Questions and answers from “How to become an LED Expert” webcast

 •

Authored by: Ethan Biery, LED Engineering, Lutron Electronics

1. What are the most popular color temperatures for lamps?
All incandescent lamps have a 2700K color temperature at high end; all halogen lamps have a 3000K color temperature at high end.  Both of those sources dim to “warmer” (lower) color temperatures when dimmed, usually down to about 2200K.  LEDs can have any color temperature, although 2700K and 3000K are popular due to their match with traditional sources.  However, some people prefer the “cooler” (higher) color temperatures, 4000K-5000K, for certain applications, which are also available with LED loads.  Note that LEDs do not inherently change color temperature when dimmed; however, some newer LED products do advertise a special “dim to warm” feature to try and mimic incandescent performance.

2. Is there an issue with the advertised life expectancy with LEDs, or lifetime implications related to short-term on and off cycles?  Specifically, are there lifetime concerns with Blue LEDs in an RGB LED fixture?
LEDs are inherently long-life devices, with most residential grade products having advertised lifetimes of 15,000 – 50,000 hours.  The expected failure mechanism for LEDs is a decrease in the maximum light output, called “lumen depreciation”.  With RGB fixtures, which combine Red, Green, and Blue LEDs to make any color, it is possible for the different color temperatures to degrade at different rates, causing potential color shift over long time periods.  However, this is likely very manufacturer and product dependent, and difficult to generalize.  LEDs are not at all affected with short-term on and off cycles, making them far superior to CFL lamps in this regard.  Note, however, that poorly-designed or improperly-installed drivers can fail before the expected lifetime of the light-producing LEDs themselves are reached.

3. Why is heat dissipation so significant with LEDs?
While it’s true that LEDs generate significantly less heat than incandescent loads, they still can generate a lot of heat.  However, the main difference is how the heat is dissipated.  Incandescent loads generate much of their heat via radiation, which is why your hand feels warm holding it near an incandescent lamp.  LEDs radiate little heat, so all of their heat is concentrated at the source itself.  Furthermore, while incandescent lamps are capable of operating at very high temperatures (more than 300 degrees F!), LEDs, and their associated drive electronics, are sensitive electronic devices whose lifetime can be severely reduced by excessive heat.  If a manufacturer does not adequately get the heat away from the LED module, or the installer does not properly account for the heat of the bulb (for example, installing an LED lamp in an enclosed fixture), then the lifetime of the LED lamp will be shortened.

4. Can you discuss forward/reverse phase dimming and how it plays into the dimming process?
Forward phase controls (also called leading edge controls), by far the most popular style, operate by “chopping off” the first portion of the AC sine wave to perform their dimming.  They’re suitable for incandescent and magnetic low voltage (MLV) loads.  Reverse phase controls (also called trailing edge controls) operate by chopping off the end of the AC sine wave.  They are suitable for incandescent and electronic low voltage (ELV) loads.  From a dimming performance standpoint, there is no difference discernible to the end user.  LEDs may use either type, or sometimes work fine with both, but most retrofit LED lamps are designed to work with forward phase controls due to their prevalence.  The LED lamps’ spec sheet should always call out the type or model of the dimmer required.  Using the wrong type can lead to poor dimming performance or premature lamp or dimmer failure.

5. Are the Lutron C•L dimmers forward phase or reverse phase?
All Lutron C•L dimmers are forward phase, since that is what most loads require.  Some dimmers, typically called “adaptive dimmers” can operate in either forward or reverse phase.  ELV dimmers are reverse-phase only.

6. Are phase adaptive dimmers only in the RadioRA 2 family, or also in a wallbox family?
Phase adaptive wallbox dimmers are available in Radio RA 2 as well as Homeworks QS.  Phase adaptive panel modules are also available in Homeworks QS.  Nearly all stand-alone wallbox dimmer families have dimmers that are capable of either forward phase OR reverse phase operation in the same aesthetic, but not in a phase-adaptive version.

7. Will LED-specific dimmers have any negative performance aspects with existing incandescent loads?
Lutron’s C•L dimmers will perform equally well with incandescent, CFL, or LED loads (subject to the constraint of the dimming performance of the CFL or LED lamp being used).

8. Can you mix incandescent, halogen, and LED loads on the same dimmer?
Yes, only Lutron’s C•L dimmers are UL-listed to support mixed loads of incandescent, halogen, CFL and/or LEDs on a single dimmer.  This allows customers to try out new LED sources one at a time if desired, rather than replacing an entire zone of light at once.  Note, however, that CFL and LED sources may provide very different dimming performance than incandescent or halogen loads; for example, they may not dim to nearly the same low-end light level as incandescent or halogen loads.

9. For dimming control types that use digital or analog low voltage wiring, such as EcoSystem and 0-10V, is this in addition to high voltage wiring for powering the LED? If so, is this second wire a series loop from fixture to fixture?
Yes, low-voltage based control methods, such as EcoSystem and 0-10V, still require line voltage wiring at the fixture itself to deliver the power.  The control signal, a low voltage pair of wires, is then either run in the same cable/conduit as the power wires (considered a “Class 1” installation) or—more commonly in residential installations—separately (considered a “Class 2” installation).  For EcoSystem, the same low voltage pair of wires goes from the control system panel to each fixture (up to a maximum of 64), in any wiring method (daisy-chain, star, etc.) and is polarity-insensitive.  Power wires to the fixtures can be run completely independently.  Grouping fixtures via EcoSystem is all done via software, so it can be performed after installation.  Conversely, with 0-10V, each group of fixtures that needs to be controlled together must have its own pair of polarity-sensitive control wires, as well as the power wires, run back to a control.  Changing what fixtures are grouped together requires rewiring of both the control and power wires.

10. Is Lutron’s EcoSystem compatible with HomeWorks QS?
Yes, HomeWorks QS has panel-mounted controllers that are compatible with EcoSystem.  Each link on the controller can connect to, and individually control, up to 64 loads (fixtures).  Lutron Grafik Eye QS with EcoSystem dimmers can also be used stand-alone to control a link of EcoSystem loads.

11. Are RadioRA2 or Caseta products directly compatible with 0-10V loads?
At this time, RadioRA 2 and Caseta are only compatible with 0-10V loads by using an interface, the GRX-TVI.  We currently have many other Lutron stand-alone and system-based dimmers that support 0-10V as a native load type, and we continue to grow our 0-10V control offering.

12. With so many new manufacturers arriving in the market all the time, how can we possibly be sure we are getting quality LED products that are compatible with dimmers?  How can I avoid problems?
It seems like every week there is a new manufacturer of retrofit LED lamps.  However, one of the problems with many of the newcomers is that they don’t understand the customers’ requirements for dimming solutions which perform well.  There are several steps you can take to help mitigate your risk of getting an incompatible or poorly-performing product;

  • Find out what dimmers the manufacturer used for their own testing, look at the manufacturers datasheet or contact them for information on the dimming performance (low end light level, etc.)
  • Contact the Lutron LED Center of Excellence to see if Lutron has information on dimmer compatibility testing
  • Do a mockup or test installation to have you and the en d customer understand the system’s performance
  • Use manufacturers you trust; ensure the control and lamp manufacturer will be able to stand behind their product over its expected lifetime if any unexpected problems occur

13. I have heard dimming some LED loads can cause static on radios.  Why is that?
LED drivers are sophisticated circuits, typically operating with high frequencies.  Without the driver designer taking into consideration proper radio frequency interference (RFI) mitigation, these circuits can radiate electromagnetic “noise” through power lines and open space.  Sometimes, adding a dimmer can increase the amount of noise.  This noise can show up as buzzing from speakers, static from radios, or RF products not functioning (such as garage door openers).  While most dimmers have RFI filters in them, they are ineffective against the large amount of noise that some LEDs may create.  If this occurs, the only mitigation is to either replace the LED load (hopefully with a load that has a better quality driver) or physically separate the LED load from the device being affected by the noise.

14. In an existing home site survey, how do I identify if an existing dimmer is LED compatible?
Most basic dimmers installed more than 4 years ago will not be compatible with LEDs, with the exception of high-end system or panel dimmers (such as Lutron’s Grafik Eye or LP panels).  Dimmers designed for LEDs will have an LED-specific rating on them, such as “600W incandescent / 150W LED.”  New LED-specific dimmers ensure the best performance on LED loads, and function properly even without a neutral wire being present in the backbox.

15. My firm is going into existing homes and upgrading to LEDs.  Can you connect me with someone at Lutron who I can partner with who can educate us to help ensure successful results?
Lutron offers a wide variety of resources to help you with successful LED installations.  Lutron’s Lighting Control Institute (www.lutron.com/lci) offers training sessions, both online and at Lutron.  The Lutron LED Center of Excellence website (www.lutron.com/leds) offers a variety of technical whitepapers, presentations, compatibility lists, tools, and other resources to help you understand the challenges involved.  And, finally, Lutron’s industry-leading technical support services are specially trained to answer LED questions at 877-DIM-LED8 or leds@lutron.com.

16. Many of us have installed lighting control from Lutron and other manufacturers for many years.  How would you suggest we approach existing installations for upgrades?
Ensuring new technology maintains compatibility with old systems is often an impossible task (for example, BluRay discs won’t play on older DVD players).  Likewise, lighting control systems installed more than a few years ago were designed before LED lamps were commonly available, and thus can present compatibility challenges.  Besides “brute force” approaches, such as installing dummy loads (incandescent lamps or synthetic load boxes), there’s not much that can be done to “force” old dimmers to work with new LED loads.  Manufacturers of LED lamps do not design them to work well with most older, more sophisticated dimmers.  However, Lutron does offer upgrade programs to entice customers to replace their older product with the latest version of RadioRA 2 or Homeworks QS.  Not only does this ensure compatibility with LED loads, but it also provides many new features and functionality, including shade integration, temperature control, and control via mobile devices.