Metal Halide Lighting Systems
Metal halide lamps produce a bright white light and are highly efficient members of the HID family. They were an outgrowth of the mercury lamp with an improvement made in their color rendering characteristic and energy efficiency. The efficiency of metal halide lamps is from 1.5 to 2 times that of mercury vapor lamps. Almost all varieties of available "white light" metal halide lamps produce color rendering which is equal or superior to presently available mercury vapor lamps.
The metal halide lamp is very similar in construction to the mercury vapor lamp. The major difference is that the metal halide lamp contains various metal halide additives in addition to mercury vapor. Metal halide lamps are commonly used in stadiums, warehouses and any industrial setting where distinguishing colors is important. Low wattage lamps are available and have become popular in department stores, grocery stores, and many other applications where light quality is important.
Metal halide lamp sizes range from 175 to 1,500 watts. Ballasts designed specifically for metal halide lamps must be used.
- Designed for general lighting applications
- Relatively long lamp life
- Interchangeable with mercury lamps in many applications
- Concentrated source is easily controlled by special fixtures
- Good color rendering characteristic
- Light output is a bright crisp white light
- Twice as efficient as mercury lamps and 6 times as efficient as incandescent
- Short life compared to other HID lamps (6,000 to 20,000 hours depending on size and manufacturer)
- Different lamps have to be used for base-up versus base down burning configurations.
- Horizontal operation may severely reduce lamp life.
- Require a ballast
- Some lamp types require 2 to 5 minutes to warm-up before giving full light output and 10 minutes to cool-down. Others have instant restart capability.
- Color may vary from lamp to lamp (color shift.)
- Many wattages require operation in enclosed fixtures due to the risk of lamp breakage upon failure.
Metal Halide systems combine high efficiency with good color characteristics. The result is a lamp that has almost universal appeal. Its color appearance is bright white and can be applied to applications ranging from commercial lighting to large scale retail to industrial and sports lighting.
For industrial applications, Metal Halide offers color characteristics superior to that of High Pressure Sodium. In facilities where the task is detailed or color recognition is important, this source makes an excellent choice. Like other HID sources, the lighting intensity allows the fixtures to be mounted on high ceilings that are generally not feasible with fluorescent lighting.
The wattage at which a lamp operates will vary from its nominal rating depending on the ballast, the supply voltage and the lamp voltage. When designing a Metal Halide installation, it's important to take these variables into account because the lumen output of the lamp varies with the wattage at which the lamp operates.
Large scale retail facilities such as grocery stores or discount stores use this source frequently because it gives adequate color characteristics while providing an efficient source of light. These lamps are also available in lower wattages so that they can be used in fixtures mounted closer to the workplane. These fixtures generally require a diffuser that spreads the light more evenly over the workplane.
Technology Types (Resource)
When a Metal Halide lamp is cooled below normal room temperature, it requires higher voltage to strike the arc. Generally, ballasts are designed to start and operate lamps at ambient temperatures down to -20°F. Information regarding the capability of a ballast is given on its nameplate or is available from the manufacturer. Industry standards for voltage are provided in publications of the American National Standards Institute (ANSI). Once the arc has been established, Metal Halide lamps will warm up to full wattage and light output at any temperature.
|100 ED-17 Med. (Enclosed fixtures only)|
|Operate on ANSI specified "M90" Metal Halide Ballasts.|
|175 ED-17 Med. (Enclosed fixtures only)|
|Operate on ANSI specified "M57" Metal Halide Ballasts.|
The arc tube of a Metal Halide lamp operates under high pressure. Because of this, reasonable precautions are necessary to ensure safe operation. In fact, certain Metal Halide lamps are recommended for operation only in enclosed fixtures. Where applicable, the fixture restrictions are listed on the lamp wrapper and are also indicated in product literature.
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