Dimming LED Lamps and Luminaires

 

For decades, dimming residential and commercial lighting was fairly straight forward – just match the total wattage to be dimmed with the wattage capacity of the dimmer.  The rise of LED has changed this simple formula to one that requires more thought and preparation.  It’s not complicated, but understanding the basics will help avoid dimming issues. 

If you plan on dimming, use LED lamps or LED luminaires that specifically indicate that they work with dimmers.  Likewise, only use dimmers that are designed to work with LED luminaires.  If you find yourself upgrading a home to LED, then make sure to replace the old dimmers with new ones rated for use with LED.  For commercial projects, electrical wall switches and remoted relays should be chosen to have extra capacity to handle the brief InRush surge, and dimmers used with LED lamps or luminaires should be rated for use with LEDs.

There are different types of LED approved dimmers.  While dimmable LED lamps typically work with any LED approved wall dimmer, many LED luminaires are offered with different drivers to accommodate different types of dimmers, so always check which type of dimmers your specific LED luminaire is designed to work with. 

While there are a number of dimming schemes on the market, there are three common and reliable types worth considering.  Standard LED rated wall dimmers, often called ELV dimmers, use the existing 120V wiring to dim the luminaire.  0-10V dimmers and DALI dimmers completely avoid load and incompatibility issues, but do require additional low-voltage wiring between the luminaire and dimmer.  0-10V type dimmers can offer greatly improved dimming performance, are simple to use, and are a top choice for residential and commercial dimming upgrades.

TRIAC type dimmers are not the best choice for dimming LED because in some cases using a TRIAC dimmer may cause humming, flicker or other issues.  If you have this problem, try switching to a ELV dimmer to resolve the issue.

When using a TRIAC or ELV wall dimmer, it is important to calculate the load correctly.  LED luminaires, as well as other electronic equipment, exhibit a condition called InRush (for more on this, see our InRush article).  InRush current can be 40-100 times higher than the rated steady state current of the power supply.  Calculating the total circuit load for a certain number of lamps or luminaires to be installed on a circuit is usually a simple question to answer.  But with LED lighting some extra thought is required.  For example, when using a standard LED rated 300W wall dimmer with 50W LED luminaires does not necessarily mean six luminaires can be used on this dimmer.  While the luminaire may only draw 50W continuously, it will have a start-up inrush current which draws a much higher load.  These higher loads are why the total LED luminaire load rating is usually less than the maximum rating of the dimmer.  When using a TRIAC/ELV dimmer for LED luminaires, you should leave at least 25% of the dimmer capacity free to accommodate the InRush condition.  To prevent problems, read the specifications and instructions of the dimmer you intend to use.

Following these basic suggestions should help you avoid dimmer related issues.  For a deeper and more technical discussion on dimming take a look at the following article:  Deep Dive in Dimming