I get many questions regarding adding an outlet or a receptacle from a switch box. This question comes up fairly often, and causes a lot of frustration for our visitors. Here is the most recent question on this subject:
The power is connected to my light and then to the switch with #14 wire. Black white and ground. I want to add a receptacle, how would I wire it from the switch? I want to run wires from switch box to receptacle box?
You cannot wire this outlet by connecting it to the switch box in this situation. This light outlet and switch are wired as a switch leg drop, and this leaves you without a neutral wire at the switch. Let me show you with a diagram.
Note that the power comes into the light fixture outlet box. The neutral is connected to the light fixture only. The hot (black) wire coming in is spliced to the white wire going to the switch (and is identified as such with black tape or felt marker as shown). The switched power comes back to the light fixture outlet box on the black wire of the 2-wire cable, and is then connected to the black wire (s) of the light fixture. The position (on or off) of the switch turns the light on or off.
Now you can see that to attempt to add an outlet or a receptacle from this switch box will not work in this particular situation. You don’t have the neutral conductor that you need for a receptacle outlet. The only way you could do this would be to change the 2-wire cable (from the light to the switch) out to a 3-wire cable. If this is not possible then the new receptacle would have to be connected from the light outlet box by running a 2-wire cable from light box to new receptacle outlet.
Remember you need to identify the white wire as being used as a hot conductor by use of black tape or felt marker (not shown in this diagram, but shown in diagram above)
Of course you need to check how many outlets are on this existing circuit before you add any outlets to avoid overloading of the circuit.
If the power comes to the switch outlet box first, and then to the light fixture, you could add a receptacle from the switch box in that situation.
Thanks for the questions! Keep them coming!
– Terry Peterman, the Internet Electrician