RenovationFAQ

Installing a lighting dimmer switch

One of the easiest and most inexpensive ways to change the mood of a room, or put the finishing touches on a new renovation, is to install a dimmer switch.  It’s a fairly easy operation even for a novice as long as safety rules and the installation steps are closely followed.  The following instructions are for the installation of a single-pole dimmer (meaning there is only one light switch controlling a particular set of lights, as opposed to multiple switches).

The first thing to do is decide on the type of dimmer switch you want to install.  There are generally four types, and the differences are mainly cosmetic. The options are dial, slide, touchpad, and the combination light switch/slider.  I personally prefer the light switch/slider type because it has the most subtle appearance and blends in well with the other non dimmer switches in my home.  The dial and the slider type switches are more susceptible to damage by bumping into them.  It’s all a matter of personal preference though.

One thing to consider when selecting your switch is to ensure that you are not overloading it.  What that means is that the combined wattage of all of the lights it is controlling should not exceed it’s wattage rating.  For example, if the dimmer has a maximum capacity of 600w, you don’t want to have it controlling more than 6 x 100w bulbs, or 12 x 50w bulbs.  Otherwise it will likely overheat and fail, needing replacement.  If you have a requirement that exceeds the rating, you’ll want upgrade to a 1000w dimmer.  Either way, you’ll want to stay roughly less than 90% of the maximum load to be on the safe side.

Now that you’ve selected your dimmer, installing it is fairly straightforward.  Most dimmers on the market come with installation instructions, and are generally all similar in the installation steps required. 

The most important first step is to shut off the breaker controlling that switch.  DO NOT even attempt to remove the wall plate of your old switch without doing this.   Once the power is off, remove the wallplate, and unscrew the switch and pull it out slightly without disconnecting the wires.  Take a look at the number of wires that are attached.  If you see two insulated wires attached to two screws (terminals) of the same color, usually gold, you’re dealing with a single-pole switch.  You may also see a bare copper wire, which is the ground.  If your setup doesn’t look like this, put it back in and consult an electrician, as you may be dealing with a more sophisticated setup.

Proceed to disconnect the wires from the current switch.  On some of the newer model switches, the wires are not attached to the screws, but actually inserted into tiny slots in the back of the switch.  If that’s the case, you need to insert a small thin object, such as a straightened paperclip, into the to release slots just below wire slots and push.  At the same time, you can pull that particular wire from its slot.

Your new dimmer should have three wires coming out of its back; two black and one green.  Using the wire caps that came with your dimmer, connect each black wire to one of the insulated wires, and the green wire to the bare copper wire.  It doesn’t matter which black wire goes with which, as long as black is with black.  There may be cases out there where the wall switch is at the end of an wiring run, and one of the attached wires will be a white one instead of black.  Treat the white wire in this case as if it was black.  In fact, if no one has done so, take a little strip of black electrical tape and wrap it around a small section of the white wire.  This will let the next person working on the box know that they’re dealing with a “hot” white wire. 

Ok where where, we?  The way to connect the dimmer wires to the house wires is to carefully wrap the thinner dimmer wire around the straightened and exposed tip of the house wires.  If the wires ends were hooked to go around the screws of the old switch and you are having difficulty straightening them, nip them off with a wire cutter than strip off about 3/8″ of the insulation with a wire stripper.  Take the wire cap, and twist it onto the end of the wire, ensureing that it’s a tight fit, and that most of the dimmer wire is now hidden underneath the wire cap.  Pull on the end of the cap slightly to ensure that it’s not loose.  Repeat this process for all three wires.

When the wires are secure, bend them in the middle and insert them back into electrical box without loosening the wire caps.  Then mount the dimmer switch followed by the wall plate.  Turn the power back on at the breaker, and test the dimmer to ensure that it works.  You’re done! 

Remember to read and follow the instructions supplied with your breaker very carefully.  If the breaker trips when you turn the power back on, you may have done something incorrectly.  Turn the breaker off again, remove the switch and inspect your work.  Make sure that none of the wire caps have fallen off.