Installing outdoor electrical receptacles enhances the value of your home and makes your home and grounds attractive. Wiring that is placed outdoors has to be protected from the elements and installed so that water and other hazards cannot short the power lines that are installed. The same principles that apply for power lines, apply for telephone extensions to outbuildings.
Call the local building authorities and inquire about the building codes for your area. Follow these codes in your work, especially as you may require an inspection of the finished project. Also this will protect you from possible liability if any accidents result from your electrical installation.
Draw a diagram of the project. You must include where you are going to tap the power line, where the outdoor lines must be run and how the lines outside will be terminated. Include as well any switches and receptacles you plan on installing.
Measure the distances and lengths of the conduit and wire that you will need for the project. Running the outside power lines through conduit is the safest method of protecting the wiring. Buried PVC conduit is the easiest to work with and hold up to weather extremely well.
Dig a 4-inch trench along the path that the wire will run. Place the conduit along this trench and cut the lengths as you are placing the conduit. Make sure that you have all the connection fittings for connecting the tubing.
Run the wire through the conduit before cementing the conduit together. Run the conduit all the way from the outside endpoint back to the house; allot enough excess wire at both ends. Cut the remaining wire off.
Trace the wire along the trench and cement the conduit together as you go. Cement the conduit together. Place the conduit into the trench and fill in the trench from endpoint back to the start point at the house.
Connect the end point to the type of receptacle that you plan to use. Insure you safely cap or terminate the wires within the receptacle.
Turn off the circuit to the point that you will be tapping for the power lines to the outside. Drill a hole through the side of the house to slip the line through and pass the power line through to the point of merging with the power source.
Use silicone caulking to seal the hole around the wire as it enters the house to keep weather and pests from entering the house. Expose the source of power for the outside line. Strip off about 0.75 cm (½ inch) of insulation, twist the source lines together with the outside extension lines, and terminate with a wire nut.
Seal the source line and newly installed outside wiring lines. This will be in the junction box or breaker box. Double check each connection and trace the line back to the termination point, visually checking each connection.
Switch the power back on to the new part of the circuit and test the receptacle at the termination point in the garden.
Run your conduit along the house foundation when possible. In order to find the lines again in the future, make a diagram of where the wires run on the property.
Always make sure to turn the power off before working with electrical wiring.