High-intensity discharge (HID) lamps, notably metal halide and high-pressure sodium, are widely installed in industrial, retail, and other applications. In recent years, the LED revolution has produced retrofit options promising up to 50 percent energy savings and long service life. Utilities now increasingly support these options with nearly 120 rebate programs offering an average $110 per LED retrofit lamp, according to BriteSwitch.


Besides energy and maintenance cost savings, LED technology offers instant-on operation (compatibility with occupancy sensors), improved lumen maintenance, universal operating position, good color quality, very little radiated heat and other advantages relative to HID.


LED retrofit lamps feature a base that screws into existing HID sockets. Generally, they are available in 30–400 watts (W) for replacement of 50–1,000W HID lamps. A popular example is replacing 400W metal halide lamps with 150–200W LED lamps. LEDs feature correlated color temperatures of 2,000–5,000K and color rendering typically in the low 80s. The majority carry an L70 service life of 50,000 hours, backed by a 5–10 year warranty. Depending on operating hours and local energy costs, short payback periods are possible.


As with tubular LED lamps, the lamp may operate with or bypass the existing ballast, offering options with differing advantages. Ballast-driven or plug-and-play lamps screw into the existing socket. They operate on the existing ballast, so it’s important to verify the lamp is compatible with the ballast technology. Light output generally ranges from around 2,000 to 20,000 lumens. While typically the quickest and lowest-cost option, operating the lamp on the existing ballasts adds 40–60W to the load, while the ballast itself presents a point of failure for the system.


Line-driven lamps operate on line voltage, eliminating the ballast and its load. Light output generally ranges from around 1,500 to 15,000 lumens. Some of these products qualify for DesignLights Consortium (DLC) listing. Many utility rebate programs use the DLC’s Qualified Products List to qualify eligible products. While saving more energy, this option typically imposes a higher installed cost because of the electrical labor required to bring line voltage to the sockets.


A third option is a retrofit kit, which packages the lamp with such components as secondary optics to provide a repeatable solution that is effectively a new luminaire. Often, an external LED driver replaces the ballast. The retrofit permanently switches the luminaire from HID to LED. Many of these products are DLC-listed. Retrofit kits typically package with standard drivers that feature 0–10V leads that optionally connect to lighting control systems, creating opportunities to accelerate energy cost savings by implementing control strategies.


A lighting retrofit’s primary purpose is to save energy while maintaining or improving lighting quality. While offering viable retrofit options, LED replacement lamps and retrofit kits require careful selection and application to achieve maximum performance.


Light output and distribution


Overall, light levels and quality should satisfy owner expectations based on need. The majority of LED replacement lamps use a corncob design that generally mimics an HID lamp’s emission. In addition, directional PAR lamps and retrofit kits often feature a flat chip-on-board design. Well-designed products should not compromise light distribution.


Light output should be compared based on the application’s required light levels and the competing technologies’ characteristics—lumen depreciation, luminaire optical efficiency and so on. If the lamp is directional, it is often desirable to consider center-beam candlepower as part of the analysis.


Environmental conditions


HID luminaires are often installed in rugged applications with extreme environmental conditions. The selected lamp should be suitable for the application and not compromise the specific job for which the HID luminaire was selected. Ideal applications are damp or dry spaces that are not subject to extreme temperatures or heavy particulates. If needed, ask the manufacturer to provide testing data or other evidence of performance claims.


A related factor is the existing sockets’ condition. If it isn’t good, it may need to be replaced. In addition, determine whether the existing socket is medium or mogul; LED replacement lamps tend to be heavier than HID lamps and require a socket that can handle their weight.


Control


The majority of LED replacement lamps are not controllable. LED retrofit kits typically package with dimmable drivers that can connect to control systems, leading to additional energy cost savings, increased flexibility and potentially extended lamp life.


With up to 50 percent energy cost savings and potential maintenance savings, LED replacement lamps and retrofit kits offer an increasingly viable retrofit option for HID luminaires. However, products must be carefully matched to applications to ensure desired performance and lighting quality. As with any retrofit, a trial installation is often recommended prior to major commitment.