Lamp Selection for 12-Volt Outdoor Lighting

By Steve Atkinson, regional sales manager, Nightscaping

A fluorescent lamp is a sealed glass tube with a small bit of mercury and an inert gas, usually argon, kept under very low pressure. Phosphor powder coats the inside of the glass. The tube has two electrodes, one at each end, wired to an electrical circuit.

Landscape lighting has traditionally placed more emphasis on lighting fixtures than on 12-volt lamps. The spectacular lighting effects created by proper use of 12-volt lamps are the heart of the contractor?EUR??,,????'???s work, with the goal of seeing the effect of the light, not the source.

 

A halogen lamp uses a tungsten filament but is encased inside a small quartz envelope. Quartz is used because the filament is close to the envelope, which would melt glass. Halogen gas inside combines with tungsten atoms as they evaporate and redeposits them on the filament. This recycling allows the filament to last a lot longer.

Today?EUR??,,????'???s 12-volt outdoor lighting industry offers a wide variety of lamps designed by manufacturers to operate within a certain range of voltage provided by a UL-approved lighting transformer, usually 10.5-12 volts. When energized by this power source, the fine filaments in these lamps produce safe, clean, clear light, and consume much less wattage than traditional 120-volt lamps.

Metal halide lamps produce light closest to natural sunlight, although the lamps can be manufactured to produce almost any color of light. A 100-watt standard metal halide lamp provides five times the lumen output of a 100-watt incandescent bulb.

Several design factors need to be addressed when deciding what lamps to use for a 12-volt outdoor lighting system: What light quality and color temperature is needed? What is the ambient light level in the area and the desired lighting effect? What are the requirements for average life expectancy of lamps? Will size limitations of the lighting fixtures dictate the lamp style? Finally, what are the site environmental conditions? Be sure to use a quality lamp manufacturer that produces lamps designed for outdoor use. Certain types of 12-volt lamps are sold only for indoor use and may not withstand harsh outdoor weather.

Reflector lamps, such as MR16 (pictured) or PAR36 lamps, use a cone of mirrors to direct light in certain patterns.

Twelve-volt lamps are labeled with two measurements: the wattage consumed (similar to a sprinkler using water) and how much light they create. Omnidirectional lamps, such as bi-pin or wedge-base, cast light in all directions. Reflector lamps, such as MR16 or PAR36, use a cone of mirrors to direct light. Regardless of style, each lamp is rated by the manufacturer in beam candlepower. Measuring the light output and pattern at regular intervals from the lamp in footcandles (BCP divided by distance squared) creates a usable chart of light output for the contractor to decide on lamp type and intensity. The footcandle unit is the light created by a small candle when measured one-foot away. Twelve-volt outdoor lighting manufacturers have these lamp charts available.

Reflector lamps control the light output from the lamp. The cone of mirrors in the lamp controls the light from a very narrow spot to a superwide flood. Although the lamps use the same wattage, the effect of a 25w narrow spot will be much brighter than a 25w superwide floodlight. Omni-directional lamps can also be used as a directional lamp when placed in a lighting fixture that is powdercoated white inside. The effect is soft, clean light that can be used close to objects or surfaces without creating harsh hotspots.

A 25-watt PAR36 incandescent narrow spot light. Incandescents (like standard light bulbs) use tungsten filaments that radiate far more infrared heat than light.

Proper design sequence is crucial to an attractive outdoor lighting. After considering ambient light levels and light needs, first select the lamps then the fixture. Next, select any options for the fixtures and the appropriate size UL-1838 approved lighting transformer with your desired control features. Not all lighting need be harsh or bright to be effective. Any light beyond what is needed to see is glare. Mother Nature did not intend midnight to look like noon. Proper selection of 12-volt lamps for an outdoor lighting system will create a safe, attractive, and functional environment for your clients.

Steve Atkinson may be reached at 530-409-0795, or you can e-mail him at stevea@nightscaping.com