For Effective LED Installations, Ask the Right Questions
Before embarking on a plan to implement LED lighting throughout a facility, it is important to first know what you want to achieve.
By Andy Wakefield, M.SAME
LED light sources offer energy savings, long life, excellent light quality, and new fixture options—allowing them to be used in almost any application. These advantages make LEDs (light-emitting diodes) an excellent choice for many facilities. However, there are challenges associated with making sure that LEDs meet end-user expectations. They can be a longer-lasting and more efficient light source than existing technologies, but their dimming performance can vary widely by manufacturer and model.
When selecting an LED solution, issues with dimming compatibility probably create the greatest source of frustration. Ensuring compatibility between LED lamps, fixtures, and controls can be confusing. And if the components are not compatible lighting performance will suffer. To ensure a successful project installation, you have to choose the right combination of LED loads and controls.
WHY CONTROL IS IMPORTANT
For many customers, energy savings is top-of-mind. LEDs are energy efficient by design. A simple LED lighting retrofit can help meet building and energy codes while reducing electricity consumption. So why include dimming control with LEDs? For the same reasons you would use dimming control on any light source: to maximize energy savings, extend system life, enhance flexibility, increase productivity, and provide a comfortable environment for building occupants. Regardless of the solution— from a single switch or dimmer to a centralized lighting control system—a bit of research can help guarantee compatibility and satisfactory performance, eliminating many of the common concerns and issues that can be seen with LED installations.
Similar to fluorescent sources, dimming LEDs saves energy at a roughly 1:1 ratio. For example, if you dim LEDs down to 50 percent of their light output you save nearly 50 percent of the associated energy use. Dimming LEDs also makes them run cooler, further extending the life of both the driver and the phosphor in the LEDs. This can double or triple the useful life of this already long-life source.
CHOOSE THE BEST COMBINATION
LED lamp and fixture manufacturers provide solutions of differing price, performance, and quality. Likewise, controls vary widely, and not all controls deliver suitable dimming when used with LEDs.
If all the parts and pieces are not properly selected, the result can be “dimmable” LEDs that do not work as claimed, that never turn off completely, or that flicker, pop-on, or drop out will leave the end-user unsatisfied…and leave you with a costly call back to the job.
Dimming LEDs saves energy at a roughly 1:1 ratio. IMAGES COURTESY LUTRON ELECTRONICS
ASK THE RIGHT QUESTIONS
Answering a few simple questions can help align building occupant expectations with the performance of a given LED dimming system.
What is the application type: retrofit or new construction? New construction enables you to use either LED bulbs or LED fixtures, allowing a wide variety of control options. Retrofit applications are often more restrictive, and the control options will be limited as well.
LED bulbs with Edison-base sockets are usually the lowest-cost option. They generally replace standard incandescent or compact fluorescent bulbs making them especially suitable for retrofits. These lamps have integral drivers that determine whether they are dimmable, and define the dimming performance.
LED fixtures can vary from cove lights to down lights and usually have an external driver mounted on their enclosure. Some fixture manufacturers offer different driver options on the same fixture to support different control technologies or applications (such as dimmable vs. non-dimmable). LED fixtures are typically reserved for use in new construction or major retrofit. They come at a higher price, but are typically selected for their higher level of performance (better light quality, aesthetics, and beam control) and their wider variety of control options.
LED bulbs are especially suitable for retrofits.
What type of control does the LED product require? Advancements in LED lighting and control solutions have encouraged many engineers to consider moving away from phase control, which was the only choice for standard incandescent loads. Additionally, various codes, mandates and mission requirements make it more likely projects will incorporate controls. Therefore, it is important be educated on the various control options (0 to 10-V, forward or reverse phase, EcoSystem, and others) to ensure the proper pairing of the controls with fixtures that support that technology.
How many fixtures/lamps can be connected to one dimmer? Even in small applications, overloading the dimmer can be a potential problem with LED installations. All dimmers are rated for a maximum load (in volts, amps, and/or watts) that must not be exceeded. Many recent dimmers have specific ratings for LEDs, making it easy to determine how many loads can be connected to them. This is done by dividing the dimmer’s LED load rating by the wattage of each load. For dimmers without LED-specific ratings, the incandescent rating cannot easily be used to determine the appropriate LED load, or number of bulbs/fixtures. LED loads can produce inrush or repetitive peak currents that are greater than their wattage indicates, stressing the dimmer and potentially causing premature failure. The lamp or control manufacturer’s recommendations must be consulted in these cases.
Furthermore, some dimmers may not perform well if they are required to control a very small load. With incandescent bulbs, it was easy to meet a dimmer’s 25- to 40-W minimum load requirement; but with LEDs, additional bulbs may be needed for the dimmer to operate properly. And, since LED loads have different electrical characteristics than their incandescent predecessors, even using sufficient LEDs to meet the minimum load may not ensure proper dimmer operation. Dimmers specifically designed for LEDs have much smaller minimum loads than standard dimmers, usually just one lamp.
What is the dimming range of the LED bulb or fixture? It’s critical to understand the product’s dimming range, and understand how the space will be used. For example, a product that dims to 20 percent measured light (45 percent perceived light) would not make sense in a briefing room or private office, but may be an appropriate energy-saving solution for general office lighting.
What kind of dimming performance can you expect? Occupants expect smooth, continuous dimming with no abrupt changes in light. They also expect dimming performance that is free of flicker, pop-on and dropout. A good driver (whether in a bulb or a fixture), paired with the proper control, will provide this assurance.
Choosing the right dimming control for the bulb or fixture will ensure compatibility: providing the necessary control signal, reducing the chance of flicker, achieving the desired dimming range, and supporting the amount of connected load. However, the driver integral to the bulb or fixture is what determines the best achievable dimming range and the best possible dimming performance (dimming smoothness, low end light level) of the lamp or fixture. Therefore, choosing the proper LED load to begin with is critical to achieving the desired outcome. In the case of fixtures, explicitly specifying a driver that is guaranteed compatible with the selected controls can go a long way to ensuring a trouble-free installation. In the case of lamps, make sure there is test data that shows acceptable operation between the lamp and control system.
Make sure the dimming range is acceptable for the customer’s application.
To truly maximize the impact on an LED project, serious consideration needs to be given to using intelligent LED drivers paired with smart controls. Digitally addressable LED drivers and controls provide the ability to assign individual fixtures or specific groups of fixtures to one or more controls without rewiring or complicated programming. Digital drivers and controls also enable status feedback from the loads. This can open up an entire suite of energy-saving and system-monitoring control schemes where the design and setup is all done within the software, further simplifying electrical and control design and reducing installation and programming costs. Power is circuited separately from control wires, so the 120-V or 277-V circuit can be fully loaded.
Intelligent control not only ensures a simpler, more robust, efficient system when it is installed, but can help future proof your installation. Because system analysis and adjustment is easily done via software, the system can be easily expanded, altered, or reprogrammed to accommodate changes to the space layout, use or tenant needs. Additionally, the proliferation of available wireless controls and sensors makes it even easier to expand or adjust systems in the future. When all of these factors are considered, digital controls save energy, save time, save money, improve occupant comfort and enhance mission effectiveness.
Controlling LEDS is no longer the wild west of the lighting control industry. Technologies are improving, and control options, literature, selection tools, and general knowledge is expanding. LEDs can now be effectively used in virtually any type of commercial or residential application.
Using LEDs does necessitate more careful product selection. By choosing the right solutions and being aware of key issues, it is possible to provide installations with an LED lighting and control system that meets energy-saving, performance, and aesthetic expectations for every project.