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Do’s and don’ts in high-intensity-discharge lighting
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High-intensity discharge (HID) lighting systems illuminate most architectural and billboard installations. HID’s energy-saving features have traditionally made it the most popular system for street lighting. An HID lamp is roughly two-and-a-half to three times more efficient than the best, production LED.
Even if these lamps seem foolproof, their proper use isn’t. Also, in the past 10 years, many different types and systems have emerged on the market, so it’s time to point out a few HID characteristics to observe before problems arise.
All HID lamps are so-called arc lamps (they are classified as gas-discharge lamps), where the electric arc is generated within a defined atmosphere of gases and vapors. Confining the arc in a rather short (the electrode distance is 1⁄10 to 4 in.), transparent, heat-resistant quartz-glass or ceramic container produces the high light intensity. The electrodes, which are thermal emitters (they’re not preheated), mainly comprise wire coils or pinpointed pure or doped-tungsten rods.
Because the gas or vapor pressure inside the lamp is, in most cases, higher than atmospheric pressure during operation, an outer glass envelope protects most lamps from an explosion and UV damage.
I won’t be covering rarely used types of HID lamps, such as super-pressure mercury or xenon arc lamps, because they’re used only in very special applications. Just keep in mind that super-high-pressure lamps can explode worse than a grenade. Always protect the lamp and yourself when working with this type.
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