Dimming Low Energy LED Lights, Difficult Not Impossible!

Published: 13th January 2012
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Depending on which type of light you want to dim, choosing a dimmer switch can go from being a fairly simple task to a very complicated one. If you are dimming halogen or incandescent lighting loads then this is straightforward as most will function perfectly well. However, dimming Compact Fluorescent Lamp (CFL) or Light Emitting Diode (LED) can be complicated as both the dimmer switch and the light must be compatible. LED in particular is the hardest as there are many different types available, all containing different types of dimming technology.
Most dimmer switches were never originally designed to dim low energy lights as they were not available to perform tests with at the time of the initial design. Dimmer switch manufacturers have reacted slowly, if at all to the advance in LED lights making the task of choosing a compatible dimmer switch a guessing game.
Over the past few years I have worked closely with both lighting and dimmer switch manufacturers to provide the most up-to-date advice and pre-sales support. Although my findings cannot always be 100% accurate as lighting manufacturers often change the components in their lamps or fittings causing the once compatible switch to no longer work.
When a non compatible dimmer switch is used with a low energy light, it causes the light to flicker. The flickering generally occurs when the light is dimmed to low levels or sometimes at full brightness. This is usually because the load of lights are too low for the dimmer switch to react to.
One of the regular questions I get asked when customers start looking for LED compatible dimmer switches is what is the difference between leading edge and trailing edge? Leading edge and trailing are two different types of dimmer technology and until the arrival of LEDs nobody cared which one they used.
Leading edge is the most popular because it is cheaper. It contains a triac and a coil and may buzz slightly when in operation; the minimum load is quite high, usually around forty watts. This is not a problem when dimming incandescent or halogen but can be when dimming CFL or LED which are usually just ten watts per light. Leading edge dimmers are now available that have a minimum adjustment dial, turning the dial down to its lowest setting allows fewer lamps to dimmed to a much lower setting IE down to 1%.
Trailing edge technology uses solid state components such as insulated gate bipolar transistors (IGBT) and has no triac or coil. This provides a totally silent and smoother dimming action. The other advantage of using trailing edge is that the minimum load is lower. When dimming some LED downlights the load can be rated at ten watt instead of fifty watt which allows for far more lights to be dimmed. Potentially up to thirty lights can be dimmed on just one switch.
When dimming CFL you must ensure that the lamp is dimmable. There are very few dimmable CFL lamps on the market mainly because LED has overtaken it. CFL lamps should be turned up to full brightness on start up and left at full power for a few minutes before it is dimmed or the life expectancy of the lamp will be reduced. Depending on the minimum and maximum wattage, there are a few dimmer switches that are compatible. Although cheaper in price, dimming CFL is not worth the hassle; LED is better in every way:
Like with CFL, you must always ensure that the LED you choose is dimmable as most are not. LED lighting technology has developed rapidly over the past few years but dimmer switch technology has not. There are many different types of dimmable LEDs available. Consequently, consumers are often challenged to understand which combinations of LEDs and dimmers are compatible. It is not just a case of choosing a leading edge or trailing edge dimmer but more importantly which brand and model number will work best for your installation.
There are two types of dimmable LED lights; LED bulbs and complete LED downlights. LED bulbs are harder to dim than downlights.This is because downlights have their own built in driver and the manufacturer of the driver can usually recommend a few dimmer switches as they have tested them before they are released.
Having decided on which LED you want to install, selecting the correct LED dimmer switch should be based on the following:
1. Compatibility; ideally, the LED manufacturer will have a list of recommended dimmer switches. Selecting a random dimmer switch may work perfectly well however, a dimmer switch that is incompatible can cause flickering and in some cases, permanent damage to the LED.
2. Quantity of LEDs; dimming results can vary depending on how many LED lights are in the circuit. LED loads are not rated the same as halogen, for example ten, five watt LEDs is not the same as one fifty watt halogen. De-rating factors may need to be considered and vary from brand to brand. Selecting a compatible dimmer for the wrong quantity of LED lights could cause flickering and reduce the range of dimming, i.e. the lights won't dim down to 10%.
3. Aesthetics; if you like the look of your current dimmer switch but it is not compatible and causes your LEDs to flicker you can replace the module inside. This can be done by rewiring the module and swapping it over. Around ninety percent of dimmer switch modules will interchange with each other. This allows you to keep the look but upgrade the technology.
Advanced dimming can be done by using lighting software controlled from a PC that allows you to control or dim your lights from anywhere in the world. From remote control operated dimmer switches to wirelessly controlled lighting solutions. The possibilities are endless by choosing the correct, compatible components you can have total control over your lights from a PC, iPad or even iPhone.

Written by Chris Horridge, resident lighting expert for http://www.downlightsdirect.co.uk”> for more information on dimmer switches, including data sheets and videos, please visit http://www.downlightsdirect.co.uk/switches-and-sockets/dimmer-switches.html


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