Planning a Circuit Extension and Wiring Job - Indoors or Outdoors - Educational Info
No matter how simple or how ambitious a wiring job plan, the number of steps in the order in which they should be done is the same in every type of home lighting situation. The job goes much faster if you follow this logical sequence for putting in new breaker boxes, running cable and connecting cables and circuits.
Always calculate whether the existing branch circuit has enough spare capacity to permit extension and whether it is grounded. Only a grounded circuit with spare capacity may be extended. Most grounded sockets will have three slots outlets.
Shut off power at the service panel and use a voltage tester to make sure that the power is indeed off. Remove the cover plate of the existing breaker box. Check the wiring inside to see if you can connect the new cable wires to the existing wires or terminals.
Estimate the amount of cable you will need to reach a new circuit box. Providing extra 8 inches of cable for connections and each box and an extra 20% to allow for the fact that the cable won't rarely run vertically straight. For most purposes choose type and MC cable that is the correct gauge for the circuit.
Test the branch circuit extension. First with the power to electrical lighting still off, and all switches off, clip a continuity tester to the black wire in the box at the end of the run, and touch the probe to the white wire, the bare wire, into the box. The tester bolt should not flow in any of these tests. If it does there is a short-circuit to the new extension.
Patch of all holes you have made in the walls or ceilings. Then turn on the power again. Your new power source is ready for use.