Volume 11 Issue 1
What other considerations are there when selecting an under-cabinet luminaire?
Additional factors to consider when purchasing an under-cabinet luminaire are the color of the light produced, warranty, the ability to electrically link multiple luminaires, and the shadows they create.
Correlated color temperature (CCT) indicates the “warmth” or “coolness” of the light, as shown in Figure 4. Lower CCTs provide a warmer appearance with a more yellow tone. Higher CCTs provide a cooler look with a bluer tone.
ASSIST recommends Volume 2, Issue 1: A Homeowner's Guide to Residential Under-cabinet Lighting: Getting Good Lighting for Your Kitchen Counters suggests that for wood tones, warm-colored tiles, copper-toned metal backsplashes or warm-toned walls, look for warm CCTs in the 2700–3500 kelvin (K) range. For decorative glass tiles, glass shelves, cool-toned tiles or gray-toned metal colors, look for cool CCTs in the 3500–5000 K range. Also, consumers may want to match the color temperature of the overhead lighting in the kitchen. There is no good or bad color temperature; the consumer’s preference, taking into account the above guidelines, should determine this specification. Table 7 shows the CCT values of the under-cabinet luminaires tested by NLPIP. The values listed are the weighted means for each luminaire calculated by measuring the CCT of the light falling on a grid of measurement points on the horizontal surface and weighted by the illuminance at each point.
Color rendering index (CRI) is a measure of a lamp’s color rendering quality. Higher CRI values indicate that objects will appear more natural and viewers will be able to distinguish between different colors on those objects more easily. Table 7 shows the CRI of the under-cabinet luminaires tested by NLPIP. NLPIP staff measured the CRI of the LED under-cabinet luminaires using an integrating sphere following the IESNA LM-79 test standard. The CRI of the fluorescent luminaires was determined from the codes printed on the lamps by the manufacturers. The CRI of the xenon lamps is assumed to be 100 based upon the spectral power distribution of an incandescent filament.
The results of NLPIP testing shown in Table 7 indicate that the LED and fluorescent luminaires are available with either cool or warm light, while the xenon luminaires provide warm light.
The under-cabinet LED luminaires identified for this study have no user-replaceable parts. Instead, the entire luminaire must be replaced. Despite the fact that manufacturers sometimes claim long lifetimes of LED products (e.g., the packaging of the Utilitech 283278 lists its lifetime as 50,000 hours) and that the cost of ownership is highly dependent on the lifetime, the warranty provided by manufacturers is similar to that of the fluorescent and xenon under-cabinet luminaires, as shown in Table 6. The packaging materials of only two of the luminaires provided details of the warranty, the Utilitech 283520 and Utilitech 283542; these luminaires are warranted “to be free from defects in materials and workmanship for a period of (1) year from the date of original purchase by the consumer… [Good Earth Lighting] will repair or replace (at [their] option) the unit in the original color, and style if available, or in a similar color and style if the original item has been discontinued, without charge, exclusive of bulbs.”
Some luminaires offer the feature of allowing “linking” or wiring from one luminaire to the next, which can be useful when installing a row of luminaires under long cabinets. The fluorescent models come with wire leads that provide the flexibility to be wired to either a junction box, a lead with a plug, or to an adjacent luminaire.
None of the luminaires tested come with continuous dimming controls built in. The Utilitech 283542 can be turned on to a high or low setting.
NLPIP recommends using under-cabinet luminaires with a built-in dimmer switch or bilevel switch in order to give the user the flexibility to find a pleasing light level. Also, operating the luminaire at lower illumination levels when possible will save energy.
The Utilitech 283542 is capable of tilting forward or backward to aim the light. The light distribution of other luminaires has a fixed direction — directly down toward the horizontal application area (countertop).
Objects illuminated by under-cabinet luminaires with multiple lamps create multiple shadows on the counter surface, as shown in Figure 5, which some may find to be aesthetically displeasing. These discrete multiple shadows (left) are created by all of the LED models and the GE 10136 xenon model. The two fluorescent luminaires have lower-luminance light sources and a diffuser, so they create softer, graded shadows (right). The Utilitech 283542 is an intermediate case; sandblasted glass over the three halogen lamps provides a moderate amount of diffusion.