Screw Mount Lens
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Allscape’s Approach to In-ground Lighting
The well-light has a light and ballast module suspended inside an outer housing, forming a well. The main benefit of this design approach is the ability of the fixture to exhaust heat, and thus run cooler. However, the exhaust apertures that allow the heat to escape also allow water and other materials to enter the well. It is imperative when using well lights to provide excellent drainage and keep the well and exhaust apertures clear of debris. If the ballast and light modules stand in water for prolonged periods of time, problems can occur. If landscape materials block the exhausts, then over-heating can occur. ALLSCAPE® moved away from the well-light approach over a decade ago due to the problems mentioned above, and the need for preventive landscape maintenance which is outside its control.
ALLSCAPE fully embraced the in-ground design approach in the 1996 with the release of the SL-33, its composite single housing fixture. In-ground light fixtures do not allow water and heat to flow through the well, but seal it at the top and bottom. The main advantage of this design approach is that fewer parts are required to be watertight, such as the entry point at the ground surface and the electrical entry point at the bottom or side of the fixture. The in-ground design approach also allows for single piece composite, aluminum, stainless, or bronze housings, which again minimize the sealing surfaces. In-ground fixtures are less susceptible to poor drainage and debris build-up issues, but are not immune. The picture below shows the SL-43 a modern in-ground light fixture design with separately seal junction, ballast, and lamp compartments.
The majority of North American manufacturers of in-ground light fixtures now provide composite technology housings. They have been available for over twenty years, use proven aerospace grade materials, and are the preferred material for landscape and pedestrian installations.
Rhinolite™ the composite material used by ALLSCAPE is manufactured with a mixture of glass fiber, thermosetting resins, and other proprietary ingredients to provide maximum product strength, rigidity, and durability. The key benefit of the material is the protection it provides in corrosive and chemical environments, where high alkalinity, acidity, salt, lime, and similar substances are present. Examples of corrosive environments are landscape areas using recycled water and fertilizers, and lime in concrete. Rhinolite™ is also used in pool and water filtration units which contain high levels of chlorine, and in many commerical and marine applications. Other benefits of composite material is its ability to be molded into complex shapes and hold molded-in brass inserts which are incredibily strong. This eliminates the need for secondary drilling and tapping operatons and makes the production parts very consistent. The composite material also has excellent dielectric properties affording additional protection against electric shock. With a continuous operating temperature of 150?, and built in protection against ultraviolet radiation, Rhinolite™ is the most feature rich material used in in-ground technology today.
Cast aluminum housings are still provided by some manufacturers, but without additional protection are susceptible to severe degradation from chemicals found in today’s recycled water and fertilizers. Brass or bronze housings are used sometimes in the landscape setting but are much more expensive and very heavy. Cast metal housings also suffer from porosity and the need for secondary drilling and tapping operations making them inherently less consistent. Aluminum housing must use brass inserts to prevent galvanic action with stainless steel screws. Several manufacturers use drawn stainless steel housings that suffer from the need for secondary drilling and tapping, or pressed insert and the resultant reduced consistency. Metal housings may provide some advantages thermally; they offer no electrical isolation and must be appropriately grounded.
Several manufactures now offer above-ground fixtures, pioneered by ALLSCAPE, that minimize and even eliminate issues caused by standing water and debris. The above-ground fixture or semi-in-ground fixture are in-ground fixtures protruding from a few inches up to several feet above grade level, usually with an external sleeve. The added benefit of this approach is the ability to position the light fixture at the same height as (or above) the surrounding foliage. This allows the fixture to properly function even after several years of plant growth. Above-ground fixtures are becoming more popular and should be considered when ground vegetation surrounds the object to be illuminated. ALLSCAPE’s SL-34 is shown in the picture below placed in the entryway median of a gated community in Southern California. Notice how the height allows the fixture to function, even after the Bird of Paradise plants have fully grown.
Things to Consider.
Careful choice of fixture location is critical to a successful installation and understanding how the fixture will interact with the surrounding environment is the key.
One should avoid locations where water can stand. If this is not possible, make sure that there is adequate drainage below and around the fixture.
If the fixture is to be installed in locations near ground cover either elevate the fixture using an above-ground sleeve, or make sure there is adequate clearance around the fixture.
Understand how the light from the fixture interacts with the object to be illuminated. Make sure the in-ground fixture is setback from the object to be illuminated correctly. For example, spot (narrow beam) optics may require the fixture to be placed one or two feet away from the object to be illuminated. Placing a narrow spot further away may result in no light hitting the object. If it is not possible to locate the fixture correctly due to existing root systems or foundations, evaluate using flood optics or a tilt mechanism. The picture below of a church in Mexico illustrates how fixtures placed appropriately can enhance a building at night.
If people can walk on the fixture make sure you are aware of the temperatures on the fixture lens. High wattage lamps can easily generate enough heat to burn skin. ALLSCAPE offers dual lens units with the designation HPBB that considerably reduce the surface lens temperature. ALLSCAPE is also one of the few manufacturers who fully document its test method for measuring the lens temperatures. Care should be taken when comparing the lens temperatures reported by different manufacturers as the measurement points and ambient temperatures used to normalize the results may be different. North American companies usually use 25? whereas some European companies use 15?.
Choosing a carefully designed in-ground fixture is key. Always make sure that the fixture is ETL or UL listed for wet location in North America and CE listed in Europe. If possible make sure that the fixture has an IP (Ingress Protection) rating of 67, which is dust tight and water-proof (Protected against the effects of immersion between 15cm and 1m).
Use lamp sources that have a long life. Metal halides and fluorescents have 10,000 hours or more. LED’s can have even more. Minimizing the need for lamp replacement greatly reduces problems over the life of the installation. It also makes good environmental sense to avoid incandescent lamps with short life spans. Try to minimize post installation maintenance as much as possible.
Fixtures with sealed ballast compartments and anti-wicking devices between the junction box and ballast compartment should be used. In-ground fixtures with small amounts of moisture inside them will often run without problems if the ballast is kept dry. Anti-wicking eliminates the siphoning of water through stranded cables due to pressure changes in the fixture. Note that many European manufacturers do not provide any anti-wicking capability. This is in part due to the method of electrical entry, i.e. a cord with cord grip, compared to the requirements of conduit and a separate junction box in North America.
Die cast bronze lens rings with captive screws and high temperature injection molded silicone gaskets ease the installation process. The bronze will not degrade in the landscape and its strength allows high torque tightening of the lens-sealing surface. Captive screws are mandatory, as missing or incorrectly replaced screws often do not provide sufficient compression to keep water out of the fixture.
In North America always use water-proof wire nuts to make electrical connections in the junction box. The more experienced North American manufacturers supply them as standard with the fixtures.
Professional grade in-ground fixtures do not require covers to protect them from lawn mowers or other maintenance devices. Using external grates or louvers can be useful to reduce glare, but be careful as these devices can also collect local debris and mask the light output. Internal glare shields are preferred and commonly available. A typical internal glare shield offered by ALLSCAPE is shown in the picture below. It caps the lamp and shields pedestrians from direct light without blocking the direct light from the lamp arc tube to the surrounding reflector. One additional advantage of the ALLSCAPE internal glare shield design is double open chimney which allows hot air to escape, eliminating the chance of the lamp overheating.
Many in-ground fixtures now provide drive over capability as standard or available as an option. Be careful when evaluating the lens weight claims of different manufacturers as some use GVW (Gross Vehicular Weight) and others maximum weight. Both weights are somewhat ambiguous without more information. ALLSCAPE reports GVW to allow direct comparison with other products. It also provides the maximum pounds per square inch that can be applied to the lens which is the best way to report the information.
Although it is impossible to stop a determined vandal, specify tamper-proof screws in high-risk areas. Use a rock guard to protect the surface lens from being easily damaged, but be careful not to create a trip hazard at the same time.
The following example installation illustrates the use of in-ground and above-ground light fixtures to provide a dramatic entrance to a gated community.
The prestigious, twenty-four-hour gate-guarded community of Ritz Pointe, is situated in the Monarch Beach area of Dana point in Southern California. It has two entrances – both are lined with palm trees on each side of the entrance and exit lanes, and in the median strip. The original tree-strapped bullet lights came with the usual problems – degrading the visual appearance during the day, not anchoring the trees to the ground with light at night, and most of all not providing adequate ambient light to ensure a secure environment.
The task handed to ALLSCAPE by the landscape architect was to upgrade the lighting of the entry points to provide enough light for security, with fixtures that could not be seen. The obvious choice was in-ground fixtures. Three different types were used.
The Royal palms lining the sides of the roadway were illuminated with 50W metal halide medium floods. The palms are about thirty feet tall and the leaves will spread with age. They were mounted as close to the tree as possible in a pea-gravel sleeve to provide excellent drainage and a foliage and maintenance (weed whacker) barrier.
The Royal palms in the median are surrounded with Bird of Paradise plants that can grow several feet tall. Here 50W metal halide floods were again used, but were installed in a direct-burial sleeve to raise the height of fixture to the top of the plants. This allowed the light to function without being enveloped in foliage.
About the Author
Ian R. Ibbitson, Vice President and General Manager of ALLSCAPE has over twenty years experience in the lighting, entertainment and electronics industries. Dr. Ibbitson joined ALLSCAPE a Philips group brand in 1995 and is currently in charge of several commercial outdoor lighting divisions, including Quality Lighting, and Metrolux. Dr. Ibbitson has a BSc. in electrical/electronic engineering and a PhD in computer aided design from the University of Sunderland in England.