How to Install a Dimmer Switch
February 22, 2007
This is a simple project that most homeowners can tackle themselves and complete in less than 30 minutes.
The first thing you need to do is determine which size and type of dimmer switch you need to install.
Sizing your dimmer switch is very easy. Dimmer switches are rated according to the lighting load they will dim. Let’s say you want to dim your dining room chandelier. This chandelier has 8 – 100 watt light bulbs in it. This means that the total lighting load you want to dim is 800 watts. You can reduce this load by changing the light bulbs to 60 watts each. This would give you a total lighting load of 480 watts.
The smallest dimmer switch you can get is 600 watts. From here the next size is 1000 watts, 1500 watts, 2000 watts, etc… The 600 watt and 1000 watt dimmers are the most common. Anything above 1000 watts will no longer fit into your standard single gang switch box. These larger switches typically require their own 2-gang switch box.
Now let’s talk about type; I would like to discourage you from getting those cheap rotary style dimmers. These control the light level through a variable resistor. Less resistance increases the light level and more resistance decreases the light level.
The problem with this solution is that you end up using a lot of energy to heat the resistor, which doesn’t help you light up the room but still costs you. In addition to be being inefficient, these switches tend to be cumbersome and potentially dangerous, since the variable resistor releases a substantial amount of heat.
The newer style resistors rapidly turn the light circuit off and on to reduce the total amount of energy flowing through the circuit. This results in better efficiency and less energy loss through heat. To learn more about this style, I recommend reading “How Dimmer Switches Work“.
You also need to determine if you need a single pole or 3-way dimmer switch. A single pole switch will only turn on or off the light from 1 switch. A 3-way switch will turn on or off the light from 2 or more switches.
With 3-way switches you only need to replace 1 of the 3-way switches with a dimmer. If you want to dim your light from multiple switches in a 3-way circuit, you will need a master and slave(s) combination. The Lutron Maestro series is one I recommend here.
To replace your switch, you first need to turn off the power supplying this circuit. Now go remove the cover plate and use a voltage tester to ensure that the power is indeed off. Never assume the power is off. I have seen some very scary stuff over the years, resulting in me getting shocked by assuming the power is off. Never assume the power is off and always test before touching any wires or devices.
Loosen the screws on your old switch and pull it out of the box. Now, before you disconnect the wires, make a note of how they are connected to your existing switch. This is very important to make your 3-way switches work porperly. I recommend writing this information down or taking a picture with a digital camera.
When reconnecting your dimmer switch, it is very important to ensure the ground wire is connected to the new dimmer. If the dimmer switch has screw terminals to connect your wires to, be sure you wrap the wires clockwise around the screw terminals. This will allow the loop in the wire to close with the final turn of the screw resulting in a better electrical connection.
If you have questions or need further clarification on this matter, please submit your questions in the comment section of this post.
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