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LED Lamp Dimming: Some care is needed to ensure good performance

By Craig DiLouie | Feb 15, 2024
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As the residential market completes its shift to LED, lighting system owners making the switch may find themselves adapting the technology to existing control needs. For example, system owners may want to add dimming functions to multipurpose rooms that require various light levels. The good news is that, as a light source, LED is inherently controllable. The challenge is that some care is needed to ensure good performance.

The LED product must be dimmable. LED lighting products work with a driver that converts input power to the low-­voltage constant current LEDs require. The driver may be fixed-output or dimmable, reducing light output based on changes to current. Operating a nondimmable LED product with a dimming control can result in heavy flicker and damage to the lamp, reducing its life. It is therefore important to verify that the given LED product is dimmable.

The dimming device should be designed for LEDs. Older incandescent dimmers are designed for incandescent lamps. Using them to control LED lamps may result in limited or inconsistent performance. For best results, consider a dimmer rated for LED loads or a universal dimmer, which accommodates multiple light source types and potentially many LED lamp variations.

For optimal performance, match the LED product and control device based on application. Dimming performance for LED products is not as straightforward as with incandescent lamps. Incandescents were essentially all manufactured to the same standard, while LED lamps have greater variation in design and manufacturing.

To ensure basic compatibility, the National Electrical Manufacturers Association released Standard SSL-7A. 

“This was a great start toward compatibility between LED bulbs and dimmers,” said Zach Schroeck, director of product management for Lutron Electronics Co., Coopersburg, Pa. “Unfortunately, the standard does not include requirements to address how well an LED will dim. An LED can have a low-end range of only 50%, buzz and have slight flickering and still be considered SSL-7A compatible.”

To evaluate quality of dimming, manufacturers such as Lutron and Leviton Manufacturing, Melville, N.Y., test various combinations of their devices with LED products and then feed the results into online compatibility tools. This offers valuable information for predicting installed performance for a desired combination.

Dimming performance is also directly related to product components’ quality. In some applications, basic-grade products may produce an acceptable control experience. In others, the customer may require certainty of high-quality dimming.

“It is important to determine what kind of performance your application needs and select components appropriate for that level of performance,” said David Buerer, director of product management, controls, for Leviton. “For example, if you are doing a design-build job for a high-end restaurant, consider higher-end fixtures, drivers and controller combinations rather than phase-cut/two-wire dimmers with the lower-end residential LED light bulbs. Your customer will be happier with the performance of a little higher-end fixtures, drivers and controller combinations.”

For discerning dimming applications, consider different approaches. LED lamps are compatible with line-voltage dimming, which will likely continue to dominate residential applications due to its cost and ease of use with LED lamps with integral drivers. As LED further establishes itself as the predominant light source, however, designers may reach for other approaches such as 0–10V dimming and trailing-edge dimming, particularly for discerning applications.

“For higher-end homes and niche applications, trailing-edge dimmers have grown in popularity,” said Tom Babich, senior product manager, lighting controls, at Leviton. “They are friendlier with LED fixtures, though they come at a premium to forward-phase. An example application could be for exotic lighting fixtures/chandeliers where there are multiple LED load types in the same fixture.”

The best way to fix a problem is in advance. Upgrading an existing home lighting system may lead to dimming issues such as flicker, flashing, pop-on, drop-out, ghosting, audible noise and poor dimming range. Contractors can troubleshoot by ensuring all lamps are the same load type, dimmable and installed with a compatible dimmer rated for LED loads. They can also determine if the dimmer has a mechanism to adjust dimming range.

“When LED lamps and controls have not been designed using robust, tested and proven components, flickering, buzzing and dropping out are common issues with no easy fixes,” Schroeck said. “The key is to do your homework.”

Consider wireless, color tuning and home automation. LED lighting offers so much more in terms of capability. Similarly, smart controls and wireless can increase flexibility and ease of application. Every upgrade to LED is an opportunity to evaluate these capabilities with the customer.

“The future of lighting is LED, and the future of control is smart, cloud-connected systems that integrate seamlessly with other smart home or smart building systems,” Schroeck said. “When you’re working with customers on a lighting upgrade, talk to them about the benefits and the opportunity to install a system that continues to add value and features over time.”

stock.adobe.com / Prostock-studio

About The Author

DiLouie, L.C. is a journalist and educator specializing in the lighting industry. Learn more at ZINGinc.com and LightNOWblog.com.

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