In this presentation, Eric Bronson, senior lighting specialist with Anixter International, led with a simple yet clear message: LED lighting is not maintenance free. In fact, there are a number of operational issues and failure modes associated with LED lighting systems that designers and installers should be aware of. More importantly, if you encounter these issues in the field, you should know how to resolve them through proper maintenance, troubleshooting, repair, and replacement techniques.
According to Bronson, a few of the maintenance activities you should consider implementing include: regularly scheduled inspections of luminaires and components; routine cleaning to get rid of dust, dirt, etc. (mild cleaning schedules are suggested); testing of emergency/life safety features; and measurement of light output with a light meter. One additional item to check is controls adjustments (especially if the drive currents were set lower during commissioning).
It’s also important to note that when it comes to LED luminaires, it’s all about replacement of components when a failure occurs. You don’t really repair LEDs like you’ve done in the past with traditional-type luminaires. You basically remove and replace modules or components when they fail. Typically, failures are seen in two key areas: equipment and performance.
Equipment failure modes include drivers, light engines, protective devices, and controls.
• Driver failures — infant mortality (defective materials, errors in manufacturing process, random failures, wear out, over stress (temperature exceeding specs, moisture/condensation, poor input power quality), wrong driver.
• Light engines — packaging related (epoxy degradation, thermal stress, phosphor degeneration), semiconductor and metal related (electro-migration, ionizing radiation, metal diffusion, short circuits), stress related (thermal runaway, electrostatic discharge, reverse bias, catastrophic optical damage).
• Protective devices — failure of fuses, surge suppressors, TVS diode, temperature coefficient device.
• Controls — hardware failures (electrical, mechanical temperature effects), software failures (inadequate memory, noise, resource starvation), and operational errors (human error).
Performance failure modes include temperature, color shift, degradation of light output, and system start-up issues.
• Temperature failures — higher temperatures typically reduce light output and increase junction temperature; this leads to premature failure.
• Color shift — can be temporary (power quality, heat rise) or permanent (differentiated phosphor degeneration) or dimming of colored arrays.
• Light output degradation — LED no longer produces a certain percentage of its initial light output (typically 70%).
• System start up issues — lack of compatibility (ballasts, drivers, retrofit lamps, controls, lamps and luminaires), individual system component failures, control system issues.
Many in the industry believe that once you install an LED lighting system, you can rest assured it’s going to operate without problems for many years. But as this session clearly outlined, that could be a costly assumption to make.