codes require all outlets and fixtures to be grounded, meaning a separate conductor must be provided for current to follow in the event the wiring is compromised. An open ground means the safety path is open, or incomplete. This should be fixed as soon as possible.
Identify an open ground using the neon lamp tester. Insert one lead into the receptacle's hot side and the other lead into the ground slot. See the illustration to identify the receptacle slots. The light on the tester should illuminate. If it doesn't, check that the receptacle is live by removing the lead from the ground slot and inserting it into the neutral slot. The lamp should illuminate if the power is on.
Turn the power to the receptacle off and verify it is off with the neon lamp tester. Remove the faceplate and the screws that attach the receptacle to the box. Gently pull the receptacle out and observe the wires attached to it and also the wires in the box. There should be two wires attached to the lugs on the sides of the receptacle, and one to the ground lug.
Ground the receptacle by attaching a ground wire from the receptacle ground lug to the ground wire in the box. Some metal boxes are grounded by conduit and don't have ground wires. In this case, attach the ground wire to the metal box with a green ground screw.
Turn the power on and carefully check that the receptacle is now grounded. Touch the leads of the contact tester to the hot receptacle lug and to the ground lug. The lamp should illuminate if the receptacle is grounded. If not, perform Step 5.
Run a ground wire or cable from the box to a properly grounded box or to the circuit panel. Do this only if the ground cannot be made by attaching the receptacle ground lug to the box or grounded wire in Step 4. In the circuit panel, attach the cable or wire to the grounded bus bar. When running the ground wire to another box with a working ground, attach it to the grounded wire in the box or to the box itself if the box is properly grounded.
Turn the power off and verify it is off using the non-contact voltage tester. Run a ground wire or cable of the proper gauge from the outlet box to the circuit panel. Attach the wire or cable to the grounded bus in the circuit panel.
Attach the ground wire or cable to the metal box and to the receptacle ground lug. Briefly turn the power on and test that the receptacle is grounded by touching the leads of the neon tester to the ground lug and to the hot lug of the receptacle. Use a new receptacle if the old one does not have a ground slot or ground lug.
Turn the power off. Carefully push the wires back into the box and install the receptacle. Replace the cover plate and turn the power back on. Double-check the ground one more time, and the job is finished.