Understanding Lamps is Key to Proper Selection

Gregory V. Harris, assistant editor

High-pressure sodium lamps, such as the Cityliner series by Selux, are not designed for residential landscapes. Instead, they serve as security lighting and flood lighting for pedestrian areas.

The market includes halogen bulbs, sodium vapor, mercury vapor, LED and Xenon applications. The key for contractors and their customers is selecting the most appropriate lamp for the project.

A halogen bulb is often 10 to 20 percent more efficient than an ordinary incandescent bulb of similar voltage, wattage, and life expectancy. Halogen bulbs may also have two to three times as long a lifetime as ordinary bulbs, sometimes also with an improvement in efficiency of up to 10 percent. Xenon light bulbs are similar in performance to halogen bulbs. They have a longer life, burn cooler, have no harmful UV rays, and may be handled with bare hands.

Halogen, Xenon and LED

Halogen lights have been a very popular choice in the landscape lighting industry. In-ground lights, such as this unit that features an MR16 20-watt lamp, produce soft light that serves to accent landscape features.

Essig noted that the halogen and xenon bulbs are ideal for his customers in the Tucson area, as these lights work well against the backdrop of the desert.

Mercury vapor lamps use bulbs that are extremely efficient and the phosphor that coats the bulb?????s exterior is perfect for color rendering. Mercury vapor lamps offer better color rendition than either high or low-pressure sodium lamps. The long lifespan of mercury vapor lighting fixtures has made them a popular choice, especially in the commercial sector. These lights belong to a group of illumination fixtures called HID or high intensity discharge. Illumination devices in this category produce an intense light source, which is useful in some environments.

Xenon bulbs are becoming prevalent in the landscape lighting industry as customers appreciate the longer life of these bulbs over halogens and the fact that they burn cooler than halogens.

Mercury vapor is often used in landscaping because of its long lamp life, ability to make vegetation appear blue/green and because its relatively inexpensive. One drawback to using mercury vapor in a landscape is that flowers will be reduced to a blue/green color.

The bottom line for landscape contractors and landscape lighting consumers is that there are no bad lamps, just potentially bad uses for the lamps. A high-pressure sodium lamp would not be appropriate for a residential backyard. Conversely, soft halogen lighting would not be suitable as the sole security lighting at large public spaces.

LEDs are becoming the preferred choice in some modern landscapes because of their low energy consumption, low temperatures and high lamp life. LEDs, such as the Paso and TriPalm models, blend seamlessly into the landscape.

Illuminating Info

482: Degrees, the minimum surface temperature of a bulb required for the halogen process to work. The halogen may not adequately vaporize or fail to adequately react with condensed tungsten if the bulb is too cool.

Source: Don's light, lamp and strobe site