GLOSSARY TERMS CONTINUED
Light Distribution Pattern of light produced by a fixture or created in a room or in an area. Line Voltage The voltage supplied by a power line, measured at the Interior lighting where the roof trusses or ceiling height is approximately 25 feet or less above the floor. Common in warehouses, athletic facilities, and industrial settings. Low Voltage Lighting Lighting system that operates on a system that supplies ≤50 volts to the lamps or light sources. Lumens Per Watt (LPW) point of use. Low-Bay The number of lumens produced by a light source for each watt of electrical power supplied to the light source. Also known as efficacy. Lumen Unit of total light output of a light source in all directions, expressed in lumens. Lumen Depreciation The decrease in lumen output of a light source over time. The decrease in lumen output that occurs as a lamp is operated, until failure. Also referred to as lamp The ability of a lamp to retain its light output over time. Greater lumen maintenance means a lamp will remain brighter longer. The opposite of lumen maintenance is lumen depreciation, which represents the reduction of lumen output over time. Luminaire A complete lighting fixture consisting of lamp or lamps together with the socket and parts designed to distribute the light, to position and protect lights, and to connect the lights to their power supply. Luminaire Efficiency The ratio, expressed as a percentage, of the light output of a luminaire to the light output of the luminaire’s lamp(s) (percentage of the light generated by the light source that actually makes it out of the luminaire). Luminaire efficiency accounts for the optical and thermal effects that occur within the luminaire under standard test conditions. Mean Lumens The average lumen output of a lamp over its rated life. Mean lumen values for fluorescent and HID lamps are typically measured at 40% of their rated lives. Mercury Vapor (MV) Lamp lumen depreciation (LLD). Lumen Maintenance A high-intensity discharge lamp type that uses mercury as the primary light-producing element. Mercury vapor lamps produce light with a CCT from 3000 to 7000 K. Mercury vapor lamps are less efficacious than other HID lamp types, typically producing only 30 to 65 LPW. Metal Halide (MH) Lamp A high-intensity discharge lamp type that uses mercury and several halide additives as light-producing elements. MH lamps have better color properties than other HID lamp types because the different additives produce more visible wavelengths, resulting in a more complete spectrum. MH lamps are available with CCTs from 2300 to 5400 K and with CRI values from 60 to 93. Efficacies of MH lamps typically range from 75 to 125 LPW.
Multi-Facet Reflector Lamp (MR Lamp) Multi-facet reflector lamp, of which the most popular is MR16. Occupancy Sensor A device which activates a fixture upon sensing the presence of a person in a space. Parabolic Aluminized Reflector Lamp (PAR Lamp) Incandescent PAR lamps are constructed of hard glass with a separate back reflector. Also available in CMH and LED. LED PAR lamps typically have a similar overall shape and beam angle of light, but do not actually use the parabolic reflector. Photocell Light-sensitive device used to operate fixtures according to available daylight. They are used to integrate an electric lighting system with a daylighting system so lights operate only when daylighting is insufficient and turn outdoor or security lights on and off at dusk and dawn. Programmed Start A method of starting fluorescent lamps, associated with electronic ballasts, where low voltage is applied to the cathode to pre-heat prior to lamp ignition. Recommended for use with occupancy sensors. Rated Lamp Life
Task Lighting Lighting directed to a specific area or surface that provides illumination for visual tasks, such as reading, writing, wiring, or grinding. Thermal Characteristics The manner in which a luminaire manages heat, either dissipating heat or retaining it. Timer Device that turns lights on and off at pre-programmed times. Track Lighting Lighting system that utilizes multiple fixtures which operate off a track or strip mounted to the wall or ceiling. May be low voltage or line voltage. Trim The edge or visible part of a recessed downlight. The finishing section of the exterior of a recessed fixture. Troffer Recessed fluorescent fixture for use in a suspended ceiling; derived from the words “trough” and “coffer.” TRT vX.X Acronym for DLC’s Technical Requirements Table followed by version number. U Lamp Linear, double-ended fluorescent lamp, usually T8 or T12, bent into a “U” shape. UL Underwriters Laboratory. An independent organization whose responsibilities include rigorous testing of electrical products. Watt A unit of electrical power. SOURCES Terms defined in the Glossary were referenced from the following sources: products.gecurrent.com/sites/products.currentbyge. com/files/documents/document_file/35311-GE-Retail- Lighting-101-eBook.pdf focusonenergy.com Lightsearch.com/resources
See: Average Rated Life Recessed Fixture
A fixture mounted in the ceiling. With downlights, only the aperture and trim are visible from below. With fluorescent troffers and luminous ceilings, only the light shield is visible. R Lamp Reflector lamp whose interior is coated with a reflecting material so as to direct the light forward. Relamping A project where the existing lighting fixtures are cleaned and new lamps installed. Re-Strike Refers to the restarting of a previously operating HID lamp shortly after turn off. Typically requires a minimum of 4-15 minutes to restart after turn off. Retrofit Upgrading a fixture by installing new lighting fixtures, parts or equipment. Semi-Specular A reflective but somewhat diffuse surface. Soffit In architecture, the underside of an overhead component. Often used to describe an exterior element under the roofline. Solid State Electronics that use semi-conductor chips and circuitry. Specular A highly polished or mirrored surface. Spot Lamp Reflectorized lamp with a narrow light distribution.
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