table and floor lamps, and undercabinet and task lighting. Lighting levels are lower than in commercial or industrial applications. Color, brightness, dimming capability, and appearance are extremely important.
Residential users expect SSL to look and act just like their incandescent counterparts. Such attributes as smooth dimming with existing residential dimmers, absence of flicker, absence of radio interference, great color rendition, and equal light output and similar brightness to incumbent lighting technologies will all be imperative for the successful SSL introduction into the residential market. Users also expect to be able to use the new lamps without having to replace existing luminaires (i.e., fixtures using screw-in lamps).
SSL is easily controlled in principle. Dimming is readily available, but flicker, so called “pop-on” effects and lower end drop-out are still apparent in some products. Pop on occurs in two ways: (1) when a preset dimming control is used and lights do not turn on to their pre-set dimming level, but first come on (near) full and then dim down automatically to the preset level and (2) when a slide (or rotary) dimmer is used, lights do not turn on at the low end, but require the slider to be raised to a relatively high level to start the lamp, before dimming to a lower level can be achieved. Lower end drop-out occurs when lights are dimmed but turn off before reaching the desired low level. All of these are symptoms of incompatibility between the LED lamp driver electronics and incandescent dimmers and can be mitigated when the drivers are designed for better compatibility using an industry standard such those of the National Electrical Manufacturers Association (NEMA) on SSL 6 (see Chapter 4). Alternatively, the dimmer can be replaced with a new-generation device that is being designed to operate LED lamps. Existing incandescent dimmers may not work with LED replacement lamps (even though the LED lamps are labeled “dimmable”). In some cases, the dimmers may have to be replaced.
FINDING: Replacing incandescent or fluorescent lamps with LED lamps provides an opportunity to greatly reduce power load and increase lamp life. They can also turn on instantly and are able to dim. The market for these lamps will only expand as the light and color quality improve and the costs are reduced.
If SSL meets the above performance criteria, then long life and low energy use will attract users. If SSL does not meet the criteria, then disappointment and frustration will damage the market, as happened with compact fluorescent lamps (CFLs) (see Chapter 2). Appropriate policies, regulations, and educational campaigns can help avoid this result.
Ambient lighting in commercial sites has been traditionally supplied with linear fluorescents in either recessed troffers, recess parabolics, semi-recess indirect, or pendant mounted with direct/indirect distribution.1 All of these provide uniform omni-directional light distribution, creating uniform ambient lighting.
Accent lighting adds visual interest to an area and is frequently implemented with track lighting supplied with tungsten halogen or ceramic metal halide lamps. Ceramic metal halide track lighting is used in many grocery stores because of the higher light output.
Task lighting offers higher lighting levels for specific areas and has been traditionally supplied with tungsten halogen or CFLs. Task lighting is used primarily in office areas in the form of under-shelf or free-standing desktop luminaires.
In most commercial applications, the lighting system is expected to last for many years, requiring very little maintenance with easy accessibility. Occupants expect controls to perform daylight dimming, occupancy/vacancy sensing, scene controls, and manual dimming.
SSL is becoming more common in commercial applications, especially for use with surface grazing (wall washing, white board lighting, and cove lighting). SSL is ideal for task or personalized lighting and for accent or track lighting. The more difficult applications are general omni-directional ambient lighting now supplied by fluorescent luminaires. The one exception is lower light output, semi-recessed indirect luminaires, which are becoming popular for ambient lighting.
FINDING: The best LED applications take advantage of the directional light put out by LEDs, such as downlights, wall washers, and grazing and accent lighting.
FINDING: Omni-directional LED lamps are not as efficient as linear fluorescent lamps. In order to become a viable replacement alternative for linear fluorescent lamps, SSL products need to improve efficacy, become more omnidirectional, and reduce initial cost in order to compete with fluorescent lamps.
Total harmonic distortion (THD) of the line current and the power factor (PF) of the LED lamps are serious concerns. Most existing commercial buildings have 120/208 or 277/480 volt three-phase electrical distribution systems, where three phases share a neutral. If the THD is too high, the neutral conductor may be overloaded, especially in existing buildings with older electrical distribution systems. In new construction, the most recent National Electrical Code recommends separate neutrals for each circuit to avoid this problem. This issue is discussed in more detail in Chapter 4,
1 A troffer is “a long, recessed luminaire installed with the opening flush with the ceiling.” A pendant is “a luminaire that is hung from the ceiling by supports.” A parabolic is “a luminaire with the light source at or near the focus of a parabolic reflector producing near-parallel rays of light.” Both troffers and parabolics are installed as recessed luminaires. Indirect lighting involves “luminaires that distribute 90 to 100 percent of the emitted light upward” (ANSI/IES, 2010).