Install and wire a dimmer switch

Do you have an old dimmer switch you want to replace? Or maybe you have a light you want to control the brightness on and are ready to install a dimmer switch? No matter the case, you’re in luck–because installing and wiring a dimmer switch is easy. Let’s take a look at how to put in a dimmer for your lights and also some advantages and potential problems you might have with a dimmer switch.




How does a dimmer switch work?
Today’s dimmer switches (modern ones, meaning since the ’90s), dim your light very efficiently. Essentially, the technology inside the dimmer switch controls the flow of electricity to your lights by turning it on and off many, many times per second. Your eye doesn’t notice the ons and offs, but it does notice the overall effect: a dimming or less intense light brightness.

Older dimmer switches, such as the kind you turn using a dial worked differently. They dimmed lighting by resisting electricity flow to the dimmer switch. The problem was that the electricity had to go somewhere (no, not back down the wire it came from!), so it dispersed as heat. Not very efficient you might say.

How to wire a dimmer switch
Wiring a dimmer switch is straightforward if you know how to turn off the electricity to the dimmer switch and connect a few wires…really, that’s all there is to hooking up a dimmer switch.

  • First, turn off the power going to this switch (flip your circuit breaker off and use a tester after the next step to confirm this).
  • Now, unscrew and remove the dimmer switch’s faceplate and dimmer knob (if yours has one)
  • Disconnect all wires coming from or going into the existing switch (most dimmer switches have wire leads coming out of them instead of screw or push terminals).
  • Your new dimmer switch then gets wired the same way as the previous switch, i.e. black(hot) to black and the wire marked common, white or neutral to home’s white(common) wire. Twist wires together using a wire-nut. Straighten wire ends if needed and strip new ends if ends are corroded or dirty.
  • Insert and fold all wiring into the electrical box, making sure to leave room for the dimmer switch, which can sometimes be bigger than the previous switch.

Wiring a 3-way dimmer switch
Follow the above steps for a standard dimmer switch, except that you’ll need to purchase a special 3-way dimmer switch (a standard one will not work for your 3-way switch) and use the following wiring tips.

  • To properly wire your 3-way dimmer switch, mark or tag the existing wires coming from your house so you can connect them the same way to the new switch.
  • You’ll most likely see three wires in addition to the a copper/green ground wire. The three wires, colored black, white and red are considered to be “hot” wires, with one acting as a “common” wire (usually black) and the other two as “traveler” wires (red and white, with the white wire probably marked with electrical tape). Again, find and mark the common wires. This will usually be attached to a terminal marked “COM” or to a screw that is darker in color. The other two wires will be connected to matching lighter colored screws.
  • Once you know which wire is which, simply attach the common wire to the “common” terminal on your switch and the other two wires to the “traveler” terminals. As above, you’ll be connecting to lead wires coming out of the 3-way dimmer switch, and will be using wire nuts.

Dimmer switch tips and troubleshooting

  • When buying a dimmer switch, check the maximum load it’s rated for. For example, if it has a limit of 600 Watts, you wouldn’t want to install the dimmer on a switch that controls 8 100 Watt recessed lights. A good rule is to not exceed more than 80% of the rate maximum for the dimmer switch.
  • When installing dimmers for 3-way switches, remember to buy a special 3-way dimmer switch (it will say at the store and on the package). Also, only one switch in this setup can be on a dimmer.

Humming or buzzing dimmed lights? If your lights buzz when dimmed, it’s probably because the filaments in the bulbs are vibrating as the dimmer switch turns electricity off and on repeatedly to “create” the dimming effect. One remedy is to use a 130-volt bulb like these. The filaments in these are stronger and tend not to vibrate. You can always try a new dimmer switch if that doesn’t solve the problem.

Do dimmer switches save you money and electricity? Yes, dimmer do cut down on electricity use. Old dimmer switches (the kind that really heat up), do not. Energy efficient fluorescent bulbs would save you more, however.

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