How to Identify the Hot Wire in Lamp Cord, Adding a Switch and Light to a Receptacle Circuit and Adding a Receptacle to a Switch Box
May 26, 2010
The hot side is the unmarked wire. The National Electrical Code requires the neutral wire be identified. Typically, you will find writing or ribs on the neutral wire.
Michele Brown asks:
I am installing all new electrical wire in an old home (1944). My ? is, In my living room I have installed new outlets using 12/2 on a 20 amp breaker. Can I tie into the last receptacle and wire in a switch and 2 lights? There are only 3 receptacles on this breaker. How do I tie into the receptacle to switch to light?
Yes you can tie into the last receptacle and wire in a switch and 2 lights.
Start by installing a 12/2 from the receptacle to the switch box. Now install a 12/2 from the switch box to the light box. When terminating, I prefer to work back towards the power source. This way no one can turn on the circuit you are working on and hurt you. So let’s start terminating in the light box. Connect the ground wire on the light fixture to the ground wire in the 12/2. Next connect the white wire from the light to the white wire in the 12/2 together. Now connect the black wire from the light to the black wire in the 12/2 together. Now install the light fixture, lamp (bulb) and lens (if there is one).
Now go to the switch box and connect all of the ground wires together and leave an approximate 6 inch tail to connect to the ground screw on the light switch. Connect both of the white wires together with a wire nut and tuck them into the box. Connect one of the black wires to one of the brass colored screws on the light switch; it doesn’t matter which one. Connect the other black wire to the other brass colored screw on the light switch. Install the switch and cover plate.
Now go turn off the power to the receptacle circuit and verify that it is off with a voltage tester. Her you just need to connect the ground to ground, neutral to neutral and hot to hot. The ground wires need to be tied together and leave an approximate 6 inch long tail. You may connect the neutral and hot wires to the respective terminals on the receptacle. However, you are not permitted to install 2 wires under the same screw. If you have more than 2 cables in the box, then you need to pigtail the wires. Simply connect all of the neutral wires together and leave and approximate 6 inch long tail to connect to the receptacle. Do the same thing with the hot wires. Install the receptacle and cover plate. Turn on the power and test.
You can also run the power to the light box first and then down to the switch box. If you need instructions for this option, just let me know.
Dr. Eileen Steele asks:
How do I change from just a light switch in a single box to a double box that includes the light switch and a plug in receptacle?
The first thing that you need to do is check the switch box to see if there is a neutral wire in there. If there is then you can add the receptacle. If you only need one place to plug into, then you do not need to increase the box size. You can buy a single device which contains a single pole or 3-way switch and receptacle.
If you need 2 places to plug into, then you need to start by turning off the power and verifying that it is off with a voltage tester. Now remove the single gang box and cut-in a 2 gang box. I’m going to assume that the switch box just had power in and power out to the light.
So, first connect all of the ground wires together and leave 2 tails approximately 6 inches long to connect to the ground screws of each device. Now connect all of the white wires together with an approximately 6 inch long tail to connect to the silver colored screw on the receptacle. Now connect 2 tails approximately 6 inches long to the power supply wire. One tail will connect to the brass colored screw on the receptacle and the other to one of the brass colored screws on the switch. Now connect the final black wire to the other brass colored screw on the switch. Install the receptacle, switch and cover plate. Turn on the power and test.
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