A light dimmer switch is a convenient way to control the intensity of any light fixture or ceiling fan. Typically, they are installed as an alternative to regular single-pole switches. Installing a dimmer switch is a straightforward process that takes less than a few minutes. However, you need to be familiar with the wiring in your home and ensure that it meets electrical code requirements before installing a dimmer switch.
The Wiring for a Dimmer Diagram
First, you should check the circuit in your house for current and test the existing light switch before you begin the process of wiring your new dimmer. If the existing switch is not working, shut off the power to that circuit at your fuse box.
Next, use a multimeter to test each wire on the light switch to see if it functions as a hot or neutral wire. Generally, the black wire is considered live and the red is live as well, but this may vary depending on the type of switch and your house wiring.
Once you’ve determined the proper function of each wire, cut it short. Wrap it in a plastic wire cap to protect the connection. Then, connect it to the corresponding wire on your dimmer switch.
You’ll need to connect a wire to your new dimmer to act as the ground. This is a copper wire that usually comes with a green wire cap.
Identify the Wires in Your Wall Socket
The wires running from your light fixture to your on-off switch will have three cables. One for the hot (red) wire, one for the neutral, and a separate copper grounding wire.
This is common in houses that were built before the 2011 National Electrical Code update. The wires that run from the light fixture to the on-off switch are referred to as “traveler” wires. The traveler wires are commonly marked in red on the wall, but are also often taped off or labeled in white or black.
If you’re replacing an existing dimmer, it’s important to note that the wires in your wall socket are not always grounded, even if the switch is in a grounded metal box. If you suspect that your switch box isn’t grounded, make sure to remove the cover plate and test it with a voltage tester before removing the old dimmer.
A common mistake is to simply connect the hot and neutral cables together. This is incorrect and can cause a dangerous circuit. Rather, you should follow the wiring in the following diagram to create an accurate and safe circuit that will work properly when dimming your lights.
The most important thing to remember is that the dimmer wire should be connected to your house’s copper grounding wire(s). If your house is equipped with plastic-sheathed cable, you’ll need to find and connect your bare copper grounding wire. If your house is not wired with grounding wires, it’s best to purchase an additional dimmer that’s rated for connecting to a copper grounding source.