Just to clarify, a common line with several outlets is always wired up in parallel since there wouldn't be any current flow through an outlet with something plugged into each outlet to complete the circuit, and even then, the line voltage would be divided (reduced) between each outlet, rendering the whole line inoperational. So what this refers to is rather a series of outlets along one common power line, but wired in parallel to it.
It’s not too difficult to wire a series of outlets to a common line. It’s a good way of wiring outlets together if you want them all to work off a single switch. You do need to have some basic confidence in working with electricity, but this is essentially a job for a novice. The tools are those you’d probably already have at home. Besides that, all you need is some electrical wire.
Step 1 - Prepare
Before working with anything electrical, make sure that the power to the area is off. Locate and TURN OFF the circuit breaker, in the main electric panel, that feeds the line or circuit to be worked on. You can check by using a multimeter on the outlet to see if there is any current there.
Step 2 - Run the Wire
Disconnect the hot, neutral and ground wires from the first outlet, but leave them in the box. Now you need to run a length of wire from the second outlet to the first. In new construction this is easy. Drill holes in the studs and run the wire from outlet to outlet through those.
With older construction, you have no option but to take out some of the drywall in order to do this. There will be a small knockout plate on the side of each box. Knock this out with a screwdriver. Allow about 8 inches of wires in each of the boxes and then cut the ends with a knife.
Step 3 - Cut the Taps
To wire outlets in series, you’ll need to cut taps (they’re also called pigtails or conductors). These are short lengths of wire. Cut three of them, one for the hot, one for the neutral, and one for the ground wires. They only need to be a few inches long. Strip ½ inch of the insulation off both ends of each wire and set the wires aside.
Step 4 - Wire the Outlet
You can now wire the second outlet. Cut 4 inches of the sheath off the wire in the junction box. Separate the three wires and strip off ½ inch of insulation from each one. Connect the end of the hot (black) wire to the brass terminal. Screw the end of the neutral wire to the silver terminal. Finally, screw the ground or green wire to the metal screw in the box.
Step 5 - Wire the Series
In the first outlet box strip ½ inch of the insulation off the ends of the wire you’ve just run. Bring together the black wire that goes to the second outlet, the black wire coming into the first outlet, and the black tap. Twist the bare ends of all three together. Secure them together with a wire connector and cover that with electrical tape. You should have the other end of the tap free. Do the same with the neutral wires, and finally connect all three ground wires together.
Now connect the loose end of the black tap to the brass screw, the end of the neutral tap to the silver screw, and the end of the ground tap to the ground screw in the box. You’ve now wired the outlets in series.