What is a Rotary Dimmer Switch?

Dimmerswitch on neutral wall
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A rotary dimmer switch has sort of a fancy name, but it's something you're probably already familiar with. It's a dimmer switch with a dial on its face. They were pretty popular during the 1970s and 80s and are still widely available. So if you need a dimmer switch and you like the rotary action and somewhat retro look of a dial-type dimmer, this might be your next switch. 

What's the Rotary Dial Used For?

In case you're not familiar with rotary dimmers, the dial is used to control the amount of brightness of a light fixture.

It can be adjusted from a very dim, moon-glow level, to the bulb's full brightness. The rotary knob turns from left to right. It's in the lowest setting when turned to the far left and at full brightness when turned to the far right. Most rotary dimmers have a push-on/off function. You push the dial straight in until it clicks to turn the light fixture on or off. Others turn all the way to the left until they click to turn on or off. 

Heat Dissipation

A dimmer switch is basically a switch with a big variable resistor built into it. It consumes a little bit of energy, and this creates heat. To help dissipate the heat, the switches often come equipped with cooling fins or aluminum faces. Dimmers should be installed in electrical boxes that provide a little bit of breathing room, to prevent overheating. Don't cram one into a small switch box or a box that's full of wires. If you need to, you can replace the box with a deeper model.

Use an "old work" box that's designed for remodeling. This allows you to install the box without cutting into the wall. 

Dimmer Switch Wiring

Like other types of light switches, rotary dimmer switches can be wired to control lights from one, two, or three locations. One location calls for a switch. Two locations require a pair of matching three-way switches.

Three locations require a four-way switch installed between a pair of three-way switches. Most dimmers have short wires, called leads, instead of the screw terminals you find on standard light switches. You connect the leads to the household circuit wiring using wire nuts. 

Other Types of Dimmer Switches

There are other types of dimmer switches available to control your lighting. They all do the same basic thing but have their own look and switching action. 

  • Toggle-type dimmers look just like standard switches, but the little toggle controls the dimmer level. 
  • Rocker-style dimmers have a rocker panel for control. With some, the rocker is used for the dimmer adjustment. With others, the rocker merely turns the light on or off, while the dimmer level is controlled by a little slide-bar next to the rocker. Toggle-type dimmers also can have this setup. 
  • Slide-type dimmers have a little lever that slides up and down. Some of these feature built-in illumination, making it easy to see the switch at night when the lights are out.
  • Automatic dimmers are a favorite. They have on, off, and automatic settings on the switch. When set to automatic, the switch uses a light sensor to detect the level of room lighting and adjusts the light fixture accordingly. If it's a sunny day and then it suddenly becomes cloudy and dark outside, the dimmer increases the brightness of the light to maintain the same level of brightness in the room.

    Dimmers and Energy-Efficient Bulbs

    Dimmers can be tricky with today's LED and CFL (compact fluorescent) light bulbs. A lot of CFLs won't work with dimmers, and many LEDs won't give you full range of adjustment with old or standard dimmers. To prevent problems, choose a new bulb that is fully dimmable and/or a dimmer that is designed to work with newer bulbs. You can still end up with some range limitations, but you might not notice a problem. In case you haven't noticed, CFLs are on the way out (with good reason), so it's best to choose products optimized for LED.