To install an outdoor GFCI outlet, you’ll need to acquire power from another source at your house. This could be an exterior fixture that already has power running to it. Or you can choose a location that’s opposite an indoor outlet in your home. Before proceeding, you’ll need to make sure the circuit you’re using can handle the new exterior GFCI outlet without overloading it. Confirm that the polarity and proper ground of your interior outlet is running correctly. You’ll also need to check your box fill requirements to ensure that the electrical box can hold the new conductors being added. In some cases, it may be necessary to swap the electrical box out with a larger one.
** Shut off the circuit at the breaker box and clearly mark it out of service so no one else will turn the breaker back on while you’re working. Confirm that the power to the interior outlet is off.
Start by taking off the wall plate on the existing outlet. Remove the two screws connecting the receptacle to the electrical box and pull it out from the wall. Disconnect all the wires running to the outlet and push them out of the way.
Use a hammer and a flathead screwdriver to knock out one of the holes in the back of the box. With a long bit, drill through the hole in the box until you reach through to the outside. Place the electrical box for your new outdoor GFCI outlet against the wall, making sure it covers the hole you just drilled. If you’re planning to recess it into the wall, make a light marking around the outside with a pencil. Drill holes in each corner, then use a keyhole or saber saw to cut around the outline. Test fit the electrical box into the cutout, and trim if necessary to make it flush. Now pull out the box and use a hammer and screwdriver to knock out a hole in the back of the box for the wiring. Take a length of Romex cable and feed it through the hole in the electrical box from the inside. Run it through the wall and out through the cutout section you created on the exterior of the house. Cut the cable with a pair of wire cutters, leaving about a foot sticking out of each opening.
Remember, it’s better to be too long than too short because you can always trim it back later. Now feed the outside part of the Romex through the hole you created in the back of the GFCI electrical box, and push the box into place in the hole. Secure the box to the outside wall with screws or by tightening the clamping tabs on the box to create a snug fit. If needed, use a strain relief plug in the electrical box to hold the wiring in place. If the wires are too long, you’ll have difficulty fitting them all inside, so cut back the Romex cable, leaving about four inches sticking out of the electrical box.
Remove the sheathing on the cable, exposing the wires all the way down to about 1/2 inch from the back of the box. With a pair of wire strippers, take off about 1/2 inch of insulation from each individual wire. Now you’re ready to install a tamper resistant, self-testing GFCI outlet into the new box. Attach the bare ground wire to the green screw of the outlet, which is usually on the bottom. Attach the white wire to the neutral screw on the opposite side, which will be silver. Now attach the black wire to the common screw on the side of the outlet. This will be gold or brass colored. Carefully push the wires and outlet into the box and screw it down on both sides. On the inside, cut back the Romex cable if needed and remove the sheathing down to about 1/2 inch from the plug.
For a better fit, trim the wires to and even length. Then use wire strippers to remove about 1/2 inch of insulation from each wire. To properly tie the new outdoor outlet wires to the interior outlet, cut a separate piece of Romex about six inches long and remove the sheathing. Now strip off about 1/2 inch of insulation from each end of the black wire and the white wire. Depending upon your outlet’s location, a tamper resistant receptacle may be recommended for the installation. Attach the black wire to the top brass screw on the side of the outlet. Attach the white wire to the silver terminal on the opposite side, and attach the bare ground wire to the green grounding screw on the outlet. Take the other end of the six-inch copper wire you attached to the outlet and pigtail it to the other two copper ground wires. Place the ends together, twist them, and screw on a wire nut.
Do the same with the three white wires. Take the wire from the outlet, the one coming from the house and the one going to your outdoor GFCI, and pigtail them together in the same way. Finally, go through the same procedure with the three black wires. Pigtail them together and attach a wire nut. Now add electrical tape to each of the connections to keep them from coming loose. Carefully push all of the wires into the box and screw the outlet down into place. Reattach the cover plate. Some outdoor GFCIs utilize a gasket to secure the outlet to the electrical box. Screw it down. Then turn the power back on at the circuit and test out the outlets. With a voltage tester, confirm that you now have power running to each one.
Make sure the reset button works properly on your outdoor GFCI. If everything is functioning correctly install the cover. This will keep it safe from the elements and give you year round power to use outdoors.
As found on Youtube