Dimmer and Switch Technology
When first looking at dimmers and switches you might think they all work the same and will work for everything the way your dumb switch does. This is not the case! Dimmers and Switches fall into several categories
- Dimmers and switches that work with most LED bulbs (trailing-edge dimming)
- Dimmers and switches that work with incadenscent and some LED bulbs, or multiple LED bulbs in parallel (leading-edge dimming)
- Dimmers that work without a neutral wire
- Dimmers and switches for ceiling fans
- Switches that work with fluorescent lights
- Switches for high loads and inductive loads
Dimming
Trailing edge vs leading edge dimming and LED bulbs
I could try to explain it, but this article does a way better job. What you need to know is that LED bulbs generally play nicer with trailing edge dimmers. As far as I know, only Lutron makes those and they’re quite expensive. You can use leading edge dimmers, but you’re likely to get flickering or a buzzing noise, especially with cheaper bulbs. You also won’t get a linear dimming experience and it usually requires more than 1 bulb in the circuit to dim without issues. I really do recommend reading that article.
If a box doesn’t have a label on it, it’s doing leading edge dimming.
All of that said, I use leading edge dimmers with all of my LED bulbs. I also get bulbs that are rated for dimming. I can fill up a whole nother post on LED bulb technology.
Dimming loads
Dimmers will have different load ratings for LED and incandescent bulbs. They will usually say on their packaging that they support up 150W LED, 600W incadescent or something similar. Every switch is different and if you ahve multiple bulbs in your circuit you should check the load rating before buying the dimmer or switch.
Variable speed ceiling fans
Ceiling fan smart switches often look very similar/exactly the same as a light dimmer, however the internals are different. You should not use a light dimming switch as a variable speed fan controller! Read this post if you want to fully understand why not. I use a z-wave homeseer hs-fc200+ to control my ceiling fans.
No neutral wire
There are some dimmers that work without a neutral wire. They’re usually only labelled to work with incadescent bulbs. They do this by still allowing a few milliamps of power through the circuit to power itself, but not enough to turn on an incadescent bulb. Since LEDs require considerably less power and have circuity to convert AC power to DC, using these sorts of dimmers can considerably shorten the lifespan of an LED bulb.
Switches
Resistive vs Inductive loads
Most electronics that don’t have a motor are resistive loads. All switches should handle these without issue. The Insteon 2487S switch, for example, can handle a 17amp resistive load. An inductive load is a bit different and usually involves motors and a high inrush current. This is getting into an area that I’m not the best at explaining, especially with my limited understanding, but switches will usually have a separate rating for inductive loads. In the case of the Insteon switch, it will support up to 1HP motors. The Zooz 30 relay part of the switch will support 15amp resistive or 1/2HP motor loads.
Florescent bulbs
Florescent bulbs are different than LED or Incadescent bulbs. Starting a florescent bulb can take upwards of 600 volts. They use a ballast that changes the output voltage and you need a switch that can support them. For example, a Insteon Switch can support a 10amp ballast. GE by Jasco z-wave light switches also support florescent lights. Some switches have been reported to cause flickering when they don’t support florescent bulbs. I don’t know why.
Summary
Hopefully this information will help save you a lot of time and frustration with getting switches only to watch lights flicker instead of working correctly.