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Shedding Light on LED Dimming Issues

Shedding Light on LED Dimming Issues

Things have gotten better when it comes to adjusting the light output from LEDs. It’s true! Yet there’s still a lot of work to be done with interoperability. There are dozens of product lines and hundreds of luminaire options that are a great fit for a variety of applications – It’s enough to make someone’s head spin. Thankfully, manufacturers are doing their part to help distributors understand the best fits for their lines.

Where Things Were With Dimming

How much dimming does the lighting designer want? If you’re Naomi Miller at Pacific Northwest National Laboratory, it’s the first thing that would be nice to know. At the time of the interview, she was working on a residential application for a friend and even there she had issues.

“Some LED replacement lamps list dimmer compatibility, but then they don’t actually dim below 50% with the listed dimmer,” she notes. “Some products dim down to 5% or less, but then when you switch them on after switching them off from that low level, come back at a level of 40%. Whoa! Not what you were expecting after a romantic dinner!”

Those kinds of difficulties continue to be an issue for consumer applications when they can only dim to 50 percent and those that can go further often have issues with flicker and other instabilities, she notes. Commercial applications are somewhat different but have similar issues because of differences in dimmer design like DMX, DALI and ELV. For circuit design this can be very problematic for trying to even light a single room.

Where We’re At Now With Dimming

Ethan Biery, design and development leader at Lutron, notes that as with other elements of the LED industry, dimming is getting better because of some voluntary standards such as NEMA SSL-7A, as well as efforts by Energy Star to endorse good dimming performance.  Furthermore, NEMA is working on a “dimming compatibility mark” that should help customers find dimmers and lamps that will perform well together.

He also sees the same issues as Miller, however, because it’s up to manufacturers to go beyond these standards, few of which “enforce the high level of performance (smooth, continuous, and deep dimming) that end users may be used to out of traditional lamps.”

Luminaire manufacturers like Lutron do offer compatibility charts for their products, based on testing hundreds of combinations, which are frequently updated. He adds that manufacturers you can trust are more likely to offer support. Miller notes that not all do, as some compatibility charts are out-of-date per her experience.

Distributors, Beware: Last-Minute Changes, Long-Term Headaches

Distributors have worked hard to create portfolios of products because of their experience in trying to meet the needs of lighting designers and construction managers. Unfortunately, the process for most still requires cost-savings backtracking, which inevitably leads to changes in luminaires. As Biery notes, “The selection of a lighting control and LED load is a system, and changing one aspect of that system without fully understanding the impact on the overall system (wiring, performance, etc.) is very risky.

Some distributors recognize this and work earlier in the procurement process with construction managers. To that end, Biery adds, “Understanding the potential impact up front if the customer’s expectations are not met, and who will take responsibility for fixing these issues, can also minimize the likelihood of last-minute product substitutions.  In the world of LED lighting, it’s usually true that you get what you pay for.”

Especially in the case of specifications, relying on compatibility charts and ongoing communications with the dimmer system and luminaire manufacturers is critical. Both Miller and Biery say that otherwise, ongoing testing with small-scale installations are likely the only way to be able to find any potential issues.

If they do arise, distributors and project managers alike are well aware of the outcome: overruns and delays. But maybe not as many as there once were.

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John Curran

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