Before we get into the details of smart switch wiring, let’s cover basic switch wiring for a regular (non-smart) switch. This knowledge will serve as a good base to build from for wiring a smart switch.
Home Wiring Basics
Home electrical wiring contains two wires – the black wire (hot) and the white wire (neutral). There is also a green wire for the ground. The ground wire is important for proper grounding, but not relevant to how a switch works.
A circuit is completed by the black wire carrying power to the device (like a light), and the white wire completing the circuit and returning to the circuit box. So if you look at anything that is powered in your home, like a plug, light, dishwasher, etc., they all have black and white wires running to them. These are usually carried in a single bundle of wires wrapped in a white sheathing, such as Romex.
Basic Switch Wiring Diagram
Figure 1 below shows the wiring diagram for a basic switch. For a device controlled by a switch, like a light fixture, the switch breaks the black (hot) wire. This is shown in the figure. When the switch is on, the black wire is connected through the switch. And when the switch is off, the black wire is not connected. So all you are doing when you flip the switch is toggling the connection of the black wire. That is what turns the light on and off. Pretty simple so far, right?
The white wire (neutral) must connect to the light fixture to complete the circuit. So the white wire will not connect to the switch. It usually passes through the switch junction box, and then connects directly to the light. This is the basic way that a switch works.
That’s all there is to a basic switch. It is a pretty simple concept!