Outdoor Lighting Glossary
Come across a lighting word you aren't sure of? Completely new to the world of lighting? We feel your pain! Here you will find a collection of terms and concepts that should help to make your life easier.
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Select the first letter of the word from the list above to jump to appropriate section of the glossary.
Halogen - See Tungsten Halogen Lamp
Head - Luminaire for a track-lighting system.
Heat Extraction - The process of removing heat from a luminaire by passing return air through the lamp cavity
HID - Abbreviation for High Intensity Discharge. Generic term used to describe mercury vapor, metal halide, high-pressure sodium and (informally) low-pressure sodium light sources and luminaires.
High Bay - High ceiling, usually in an industrial plant. Because of height, it may be hard to reach for lamp changers without special ladders or scaffolding. Usually above 20 ft.
High Hat - A luminaire that is recessed, usually into a ceiling.
High Intensity Discharge (HID) Lamp - A discharge lamp in which the light producing arc is stabilized by wall temperature, and the arc tube has a bulb wall loading in excess of three watts per square centimeter. HID lamps include groups of lamps known as mercury, metal halide, and high pressure sodium.
High Output (HO) Fluorescent - A fluorescent lamp designed for use with an 800 milliampere (MA) ballast; will usually operate at low temperatures (down to zero) while still producing high light levels.
High Pressure Sodium (HPS) Lamp - High intensity discharge (HID) lamp in which light is produced by radiation from sodium vapor. Includes clear and diffuse-coated lamps.
High pressure sodium lamps rely on an ignitor to send a high voltage pulse to the lamp electrodes in order to start the lamp. This results in a quick ignition time: 1 to 3 minutes. High pressure sodium systems provide higher efficiencies (lumens/watt), lumen maintenance, and greater component life than traditional metal halide systems, but similar to mercury vapor. The color rendering index (CRI) of these systems, however, is substantially less than metal halide and closer to that of mercury vapor lamps, 22 to 25. There are "color corrected" lamps available, but which are somewhat cost inhibitive, but will reach CRI values up to 65.
High Voltage - Voltages of 208 and higher
Hot cathode lamp - An electric dis-charge lamp whose mode of operation is that of an arc discharge. The cathodes may be heated by the discharge or by external means.
Hot Re-Start Time - The amount of time from a momentary power interruption to return of full light output
Hot Restrike - A phenomenon of re-striking the arc in an HID light source after a momentary power loss. Hot restart occurs after the arc tube has cooled a sufficient amount.
