LIGHTING GLOSSARY TERMS CONTINUED
High-Bay Interior lighting where the roof trusses or ceiling height is greater than approximately 25 feet above the floor. Common in big box retail, warehouse, and industrial settings. High-Intensity Discharge (HID) An electric lamp that produces light directly from an arc discharge under high pressure. Metal halide, high-pressure sodium, and mercury vapor are types of HID lamps. High-Pressure Sodium (HPS) Lamp type that uses sodium under high pressure as the primary light-producing element. HPS lamps produce a yellow light with a CCT of approximately 2,000K. HPS lamps are among the most efficacious light sources, with efficacies as high as 150 lumens per watt, although those with higher CRI values have efficacies as low as 25 lumens per watt. High Voltage Voltage that exceeds 50 volts. Illuminance The density of luminous flux on a surface, is measured in footcandles (one lumen per square foot) or lux (one lumen per square meter). Incandescent Lamp Produces light with a wire filament, which creates light as it is heated by electric current. Induction Lamp An electrode-less fluorescent lamp that is powered by an electromagnetic induction generator to excite gases within the lamp to light rather than using electrodes internal to the lamp, which can wear out. Initial Lumens The lumens produced by a lamp after an initial burn in period (usually 100 hours). Input Watts The total wattage required by both the ballast or driver and the lamp or light source
Kelvin Color temperature is measured in Kelvin, which indicate the hue of a specific type of light source. Higher temperatures indicate whiter, “cooler” colors, while lower temperatures indicate yellower, “warmer”
Lumens Per Watt (LPW) 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 lumen depreciation (LLD). Lumen Maintenance 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 A high-intensity discharge lamp type that uses mercury as the primary light-producing element. Mercury vapor lamps produce light with a CCT from 3,000K to 7,000K. Mercury vapor lamps are less efficacious than other HID lamp types, typically producing only 30 to 65 LPW.
colors (see CCT). Kilowatt (kW) 1,000 watts Kilowatt-Hour (kWh)
A unit of measurement for electrical energy usage. One kilowatt hour equals 1,000 watts of energy used for one hour. Job Site The physical location and address where the measures were installed. Lamp The light source within a fixture. Some types are referred to as a bulb or tube. Lamp Disposal Refers to the proper recycling of lamps containing mercury or other hazardous materials. Lamp Holder Socket inside a housing, which holds the lamp in place and connects it to the electrical source. Lens A glass or plastic diffuser used in luminaires to seal a fixture or control the exiting light. Light Emitting Diode (LED) A semiconductor diode (electronic components that let electricity pass in only one direction) that emit visible light when electricity is applied and is used in lamps and digital displays. LED is available in a wide variety of colors and lighting fixture types and typically has a much longer-rated life than traditional lighting technologies. Lighting Controls Devices that adjust lighting systems to vary light level or turn on or off. 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 point of use. Low-Bay 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.
in a luminaire. Instant Start
Ballast starting type. Applies high voltage across the lamp with no preheating of the cathode. The higher voltage is necessary because the electrodes are not heated prior to starting. It is more energy efficient than rapid or preheat starting, but results in greater wear on the electrodes during starting. The life of instant-start lamps that are switched on and off frequently may be reduced by as much as 25% relative to rapid-start operation. However, for longer burning cycles (such as 12 hours per start), there may be no difference in lamp life for different starting methods.
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