D I C T I O N A R Y
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Absorption Factor: The absorption factor is the ratio of absorbed light to incident light. A matt black solid absorbs almost all incident light, while a white solid absorbs very little. AC: Abbreviation for "Alternating Current". The flow of electricity which travels in waves and pulses on and off in cycles many times per second. The most common frequency of electricity used in this country is 60 cycles per second (hertz). AC Power System: An independent system of stand-by AC power for use where potential utility power interruption threatens critical electrical loads. Accent Lighting: Directional lighting used to emphasize a particular object such as a piece of art, a retail display, or draw attention to a specific location or area. Access Floor System: A floor system that provides a hollow space for power distribution and other wiring systems that can be exposed and rearranged to accommodate change. This type of floor is commonly seen in rooms housing mainframe computers and open offices with modular furniture, usually in a data or information processing center. Acrylic: The generic term for a family of transparent plastics used in making lighting fixture lenses, diffusers and refractors. Accomodation: The human eye is capable of focusing on objects at various distances and creating a sharp image on the retina. This process of adjustment within the human eye is called accommodation. In the case of inadequate lighting conditions (less than 100 lx or in thick mist or fog) accommodation of the human eye is reduced. It also declines as people grow older starting at the age of about 40-45. Adaptation: Adaptation is the ability of the human eye to adjust to average Luminance in the field of vision. The human eye is capable of adapting within a luminance range of 10-6 cd/m2 to about 105 cd/m2. Air Boot: An air diffusing device that fits over an air-handling troffer and allows air to be supplied through the side slots of the fixture into the room; usually manufactured by HVAC equipment manufacturers and supplied under the mechanical subcontract. Air Gap Switch: A mechanical switch or relay used to physically disconnect the lighting load from the dimmer when the dimmer is switched off. Air Handling: A type of troffer that can either supply air (heating or air conditioning) to a room, remove air from a room, or do both. Air handling units incorporate a floating door appearance by use of a black housing reveal. Alternating Current: The flow of electricity which travels in waves and pulses on and off in cycles many times per second. The most common frequency of electricity used in the US is 60 cycles per second (hertz). Alzak(TM): A finish produced by electrochemically brightening and anodizing a special high purity aluminum alloy. It is used to provide reflectors with a highly specular permanent finish, resistant to corrosion and abrasion. It is a registered trademark of the Aluminum Company of America (ALCOA). Ambient: The surrounding environment of a device such as a fixture or ballast. It usually refers to temperature or sound conditions. Ambient Lighting: Lighting designed to provide general uniform illumination throughout the work area. Ambient Temperature: Surrounding - the ambient temperature is the temperature of the air that surrounds the fixture in the room. A critical criterion for fixture selection especially in extreme temperature environments. Amp: (SEE Ampere) A common abbreviation for Ampere. Ampacity: The allowable volume of amperage for a given conductor. Ampacity is directly proportional to the cross-sectional area of the conductor, and is measured in amperes. Ampere: The standard unit of measurement for electric current that is equal to one coulomb per second. It defines the quantity of electrons moving past a given point in a circuit over a period of time. Ampere Hour: The constant supply of 1 ampere of current over the duration of one hour. Typically used in reference to batteries. Ampmeter: A device used to measure the flow of current in an electrical circuit. Analog Dimmer: Dimmer controlled by a continuously variable low voltage signal, normally 0 to 10 volts DC. Anchor Bolt: A mechanical device used to secure the pole base (also called a standard) to its foundation. Angle of Diffusion: The plane angle of diffusion describes the rotation-symmetrical light distribution of a spot or flood. Anodized: An electrolytic process for converting an aluminum surface to aluminum oxide. Anodizing creates a transparent finish that is physically part of the metal. Anodized finishes are generally colorless, but may be dyed in a variety of colors. The coating is hard and highly resistant to corrosion. ANSI: Acronym for American National Standards Institute. A professional institute comprised of representatives from safety protection agencies, manufacturers and consumers. This institute publishes testing standards for products and components. Aperture Size: Inside diameter measurement (that light can pass through) of an optical assembly at its lowest part. Application: This term refers to how a product is used; i.e., a vandal-resistant fixture in a prison is a good "application" of this particular product. Arc: A sustained visible discharge of electric current across a gap in an electric circuit. Arc Tube: A tube enclosed within the outer glass envelope of an HID lamp and made of clear quartz or ceramic that contains the arc stream. Arc Tube Voltage Rise: An operating characteristic of high pressure sodium lamps whereby the arc tube voltage gradually rises over the lamp life. Accelerated arc tube voltage rise occurs when light is improperly reflected back through the arc tube (such as with an incorrect reflector) increasing temperature and voltage, and thereby shortening lamp life. Area Coverage Factor: Pertains to control systems and emergency lighting equipment and is used to estimate the number of fixtures (or lamp heads) required to produce the desired light level. ASHLAR: A term used to describe a lighting design that is laid out in a "checker board" fashion. Asymmetric Distribution: Non-symmetric distribution of light. In many cases, the luminous intensity may be more pronounced in one direction. Auto Regulator: More often called a "constant wattage transformer", which is used in many HID ballasts. This is the most popular ballast circuitry because it offers good regulation and efficiency characteristics at a moderate cost. It is considered to be the industry standard. Auxiliary Circuit for Run-up and Restrike: After ignition High-pressure Discharge Lamps generally require a run-up time of up to 10 min. before they develop full Luminous Flux and gas discharge is stabilized.To bridge this period, in which neither illuminance nor Color Appearance conform to lamp rating, an auxiliary lamp with instant start characteristics can be incorporated in the luminaire The auxiliary light source provides the minimum required illuminance. Once the primary lamp has stabilized, the auxiliary is switched off. Should the high-pressure lamp be extinguished briefly, the auxiliary circuit is again employed until Re-ignition occurs. Average illuminance (Eav) : over a surface, Illuminance averaged over the specified surface. Average luminance coefficient (Qo) : a measure for the lightness of a road surface being defined as the value of the luminance coefficient q averaged over a specified solid angle of light incidence. Average Maximum Candlepower: The average of the 10 highest readings in a floodlight beam.
Back Mounted: Refers to a type of mounting of an emergency lighting unit or exit sign allowing for the direct mounting of the back of the fixture to the wall. Back Plate: A bracket on a surface or wall mounted luminaire used to fasten the luminaire and to cover the outlet box. Baffle: A shield of metal, wood or plastic used to screen a light source from normal angles of viewing. Aluminum baffles are commonly used in parabolic fixtures or, a grooved cylinder dropped below a light source to conceal the lamp and provide light cutoff. Ballast: A device used in fluorescent and HID luminaires to provide the necessary starting voltage and to limit the lamp current during operation. Ballast (Cold Weather): A ballast designed to provide sufficient starting voltage for fluorescent lamps in cold weather, generally down to 0 degrees F. Ballast (Dimming): Dimming ballasts are special ballasts which, when used together with a dimmer control, will vary the light output of a lamp. Ballast (Electronic): A ballast that operates fluorescent lamps at high frequencies using semi-conductor components to increase the frequency in combination with smaller inductive components to provide the lamp current control. Ballast (Fluorescent): A ballast is required to start and operate a fluorescent lamp. In combination with the starter the ballast delivers the striking voltage needed to start the lamp. During lamp operation the ballast maintains the required current for the lamp. Ballast (Magnetic): Magnetic ballasts are chokes which limit the current passing through a lamp connected in series on the principle of self-induction. The resultant current and power are decisive for the efficient operation of the lamp. A specially designed ballast is required for every type of lamp so as to comply with lamp rating in terms of Luminous Flux, Color Appearance and service life. Ballast (Potted): The ballast case is filled with a potting compound to minimize the noise caused by vibration of the case (due to the actions of the magnetic field in the laminated core of the ballast). Ballast Cycling: Undesirable condition whereby the ballast turns lamps on and off (cycles) due to the overheating of the thermal switch (class P device) inside the ballast. This may be due to incorrect lamps, improper wire connections, improper voltage being supplied, and high ambient temperatures around the fixture or the early stage of a ballast failure. Ballast Efficiency Factor: The ballast efficiency factor (BEF) is the ballast factor (see below) divided by the input power of the ballast. The higher the BEF (within the same lamp-ballast type ( the more efficient the ballast. Ballast Factor: A light loss factor that must be applied to lumen calculations for fluorescent and HID lamps. It is the ratio of actual lumen output of a lamp operating with a commercial ballast to the rated lumen output operating with a laboratory reference ballast. Ballast Losses: The amount of additional energy a ballast consumes to operate the lamp (line watts minus lamp watts). There is usually a trade-off between ballast losses and ballast regulation. Ballast Regulation: The ability of a ballast to control lamp wattage (and therefore light output) when subject to changes in line voltage. Barn Door: A track fixture accessory. Adjustable doors that are attached to the track light to shape the light beam and add additional shielding. Battery: A chemical device that provides DC (direct current) voltage. It is a source of electrical energy. Battery Date Code: A date code marked on the battery that, for warranty purposes, indicates the date the battery was manufactured. Battery Pack: A self-contained power pack, which is installed in fluorescent fixtures, enabling the fixture to produce some light output in case of a power failure. Fluorescent fixtures that contain a battery pack are generally used for emergency lighting purposes. Beam Angle: the angle between the two directions for which the intensity (candlepower) is 50% of the maximum intensity as measured in a plane through the nominal beam centerline (center beam candlepower). Beam Lumens: The lumens contained within the beam spread of a floodlight. Beam Spread: (in any plane) the angle between the two directions in the plane in which the candlepower is equal to a stated percent (usually ten percent) of the maximum candlepower in the beam. Bezel: A rim that holds a transparent covering which holds the glass lens in place. Bi-Level Switching: Applies to fixtures that have two or more ballasts, and thus have the ability to switch a multi-lamp fixture in such a way as to provide two or more levels of light; i.e., the ability to switch a 2-lamp unit so that only one lamp or both lamps are energized at a given time. Bi-Metal Switch: A small thermal switch made of two different metals which expand at differing rates when heated causing the switch contacts to open. BIAX: Twin-tube fluorescent lamp used in some Emergency Lighting, Downlighting, and Fluorescent products. The lamp life is about 10 times that of incandescent lamps and uses less power. Blinding Glare: is glare which is so intense that for an appreciable length of time after it has been removed, no visual perception is possible. Bollard: A type of architectural outdoor lighting that is a short, upright ground- mounted unit typically used to provide cutoff type illumination for egress lighting, to light walkways, steps, or other pathways. Boot: An air diffusing device that fits over an air-handling troffer and allows air to be supplied through the side slots of the fixture into the room; usually manufactured by HVAC equipment manufacturers and supplied under the mechanical subcontract. Boundary Zone: If a room is not utilized right up to the walls, calculations for the lighting system can be limited to a working plane reduced by a peripheral margin of 0.5 m for each wall. In such a case it is sufficient if the requirements for mean illuminance Uniformity are met for this reduced area. A drop in illuminance towards the boundary zones does not affect lighting conditions for the workstations. Branch Circuit: That part of the building wiring system between the final over current protective device (typically a fuse or circuit breaker at the electrical panel) and the electrical equipment that consumes power. Bracket: (Mast Arm): An attachment to a lamp post or pole from which a luminaire is suspended. Breaker: An electromechanical device that acts as a switch-and- fuse combination to protect and disconnect a circuit in case of an overload or short circuit. Brightness: Although the effect of brightness emanating from an object depends primarily on its luminance, luminance cannot be treated as an absolute measure for the perception of brightness. Given different levels of surrounding brightness, surfaces of identical luminance can in fact lead to varying subjective assessments of brightness. Luminance is a quantifiable physical value, where as Brightness is an expression of a subjective response. For photopic vision, brightness is roughly proportional to the logarithm of luminance. Brown-Out: A system-wide momentary reduction in voltage, causing fluorescent and HID lamps to partially extinguish, thus reducing available light. Brown-Out Protection: Circuitry designed to sense a reduction in line voltage and switch to emergency power prior to reaching the critical point at which HID or fluorescent lamps are extinguished. This is a safety feature. Brushed Aluminum: A non-specular aluminum finish grainy in appearance. BX(TM ): The trade name for cable originally manufactured by General Electric. It is comprised of a flexible metallic covering with two or more insulated wires without a grounding conductor inside for carrying electricity. (See type AC cable in the National Electrical Code.)
CAD: Acronym for Computer-Aided Design. A method of designing and drafting interactively (and graphically) using a computer system. This saves time and labor, especially for revision work. CAM: Acronym for Computer-Aided Manufacturing. A method that uses a computer to automate certain processes in manufacturing. Cam-action latch: A latch that puts the pressure point forward of the center pivot line. This forward point causes the latch to tighten instead of loosen when downward pressure is applied to the door or housing to which it is installed. This latch requires physical closure as opposed to a spring-loaded latch that utilizes a spring-action that automatically latches when pressure is applied. Can (Low End): Jargon for an inexpensive (low-end) downlighting product that is recessed into the ceiling. Called a "can" or "pot" because of its shape. Canadian Standards Assoc. (CSA): The official electrical standards writing and enforcing agency for Canada. Candela: Unit of luminous intensity, describing the intensity of a light source in a specified direction. Candela Distribution: A curve, often on polar coordinates, illustrating the variation of luminous intensity of a lamp or luminaire in a plane through the light center. Candlepower: Older terminology for luminous intensity; the intensity in candelas of light from a source. Candlepower Distribution: a curve that represents the variation in luminous intensity (expressed in candelas) in a plane through the light center of a lamp or luminaire; each lamp or lamp/luminaire combination has a unique set of candlepower distributions that indicate how light will be spread. Candlepower Distribution Curve: a curve, generally polar, representing the variation of luminous intensity of a lamp or luminaire in a plane through the light center. Canopy: A metal plate or dish on the ceiling or wall that covers the junction box and the wiring connections. This is seen on pendant- mounted fixtures, exit signs or track fixtures. Capacitor: An electrical circuit component that stores energy in an electrostatic field. Capacitors are fitted to luminaires that operate with discharge lamps either to improve the power factor (Power Factor Correction; or to suppress radio noise voltage in the long and medium-wave ranges. Capacity: The allowable volume of amperage for a feeder at its particular current carrying capacity. Each conductor is sized, giving it a certain capacity to feed current to a load. Carrier Signaling System: A communication method that superimposes digital signals on an AC voltage wave. Cathode Ray Tube (CRT): Cathode Ray Tube or CRT refers to a computer terminal screen. This TV-like screen allows a person to view information on their computer. Also called "screen," "monitor" or "VDT." Cave Effect: Sensation of being in a "cave" resulting from the top of the walls and ceiling being dark. Cavity: An upper, lower or intermediate zone or region of a room designated as ceiling, floor or room cavity. Cavity Ratio (CR): Geometric proportions of the ceiling, floor and room cavities. (See Room Cavity Ratio). CBM / ETL (Ballast): CBM - Certified Ballast Manufacturers Association - a group of fluorescent ballast manufacturers who produce ballasts that conform to certain ANSI specifications. ETL - Electrical Testing Laboratories, Inc. - a private independent organization and recognized authority in the field of measurements and testing of lamps and lighting equipment (used by CBM). Center Beam CandlePower, (CBCP): the intensity of light produced at the center of a reflector lamp, expressed in candelas. Channel: 1. The portion of a fluorescent fixture used to house the ballast and conceal the wires. 2. A group of lights whose intensity is controlled as one. Any number of lights and dimmers may be grouped to form a single channel (sometimes called a "zone"). Channel Cover: Component part of fixture. Installed to cover ballast and wiring harness; also referred to as a "wireway cover". Channel Intensity Display: Means of identifying dimmer intensity settings at a control station. May be displayed by either slider position or electronic display. Charger Board: The electronic circuitry (printed circuit board, PCB) that maintains the batteries in an emergency exit or unit. In addition to maintaining a charge on the battery, the PCB converts the unit from AC to DC power in the event of a power outage. Chevron: A directional indicator consisting of two broad strokes meeting at an angle of 45 to 120 to form a V shape and rotated through 90. Chimney Effect: A luminaire optical system that is open both at the top and bottom allows air to flow up past the lamp and internal reflector surfaces keeping them free from dirt accumulation. This is referred to as the "Chimney Effect". Choke: An inductive electrical component used to filter electromagnetic interference and lamp filament hum from electronic dimmers. Chromaticity: the aspect of color that includes consideration of its dominant wavelength and purity. CIE: (Commission Internationale de l'Eclairage) - The International Commission on Illumination - An organization based in Europe which creates standards for lighting, science, design and application. Circuit: A completed path of electrical elements including the electric source, the wiring and the load. Class 1 Circuit: An electrical circuit used to carry a control signal. May be either line voltage or low voltage, but must be treated as a line voltage circuit (run in conduit). Class 2 Circuit: An electrical circuit used to carry a control signal. Must operate at low voltage and remain separated from line voltage conductors. May often be installed without conduit. Class P: A ballast with a thermal disconnect switch that switches the ballast off if the ballast case temperature rises above 105 degrees F. It is a safety feature. Coefficient of Beam Utilization: The percentage of light from a floodlight which reaches the seeing task relative to beam lumens. Coefficient of Utilization: (Also called "CU") the percent of rated lamp lumens reaching a work plane. Color Anodize: A method of subjecting metal to electrolytic action in order to finish it with a protective or decorative film. This is done mainly to add color and to put a hardening finish on the aluminum. Color Appearance: The color appearance of a self-luminous unit, hence of a light source, is described as light color (in contrast to the body color of an object, which originates only from irradiation). The light color results from the spectral composition (spectrum) of the emitted light. Color Rendering : general expression for the effect of an illuminant on the color appearance of objects in conscious of subconscious comparison with their color appearance under a reference illuminant. Color space: Geometric representation of colors in space, usually of three dimensions. Color Rendering Index (CRI): A measure of the degree of color shift that an object undergoes when illuminated by a light source as compared with the color of the same object when illuminated by a referenced source of comparable color temperature. CRI is expressed as a number where 100 indicate that there is no color shift. Color Temperature: The "whiteness" of a light source indicated in degrees Kelvin, typically between 0-6000 degrees K. High numbers are considered "cool" colors and are blue in appearance. Low numbers are considered "warm" and are more red/yellow in appearance. Common Neutral: A wiring method which allows multiple lighting loads and dimmers to share a single neutral conductor. Dimmers should be rated for common neutral use to avoid interaction among dimmers. Compact Fluorescent: Twin-tube fluorescent lamp used in some Emergency Lighting, Downlighting, and Fluorescent products. The lamp life is about 10 times that of incandescent lamps and uses less power. Also referred to as "PL", "Twin-Tube", or BIAX lamps. Conductor: A substance or material (typically wire) capable of carrying electric current. Conduit: A metal tube or "pipe" used as an enclosure to protect electrical conductors; also a type of electrical raceway. Constant Wattage (CW) Ballast: A premium type of H.I.D. ballast in which primary and secondary coils are isolated. Considered a high performance, high loss ballast featuring excellent regulation. Constant Wattage Autotransformer (CWA) Ballast: A popular type of H.I.D. ballast in which the primary and secondary coils are electrically connected. Considered an appropriate balance between cost and performance. Contrast: The relationship between the luminance of an object and its background. Contrast Rendering Factor (CRF): A lighting system with good contrast rendition will present few if any problems with reflections. In addition to the finish of the objects or surfaces in the visual field, reflections depend on the incident angle of the light from the luminaires in the room, and on their Luminous Intensity Distribution Patterns and Luminance. Control Assignment Station: Device used in rooms with moveable walls to properly identify which lights a control station should operate. Each time the walls are moved, control station functions must be redefined accordingly through the control assignment station. Convenience Outlet: Electrical outlet provided on some fixtures (such as under cabinet lighting for plugging in a radio or other electrical device). A grounded convenience outlet accommodates 3- prong cord plugs. Cool-Beam Reflector: Cool-beam reflectors are made of glass with a special multiple coating that makes them transparent for infrared radiation but not for radiation at the wavelength of light. They are made of glass and multi-coated in a special finish (dichroic lamp). Cord Set: Electrical cord with attachment plug which is built into the fixture so that it may be plugged into a standard electrical outlet. Correlated Color Temperature, (CCT): a specification of the color appearance of a lamp relating its color to that of a reference source heated to a particular temperature, measured in degrees Kelvin (K); CCT generally measures the "warmth" or "coolness" of light source appearance. Coulomb: A unit of electrical charge equal to 6.24 x 10 (to the 18th power) electrons. CRI: A measure of the degree of color shift that an object undergoes when illuminated by a light source as compared with the color of the same object when illuminated by a referenced source of comparable color temperature. CRI is expressed as a number where 100 indicate that there is no color shift. Cross Arm: A support device used on outdoor poles for mounting flood lights. Often seen in sports lighting. CRT: Cathode Ray Tube or CRT refers to a computer terminal screen. This TV-like screen allows a person to view information on their computer. Also called "screen," "monitor" or "VDT." CSA: The official electrical standards writing and enforcing agency for Canada. CSI: Construction Specifications Institute - An organization that works toward the uniformity and standardization of building plans and specifications CU: Coefficient of utilization. The percent of rated lamp lumens reaching a work plane. Cuboid: A square cylinder luminaire mounted on a wall or ceiling Current: The flow of electrons in an electrical circuit (measured in amperes) Current Rise-Time: A dimmer performance characteristic that indicates the degree of filtering provided with the dimmer Cut Sheet: Data sheet that shows fixture dimensions, descriptions, options and photometrics. These sheets are submitted by Lithonia Lighting agents through the contractor, engineer and architect to obtain final approval on the specific equipment to be furnished. Cut-Off Angle: The angle from the photometric vertical axis at which a reflector, louver, or other shielding device cuts off direct visibility of a lamp. It is the complementary angle of the shielding angle. Cut-Off Lighting: Outdoor lighting accomplished by means of "cut off" fixtures which essentially begins to rapidly decrease light output above 70 degrees from nadir. This generally results in better glare control. Cut-Off Luminaire: An outdoor luminaire that emits most useful light at lower angles. Essentially, no light above 90 degrees is displayed. Sometimes called a "shoebox" because of its physical shape. CW: A premium type of H.I.D. ballast in which primary and secondary coils are isolated. Considered a high performance, high loss ballast featuring excellent regulation. CWA: A popular type of H.I.D. ballast in which the primary and secondary coils are electrically connected. Considered an appropriate balance between cost and performance.
Damp Location (Fixtures): Damp Location: Partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some cold-storage warehouses. Damp Location Fixtures: Fixtures which are suitable for use in these locations. Date Code: A date code marked on the battery that, for warranty purposes, indicates the date the battery was manufactured. Daylight: Daylight derives mainly from the gefilterte Thermal Radiation of the sun filtered through the atmosphere. It forms a continuous Spectrum comprising wavelengths from about 300 to 4500 nm with a mean Color Appearance of 5000 K (for Central Europe). Daylight Compensation: Dimmer controlled by a photocell so the intensity of the lamps tracks opposite the daylight level detected by the photocell. As daylight levels increase, lamp intensity decreases. An energy-saving technique used in areas with significant daylight contribution. Daylight Tracking: Dimmer controlled by a photocell so the intensity of the lamps tracks with the daylight level detected by the photocell. As daylight levels increase, lamp intensity increases. A technique used to match inside and outside lighting levels. Daylighting: Lighting scheme that uses a dimmer controlled by a photocell so the intensity of the lamps tracks opposite the daylight level detected by the photocell. As daylight levels increase, lamp intensity decreases. An energy-saving technique used in areas with significant daylight contribution. DC: Flow of continuous electricity in one direction from positive to negative. DC Flasher: An option used in exit signs. When regular power fails and battery-powered DC lamps take over, the flashing control board interrupts the flow of electricity, so that the lamps flash off and on. Design Factor: Loss of illuminance caused by ageing and contamination in a lighting system can be anticipated in the planning phase with the help of design factor p. This means that more "light" is installed at the beginning of the service life of a new system, so that required service illuminance can be guaranteed over a longer period of time. Die-Cast: A metal molding process where hot molten metal is injected into a "hard" mold. After the molten metal hardens and cools, it is removed and trimmed to complete the finished part. Die-embossed: Embossments or forms built into the fixture tooling to add strength and rigidity to channels, housings and/or reflectors. Diffuse: Term describing the lack of directionality in light distribution. Refers to the scattering of light. Diffused Lighting: Lighting provided on the work-plane or on an object that is not predominately from a particular direction. Diffuser: A translucent piece of glass or plastic that shields the light source in a fixture. The light distribution through the diffuse piece of glass or plastic will be even or "soft." Digital Dimmer: Dimmer controlled directly by a series of computer generated digital signals. Dimmer: A device which changes lighting intensity by regulating electrical power delivered to the lamp. Dimming System: An arrangement of cabinets containing multiple dimmers operated from remotely mounted control stations. The two are normally connected with low voltage control wires. Dip Tolerance: The amount of line voltage drop a ballast can sustain before the lamp extinguishes. Usually expressed as a percent; the higher the percentage, the better. Direct Current (DC): Flow of continuous electricity in one direction from positive to negative. Direct Glare: is glare resulting from high luminances in the visual environments that are directly visible from a viewer's position. Examples can be a sunlit surface inside or outside a building, or an insufficiently shielded luminaire. Direct/Indirect Lighting: A variant of general diffuse lighting in which the luminaires emit little or no light at angles near the horizontal. Directional Lighting: Lighting provided on the work-plane or on an object predominately from a particular direction. Disability Glare: is glare which reduces the ability to perceive the visual information needed for a particular activity. Disability glare is caused by light scattered within the eye, causing a haze of veiling luminance that decreases contrast and reduces visibility. Discharge: The removal of stored energy in a battery. Discharge Lamp: In gas-discharge lamps light is produced through the ionization of a gas in the discharge tube. In the process the gas becomes conductive. There are low-pressure, high-pressure and very high-pressure discharge lamps. Discharge lamps offer a much higher luminous output than incandescent lamps. They are operated with Ballasts (for current limitation) and usually with an Ignitor. Discomfort Glare: is glare which is distracting or uncomfortable, which interferes with the perception of visual information required to satisfy biological needs, but which does not significantly reduce the ability to see information needed for activities. Disconnect Socket: (CIRCUIT-INTERRUPTING LAMPHOLDER) - Prevents shock by de-energizing the electrodes in the sockets when the lamp is removed. Used with dimming ballasts and emergency lighting. Distribution (Bat Wing): A candela distribution pattern where the light is directed between 30 and 70 degrees. There is less light directly under the fixture, giving this particular distribution a "bat wing" shape. This type of distribution is seen with parabolic fixtures. Division 16: The section of the CSI Construction Specifications that applies to the electrical distribution requirements; 16500 is the lighting section of this division. Door Frame: Metal trim around the lens in a light fixture that supports the diffuser. This door is typically hinged so it can be opened for relamping, cleaning, etc. Double-Face: An exit sign that displays the word "exit" on both sides so it can be seen from two directions. Downlight: A type of point source ceiling luminaire, usually fully recessed. May feature an open reflector or may incorporate a shielding or directing device. DR acrylic: DR is an additive to acrylic that provides flexibility and therefore impact resistance. The higher the percentage of DR, the higher the impact resistance. Drum: A surface-mounted fixture with a drum-shaped white diffuser. Dual Circuit: Refers to a branch circuit configuration in which two hot conductors are used with one or two neutral conductors as a grounding conductor to form a circuit. Dual Circuit Switching: Two circuits in one area that are switched to a given level. Dual Voltage: A fixture or product having the capability to operate by either 277 or 120 voltage. A fixture or product having the capability to operate at two differing supply voltages.
E.M.I.: Abbreviation for Electromagnetic Interference. High frequency interference (electrical noises) caused by electronic components or fluorescent lamps which interferes with the operation of electrical equipment. E.M.T.: Abbreviation for Electrical Metallic Tubing; a type of electrical raceway (pipe). (Also see Article 348 in the National Electrical Code) E.P.A.: A value given to outdoor pole mounted lighting equipment based on fixture surface area and shape. Used in outdoor applications to calculate wind loading data to determine proper pole size necessary to support fixture. E.S.T.: Abbreviation for Energy-Saving Tandem. Two fluorescent luminaires in which a ballast in one is used to operate lamps in both fixtures. Typically used with three lamp troffers using three two-lamp ballasts. EFC: An acronym for the Electro Federation Canada. EFC is a Canadian electrical industry organization comprised of manufacturers and distributors. Effective Projected Area: A value given to outdoor pole mounted lighting equipment based on fixture surface area and shape. Used in outdoor applications to calculate wind loading data to determine proper pole size necessary to support fixture. Efficacy: A metric used to compare light output to energy consumption. Efficacy is a ratio of lumens to watts and can be defined for bare lamps or for luminaires. Efficiency: The ratio of the lumen output of the luminaire to that of the bare lamp. Egress: Quickest way out of a facility, usually under emergency conditions. Electroluminescent: A light source technology used in exit signs that provides uniform brightness, long lamp life (approximately eight years), while consuming very little energy (less than one watt per lamp). Electrolyte: The chemical fluid used in batteries which supplies electrons. Electromagnetic Interference: High frequency interference (electrical noises) caused by electronic components or fluorescent lamps which interferes with the operation of electrical equipment. Electronic Ballast: A ballast which operates fluorescent lamps at high frequencies (20 - 25 kHz) using semi-conductor components to increase the frequency in combination with smaller inductive components to provide the lamp current control. Provides energy savings and quiet operation. Electronic Dimming Ballast: A variable output fluorescent ballast which operates the lamps at high frequencies. Ellipsoidal: A downlighting fixture that is recessed into the ceiling, whose reflector has an ellipsoidal shape, and which provides an ellipsoidal light distribution. Emergency Lighting: Emergency lighting is designed to be available when the power supply to the regular lighting system fails. Emergency lighting comprises safety lighting for escape routes and standby lighting. Electro-Magnetic Iinterference: High frequency interference (electrical noise) caused by electronic components or fluorescent lamps that interferes with the operation of electrical equipment. EMI is measured in micro-volts, and can be controlled by filters. Because EMI can interfere with communication devices, the Federal Communication Commission (FCC) has established limits for EMI. End-of-Run Fixture: A fixture that cannot be wired in a series with other fixtures. (Opposite of a thru-wire fixture) Energy: a measure of work done by an electrical system over a given period of time, often expressed in kilowatt-hours (kWh). Energy-Saving Ballast: A type of ballast designed so that the components operate more efficiently, cooler and longer than normal ballast. Specifically EPACT compliant ballast that bares the Circle E on its label. Energy-Saving Lamp: A type of lamp designed to operate more efficiently, producing more lumens per watt than standard lamps, and thus operates at a lower wattage than a standard lamp. Enhancing Reflections: reflections which enhance appearance described in such terms as sparkling, glittering, etc. Equivalent Sphere Illumination (ESI): The amount of light in foot-candles produced by a luminous sphere on a seeing task in the center of the sphere that will render the same "see ability" as the raw foot-candles render the same task in the specific seeing environment under consideration. ETL: Abbreviation for Electrical Testing Laboratories. ETL has been particularly active in the testing of fluorescent ballasts and is affiliated with CBM (Certified Ballast Manufacturers). Exit Sign: An illuminated sign used to direct traffic flow to safety in an emergency situation. Explosion-Proof Luminaire: a luminaire which is completely enclosed and capable of withstanding an explosion of a specific gas or vapor that may occur within it and preventing the ignition of a specific gas or vapor surrounding the enclosure by sparks, flashes or explosion of the gas or vapor within. It must operate at such an external temperature that a surrounding flammable atmosphere will not be ignited. Extruding: A method of shaping metal or plastic by forcing the material through a shaped orifice, die, or pattern roll. Individual pieces are then obtained by cutting the resulting "extrusion" into desired lengths.
F.M.C.: Abbreviation for Flexible Metal Conduit, a type of electrical raceway (also called Greenfield or flex). See Article 350 in the National Electrical Code. F.M.T.: Abbreviation for Flexible Metallic Tubing; a type of electrical raceway (also called Greenfield or flex). See Article 349 in the National Electrical Code. Façade Lighting: This term typically refers to the exterior of a building and the lighting of the vertical building surface. This is usually accomplished with floodlights or spotlights or ground mounted landscape luminaires. Fade Rate: Time required for a dimmer to change from one intensity level to another. Fade rates may be either user adjustable or factory set. Normally used with PRESET SCENE control. Fast Transfer: A type of central inverter system that has a very small interruption (measured in milliseconds) between the loss of power and start-up of the inverter. FC: The English unit of measurement of the illuminance onto a surface. One foot-candle is equal to one lumen per square foot. FDA: Food and Drug Administration. Has specific requirements for products used in food processing areas. Fenestration: Any opening or arrangement of openings that allows daylight into a room. Field Angle: The angle through which the luminaire emits at least 10% of the maximum intensity measured in a plane through the nominal beam centerline. Filter: Electrical components within a dimmer intended to reduce the effects of EMI and lamp filament hum. Filter (RFI, EMI): A device used to screen out radio frequency signals and/or electromagnetic signals which could cause interference with other electrical equipment or devices. Filtered Charge Output: A protection feature in emergency lighting circuitry. Minimizes voltage ripple that results in repeated heating and cooling of battery terminals. Prevents excessive corrosion and prolongs battery life. Fire Alarm Interface: A device that causes an exit sign to flash in synchronization with the sound of the fire alarm. Designed to protect hearing-impaired persons in emergency situations. Fire Rating: A designation given to a building assembly (wall, ceiling, floor, design) that meets UL test requirements and can resist the spread of flame for a given number of hours. Complete assemblies, not the components, are fire rated. Fixture: The components which when assembled make up the complete housing of a light fixture (this includes parts such as a reflector, lamp socket, etc.) Fixture Schedule: A construction document that lists all luminaires used on a particular job. The list typically includes fixture, type, fixture catalog number, fixture quantity, lamp type, lamp catalog number, ballast type and voltage. (Also known as luminaire schedule) FL: Unit used in lighting to describe the luminance of an area. Today, it is more common to use candelas per meter squared (Candela/meters squared). This term is still occasionally referred to as foot-lambert. Flange: Overlapping metal portion of a recessed luminaire at the ceiling line. It serves to trim the ceiling opening around the luminaires. Flange Kit: A kit used to field-convert a standard grid troffer to a flanged troffer. The Flange kit also requires a swing gate kit. Floating Door: A type of door on a fixture that appears to have no support because of "black reveal" or a narrow band of metal that is painted black surrounding it. Usually seen on air-handling fixtures. Floodlight: A type of outdoor luminaire mainly used in parking lots or sports fields. Floodlighting: A system designed for lighting a scene or object to a luminance greater than its surroundings. It may be for utility, advertising or decoration purposes. Floor Cavity: The cavity formed by the floor, the workplane and those portions of the walls between these two planes. Floor Cavity Ratio (FCR): A number indicating the dimensional proportions of a floor cavity using its length, width and height. For a rectangular floor cavity: FCR = 5H(L+W)/(L*W) Fluorescent: A linear light source consisting of a tube filled with gas. When electrical current is applied, the resulting arc emits ultraviolet light that excites the phosphors on the inside of the lamp wall, causing them to radiate visible light. Flux (Luminous Flux): (See Lumen). Footcandle (FC): The English unit of measurement of the illuminance onto a surface. One foot-candle is equal to one lumen per square foot. Footlambert (FL): Unit used in lighting to describe the luminance of an area. Today, it is more common to use candelas per meter squared (Candela/meters squared). This term is still occasionally referred to as footlamberts. 1 fL = 0.3183 (1/pi) cd/feet squared Forced Air Cooling: Use of ventilating fans to cool dimmer cabinets. Form Factor: The proportion of light reaching surface no. 2 from surface no. 1 to the total light leaving surface no. 1. Four-Way Switch: A type of switch that is always used in conjunction with two three-way switches and which allows three or more entrances into a room to be switched. Frequency: the number of times per second that an alternating current system reverses from positive to negative and back to positive, expressed in cycles per second or hertz, Hz. Fresnel Lens: A lens consisting of an array of concentric circular prisms that may be used to focus, collimate, or spread light. Fuse: An electrical safety device, made of wire or thin metal, and usually enclosed in glass, that will melt and "break" the circuit in the event of a current overload.
Gasket: A fibrous or rubber device used to create a seal around two separate parts that are to be joined together to prevent penetration of dust, water, oil, light leaks or other contaminants. General Diffuse Lighting: Lighting from luminaires that distribute 40% to 60% of its emitted lumens downward and the balance upward. General Lighting: Lighting designed to provide essentially uniform illumination throughout the work area exclusive of any provision for any special, localized requirements. Glare: The effect of brightness or brightness differences within the visual field sufficiently high to cause annoyance, discomfort or loss of visual performance. Glare Control Mark: number denoting the degree to which discomfort glare is controlled. Glare, Direct: Glare resulting from high luminances or insufficiently shielded light sources in the field of view. Glare, Disability: Glare resulting in reduced visual performance and visibility and often accompanied by discomfort. Glare, Discomfort: Glare producing discomfort. It does not necessarily interfere with visual performance or visibility. Goniophotometer: A device for measuring the directional pattern of light distribution from sources, luminaires, media and surfaces. Grazing: Downlighting or uplighting indoor or outdoor application used to show texture on surfaces, walls and fabrics. Grazing Angle: The angle between the main floodlight beam and the building facade when using grazing floodlighting. This shallow angle is created by ground mounting the floodlights very close to the building facade and aiming them upward. Greenfield: Brand name of flexible, metallic conduit which has become a generic term within the industry to describe FLEX. Grid Tee Ceiling: A modular ceiling type in which the supports are suspended directly from the building structure in a rectangular grid. The ceiling tiles and lighting fixtures lay into and are supported by this grid. The most common sizes of these ceiling tiles are 2'x 4', and 2'x 2'. Grommet: A rubber insulating eyelet used to prevent water entry into the fixture at the wire exit. Ground Light: Light from the sun or the sky after it has reflected from surfaces located below the horizon. Ground Wire: (a wire that makes) a connection between a piece of electrical equipment and the ground, so the user is protected from electric shock if the equipment develops a fault
H.I.D.: Abbreviation for High Intensity Discharge. Generic term used to describe mercury vapor, metal halide, high pressure sodium light sources and fixtures. H.P.F.: A ballast with a .9 or higher rating power factor, which is achieved by using a capacitor. Halogen: Gas used in tungsten-halogen lamps which increases lamp life and enhances lumen output. Hard Light: Lighting that causes an object to have a sharp, clearly defined shadow. Hard Wire: A term referring to permanent, traditional electrical wiring methods such as EMT and wire (also called pipe and wire) or other methods containing no pluggable or relocatable features. Harmonic: an electrical frequency that is an integer multiple of the fundamental frequency; for example, if 60 Hz is the fundamental frequency, then 120 Hz is the second harmonic and 180 Hz is the third harmonic; some electronic devices, such as ballasts or power supplies, can cause harmonic distortion, directly affecting power quality. Hazardous Location: A location requiring a fixture to have special features to protect it from damages. Hazardous location divisions and classes are defined in Chapter 5 of the National Electrical Code. Heat Extract (Heat Removal): A type of air-handling function in a fluorescent fixture designed to remove heat from within the luminaire. This prevents heat from being dissipated into the room. Heat Radiator: A device used to transfer heat away from a ballast or fixture in order to lengthen ballast lamp life and protect its components. Heat Sink: A device or component designed to drain heat away from a heat sensitive or heat generating component. Heavy Duty Floodlighting (HD): A weatherproof unit having a substantially constructed metal housing into which is placed a separate and removable reflector. A weatherproof hinged door with cover glass encloses the assembly but provides an unobstructed light opening at least equal to the effective diameter of the reflector. Hertz (Hz): The standard unit of measurement for frequency. One hertz equals one cycle per second. HID: Abbreviation for high intensity discharge. Generic term describing mercury vapor, metal halide, high pressure sodium, and (informally) low pressure sodium light sources and luminaires. High-Bay: Pertains to the type of lighting in an industrial application where the ceiling is 20 feet or higher. Also describes the application itself. High End Trim: An adjustment which limits the maximum output of a dimmer. Usually used with incandescent lamps as a lamp life extender and energy saving technique. Highmast Lighting: Illumination of a large area by means of a group of luminaires which are designed to be mounted on the top of a high mast generally 60 feet or higher. High Output (HO): A lamp designed to operate at higher current and produce more light than a standard lamp. Available in T12, T8 and T5 sizes. High Power Factor: A ballast with a .9 or higher rating power factor, which is achieved by using a capacitor. High Power Factor: A ballast with a .9 or higher rating power factor, which is achieved by using a capacitor. High Pressure Sodium: A high intensity discharge (H.I.D.) lamp in which light is produced by radiation from sodium vapor operating at a partial pressure of about 1.33 x 10,000 Pa (100 Torr). High-Mast: A type of very tall pole with top mounted fixtures used in applications such as lighting highways. These poles are 70 feet tall or more and are equipped with a lowering device to maintenance luminaires on the ground. Home Run Location: A term that indicates the location where several separate circuits come together for a continuous "run" back to the electrical panel in one conduit. Horizontal Illumination: Illumination of a horizontal surface, such as a desktop or assembly line. Hot Restart: The phenomenon of reinstating or re-striking the arc in an H.I.D. light source after a momentary power loss. Hot restart occurs when the arc tube has cooled a sufficient amount. Hot Restrike: The phenomenon of reinstating or re-striking the arc in an H.I.D. light source after a momentary power loss. Hot restart occurs when the arc tube has cooled a sufficient amount. Housing: The body of a fixture. HVAC: Abbreviation for Heating, Ventilation and Air Conditioning. Hydroforming: A method of forming sheet metal in which the metal is placed on a flexible rubber diaphragm which is supported by oil under pressure. The metal is formed around a male punch as the diaphragm is raised. The resultant part is generally of uniform thickness and quite strong. Hz: The standard unit of measurement for frequency. One hertz equals one cycle per second.
I.P.S.: Abbreviation for Interruptible Power System. IALD: Abbreviation for International Association of Lighting Designers. IBEW: Abbreviation for International Brotherhood of Electrical Workers. American union whose members work in many lighting manufacturing plants. IBI: Abbreviation for Intelligent Building Institute. IC: Abbreviation for Insulated Ceiling. Any ceiling that has insulation material. IESNA: Abbreviation for Illuminating Engineering Society of North America. IESNA Photometric Data: A standard format defined by IESNA (LM-63) for the electronic transfer of photometric data. Ignitor: A device that generates a voltage pulse to start certain discharge lamps without having to pre-heat the electrodes. Illuminance (E): A photometric term which quantifies light striking a surface or plane at a point. It is expressed either in lumens per square foot, foot-candles (the English metric) or lumens per square meter, lux (the metric unit). Foot-candle 1fc = 10.764 lux IMC: Abbreviation for Intermediate Metal Conduit; a type of electrical raceway (pipe). (See Article 345 in the National Electrical Code.) Incandescent Filament Lamp: a lamp in which light is produced by a filament heated to incandescence by an electric current. Indirect Glare: Glare produced from a reflective surface. Indirect Lighting: Lighting by luminaires that distribute 90 to 100% of the emitted light upward. Inductor: An electrical circuit component (essentially a coil of wire) that stores energy in an electromagnetic field. Initial Lumens: The lumen output of a lamp after about 100 hours of operation. Injection Molding: Process for manufacturing plastic lenses whereby hot liquid plastic is injected into a lens mold of desired shape and size. Injection molded lenses are a premium over extruded lenses and offer superior prisms and excellent light control, in addition to high strength. Input Watts: Input Watts refers to the total watts required to operate both the ballast and lamp together as a system. Since most ballasts do not operate the lamps at full wattage, ballast watts and lamp watts cannot be added together to provide an input watts. An input watt is the more accurate measurement of system watts since it includes the actual lamp operating wattage. Ballast Losses refers to the wattage used by the ballast alone. If only ballast losses are specified, the total input watts equal ballast losses plus lamp wattage. However, this calculation can be misleading as it assumes that the lamps are operated at full wattage. Insertion Loss: A lowering of the maximum voltage supplied to the lamps caused by losses within the dimmer. Instant Start Fluorescent Lamp: A fluorescent lamp designed to start using a high voltage without preheating the electrodes; this is also known as a cold-start lamp in some locations. Insulated Ceiling (IC) Rated Fixture: Fixtures that can be buried directly in insulation. Insulator: A substance or material (such as rubber or glass) that will not permit the flow of electric current. Integrated Dimmer: A multiple channel dimmer assembly that offers dimming system type features in a wall box footprint. May be used instead of ganged wall box dimmers or small dimming systems. Integrating Photometer: A device for measuring the total output (luminous flux) of a source with a single measurement. Intensity: The luminous flux per unit solid angle in a particular direction; may be expressed in candela or lumens per steradian. Interreflected Component: Light that reaches the work plane after one or more reflections from room surfaces. Inverse Square Law: The law stating that the illuminance at a point is inversely proportional to the square of the distance between the source and the point. Inverter: An electrical circuit that changes direct current (D.C.) to alternating current (A.C.) or vice-versa. IP (Ingress Protection): The IEC (International Electrotechnical Commission) uses the term "Ingress Protection" or IP to define the environmental protection of an enclosure. This is described in IEC Standard 529. The IP classification system designates by means of a two digit number, the degree of protection against ingress of dust and moisture. The first digit defines the level of protection against solid objects, while the second digit defines the level of protection against moisture. The higher the digit, the greater is the level of protection. Iso-Footcandle Curves: Graphical representation of illuminance levels created by passing a curve through all points of equal illuminance on a given plane. When generated for a single pole configuration, this may be referred to as a template. Iso-Intensity Diagram: array of iso-intensity curves. Iso-Luminance Curve (diagram): locus of points on a surface at which the luminance is the same, for given positions of the observer and of the source or sources in relation to the surface. Iso-Lux: Metric equivalent of iso-foot-candle. Isolux curve (diagram): locus of points on a surface where the illuminance has the same value. ITL: Abbreviation for Independent Testing Laboratories. This independent laboratory is located in Boulder, CO. Lighting manufacturers use this laboratory to conduct photometric or environmental tests for luminaires.
J Box: An enclosure where conductors or wires are spliced or terminated. J-Box: Jargon for junction box. A code-approved steel or plastic enclosure in which several wires come together for connection, such as the taps for fixtures. Joist: A small structural beam, generally a member which directly supports a floor or roof.
K.O.: A portion of a metal enclosure that has been partially cut out, but remains in place. It can be easily removed or "knocked out" to permit an electrician to attach switches, convenience outlets, conduit connectors, etc. Kelvin: A measurement of temperature. 1o F = 256o Kelvin. 1o C = 274o Kelvin. Used to measure color temperature. Kerb Ratio: the ratio of the, average illuminance on the footpath of a specified width to the average illuminance on the same width of adjacent carriageway. Lamp Mortality (Morality rate): the number of operating hours elapsed before a certain percentage of the lamps fail. Kilo: 1,000 in metric units. Kilogram: A metric measure of mass equal to 2.2046 pounds. Kilometer: A metric measure of length equal to .62137 miles or 3280.8 feet. Knock-Out: A portion of a metal enclosure that has been partially cut out, but remains in place. It can be easily removed or "knocked out" to permit an electrician to attach switches, convenience outlets, conduit connectors, etc. Often referred to as a "KO."
L.C.D.: Liquid Crystal Display. Commonly used in computer displays, watches, etc. L.E.D.: Light-Emitting Diode. L.L.D.: The fractional remainder of lamp lumens lost, at rated operating conditions, due to lamp degradation. Mean lumen output divided by initial output. L.V.D.: Protection feature in an emergency lighting unit in which the load is automatically disconnected when battery voltage drops to a critical point. Lambertian Surface: A surface that emits, reflects or transmits light according to Lamberts cosine law; i.e. the surface has the same luminance regardless of the viewing angle. Lamp: The actual source of light in a fixture. Some people refer to fluorescent lamps as "tubes" and incandescent lamps as "light bulbs." Lamp - Compact Fluorescent: Compact fluorescent lamps operate on the same principle as tube-shaped fluorescent lamps. They are particularly suitable for installation in smaller luminaires, and this has opened up many new areas of application for fluorescent lamps. The compact fluorescent lamp likewise requires a ballast for starting and for current-limiting in operation (2-pin cap) as well as a starter, or better still an electronic ballast (only with 4-pin cap). Amalgam lamps have been optimized for use in hot luminaires. The so-called energy saving lamps are compact fluorescent lamps with a ballast (mostly an electronic ballast) integrated into the screw cap (E14, E27). They are suitable for replacing conventional incandescent lamps; they are, however, not dimmable. Lamp - Fluorescent: The fluorescent lamp is a mercury-vapor low-pressure discharge lamp, consisting of a tube-shaped glass bulb with electrodes at both ends. The gas fill of the tube is a mixture of argon and krypton with a few milligrams of mercury. The interior of the glass is coated with a thin, fluorescent powder layer. When current flows, the gaseous discharge mainly generates invisible ultraviolet radiation, which is only converted into visible light by the fluorescent material. The fluorescent material determines the light quality and efficiency of light generation. Lamp - High Pressure Mercury: Mercury-vapor high-pressure lamps are amongst the oldest discharge lamps on the market. With moderate luminous efficiency and less satisfactory color rendition properties but comparatively low costs and very low failure rate, they are mostly used in industrial bays and outdoor areas. The lamps are only conditionally suitable for indoor applications with permanently occupied workstations. The mercury-vapor high-pressure lamp is operated with a ballast, but requires no additional igniting equipment. The lamps can also be operated in energy-saving mode at reduced power (half-night mode). Lamp - High Pressure Sodium: Conventional sodium-vapor high-pressure lamps have a very high luminous efficiency in conjunction with poor color rendition properties, however. Because of their compact design and their long average service life, they are used only in street and tunnel lighting. The sodium-vapor high-pressure lamp is operated with ballast and igniter. The lamps are not suitable for interior applications. Lamp - Incandescent: Incandescent lamps are thermal radiators. Light is produced because of the high temperature of the spiral-wound filament during the current flow. Although incandescent lamps have a low luminous efficiency and a short service life, they are frequently used in domestic areas as well as in hotels, restaurants and catering because of their pleasant, warm light color with excellent Color Rendition and because of their low purchase cost. Lamp - Low Voltage Halogen Capsule: Because of the small light point, low-voltage halogen incandescent lamps enable the precise focusing and optimum direction of light. They are particularly suitable for installation in very small luminaires which are used for accentuating with strong light points. Low-voltage halogen incandescent lamps are operated by a conventional (magnetic) or electronic transformer. There are different model ranges for commercial/professional areas and the private area. Lamp - Main Voltage Tungsten Halogen: A gas fill and free halogens are encircled in the bulb of the halogen incandescent lamp. Tungsten molecules torn from the spiral-wound filament are taken up by the halogens and fed back to the filament (halogen cycle). In this way the service life of the lamp is increased as compared with the conventional incandescent lamp, and bulb blackening is reduced. The latest reflector lamps are hardly larger than low-voltage reflector lamps. Lamp - Metal Halide: Metal halide lamps are a further development of mercury-vapor lamps. They offer high luminous efficiency and a long service life, and are also of small design. Although these lamps require a starting time of several minutes, they are used in many applications in industrial and sales areas because of their good to very good color rendition properties. They require a ballast and an igniter. There are also electronic ballasts for lamps up to 150 W. The lamps have been optimally designed for full-load mode and are not suitable for dimming. The more recent ceramic lamps with burners improve exemplary diffusion with color temperature and the color drift over the entire service life. Lamp Burnout Factor: The fractional remainder of light lost due to burned out lamps being left in place. Lamp Current Crest Factor (LCCF): The peak lamp current divided by the RMS (average) lamp current. Lamp manufacturers require <1.7 for best lamp life. An LCCF of 1.414 is a perfect sine wave. Lamp Efficacy: A metric used to compare light output to energy consumption. It is the ratio of lumens per watt. Lamp Life: The number of burning hours at which 50% of any large group of installed lamps are still operational. Lamp Lumen Depreciation Factor (LLD): The fractional remainder of lamp lumens lost, at rated operating conditions, due to lamp degradation. Mean lumen output divided by initial output. Lamp Position Factor: The fraction of lumens emitted by a source at a particular position relative to its output in the position as rated. Lamp rupture containment: Lamp rupture containment requires that HID products contain hot lamp fragments in the event that the lamp ruptures. Containment is accomplished by using a glass or acrylic enclosure on the bottom of the reflector. Certain metal halide lamps can rupture at the end of their rated life if not turned off for at least 15 minutes per day. Lampholder: The part of the light fixture that supplies the power to the lamp and also holds the lamp in place. Also called a socket. A lampholder bracket is the part of the fixture that holds the lampholder (socket) in place. Lay-In Troffer: A fluorescent fixture that "lays" into a grid tee suspended ceiling. Layout: A drawing that shows the locations of the fixtures in a specific ceiling. Lead Lag: A type of 2-lamp ballast (used in both H.I.D. and fluorescent fixtures) so that one lamp is inductively controlled and the other is capacitively controlled, resulting in inherently high power factor (HPF). Lead-Acid: (Also Lead-Antimony) this is a "wet" battery, which means that it needs to be filled periodically with water. "Acid" refers to the materials found in the grid (plates) of the battery. This battery is usually found in large emergency unit equipment (200 watts & up) and in central inverter systems. Lead-Calcium: A type of sealed battery that is non-maintainable, or maintenance free. Calcium refers to the materials found in the grid (plates) of the battery. This battery is usually found in small unit equipment and in emergency exit signs. Leakage Reactance: A type of H.I.D. ballast which makes use of the excess reactance in the transformer coil; it is furnished with a capacitor (H.P.F.) or without a capacitor (N.P.F.). LED: Abbreviation for light emitting diode. An illumination technology used for exit signs. Consumes low wattage and has a rated life of greater than 80 years. Lens: Transparent or translucent medium which alters the directional characteristics of light passing through it. Usually made of glass or plastic. Lens Frame: The retainer (usually metal) to hold the lens in place in a fixture. Life Cycle Cost Analysis: An economic evaluation which include initial (purchase) costs as well as all significant owning costs over time. Life Cycle Costing include the time value of money (interest rates). Life Safety Code: A code written by the NFPA to ensure that building owners place equipment that will help to save lives in an emergency. For example: emergency lighting equipment meets Life Safety Code requirements by placing one foot-candle of light on the "path of egress" or exit path in a building. Light: is visible radiation as perceived by the human eye. As such it constitutes only a small segment of the total spectrum of electromagnetic radiation, which comprises not only visible light but also gamma radiation, x-rays, infrared and UV radiation, and radio waves, etc. The spectral range of light is 380 -780 nm. Within this range of wavelengths the colors of the spectrum can be distinguished, i.e. red, orange, yellow, green, blue, indigo and violet. Radiation outside of this range cannot be seen by the human eye. Light Center (of a Lamp): The center of the smallest possible sphere which would completely enclose the light emitting portion of the lamp. Light Center Length (of a Lamp): The distance from the light center of the lamp to a specified reference point on the lamp. Light Loss Factor (LLF): A factor used in calculating illuminance that takes into account dirt accumulation, lamp depreciation, temperature and voltage variations, maintenance procedures and environmental conditions. Total LLF also includes the ballast factor. Light Output Ratio: of a luminaire. The ratio of the total flux of the luminaire, measured under specified practical conditions, to the sum of the individual luminous fluxes of the lamps operating outside the luminaire under specified conditions. Light Pollution: Light distributed in outdoor areas where light is not desired. Light pollution is typically caused by outdoor lighting fixtures that may emit a substantial amount of light in an upward direction. This creates a "haze" of light in the atmosphere that cannot be utilized. Light Trespass: Light that goes beyond the planned area. Lighting Economics: A cost evaluation of lighting systems. This evaluation will typically include initial costs, as well as all significant owning costs over time. Lighting Specifier: A person (architect, engineer, lighting designer, owner, etc.) who specifies the lighting equipment for an installation. Linear Response: Method of dimmer control where the measured light level is equal to the intensity control setting. For example, adjusting the control to 30% produces a measured light level of 30%. LLR - Low Loss Reactor: Non-regulating reactor LAG, used in areas with very little line voltage variation. Designed as an energy saving system, 277 volt only. For metal halide lamps only. Local lighting: lighting for a specific visual task, additional to and controlled separately from the general lighting. Note: The term is often applied to lighting designed to illuminate a particularly small area, e.g. a desk top. Localized Lighting: lighting designed to illuminate an area with a higher illuminance at certain specified positions, for instance those at which work is carried out. Lock Out: Means of disabling one or more dimmer control stations from a master station. A partial lock out disables only selected functions on the targeted stations. Lock Washer: A washer used to lock a screw or bolt into place. Longitudinal Uniformity (U1): the ratio of minimum to maximum luminance along a line parallel to the road axis through the observer's position. Louver: Grid type of optical assembly used to control light distribution from a fixture. Can range from small- cell plastic to the large-cell aluminum louvers used in parabolic fluorescent fixtures. Low Density: Combustible low-density cellulose fiberboard used to retard the spread of fire. Low End Trim: An adjustment that limits the minimum output of a dimmer. Often used to prevent dimmers from operating fluorescent lamps in unstable regions that may exist at the low end of the range. Low Power Factor: Essentially, an uncorrected power factor of less than .90. Low Voltage Lamp: A lamp that provides both intensity and good color rendition. Lamp operates at 12V and requires the use of a transformer. Popular lamps are MR16 and PAR36. Low-Bay: Pertains to the type of lighting in an industrial application where the ceiling is about 20 feet or lower. Also describes the application itself. Low-Pressure Sodium: A discharge lamp in which light is produced by radiation from sodium vapor. Considered a monochromatic light source (appears to be orange in color and renders most other colors as gray or brown). Low-Voltage Disconnect: Protection feature in an emergency lighting unit in which the load is automatically disconnected when battery voltage drops to a critical point. Low-Voltage Disconnect Reset: Pertains to the circuitry in emergency lighting equipment. The LVD is reset instantly when A.C. (alternating current) power is applied or reapplied to the units. It enables unit testing at the time of installation, before the battery reaches full charge. Low-Voltage Switch: A relay (magnetically operated switch) that permits local and remote control of lights, including centralized time clock or computer control. Lumen (lm): A measurement of the light output of a lamp, or the SI unit of luminous flux. Photometrically, it represents the luminous output of a source with a uniform emittance of 1 candela over a unit solid angle of 1 steradian. Lumen Depreciation: the decrease in lumen output of a light source over time; every lamp type has a unique lumen depreciation curve (sometimes called lumen maintenance curve) depicting the pattern of decreasing light output. Lumen maintenace: Term to describe the percentage of the initial rated lumens that the lamp emits at the end of its rated life. Lumen Method: Two names for a method to calculate the average maintained horizontal illuminance on a workplane within a space. Only the direct illumination from the luminaires to the workplane is taken into account, and the actual layout of the luminaires is ignored. Lumens Initial: The lumen output of a lamp after about 100 hours of operation. Lumens Mean: The lumen output of a lamp after it has operated for approximately 40% of its rated life. Luminaire: A complete lighting unit consisting of a lamp or lamps, the parts designed to distribute the light (housing), and any necessary starting components (ballast, socket, etc.). Luminaire Dirt Depreciation (LDD): A factor used in lighting calculations to account for the light loss due to the accumulation of dirt on the luminaire. The LDD is contingent upon environment, cleaning schedules and the type of luminaire involved. Luminaire Efficiency: Total lumen output of a luminaire expressed as a percent of rated bare lamp lumens (as determined by photometric tests). Luminaire Schedule: A construction document that lists all luminaires used on a particular job. The list typically includes fixture, type, fixture catalog number, fixture quantity, lamp type, lamp catalog number, ballast type and voltage. (Also known as fixture schedule). Luminance (L): A photometric term that quantifies directional brightness of a light source; or of a surface that is illuminated and reflects light. It is expressed as foot-lambert (English units) or candelas/meters squared (Metric units). Luminance Contrast: the relationship between the luminance's of an object and its immediate background. Luminance Limit Angle: The luminance limit angle of a luminaire is measured from the horizontal plane is the maximum angle at which the lamp is not yet in the direct line of vision. Luminance Photometry: A luminance meter resembles a film camera. The meter is aimed at the surface to be measured using a viewer. In the viewer there is a scale showing the size of the target field. The field is projected onto a photoelectric cell. The luminance meter measures the illuminance and corrects the result for the incident angle to the photoelectric cell. The reading is displayed in candelas per square meter (cd/m2). Luminance Ratio: the ratio between the luminance's of any two areas in the visual field. Luminescence: is the term used for all light radiation that is not Thermal Radiation. The most important light generation process involving luminescence is gas discharge on passage of an electric current through a gas or metal vapor (gas discharge lamp). Such lamps take advantage of the phenomenon of photoluminescence in the form of fluorescence or phosphorescence, in which invisible short-wave radiation is converted into visible light through processes within the fluorescent material. Fluorescence persists only for a fraction of a second after excitation, whereas phosphorescence persists for some time as a visible afterglow. Luminous flux (F): The luminous flux describes the photometrically evaluated luminous efficiency, hence the light quantity delivered by a light source. The luminous flux is related to the entire room, or to only a part of it (partial luminous flux in a room-angle element). Luminous Intensity (I): Luminous intensity is an expression of the amount of light beamed in a certain direction within the interior. It is calculated as the ratio of luminous flux to the relevant Element of Solid Angle. The luminous intensity of a lamp or luminaire is not equal in all directions. By plotting luminous intensity in the room (or in planes) around the lamp or luminaire, Luminous Intensity Distribution can be defined. This offers a precise description of the photometric characteristics of the lamp or luminaire. Luminous intensity distribution is normally represented in the form of either a polar or linear diagram. Luminous Intensity Diagram (table): luminous intensity shown in the form of a polar diagram or table in terms of candela per 1000 lumens of lamp flux. The diagram (table) for non-symmetrical light distributions gives the light distribution of a luminaire in at least two planes: 1).In a vertical plane through the longitudinal axis of the luminaire. 2). In a plane at right angles to that axis. Luminous Intensity Distribution: The luminous intensity distribution pattern for a light source shows in which direction and with what intensity the light is emitted. The individual values can be presented in tabular or graphic form, and a number of diagrams are normally employed for this purpose. Luminous Intensity is usually based on a 1000 lm light source. Lux (LX): The metric unit of measure for illuminance of a surface. One lux is equal to one lumen per square meter. One lux equals 0.093 foot-candles.
Magnetic Ballast: Also called electromagnetic ballast. These are the most basic and oldest type of fluorescent ballasts. The basic construction consists of a core of stacked steel plates wrapped with a coil of copper or aluminum wire (a basic electron magnet). This is then potted in an insulating material such as asphalt to conduct the heat of the ballast outward. The entire assembly is then put into a metal housing to prevent breakdown and shock hazard. Usually a separate starter of various different designs is incorporated into this housing to provide the additional voltage needed when initially starting a fluorescent lamp. Some HID ballasts require an external ignitor. Magnetic Dimming Ballast: A variable output fluorescent ballast that uses conventional ballast construction methods and operates the lamps at the normal power line frequency of 60 Hz. Magnetic Regulator: A premium type of H.I.D. ballast in which primary and secondary coils are isolated. Considered a high performance, high loss ballast featuring excellent regulation. Maintained Illuminance: Refers to light levels of a space at other than initial or rated conditions. This terms considers light loss factors such as lamp lumen depreciation, luminaire dirt depreciation, and room surface dirt depreciation. Maintenance Factor: ratio of the average illuminance on the working plane after a specified period of use of a lighting installation to the average illuminance obtained under the same conditions for a new installation. Maintenance-Free: Product that does not require maintenance for optimal performance. Describes a sealed type of battery. Manual Control: A means of dimmer control where the intensity of each channel is individually adjusted. Masking: A feature found in outdoor point-by-point applications programs which will "mask" or delete a specified area/areas from the lighting calculations. This is typically used to represent a building in the area or for non-rectangular parking lots. Master-Slave Ballasting: Labor-saving, factory-installed wiring option in which ballasts are shared by two luminaires, reducing installation labor and potential energy costs. Matt Surface: a non-glossy dull surface as opposed to a shiny (specular) surface. Light reflected from a matte surface is diffuse. Mean Lumens: The lumen output of a lamp after it has operated for approximately 40% of its rated life. Mean Spherical Luminous Intensity: The intensity in candelas of a source averaged over all possible directions; is equal to the total luminous flux output by the source divided by 12.56637 (4 pi). Mellow Light: It is a universal lighting system designed to offer balanced lighting conditions for varying office routines such as writing, reading, communicating and computer working. In addition the Mellow Light system is the ideal choice for all environments where the light must be pleasant, versatile and a source of motivation at work. Memory Retention: The ability of a dimmer to retain the last given instruction during a loss of power and to restore to that point automatically following restoration of power. Also, the ability of a control system to retain all programmed information during loss of power. Mercury Vapor Lamp: A type of high intensity discharge (HID) lamp in which the major portion of the light is produced by radiation from mercury. This lamp emits light in the blue/ green range and is favored by landscape architects. Metal Eggcrate: Metal louver of various cell sizes typically used in fluorescent troffers. Metal Halide: A type of high intensity discharge (HID) lamp in which the major portion of the light is produced by radiation of metal halides, argon and mercury vapors in the arc tube. Includes clear and phosphor-coated lamps which differ in their color-rendering characteristics. Mitered Corner: Refers to a fixture's doorframe in which the corner pieces are joined together at a 45 degree angle as opposed to square over-lapping corners. Modeling: the effect of using highly directional light to create form through shadows and highlights. Modular Wiring: Wiring system that features plug-in, relocatable components suitable for commercial wiring, industrial wiring, access-floor wiring, local switching and convenience power-applications. Modular wiring offers significant benefits over conventional hardwiring, with reductions in installation time and labor costs, as well as simplifying fixture relocation. Mogul Base: A particular size of metal screw base used on larger lamps, primarily HID and some high wattage incandescent lamps. Mounting Height: In a given application, the distance from the luminous area of the luminaire (typically the bottom) to the floor. MR-16: A low-voltage quartz reflector lamp, only 2" in diameter. Typically the lamp and reflector are one unit, which directs a sharp, precise beam of light. MRB - Magnetic Regulated Ballast: This type of ballast, also referred to as a regulated or stabilized type, has operating characteristics similar to the RLB. For high pressure sodium sources only. Multi-Level Switching: Applies to fixtures that have two or more ballasts, and thus have the ability to switch a multi-lamp fixture in such a way as to provide two or more levels of light; i.e., the ability to switch a 2-lamp unit so that only one lamp or both lamps are energized at a given time. Multi-Tap Ballast: A ballast with tapped leads (wires) on the primary side, which enables the ballast to function on more than one supply voltage.
N.E.C.A.: Acronym for National Electrical Contractors Association. Professional society for electrical contractors, most of whom are union members. N.P.F. (Normal Power Factor): A ballast/lamp combination in which no components have been added to correct the power factor; hence, normal (essentially low) power factor. Nadir: An expression used when discussing luminaire photometry. It describes the direction the light is traveling from the luminaire to directly below the luminaire (0 angle). NAED: An acronym for the National Association of Electrical Distributors. This organization consists of U.S. electrical distributors who belong to the International Brotherhood of Electrical Workers (IBEW) union. Nanometer, (nm): a unit of length equal to 10-9 meters; commonly used as a unit of wavelength. National Electrical Code (NEC): Nationally recognized standards governing the installation of electrical equipment. The document compiled by the NFPA that provides safety standards for installation and application of electrical equipment. Natural Convection: A means of cooling a dimmer by allowing sufficient natural air circulation around the components producing heat. NEMA: An acronym for the National Electrical Manufacturers Association. NEMA is a U.S. electrical industry organization comprised of manufacturers. NFPA: Abbreviation for National Fire Protection Association. Nickel-Cadmium (Ni-Cad): A battery made with nickel and cadmium, abbreviated as Ni-Cad. Generally, the Ni-Cad battery is smaller and has a longer life expectancy than a lead battery. Nomenclature: Manufacturer's derived product designation, usually made of letters and numbers (alpha-numeric). NSF: National Sanitation Foundation. Has requirements for products used in food processing areas.
Occupancy Sensor: Control device that acts as a light switch upon sensing that a person has entered a space. May be ultrasonic, infrared or other type. Ohm: The standard unit of measurement for electrical resistance in a circuit. On Center: The term used to describe the distance between the centers of luminaires. "8 feet on center" means that the distance of the luminaires, center-to-center, is 8 feet. Optics: A term referring to the components of a light fixture (such as reflectors, refractors, lenses, louvers, etc.); also the light-emitting or light-controlling performance of a fixture. Overall Uniformity (UQ): the ratio of minimum to the average luminance over the area of road considered. Overcurrent: A protective device for a branch circuit that prevents damage to the circuit due to a current surge or an overload; usually a fuse or a breaker. Optical System: The lamp cavity or environment (including diffusing media) designed as part of the fixture for the purpose of controlling the light output. Overhang: The distance between a vertical line through the center of a luminaire and either the curb or the edge of the roadway. Overlay: (1) Drawing or partial drawing which can be placed on top of others to add detail. For example, a reflected ceiling plan can be overlaid with the luminaire layout, air diffusers, sprinkler heads, etc., to create an image of all components on the ceiling. (2) Thin lens which is installed above another lens or louver in a fixture to create a desired effect (glare control, ultra violet filtering, radio frequency shielding, etc.).
Paint after fabrication: Also called "post paint". Term to describe a product that is painted after it has been fabricated, as opposed to pre-paint, which is painted before fabrication. Post paint ensures that there is no exposed metal or raw edges. Panelboard: An electrical distribution device which converts incoming electrical power into several smaller circuits and provides overload protection in the form of circuit breakers or fuses. PAR 36: A PAR lamp that is 36 one-eighths of an inch in diameter with a parabolic shaped reflector (SEE PAR LAMP). PAR Lamp: A Parabolic Aluminized Reflector Lamp. An incandescent or low voltage lamp used to redirect light from the filament in a manner resembling a parabolic reflector. Lamps are available with flood or spot distributions. Parabolic Luminaire: A popular type of fluorescent fixture which has a louver composed of aluminum baffles that are curved in a parabolic shape. The resultant light distribution produced by this shape provides reduced glare, better light control, better maintenance, and is considered to have greater aesthetic appeal. Paracube: A metallic coated plastic louver made up of small squares. Often used to replace the lens in an installed troffer to enhance its appearance. The paracube is visually comfortable, but the luminaire efficiency is lowered. Also used in rooms with computer screens because of their glare-reducing qualities. Parahex: A metallic coated plastic louver made up of small hexagons. It has qualities similar to a paracube louver. Parawedge: A metallic coated plastic louver made up of small squares that reduces glare and fixture efficiency. Path of Egress: Quickest way out of a facility, usually under emergency conditions. PE: Professional designation of a licensed engineer. A state license is awarded to qualified engineers who successfully complete engineering requirements, allowing them to be registered to practice as a licensed engineer. Peak Intensity: the luminous intensity of a luminaire in the direction of the beam axis. Peaking Circuit: A circuit design used in some magnetic dimming ballasts which provides improved dimming performance. Not available in 277 volt dimming ballasts. Pendant: Method of mounting fluorescent luminaires and track lighting. Mounting hardware consists of a stem and canopy set. Performance Specification: A job specification in which the engineer has directed the electrical contractor to furnish and install lighting equipment that meets a detailed and precise set of performance parameters. These may include photometric, electrical, mechanical, and appearance aspects; a broader directive to the contractor as to the engineer's intent compared to a Prescriptive Specification. Perimeter Lighting: Directs light at the edges of an area. Can be used to eliminate weak spots from general lighting. Phase Control: The basic operating concept of electronic dimmers where lights are turned on for only a portion of each half of the electrical cycle. Photocell: A Photovoltaic device used to control luminaires and dimmers in response to detected light levels. May provide either daylight compensation or daylight tracking. Photoelectric Cell: A device used to convert radiant or light energy into the electrical energy, often used to control outdoor light fixtures. Photometer: A device for measuring photometric quantities such as luminous intensity, luminance, illuminance and/or luminous flux. Photometric (Report) (Curve): A photometric report is a set of printed data describing the light distribution, efficiency, and spacing criteria of a luminaire. This report is generated from a test conducted in a photometric laboratory. A photometric curve is a drawing illustrating the relative intensity of light emitted from a luminaire. Photometric Data: Photometric Data includes measured product performance for lighting products, including luminous intensity, efficiency, and zonal luminous flux. Test reports are available from laboratories and electronic files are available from most lighting manufacturers. Physiological Glare: Glare that causes a loss of visual performance (e.g. reduced perception of shapes and capacity for discrimination caused by glare from the headlights of an approaching car at night). PL(TM) Lamp: A compact fluorescent source. "PL" is North American Philips' trade name for this lamp. The generic name is "twin tube." The lamp is available in wattages from 5 to 40 watts and lengths from about 4" to 24". It is increasingly used in downlighting fixtures instead of incandescent sources. Plastic Eggcrate: A type of plastic fixture lens which is usually made up of small squares of white plastic. PLC: An electronic signaling (control) system making use of the building's power distribution network. Plenum: 1) Space between the structural ceiling and the finished ceiling. It is the service area concealing the housing part of a recessed fixture, as well as containing HVAC duct work, computer and telephone cables, electrical wiring, ceiling supports, plumbing, etc. 2) A compartment or chamber to which one or more air ducts are connected. Plenum Cable: A special type of low voltage control cable installed in ceiling spaces used for return flow of environmental air. Point Source: A source for which the dimensions of the lighting emitting area are small enough, relative to the distance from the source to the illuminated area, that these dimensions may be neglected in calculations and measurements. Poke-Home: A type of electrical connection which requires only that the pre-stripped ends of the wires be pushed into the open ports of the connector. This connection may only be used with solid, not stranded, wires. Poke-Thru: A device which makes it possible to bring power, data and communications through the concrete slab from one ceiling plenum to the next floor. This device must be fire rated to delay the spread of fire between building levels. Polycarbonate: High quality light stabilized plastic used in making diffusers, lenses and refractors. Very tough and highly resistant to damage from impact of stone, pellets and in some instances, low caliber bullets. Very resistant to UV deterioration. Polyester Powder Paint: A type of polymer paint in a powder form that is sprayed on fixture parts. The paint and the metal fixture part are given opposite electrostatic charges, which cause the powder to adhere to the surface; then it goes through a baking process which melts the paint to form a resilient, durable, reflective finish. Post-Painted: Also called "paint after fabrication". Term to describe a product that is painted after it has been fabricated, as opposed to pre-paint, which is painted before fabrication. Post paint ensures that there is no exposed metal or raw edges. Pot Light: A term used in the Canadian market for a downlight. (See DOWNLIGHT) Potentiometer: 1) Intensity control device used in dimmers. May be either a rotary knob or linear slide type element. 2) A variable resistor used in analog control. Power (Clean): Electrical power delivered to the customer comprised of perfectly sinusoidal voltage and current waveforms. Power (Conditioned): "Dirty" electrical power that has had the voltage spikes and surges filtered out. Power (Dirty): Electrical power delivered to the customer that contains voltage spikes and surges. Power Factor: The Power Factor of a ballast is the measurement of how efficiently it converts the voltage and current supplied from the power source into watts of usable power consumed by the ballast and lamps. Perfect utilization of electrical current would result in a power factor of 100%. Power Factor = Input Watts / (Line Volts x Line Amps). Advantages of High Power Factor ballasts include: 1) Avoiding possible penalty charges from electric utility, 2) Reduction in wiring costs since normal power factor ballasts take about twice the line current of high power factor ballasts and may require heavier wire to carry the load. 3) More fixtures can be installed on each branch circuit. Power Groove: Similar to 1500 mA VHO except for a special 2 1/8 inch diameter tube or lamp which has grooves that increase the surface area thus increasing light output. Power Line Carrier: An electronic signaling (control) system making use of the building's power distribution network. Power Surge: A sudden surge of high voltage on a power distribution circuit usually caused by lightning or the switching on/off of heavy loads, especially motors. Preheat: A type of ballast that uses a manual starter that heats up a fluorescent lamp before high voltage is applied to start the lamp. Preliminary Drawing: Drawings created by the specifier in the early phase of a building design. These drawings are typically used for design concepts or feasibility studies. Prescriptive Specification: A job specification in which the engineer has directed the electrical contractor to furnish and install lighting equipment that has been specified by manufacturer catalog number and description; can be a one-name spec (one manufacturer) or a multi-name spec (more than one manufacturer) and can include an "or equal" phrase for alternate proposals by the contractor. (See PERFORMANCE SPECIFICATION) Preset: Pre-defined intensity instructions for multiple channels on a dimmer control which may all be implemented simultaneously with a single activity (pressing one switch). Prewired: A fixture which has electrical wires attached to it at the factory to make the installation of the fixture easier and faster. Professional Engineer (PE): Professional designation of a licensed engineer. A state license is awarded to qualified engineers who successfully complete engineering requirements, allowing them to be registered to practice as a licensed engineer. Proportional Master: A master intensity adjustment on dimming control stations which controls all dimming channels assigned to it in proportion to the individual channel control settings. Protection Class: The protection class indicates to what extent the luminaire offers protection against electric shock (short circuit). The protection class may be indicated with Roman numerals or with the help of pictograms. The provisions of the standard are designed to prevent: electric shocks when touched; operating faults in the luminaries; reduced service life for lamps and luminaries; fire hazard in the luminaire or its surroundings. Pulse Rated: A special type of socket used in certain H.I.D. fixtures. Pulse-Rated Socket: A socket designed to withstand the high voltage pulse required by HID lamps that incorporate a separate "pulse ignitor."
Quad-Tube Lamp: A compact fluorescent lamp with a double twin tube configuration. Quality of Lighting: pertains to the distribution of luminance in a visual environment. The term is used in a positive sense and implies that all luminance's contribute favorably to visual performance, visual comfort, ease of seeing, safety and esthetics for the specific visual tasks involved. Quantity of Light: the product of the luminous flux by the time it is maintained. It is the time integral of luminous flux. Quarter Turn Fastener: Type of connecting device, typically used to hold a reflector or channel cover to a channel or housing. Attaches by rotating the connector one-quarter of a turn (as opposed to a screw-type fastener). (Also called WINGNUT and SPIN NUT) Quartz Restrike System: A system utilizing quartz incandescent lamps to provide instantaneous light in the event of a power outage. It is used as a supplement to HID sources which may otherwise require several minutes to restart after a power outage.
R.C.R.: Room Cavity Ratio. A ratio of room geometry used to quantify how light will interact with room surfaces. RCR = 5h (L+W)/(L*W) Raceway: A system that encloses and protects electrical conductors. Radio Frequency Interference (RFI): Interference to the radio frequency band caused by other high frequency equipment or devices in the immediate area. Fluorescent lamps generate RFI. Rapid Start (RS): The most popular fluorescent lamp/ballast combination used today. This ballast is designed to quickly and efficiently preheat lamp cathodes to start the lamp. Uses a "bi-pin" base. Reactance: The natural opposition to AC electric current flow that is a property of coils (inductors) and capacitors. Coils have the property of inductive reactance; capacitors have the property of capacitive reactance. Reactor: A type of ballast used with H.I.D. lamps; generally regarded as the simplest form of ballasting (no transformer is included). Rectilinear Cut-Off: A type of outdoor H.I.D. fixture (rectangular in shape) mounted on a pole and typically used for parking lots and tennis courts. (See CUT-OFF ANGLE, CUT-OFF LUMINAIRE) Redline: A term used to describe the changes made on a blueprint with a red pencil. Reference Ballast: a ballast specially constructed to have certain prescribed characteristics for use in testing electric-discharge lamps and other ballasts. Reflectance: The ratio of light reflected from a surface to the light incident on the surface. Reflectances are often used for lighting calculations. The reflectance of a dark carpet is around 20%, and a clean white wall is roughly 50% to 60%. Reflected Glare: or Veiling Reflection is a reflection of incident light that partially or totally obscures the details to be seen on a surface by reducing the contrast. Reflection: the process by which flux leaves a surface or medium from the incident side. Reflector: The part of a light fixture that shrouds the lamps and directs the light emitted from the lamp. Refractor: A device used to redirect the light output from a source, primarily by bending the waves of light. (See LENS) Recessed / Regressed: The term used to describe the doorframe of a troffer where the lens or louver lies above the surface of the ceiling. Regulated Charge Voltage: A protection feature of emergency lighting products that maintains a steady voltage level, thereby preserving the battery life of the unit. Regulation: The ability of a ballast to hold constant (or nearly constant) the output watts (light output) during fluctuations in the voltage feeding the ballast. Normally specified as + or - percent change in output compared to + or - percent change in input. Relay: A device that performs the actual on or off switching of an electrical load due to small changes in current or voltages. Examples: low voltage relay and solid state relay. Remote Head: For emergency lighting, an adjustable lamp head that is controlled and powered by a separate exit sign or unit. Request for Information: A request submitted to the architect or engineer of record by the general contractor or sub-contractor in order to clarify aspects of the contract blueprints or written specifications for a given building project. Restrike: The process of re-striking the arc in an H.I.D. light source after a momentary power loss. Hot restart occurs when the arc tube has cooled a sufficient amount, which is anywhere from one to fifteen minutes, depending on the source. Retrofit: Refers to upgrading a fixture, room, building, etc., by furnishing new parts or equipment. OR, To change a fixture out in the field. Reverse Polarity Protection: A protection feature in emergency lighting products which protects the charger board from damage caused by improperly connected battery leads. Rise-Time: A measure of time required for a dimmer to switch from "off" to "on" each half cycle. Rise-time measurements may be made on either the lamp voltage or current. Resistance, (R): a measure of resistance to flow of current, expressed in ohms. RLB - Regulated Lag Ballast: LAG-type regulator, used in areas where excellent line dip tolerance is critical. Also improves lamp life and has the best ballast regulation. For metal halide lamps only. Romex: Nonmetallic sheathed electrical cable that is used for indoor wiring. Room Cavity Ratio (RCR): A ratio of room geometry used to quantify how light will interact with room surfaces. RCR = 5h (L+W)/(L*W) Room Index (K): code number, representative of the geometry of a room, used in calculation of the utilization factor. Row Mounted: A continuous row of fixtures mounted end to end so that branch circuit wiring can be run through the channels. Row mounted fixtures are commonly seen in applications such as grocery stores or warehouses. RP-1 / RP-24: An office lighting standard approved by IESNA. This standard includes a section specifically for lighting offices with Visual Display Terminals (VDTs) which was previously referred to as RP-24. RP-24 has been incorporated with the RP-1 document.
Scene: The resulting lighting effect of adjusting several channels of a light control system to desired intensity. May be implemented through either MANUAL CONTROL or PRESET selection. SCR (Silicon Controlled Rectifier): A power electronic device often used in dimmers to regulate lamp power. Two SCR's are needed to build one dimmer. Screen Glare Acceptability: A metric used to quantify the acceptability to glare on VDT screens. SGA is a subjective response expressed as the percentage of people who find the screen glare acceptable. Screw-slot Ceiling: A type of ceiling system in which room partitions are screwed directly into the metal, ceiling-mounted screw slot grids, thereby making it easy to move the partitions around. Sealed-Beam Lamp: A type of high-light-output lamp, similar to car head lights, which is sealed to prevent light loss from dust, humidity and condensation. Self-Luminous Exit Sign: An illumination technology using phosphor-coated glass tubes filled with radioactive tritium gas. The exit sign uses no electricity and thus does not need to be hardwired. Semi-Specular: Term describing the light reflection characteristics of a material. Directional reflection with some amount of scatter. Setback: The distance that the center of the luminaire is behind the area to be lighted by that luminaire. Shielding: a general term to include all devices used to block, diffuse or redirect light rays, including baffles, louvers, shades, diffusers and lenses. Shielding Angle: The angle measured from the ceiling plane to the line of sight where the bare lamp in a luminaire becomes visible. The shielding angle affects direct glare. It is the complementary angle of the cutoff angle (See CUT-OFF ANGLE). Shadow Conditions: Shadows play an important role for the perception of spatial structures and perspective, and for general orientation. Good shadow conditions are created through an appropriate mix of diffuse (non-directional) and directed light. This ensures a gradual transition from dark to light areas. The actual mix depends on the visual tasks and activities involved. Shoebox: An outdoor luminaire that emits most useful light at lower angles. Essentially, no light above 90 degrees is displayed. Sometimes called a "shoebox" because of its physical shape. Short Circuit: A circuit that has extremely low resistance causing the current to become very high. This is often caused by a current carrying wire touching a ground wire. Excessive current will damage a circuit or connected equipment; therefore protection must be included to prevent a short circuit. Short Circuit Protection: A switch or fuse used to open the circuit when a short is detected. Shroud: A vinyl or metal trim that covers the exposed edge of the ceiling tile and grid tee when a grid fixture is used in a concealed tee grid ceiling system. Side Visor: A shield which can be mounted on the top or sides of an outdoor fixture. The side visors provide 45 degree horizontal cut- off. Sine Wave: Wave form that represents periodic oscillations. Electrical voltage and current is transmitted in the form of these waves. Sinusoidal: Simulates a sine wave shape or characteristic. Slimline (SL): Instant start fluorescent lamp with single-pin base. Available in T12 and T8 sizes. Slipfitter: A mechanical device that attaches a floodlight to a pole or bracket tenon. Socket: Component that holds the lamp base and supplies electrical power. Socket (Medium Base): A particular size of socket used for low wattage lamps. Socket (Mogul Base): A particular size of socket used for high wattage lamps. Solid State Ballast: 1) A ballast composed of electronic circuitry which operates lamps at high frequency. 2) A ballast composed of electronic circuitry and which contains no laminations (no 60Hz hum). All 60 Hz core and coil components have a solid core. Spacing Criteria: Spacing criteria (SC) determines uniformity by establishing spacing guidelines between rows and columns of fixtures. In order to ensure that there is not a dark area in between a group of 4 fixtures, the spacing criteria must not be exceeded. To arrive at the maximum recommended spacing of rows and columns, multiply the spacing criterion by the distance from the bottom of the fixture to the workplane height. The lower the number, the closer together the fixtures must be spaced. Spacing to Mounting Height: Spacing to mounting height (SMH) determines uniformity by establishing spacing guidelines between fixtures in a row. In order to ensure that there is not a dark area in between fixtures, the spacing to mounting height must not be exceeded. To arrive at the maximum recommended spacing, multiply the spacing to mounting height by the distance from the bottom of the fixture to the workplane height. The lower the number, the closer together the fixtures must be spaced. Specification: The precise written detail of the building contract which accompanies the building plans. It normally includes all requirements of the general contractor and subcontractors to furnish and install the specified materials and equipment using prescribed methods and workmanship. Specification Sheet (Spec sheet): (ALSO CALLED SUBMITTAL SHEET AND CUT SHEET) Data sheet that shows fixture dimensions, descriptions, options and photometrics. These sheets are submitted through the contractor, engineer and architect to obtain final approval on the specific equipment to be furnished. Specifier: Usually an Electrical Engineer, Lighting Designer or Architect. This design professional specifies the type of lighting equipment, the layout of the lighting equipment, and the manufacturer of the lighting equipment. Spectral Power Distribution, (SPD): a curve illustrating the distribution of power produced by the lamp, at each wavelength across the spectrum. Spectrum: The spectrum of radiation describes its composition with regard to wavelength. Light, for example, as the portion of electromagnetic radiation that is visible to the human eye, is radiation with wavelengths in the range of approx. 380 to 780 nm (1 nm = 10-9 m). The corresponding range of colors varies from violet to indigo, blue, green, yellow, orange, and red. Continuous spectrum, like incandescent lamps and the sun have such a continuous spectrum. Specular: Mirrored or polished surface. Causes the angle of reflection to be equal to the angle of incidence. This word is used to describe the finish of the material used in some light fixtures. Specular Angle: That angle between the perpendicular to a surface and the reflected ray. It is numerically equal to the angle of incidence. Specular Surface: Shiny or glossy surfaces (including mirror and polished metals) that reflect incident light, providing a relatively narrow beam pattern. Spike: Voltage spikes generated by HPS ballasts as a starter for the lamp. Spill Light: Lumen distributed by the luminaire which are outside the beam spread. Spin Nut: Type of connecting device, typically used to hold a reflector or channel cover to a channel or housing. (Also called QUARTER TURN FASTENER and WINGNUT) Spinning: A manufacturing process whereby a sheet of metal is shaped into a reflector by spinning it at very high RPM on a lathe and simultaneously pressing it against a form. Spline: The metal support member in a ceiling system used to support the ceiling tile. Spread: quantity of a luminaire to indicate the extent to which the light is 'spread out' across the road. Luminaires are classified as being of narrow, average or broad spread. Square Law Response: Method of dimmer control where the perceived light level is equal to the intensity control setting. For example, adjusting the control to 30% produces a light level perceived by most viewers to be 30%. The measured level is estimated by "squaring" the perceived value. In this example, 30% squared equals 9% actual measured level. Starter: A device used with a ballast to start preheat fluorescent lamps. Static: Refers to a troffer that is non-air-handling, and thus the air is stationary or static. Straight Master: A master intensity adjustment on dimming control stations that controls all dimming channels assigned to it. All controlled channels respond uniformly, independent of individual intensity control settings. Stroboscopic Effect (Strobe Effect): Condition where high speed machinery or other rapidly moving objects appear to be standing still due to the alternating current supplied to light sources. Sometimes called a "strobe effect." Styrene (Polystyrene): The generic term for a family of plastics used in the making of fixture diffusers and lenses. Tends to yellow in time due to the effect of UV radiation from fluorescent, HID, and induction lamps. Submittal Drawing: A detailed drawing of a fixture illustrating size and location of knockouts, screw holes and components of the fixture. Submittal Sheet: (ALSO CALLED SPEC SHEET AND CUT SHEET) Data sheet that shows fixture dimensions, descriptions, options and photometrics. These sheets are submitted through the contractor, engineer and architect to obtain final approval on the specific equipment to be furnished. Supplementary Lighting: lighting used to provide an additional quantity and quality of illumination that cannot be readily obtained by a general lighting system and that supplements the general lighting level usually for specific task requirements. Surface Mounted: Any fixture mounted directly on a wall or ceiling is surface mounted. Surge: A sudden surge of high voltage on a power distribution circuit, usually caused by lightning or the switching on/off of heavy loads, especially motors. Surge Protector: A switch or fuse incorporated into an electrical circuit to prevent damage to equipment caused by a power surge. Suspended Ceiling: A grid of connecting bars ("inverted tee" is the most common shape) suspended from the structural ceiling by wires. Acoustical tiles and light fixtures rest on these metal tees. Suspension or Pendant Mounted: Any fixture hung from a ceiling by supports (chains, hangers, etc.) is suspension or pendant mounted. Swing-Gate Hanger: Metal support attached to the fixture that swings out over the structural member for support in certain types of ceilings such as plaster. The swing-gate hanger is also available in kit form and can be used with the Flange Kit. Switch Leg: The term used to describe the electrical wire that feeds power to a fixture controlled by a local switch. This enables local switching of light fixtures. Provides an outlet of switched power to be used as needed for subsequent fixtures. Ideal component to minimize system cost where switch to fixture ratio is very high. Switching Tee (ST): Enables local switching of light fixtures. Provides an output of switched power and unswitched power to be used as needed for subsequent fixtures. The component is available in a variety of drop types to accommodate the most common varieties of partition construction. Switching, 2-Level: Applies to fixtures that have two or more ballasts, and thus have the ability to switch a multi-lamp fixture in such a way as to provide two or more levels of light; i.e., the ability to switch a 2-lamp unit so that only one lamp or both lamps are energized at a given time.
T12, T10, T8, T5, T4: Industry standard for fluorescent lamp nomenclature. T = tubular and the numbers that follow represent the diameter in one-eighth inch increments. T12 = 1.5 inches in diameter, T10 = 1.25", T8 = 1", T5 = 5/8" and T4 = 15/32". T8 and T5 lamps also have a special blend of phosphors for high color rendering. (See lamp manufacturer catalogs for more detail.) Take Control: Means of transferring lighting control from one dimming control station to another. Normally effected by pressing a "take" button on the panel to be used. Some equipment designs allow for partial take control so that only selected functions transfer. Tamperproof Screw: Used on door frames and other appropriate fixture parts to prevent vandalism. A special screwdriver is required to remove these screws. Often called "vandal-resistant Tandem In-Line: Two fixtures wired so all lamps on one side can be operated on one circuit. Tandem Wiring: Fixtures wired together in pairs so they share ballasts for switching capabilities. Task Lighting: Supplements the ambient lighting when specific tasks require higher illumination. Tee-Bar (Concealed or Exposed): Metal cross sections in a standard grid ceiling used to support lighting fixtures, air diffusers or air return grills, or tiles. Tempered Glass: A type of glass used for light fixtures which has a higher resistance to breakage than normal glass. Tempered Lens: A lens made of tempered glass. Tempering: A process used in the production of glass products to make the glass more resistant to breakage. Template: A drawing tool, usually made of plastic, that contains cutouts of different shapes that can be traced onto a blueprint or drawing. Also describes a typical section of a lighting layout which can be transposed over all similar layouts. Tenon: A section of vertical metal pipe that enables outdoor luminaires or brackets with slip fitters to be mounted onto a pole. Thermal Cut-Out: A heating type element that opens the electrical circuit when the ballast becomes overheated. Thermal Factor: A factor used in lighting calculations which compensates for the change in light output of a fluorescent lamp due to a change in bulb wall temperature when using energy saving products. It is applied when the lamp/ballast combination under consideration is different from that used in running the photometric report. Thermal Protection: Protection against ballast overheating by disengaging the ballast when the ballast case temperature reaches 105 degrees C. Thermal Protector: A device that protects a ballast from overheating. The class P thermal protector is used in most ballasts today. This thermal protector is a bi-metal switch with the ability to open the circuit when the ballast becomes overheated, then close the circuit when the ballast cools down. Thermal Radiator: Solid bodies, liquids and gases radiate energy on the basis of their temperature. The higher the temperature (in Kelvin), the greater the amount of energy emitted. Thermoplastic Frame: Lightweight, injected-molded frame. Three-Way Switching: The ability to turn a circuit on or off from two separate locations, such as near 2 doors to the same room. Threshold increment (Tl): number indicating the degree to which disability glare is controlled. Throw: characteristic of a luminaire that indicates the extent to which the light is thrown in the lengthwise direction of the road. Luminaires are classified as being of short, intermediate or long throw. Thru-Wire: Fixtures that are thru-wire listed can be wired in a series with other fixtures (opposite of an end of run fixture). Tilt, angle of: upward inclination of a luminaire from the horizontal uniformity ratio of illuminance on a given plane. A measure of the variation of illuminance over the plane expressed as either. 1).The ratio of the minimum to the maximum illuminance. 2).The ratio of the minimum to the average illuminance. Time Delay: A fuse that has a built-in delay in the overload region. Time delay slows down the opening time in the overload region. Time-delay fuses are widely used for general purpose circuits and are especially suitable for loads with surge or starting currents. Time of Day Schedules: Means of automatically changing dimmer intensity settings by using a system clock to implement preset scenes at regularly scheduled times. Top Visor: A shield that is mounted on the top or an outdoor fixture. The top visor provides horizontal cut-off when a fixture is aimed 30 degrees below horizontal. Toroid: A construction technique used for most dimmer filter chokes. Torx-Head Screw: A tamperproof screw used on vandal-resistant type fixtures. Total Harmonic Distortion (THD): This term describes distortion that sometimes occurs when the need for current is not in equilibrium with the supply of this current. On one side, a fluorescent lamp can draw short pulses of current instead of asking for a constant supply of current. On the other side, when turning on a ballast, a large in-rush of electric current can occur. The ballast between the lamp and the supply current is trying to balance the needs of the lamp with the amount of current it is receiving at that moment. Low THD ballasts can also be compared to surge protectors because they act to protect themselves and other electronic components by preventing power surges. This is not a major problem for most ballasts and in most applications. In larger buildings with many fluorescent fixtures, however, THD can present a significant problem and if not pre-calculated and controlled can possibly overload the normal flow of current in the system. The lower the THD rating of the ballast, therefore, the better (below 20 percent is preferred). Track Lighting: Luminaires attached to a linear track system, used in accent lighting and other general lighting applications. The track can be recessed or suspended. Transformer: A device designed to transfer energy from one circuit to another by electromagnetic induction. Transformers are typically used to increase (step up) or decrease (step down) the voltage from one circuit to another. The turns ratio, or number of windings on the primary and secondary sides of the transformer, will affect the change in voltage. Transient: A sudden surge of high voltage on a power distribution circuit, usually caused by lightning or the switching on/off of heavy loads, especially motors. Transient Voltage: A sudden surge of high voltage on a power distribution circuit, usually caused by lightning or the switching on/off of heavy loads, especially motors. Transmission: the process by which incident flux leaves a surface or medium on a side other than the incident side, the characteristics of many materials such as glass, plastics and textiles. Travelers: Pairs of conductors that are run between three-way and four- way switches in a lighting branch circuit. TRIAC (Triode AC Switch): A power electronic device often used in dimmers to regulate lamp power. Used instead of SCR's. Trigger Start: Type of ballast commonly used with 15 watt and 20 watt fluorescent lamps. Trim: The outer frame of a recessed luminaire which engages with the ceiling, providing a finished look to the ceiling. Troffer: The term used to refer to a recessed fluorescent light fixture (combination of trough and coffer). Tube Guard: UV Stabilized polysleeve or sleeve that slips over fluorescent lamps made of extruded Lexan, Acrylic or Polycarbonate in a tube shape with endcaps on both ends to provide maximum protection against the inherent dangers of broken glass and sparks from a shattered fluorescent lamp by retaining the shattered glass and phosphors within it. Tungsten Halogen: A tungsten filament incandescent lamp filled with halogen gas, with a lamp envelope made of quartz to withstand the high temperature. This lamp contains a certain proportion of halogens, namely iodine, chlorine, bromine, and fluorine that slows down the evaporation of the tungsten. Also commonly referred to as a quartz lamp. Turret: "Turret" implies the look of the socket (like a turret on a tank) and consists of a fixed end and a spring-loaded end. This is opposed to the look of a "tombstone" fluorescent socket (both ends fixed, shaped like a tombstone). Turret style sockets can either slide into the socket track similar a tombstone or they can be enclosed in a metal "can" for durability and protection (turret-can). Twin-Tube: Compact fluorescent lamp with two lamp tubes used in some Emergency Lighting, Downlighting, and Fluorescent products. The lamp life is about 10 times that of incandescent lamps and uses less power. Also referred to as PL or BIAX lamps. Two-Level Switching: Applies to fixtures which have two or more ballasts and thus can provide two levels of lighting. For example, on a three lamp fixture the two outboard lamps can be on or the center lamp can be on. Type of Protection: The type of protection of a luminaire defines the degree of protection against the ingress of damp, water and dust. The type of protection is expressed as a two-digit IP code. The first digit relates to protection against the ingress of foreign bodies, while the second defines the level of protection against moisture. Every extra-protection luminaire must be marked with both digits of the IP code.
U.G.R.: The Unified Glare Rating method (UGR) has been developed by the CIE (Commission International de l'Eclairage) in order to harmonize glare classification procedures worldwide. The higher the UGR score, the greater the probability of glare is. U.L.: Underwriters' Laboratories (UL). An independent organization whose responsibilities include rigorous testing of electrical products. When products pass these tests, they can be labeled (and advertised) as "UL listed." UL tests for product safety only. U.P.S.: Uninterruptible Power System. A system of batteries, switching and control devices that monitors utility power and protects against blackouts, brownouts, power spikes and surges, and line "noise." U.V.: Light that is shorter in wavelength and higher in frequency than visible violet light (literally beyond the violet light). Ultra Violet (UV): Light that is shorter in wavelength and higher in frequency than visible violet light (literally beyond the violet light). Upward (Downward) Light Output Ratio (luminaire efficiency): the ratio of the flux emitted above (below) a horizontal plane passing through the luminaire to the total bare lamp flux.Utilance (U) : ratio of the utilized flux to the luminous flux leaving the luminaires. Uniform Diffuser: A uniform diffuser is a completely matt surface with equal diffusion properties throughout. Its Luminance is the same from all angles of vision. Luminous intensity decreases with the cosine of the emission angle with the normal to the surface. Uniformity: This involves maintaining a certain uniformity of illuminance at the work plane, expressed as the ratio of minimum to mean illuminance. For the Ambient Lighting in office interiors, this ratio should be greater than 1:1.5 Unit Equipment: Battery-powered, stand-alone emergency lighting units that provide emergency illumination upon loss of normal AC power, then switch off and recharge automatically after normal power is restored. Unit Inverter: (ALSO CALLED BATTERY PACK) A self-contained power pack, which is installed in fluorescent fixtures, enabling the fixture to produce some light output in case of a power failure. Fluorescent fixtures that contain a unit inverter are generally used for emergency lighting purposes. USDA: United States Department of Agriculture. Has specific requirements for products used in food processing areas. Utilization Factor: ratio of the utilized flux to the luminous flux emitted by the lamps.
V.C.P.: Abbreviation for Visual Comfort Probability. A rating system for evaluating direct discomfort glare, expressed as the percent of occupants of a space who will be bothered by direct glare. VCP takes into account luminaire luminance at different angles of view, luminaire size, room size, luminaire mounting height, illuminance and room surface reflectiveness. V.D.T.: Abbreviation for Video Display Terminal. (SEE CATHODE RAY TUBE) Vandal-Resistant: Fixtures with rugged housings, break-resistant type shielding and tamperproof torx-head screws. Vapor-Tight Luminaire: A luminaire designed and approved for installation in damp or wet locations. Also described as "enclosed and gasketed." Veiling Reflection: A type of "Reflected Glare" that results in a high brightness image reflected off of a surface resulting in a reduction of contrast. Veiling reflections often occur when an image of the light source is reflected off a specular material, such as polished marble or a glossy magazine. Vertical Illumination: Illumination of a vertical surface, such as a warehouse aisle or chalk board. Very High Output (VHO): A lamp that operates at a "very high" current (1500 MA), producing more light output than a "high output" lamp (800 MA). Video Display Terminal (VDT): Refers to a computer terminal screen. This TV-like screen allows a person to view information on their computer. Also called "screen," "monitor" or "CRT''. Virgin Acrylic: Term used to describe acrylic lenses that do NOT contain any recycled material. Recycled acrylic can be weaker due to additives and impurities in the material. Visor: A shield which can be mounted on the top or sides of an outdoor fixture. The top visor provides horizontal cut-off when a fixture is aimed 30 degrees below horizontal. The independent side visors provide 45 degrees horizontal cut- off. Visual Acuity: Visual acuity is the ability of the human eye to discriminate between adjacent objects. It depends to a significant degree on the levels of contrast and luminance in the field of vision. Visual Comfort Probability: A rating system for evaluating direct discomfort glare, expressed as the percent of occupants of a space who will be bothered by direct glare. VCP takes into account luminaire luminance at different angles of view, luminaire size, room size, luminaire mounting height, illuminance and room surface reflectiveness. Visual Field: the location of objects or points in a space where the head and eyes are kept fixed. Visual Surround: all portions of the visual field except the visual task. Visual Task: Visual task is the term given to an activity requiring visual perception and located in a certain place (e.g. reading, writing, drawing, computer working). The activity involved can change in the course of the day or from day to day. For that reason a variety of visual tasks must be taken into account when planning a lighting system. Volt: The standard unit of measurement for electrical potential. It defines the force or pressure of electricity for the satisfactory operation of an electrical device. Voltage: The potential difference between two points of an electrical circuit. Voltage Rise-Time: The time required for voltage to rise across a lamp once the dimmer is switched on. Voltage rise-time measurements offer an indication of the dimmer filter's effectiveness. Voltmeter: A device used to measure the differences in potential between different points in an electrical circuit.
Wall Box Dimmer: A single channel dimmer with an integral means of manual control. WallWash: Term used to describe lighting to illuminate vertical surfaces from ceiling to floor without shadows or hot spots. Fixtures used to accomplish this are called wallwashers. Watt (W): The unit for measuring electrical power. It defines the energy consumed by an electrical device when it is in operation. The energy cost of operating an electrical device is determined by the watts it consumes times the hours of use. It is related to volts and amps by the formula: Volts x Amps = Watts. Wavelength: is a property of monochromatic light that defines its color. Each wavelength correspondends to a respective frequency, and to a color temperature. More generally, wavelength and frequency are properties of all electromagnetic radiation, of which the light visible to the human eye is just a small subset. The visible spectrum starts at about 400 THz / 750 nm with red, and ends at about 750 THz / 400 nm with violet. In practice, most light is composed of many wavelengths, mixed together to create colors of varying intensity. The same visual appearance can be based on more than one combination of wavelengths (metamers). Wet Location Fixture: Fixtures installed in wet locations shall be approved for such location and shall be so constructed or installed that water cannot enter or accumulate in wireways, lampholders or other electrical parts. All fixtures installed in wet locations shall be marked, "Suitable for Wet Locations." A "wet location" is defined as: Installations underground or in concrete slabs or masonry in direct contact with the earth, and locations subject to saturation with water or other liquids, such as vehicle washing areas, and locations exposed to weather and unprotected. Whip: A prewired cable assembly used to connect the fixture to the building's circuit wiring. Wind Load: Wind speed in miles per hour to which an outdoor lighting pole will be subjected. Wind loads vary geographically and are listed in an AASHTO publication called "Standard Specification for Structural Supports for Highway Signs, Luminaires and Traffic Signals." Wind Zone: A chart showing the average annual wind velocities of various regions. Wingnut: Type of connecting device, typically used to hold a reflector or channel cover to a channel or housing. (Also called QUARTER TURN FASTENER and SPIN NUT) Wireguard: Assembly made of wire and usually mounted over the face of a fixture to protect the lamps or housing. Wirenut: Insulating plastic or porcelain cap with internal threads that permit it to be screwed over splices of two or more electric wires. Wireway: The part of the fixture used to house the ballast and wiring. Wireway Cover: Piece of metal used to enclose and cover the wireway. Also called a channel cover. Work Plane: The level at which work is done, and at which illuminance is specified and measured. For office applications this is typically a horizontal plane 30 inches above the floor. This measurement is important in all calculations determining footcandle levels. Wrap / Wraparound: A surface-mounted commercial fluorescent fixture that has a curved plastic lens that "wraps" around the fluorescent lamp.
Zenith: The point of direction directly above the luminaire (180 degree angle). Zero Crossing: The instant when the line voltage reverses from positive to negative, or negative to positive. For 60 cycle power, 120 zero crossings occur each second. Zero crossings are used as a time reference by dimmers to implement phase control. Zonal Cavity Method: Two names for a method to calculate the average maintained horizontal illuminance on a workplane within a space. Only the direct illumination from the luminaires to the workplane is taken into account, and the actual layout of the luminaires is ignored.
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