Maintenance has always been a necessary part of the operation of lighting systems in commercial buildings. Traditional lamps, ballasts and other components periodically fail and must be replaced. Luminaire and room surfaces should be cleaned to preserve light levels. Maintenance is key to ensuring the lighting system’s design goals are met during the long term.
The advent of solid-state lighting (SSL) sources, predominantly LED, is changing the face of maintenance. The primary issue is extended service life. LED product design has greatly improved during the last five years, resulting in high-quality products that are generally reliable and long-lasting. The long life of LED sources in turn reduces maintenance requirements, particularly in buildings where the main lighting concern is simply that the lamps are operating.
As a result, LED products are often touted as being “maintenance free” and “install and forget” devices. Accepting this claim as true, however, entails risks that escalate based on how much the owner cares about lighting quality.
As with all lighting systems, LED lighting must be maintained, though it may not require as much maintenance. Because of LED characteristics, maintenance practices may be different. And with lighting controls proliferating along with LED, including advanced lighting controls, another element of the lighting system will require more detailed maintenance than it received in the past.
LED source life continues to improve until it reaches a theoretical limit of around 50,000 hours for LED lamps and 100,000 hours for LED luminaires in about five years. The long life of LED sources in turn has prompted manufacturers to offer long-life versions of popular fluorescent and HID lamps. At 75,000 hours of life, an LED luminaire could provide light for up to 25 years without replacement. Putting infancy failures aside, these products are designed to provide service without spot relamping of ongoing lamp failures.
LED sources do not fail like most traditional lamps, which have a clear end-of-life signal. The life of LED sources is typically evaluated using lumen depreciation (gradual reduction in light output over time) and expressed using lumen maintenance (the percentage of initial light output that is emitted at some point in the future). This lumen depreciation may occur because of general lumen depreciation among lit LEDs, a percentage of the LEDs outright failing or depreciation within the luminaire. Typical service-life projections are expressed as L70, L80 or some other value. If the product has an L80 of 50,000 hours, for example, after 50,000 hours of operation under specific conditions, the product is expected to be emitting 80 percent of its initial rated light output.
Because LED is still a young illumination technology and LED products are typically purpose-built devices, life expectations are largely based on manufacturer experience and methods. The IES-LM-80 standard provides a method for testing lumen depreciation for LED sources up to 10,000 hours. IES-TM-21 then details a procedure for extrapolating that data to a target L value. Product design and environmental conditions in the field can have a big effect on light output, so LM-80 is only a baseline. Manufacturers must estimate projected life based on their own data and methods. So building owners should use the L value as a basic projection, not a precise point in time when the products should be replaced.
Further, lumen depreciation is just one indicator of life, and it may not be the predominant one. LED products are systems of components; while the LED source may promise a certain degree of longevity, other system components may fail before the light source does.