Hold the outlet box against the ceiling about midway between the joists and trace the outline with a pencil. Cut a channel from one joist to the other, the same width as the outlet box. Use a drywall saw to cut gypsum board and a reciprocating saw to cut wood lath plaster.
If the existing receptacle or switch is connected through the holes in the back, push a jewelers screwdriver or similarly shaped tool into the slot next to each hole to release the clamp pressure and pull the wire free.
Leave the wires bent into hooks if you will be using the terminal screws to connect the new device. If you will be using the holes in the back, cut the wires right below the hook so you will have a straight piece to insert into the holes. Strip about ½inch of insulation off the copper to make the connection.
The wattage rating information for a particular device may be on a label or imprinted on the back somewhere. If no wattage rating is displayed, the load can be calculated by multiplying the amps drawn (appliance amps) by the voltage of the circuit. If neither the amps nor the wattage ratings for a device is known, the chart below lists common household appliances and the average watts drawn for each to aid in calculating the load of a circuit.
An outlet for tapping into an electrical circuit usually with an appliance plug. Duplex wall receptacles are the most common type, but larger appliance receptacles are also found in household electrical systems.
If you want to use a source with the maximum wires already present, it may be possible to split the source before it enters the box. Cut access to the wiring through the wall material and add a junction box to splice the new outlet into the circuit. Cover the box with a blank plate to protect the splice.
If permitted, new electrical wiring may be run behind baseboards to serve a new wall receptacle, or to a switch and new ceiling light fixture. To pass the cable through the wall studs a notch is cut in the wood and a metal shield, sometimes called a nail guard, is fastened over the notch to protect the new wires from nail and screw punctures.
Use a wood chisel to chip out between the two cuts, deep enough to fit the plate flush with the stud surface. Keep the plates flush with the studs to ensure the baseboard won’t stick out when reinstalled.