Dimming LED Lamps: how to avoid disaster
Unfortunately dimming LED lamps can be a complicated business, and there are a few variables to be taken into account when dealing with them. They are regrettably not as straightforward as halogen lamps, which only require a voltage change in order for them to be dimmed. LEDs require a constant current, and also operate at much lower wattages than halogen, both of which can cause problems.
Let’s look at the lower wattage problem first. Many consumers don’t realize that most dimmer switches are designed to work with a minimum load of at least 40w. This is obviously fine for halogen where the average lamp is 50w, but they don’t consider that they’ll need at least 5 x 8w LEDs to be controlled by 1 dimmer for it to work correctly, so it’s a good idea to discuss this with your customer before they start.
The next issue is whether the dimmers are leading or trailing edge. As a general guide, older leading edge (triac) dimmers work with LED, while newer trailing edge (often electronic or push button) ones don’t, but this unfortunately isn’t a hard and fast rule, so you’re going to need to check with the LED manufacturer which type of dimmer their lamps work with.
When dealing with low voltage LEDs, bear in mind that you will need a constant voltage driver; a standard transformer won’t do the job. Again, check with the manufacturer which one they recommend.
If you get any of the factors wrong when dealing with LED lamps, the wrong type of dimmer, not enough lamps, the wrong transformer etc, it’s not dangerous, but it won’t work! There can be different outcomes, from no diming at all through to irregular dimming. More importantly, the LEDs might be damaged beyond repair, and as their initial cost is still relatively high, this could cause difficulties between you and your client.
As LED technology is constantly changing, it really is worth speaking to the manufacturers regularly to check the information you have about their products is up to date. There have been instances where lamps have been tested with certain dimmers and intelligent lighting systems, but then components have been changed and the two no longer work together, with costly consequences.
Where your customer has already bought the LED lamps they want to use, you obviously need to find all this out before you start installing dimmers or intelligent systems. Preferably the customer will come to you before anything has been purchased, then you can be sure from the start that you have everything right.
This blog was written by Paul Blythe, a UK blogger who enjoys writing about all things electrical, and is writing about LED lamps on behalf of Lightbulb World.