National Electrical Codes require general purpose outlets and other branch circuits to incorporate grounding. Grounding provides a path for stray electrical current so it does not pass through a human being. Initially, outlets did not have a ground slot. An adapter with a wire that connected to the outlet cover screw provided a ground connection. This was unreliable as many outlets did not have a ground wire for safety. Grounding a 2-wire outlet properly requires the addition of a ground wire. To meet code, install a new sheathed cable that includes a ground wire along with a grounded outlet.
Turn off power to the outlet that requires a ground. Test the outlet by inserting the leads of the voltage tester into the outlet slots -- if the power is off, the neon light remains off. Remove the screw holding the outlet cover on and take the cover off.
Remove the screws holding the outlet to the wiring box. Pull the outlet out of the box. Note that if the wires that supply the outlet are contained in metal conduit, the metal conduit may be acting as the ground and you only need to install a grounded outlet and attach the metal box to the green terminal screw with a bare copper wire.
Loosen the terminal screws holding the wires to the outlet and remove the wires. Pull the existing two-wire sheathed cable out of the wiring box.
Install new two-wire sheathed cable that includes a ground wire between the wiring box and the fuse box or main circuit breaker panel. Remove 8 inches of sheathing with a cable strippers and pull the cable into the wiring box. Strip 5/8 inches of insulation from the end of each wire with the cable strippers. Bend the end of all three wires into a U with the long nose pliers.
Place the bare wire on the green ground terminal, the white wire on the silver terminal and the black wire on the gold- or brass-colored terminal. Tighten the screws firmly. Push the receptacle into the wiring box and fasten it with the supplied screws. Replace the outlet cover and the cover screw.
Turn the main circuit breaker, the main disconnect or pull the main fuse block out, reverse it and reinsert it. Remove the screws holding the cover on the main fuse panel or breaker box. Remove the panel cover.
Loosen the screw holding the existing wire to the fuse terminal or the circuit breaker. Remove the wire. Loosen the screw holding the neutral wire to the neutral bus or ground bus. Remove the neutral wire.
Strip enough sheathing from the new sheathed cable to allow routing the wires neatly inside the panel.
Insert the wires into the panel where the existing cable entered the box. The ground bus and neutral bus are often the same bus. However, they may be different. A ground bus may have only one wire attached to it -- a single bare wire or a wire inside a metal, spiral shaped sheathing. It may also have a number of bare wires attached to it. The neutral bus has the white wires attached to it.
Route the bare ground wire to the ground bus and cut it to length. Loosen an empty terminal screw, insert the wire and tighten the screw firmly. Route the white neutral wire to the neutral bus and cut it to length. Strip 1/2 inch of insulation from the end and insert it into the terminal vacated by the wire you removed. Tighten the screw firmly.
Route the black hot wire to the terminal you removed the old wire from. Cut the wire to length, strip 1/2 inch of insulation and insert the wire into the terminal. Tighten the screw firmly.
Replace the panel cover and install the screws to hold it in place. Turn the power on and test the new outlet. Insert the tester leads into the two slots. The light will go on. Insert one lead into the narrow slot, and the other into the ground slot. The light will turn on if the outlet is grounded.
Items you will need
- Neon voltage tester
- Sheathed cable
- Cable strippers
- Three-slot, grounded duplex receptacle
- Wrap the U in the wires clockwise around the screws. When you turn the screw, the wire is pulled against the shaft and not pushed out and away.
- Unless you have a disconnect separate from the main panel, the large wires attached to the main fuse block or main circuit breaker are always live. Never touch those wires.
- In some rare situations, if you don't see a separate, distinct ground wire that runs to a water pipe where it enters the home, or to a rod or rods driven into the soil outside your home, your system is not grounded and will require additional work to bring it up to code. Even connected to a water pipe, additional ground rods should be added.
- "Wiring Simplified, 40th Edition"; Herbert P. Richter, et al.; 2002
- "Code Check Electrical"; Redwood Kardon, et al.; 2002
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