How to install a Dimmer switch. Wiring a Dimmer switch is as simple as Wiring a 2-way switch. If you're just replacing an already existing 2-way switch, then your objective should be as easy as swapping the wires from one switch to the other. If you feel the need to get more knowledgeable of the task at hand, I recommend going to my How to wire a 2-Way Switch page to get more familiar with your the basics of switch wiring. Also if you need to go over a little terminology so you know exactly what is being discussed. Go to my Switch Terminology page where I discuss the terms used for the different types of home electrical switches. It should also help in understanding the functions of each type of switch.
Dimmers come in two basic wiring configurations. A standard single-pole
dimmers (2-way) or three-way dimmers. With a standard 2-way dimmer, a
single switch controls a single light. With a three-way dimmer, you can control
a light from 2 different locations. For this, You’ll need one three-way dimmer and one
three-way switch. This lets you dim from one location and turn the
lights on and off from another.
When installing a Dimmer switch, all you're really doing is controlling the amount of voltage flow to a light which makes it dim at a low setting to a fully bright light at maximum setting.
Now a typical circuit will contain a 3-wire cable known as romex. (See my Romex Cable page to get familiar with the different types of wire) The cable consist of a black wire, a white wire and a bare copper wire.
Black wire = Power or Hot wire
White wire = Neutral
Bare copper = Ground
When wiring a Dimmer switch circuit, all we want to do is to control the black wire (hot wire) to turn Dim/Brighten the load. This simple diagram below will give you a better understanding of what this circuit is accomplishing.
Now in the diagram above, The power source is coming in from the left. Notice the black wire is the only wire that we are controlling through the 2-way switch. You have an incoming hot wire (black) going to one screw (it does not matter if you use the brass or silver screw) on the side of the 2-way switch and a black wire from the other screw on the 2-way switch going to the load (light, ceiling fan etc..). The white wires are wire nutted together so they can continue the circuit.
Now as for the ground wire. It is very important to connect the ground wire to the switch as well. The Green screw on the 2-way switch is for the ground so all ground wires should be connected as seen below.
All ground wires (bare copper) are all now connected (incoming ground, load ground and switch ground). This makes for a safe protected circuit by having all grounds intact.
Watch the following Video for some great tips
on installing and wiring a Dimmer Switch.