All light sources must be maintained; as lighting controls become more sophisticated, they also must be maintained. Responsible lighting design should include maintenance to preserve design integrity. In terms of sustainability, whether the lighting goal is visual comfort, highlighting merchandise, energy savings or anything else, maintenance is where the rubber meets the road.
Lighting maintenance may involve relamping luminaires, cleaning luminaires and room surfaces, troubleshooting and replacing defective parts, and re-aiming directional lamps and luminaires. It may also include periodically inspecting and reprogramming or recalibrating controls.
In the solid-state lighting (SSL) era, is this still necessary? Some early light-emitting diode (LED) sales claims promised “install and forget” lighting. For building owners whose main concern is whether the lights are on, a 20-year light source that doesn’t require spot relamping may certainly seem that way.
The truth is that LED lighting should be maintained, though maintenance best practices must be adapted to accommodate this light source’s unique characteristics.
LEDs are a long-life light source, which is a major benefit. Manufacturers have come a long way in their understanding of how drive current, temperature and other factors affect performance. As a result, today’s well-designed and properly operated LED products are generally reliable and long-lasting.
In review, LED life is often evaluated based on lumen maintenance—an L value expressing the average number of hours the product is projected to operate before light output declines to some percentage of initial lumens. For example, an L80 value of 50,000 hours means a population of luminaires, on average, will produce 80 percent of their initial output at 50,000 hours of operation.
LED products have an estimated life based on a combination of standardized testing and manufacturer-specific methodologies and experience. LED modules, arrays and packages are tested up to 10,000 hours under conditions defined by the IES-LM-80 standard. The light source is then placed in a luminaire and expected to operate longer than that. Using the IES-TM-21 standard, these results are extrapolated to produce life projections, based on manufacturers’ methods, data and on certain operating conditions, notably temperature.
According to the Department of Energy, within five years, the technological development of LED sources will result in service life reaching a theoretical limit of about 50,000 hours for LED lamps and 100,000 hours for LED luminaires. In the average building, 100,000 hours of life translates to 35 years of service. What’s more, aside from infancy failures, well-designed luminaires typically provide light with a very long mean time between failures. While fluorescent and high- intensity discharge (HID) lamps are available with very long life, they still fail steadily along their mortality curve.
The reliability of LED products may not be based on lumen maintenance, however, since they are systems of components, some of which may fail before the light source depreciates in output. In applications where color quality is important, color shift may signal replacement first. This may occur due to phosphor degradation or varying lumen-depreciation rates in differing LED types used in the same product. Color shift may be tested along with lumen-depreciation using IES-LM-80, but IES-TM-21 does not provide a procedure for extrapolating beyond 10,000 hours. It’s also not very well-defined, making evaluation subjective by application.
Finally, RTI International discovered driver electronics and other components are likely to fail before the light source, a reversal of what we’re accustomed to with traditional lighting, which is the lamp failing before the ballast. The research institute published a study about it in 2013.
One of the most important services that can be provided to a building owner is recommendation of a quality product that satisfies its promises. As LED is still a relatively young technology, there is a broad variation in quality, particularly among lower-cost products. Therefore, it is important to understand lighting and the application and qualify good products that use good components.
When selecting a product, it can be beneficial to ask the manufacturer what methods and data it used to estimate service life. The specifier should also note any application characteristics likely to affect service life, such as ambient heat and humidity, which can reduce life, and whether the product will be dimmed, as dimming may extend service life.
The specifier should also pay attention to color stability, particularly for applications such as hospitality and retail, where color is important. The specifier can review the product’s LM-80 data for LED packages as well as temperature measurement data for installed lamps and luminaires. For best results, manufacturer operating guidelines should be followed. If color stability is a concern, the specifier may attempt to negotiate a product warranty that addresses color shift if one is not available.
Another aspect of product design is whether the product is easily field-serviceable, which allows component replacement and possibly upgrades. This makes the product more durable and brings us to a challenging area of LED lighting maintenance, which is product replacement.
After LED products are installed, infancy failures may occur and would be covered by warranty. Should a product fail after the warranty expires, replacement products must be purchased unless spares are available in attic stock. The look and shape of LED luminaires are not standardized, and product cycles are compressing to as little as one to two years, resulting in new generations. This presents the risk that the manufacturer may no longer be in business or that the product may no longer be available or have a different light output or form factor.
Therefore, when purchasing LED luminaires, the specifier might ask the manufacturer about future availability of inventory and how it is servicing products today that were sold several years ago.
There is also the question of what the owner will do when the lighting has failed, which in turn raises the question of what that even means. When matching a product to an application, the specifier should not confuse the L value with an exact replacement point. This value expresses lumen maintenance, which serves as a guide but not an absolute. The Next Generation Industry Alliance recommends a broader approach based on the application, defining life as when light output falls by X percent, color shift rises above Y, Z percentage of LEDs fail, or some combination of these. The replacement point is, therefore, generally based on light levels (lumen depreciation, some LEDs failing) or aesthetics (color shift, some LEDs failing when the light source is visible in the luminaire).
While there have been some industry attempts to provide a clear end-of-life signal, a majority of products do not. The owner might benefit from incorporating periodic scheduled inspections as part of its maintenance program. This could include spot-checking light levels and, for applications with sensitive aesthetics, visual inspection for outages and color shift. Intelligent lighting control is becoming more popular because it is inherently compatible with LED lighting. Should the control system offer monitoring capability, this allows remote monitoring of lighting status, notably whether a given lighting point is operational. The system may allow remote alarm notifications.
A failing driver may either cause its LEDs to stop producing light or, less likely, become dim. Should failures occur due to the driver, being able to replace it in the field could be beneficial if the light source still has considerable useful life. Again, the luminaire should be easily field-serviceable for this purpose, with quick disconnects, though product replacement can be problematic as there are no current industry standards for drivers. Therefore, the driver must be replaced with the same product or one approved by the manufacturer for the given luminaire. If an unusual number of driver failures are encountered, it could be manufacturer defect, high driver operating temperatures or some other cause. Consult the manufacturer.
Some products also allow the field replacement of the light engine, which can experience similar issues as complete products and drivers. A light engine would normally need to be replaced due to catastrophic failure, lumen depreciation or color shift. In the future, replaceable phosphors may be available. If products are exhibiting premature lumen depreciation, this may be caused by high operating temperatures, miswiring that results in the lighting being dimmed by a dimming control, or some other cause. Again, consult the manufacturer.
Other maintenance practices
LED lighting installations may benefit from other sensible maintenance practices such as luminaire cleaning and re-aiming. Traditionally, cleaning occurs when the luminaire is relamped, if at all. As LED luminaires generally do not require spot relamping, maintenance personnel must make an effort to ensure cleaning occurs, particularly in environments such as outdoor applications where dirt accumulation can reduce light output. Additionally, as displays move, directional lighting must be re-aimed.
A growing maintenance area in LED lighting is controls, which are becoming increasingly automatic and sophisticated. Changes to the space, how the space is used, etc., may result in the controls falling out of sync. Periodic inspections, including functional testing of a sampling of control points, will reveal deficiencies that can be corrected by reorienting or moving sensors and recalibration. Maintenance ensures lighting systems perform as intended over the long term.
As lighting technology changes, maintenance is changing with it, though the fundamentals remain the same: relamping, cleaning and troubleshooting. LED lighting significantly reduces maintenance, while advanced lighting controls are providing new tools that facilitate it. The key to maintaining LED lighting and control installations is to understand the technology and proactively monitor the systems.
For more information, consult LED and control manufacturers or review IES-RP-36, Recommended Practice for Lighting Maintenance, published by the Illuminating Engineering Society in 2015. This publication, which I authored in conjunction with the IES Lighting Maintenance Committee, describes recommended maintenance practices for all popular light sources, including extensive material on LED lighting.