Absorpetion
A process by which incident radiant flux is converted to another from of energy Usually (and Ultimately) heat


AC
Alternating current, electricity delivered by US utilities at 60Hz and 120volts


Accent light
Directional lighting designed to emphasize a particular object or to draw attention to a part of the field of view.


Accommodation
The process by which the eye changes focus form one distance to another


Acrylic
The generic term for a family of high performance light stabilized plastic frequently for fixture diffusers and lenses


Adaptation
The process by which the eye becomes accustomed to varying quantities of light or to light of a different color


AFCI
Arc-fault circuit interrupter


AL
Aluminum


Altitude
The vertical angular distance of a point in the sky above the horizon Altitude is measured positively from the horizon to zenith, from 0 to 90 degree.


Alzak
A finish product by electrochemically brightening and anodizing a special high purity aluminum alloy, It is used to provide reflectors with a high permanent reflectivity and corrosion and abrasion resistant finish. It is a registered trademark of aluminum Company of America


Ambient
“Surrounding”- the surrounding environment of a device, It usually refers to temperature or sound conditions


Ambient light
Electric and/or natural lighting throughout a space that produces uniform general illumination


Ambient lighting
Is lighting throughout an area that produces general illumination


Ambient Temperature
The ambient temperature is the temperature of the air that surrounds the fixture in the room. Temperature surrounding a lamp or luminaire, A critical criterion for fixture selection especially in extreme temperature environments.


Amp-hour
Measure of flowing electrons for a period of time


Ampere (A)
The standard unit of measuring an electric current that is equal to one coulomb per second. It defines the rate of flow or quantity of electrons, moving past a given point in a circuit; the current is related to voltage and power as follows: Current(Amps)= Power(Watts(/ Voltage(Volts)


Anodized
An electrolytic process for converting an aluminum surface to aluminum oxide, Anodized coating are transparent coatings that are physically part of the metal. They are generally colorless but may be dyed in a variety of colors. The coating is hard and highly resistant to corrosion.


Anodizing
It is any electrolytic or chemical process by which a protective or decorative film is realized on an aluminum surface. (“Duranodic” and “Calcolor” are trade names for “hard coat” anodizing


ANSI
American national standards institute. A professional institute compromised of representatives from safety protection agencies, manufacturers, and consumers. This institute published industry standards from product specifications. This organization develops voluntary guidelines and product performance standards for the electrical and other industries


ANSI Codes
These are 3-letter codes assigned by the American National Standards Institute. They provide a system of assuring mechanical and electrical interchangeability among similarly coded lamps from various manufacturers.


APPA
American Public Power Association


Arc length
The dimension in inches of the arc discharge measured from one electrode tip to the other. This is useful for optical design of reflectors and affects fixture efficiency


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 ac incorrect reflector) increasing the 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.


Artificial sky
An enclosure that simulates the luminance distribution of a real sky for the purpose of testing physical day lighting models See hemispherical dome artificial sky and mirror-box artificial sky.


ASTM
American society of Testing and Material


Asymmetric
Unequal distribution about one or more axes


Atmosphere
The type of gas or vacuum the lamp filament operates within, Gas filled lamps are more efficient than vacuum lamps


Audible noise (sound)
All fluorescent lamp ballasts produce some noise. When it is sound rated A(up to 75% quieter than magnetic types). Care should be taken when mounting the ballast to reduce the vibration


Audit
An energy audit seeks energy inefficiencies and prescribes improvement


Auto regulator
More often called a “constant wattage autotransformer”, This is the most popular ballast circuitry because if offers excellent regulation at moderate cost, and is considered to be the industry standard


Average footcandle
The theoretical average amount of light falling on a surface when averaging the illuminance falling on all points of the surface


Average maximum candlepower
Is the average of the 10 highest reading in a floodlighting beam


Average rated life
An average rating, in hours, indicating when 50% of a large group of lamps have failed, when operated at nominal lamp voltage and current; manufacturers use 3 hours per start for fluorescent lamps and 10 hours per start for HID lamps when performing lamp life testing procedures; every lamp has a unique mortality curve that depicts its average rated life


AWG
American Wire Gauge


Azimuth
The horizontal angular distance between the vertical plane containing a point in the sky and the true south


Baffle
A shield of metal, wood or plastic used to screen a light source from normal angles of viewing; a single opaque or translucent element to shield a source from direct view at certain angles, or to absorb unwanted light; Aluminum baffles are commonly used in parabolic fixtures


Ballast
A magnetic or electronic device used to control the starting and operation of discharge lamps. A device used with an electric-discharge lamp to obtain the necessary circuit conditions(voltage, current and waveform) for starting and operating; all fluorescent and HID light sources require a ballast for proper operation.


Ballast /Magnetic
An electromagnetic device in fluorescent and HID luminaires to provide the necessary starting voltage and to limit the lamp current during operation, an efficient device that uses a core and coil assembly transformer to perform the minimum functions require to start and operate the lamp


Ballast basics
Ballast have two primary functions; start the lamp and control operation of the lamp once it has started


Ballast efficiency factor (BEF)
Relative light output (ballast factor) divided by input power (wats). Used to measure the level of efficiency of similar ballast models


Ballast factor (BF)
Relative light output as compared to a reference ballast (i.e. BF of 0.90 would yield 90% of a lamp’s rated lumens);A light loss factor that must be applied to lumen calculations for fluorescent lamps, It is the ratio of lamp lumen output on a particular ballast as compared to that lamp’s rated lumen output on a reference ballast under ANSI test conditions (free, unmoving air at 25Centigrade). Some fluorescent “low power factor” ballast may yield initial light output as low as 50% of rated lamp lumen output and some electronic ballasts as high as 120% of rated lamp lumen output


Ballast life
Approximately 60000 hours, to maximize life, ambient temperature should be kept as low as possible. It is also important to maintain effective dissipation of heat using the lighting fixture as a heatsink for the ballast enclosure


Ballast losses
Power consumed by a ballast that dissipates as heat instead of being converted into light. Electronic ballasts operate more efficiently than magnetic or hybrid ballasts. A typical ballast loss for one standard two lamp magnetic ballast is 20 watts, while an electronic equivalent would be only 7 watts.


Ballast regulation
Is the ability of a ballast to control lamp wattage when subjected to line voltage variation. Consideration should be given to line voltage variations expected on a given electrical systems, where HID lamps are used. Most new power distribution systems are designed to provide plus/minus 3% of a regulation provided. The better the regulation, the higher the cost, Ballast regulation can also refer to regulation of lamp wattage with variation in lamp wattage. In this series, a reactor (CWA) is better than a magnetic regulator (reg-lag)


Ballast types
There are three types of lighting ballasts. Magnetic, Hybrid and high frequency electronic


Ballast, electronic
A Ballast which operates fluorescent lamps at high frequencies above 20,000 Hz, using semi conductor components to increase the frequency in combination with smaller inductive components to provide the current control. High frequency electronic ballasts operate lamps more efficiently (30-40% at equivalent light output) and eliminate the hum and visible flicker normally associated with standard magnetic ballasts. Electronic ballasts typically have better power quality than magnetic ballasts (higher power factor and lower THD)


Ballast/ Hybrid
Hybrid or “low frequency electronic”: essentially a magnetic ballasts with a few electronic components that switch off voltage to the lamp coil obtained via more expensive magnetic core material and the absence of power to the lamp coils during operation


Bare (exposed) lamp
It is a light source that has no shielding and is visible to the eye


Base temperature
The maximum operating temperature of lamp base in Celsius


Base temperature rise
The maximum increase in temperature from ambient temperature to operating temperature in the base, the beam angle sometimes called the “beam spread” Generally beam angles 25 degrees and are considered flood, while angles less than 25 degrees are considered spots.


Battery
A collection of cells that store electrical energy; each cell converts chemical energy into electricity or vice versa, and is interconnected with other cells to form a battery for storing useful quantities of electricity


Beam angle
It is the number of degrees in the horizontal and vertical planes at which 50% of the maximum candle power occurs


Beam component
That component of flux received directly (or by specular reflection or transmission) from a point source (such as the sun or small lamp). It is a direct component.


Beam flux (formerly beam lumen)
The lumens contained within the beam spread of a flood light


Beam lumen
The lumens contained within the beam spread of a flood light


Beam spread
It is the vertical and horizontal displacement of the beam in degrees, bounded by the angle at which 10% of the maximum candlepower occurs. Maximum candlepower is the highest intensity in the beam


Bi-metal switch
A small thermal switch made of two different metals, which expand at different rates when heated causing the switch contacts to open.


Biax R
GE trademark for the biaxial family of high-efficiency and long life compact fluorescent bulbs


Blacktop
The coating on top of miniature lamps which is used to control unwanted brightness or glare


Blinding glare
Glare that is so intense that, for an appreciable length of time after it has been removed, no object can be seen


Bracket
It is an accessory attached to the top of a pole for mounting one or more lighting fixtures. There are cross-arm brackets. Pipe/wall brackets and steel bullhorn brackets available for 1 to 5 fixtures


Branch circuit
That part of building wiring system between the final over-current protective device (typically at the electrical panel) and the electrical equipment that consumes power


Breaker
An electromechanical device that acts as a switch and fuse combination to protect and disconnect a circuit in case of an overload;


Brightness
The light intensity from surface which directs light into eyes, “ brightness” does not refer to the amount of light coming from a given light source, but rather to the way your eye perceives that light.


Brownout
A system-wide reduction in voltage, causing fluorescent and HID lamps to partially extinguish, thus reducing available light


BTU
British thermal unit, the amount of heat required raising the temperature of one pound of water one degree Fahrenheit; 3411 BTUs equal one kilowatt-hour


Bulb
The glass outer envelope component of a lamp; a bulb designation consists of a letter(s) to indicate the shape and a figure(s) to indicate the approximate maximum diameter in eights of an inch. Thus, an ED17 is an ellipsoidal shape, 17/8 of an inch or 2 1/8” in diameter or a f-15 bulb is a flame-shape, 15/8 of an inch or 1 7/8” in diameter


Candela (cd)
The SI unit of luminous intensity (formerly called candle) describing the intensity of a light source in specified direction. One candela equals one lumen per steradian-the luminous intensity, in a give direction, of a source that emits monochromatic radiation at a frequency of 540E12 hertz and of which the radiant intensity in that direction is 1/683 watts per steradian.


Candlepower
An older terminology for luminous intensity, defined as the intensity in candelas of light from source;


Candlepower distribution curve
A curve, representing the variation of luminous intensity of a lamp or luminaire in a plane through the light center; each lamp or lamp/luminaire combination has a unique set of candlepower distributions that indicate how light will be spread


Capacitor
An electrical circuit component which stores energy in electrostatic field, capacitors are used as power factor correcting or current regulating device and provide the control necessary to ensure proper lamp and ballast operation. Different wattages, voltages, and ballast types require a variety of different capacitor values. The ballast I.D. label specifies the microfarad and voltage rating needed to operate properly. If the capacitor is incorrectly wired, improper operation of the fixture as well as other component failure could result


Cathode resistance
Resistance to the cathode in a fluorescent lamp, it is measured “cold” before the lamp is turned on (Rc) or “hot” after the lamp is turned on(Rh). The ratio of the hot resistance to the cold resistance is also measured(Rh/Rc)


Cavity ratio (CR)
Geometric proportions of the ceiling, floor and room cavities


Center beam candlepower (CBCP)
The intensity of light produced at the center of a reflector lamp, expressed in candelas


Chromaticity
Refer to the dominant or complementary wavelength and purity aspects of the color taken together, or of the aspects specified by the chromaticity coordinates of the color taken together.


Clerestory
That part of a building rising clear of the roofs or other parts, whose walls contain windows for lighting the interior.


Coefficient of beam utilization (CBU)
The percentage of light from a floodlight which reaches the illuminated task relative to total beam lumens


Coefficient of utilization (CU)
The percent of initial generated lamp lumens that reaches the work plane as determined by the surface reflectance, room shape (RCR), and fixture distribution. A portion of rated bare-lamp lumens that exits the fixture and reach the workplane, the CU accounts for the light directly from the luminaires as well as light reflected directly from luminaire as well as light reflected off the room. The ratio of lumens from a luminarie received on the work plane to the total quantity of lumens emitted by the lamps of the luminarie. The CU value is used in lighting calculations to estimate light levels or number of luminaires needed. The CU is determined from a photometric test and is typically published on product catalog sheet in tabular form.


Color
It refers to the spectrum of light. We talk about the color of an object the human eyes sees. Actually that color depends up on the amount and nature of the light received by that object and then reflected by it. If all the light were absorbed by an object, it would be black. If all the light ere reflected by the object, it would be white. There are no known surfaces that absorb all, or reflect all, of the light received. A partial reflection would yield different colors depending on the wave-length of the spectrum which is reflected. Thus, color is a characteristic of light by which a person may distinguish between two patches of color of the same size and shape.


Color rendering
It is a general expression for the affect of a light source on the color appearance of object in conscious or subconscious comparison with their color appearance under a reference light source


Color rendering index (CRI)
A measurement of the amount of color shift that objects undergo when lighted by a light source as compared with the color of the same object when illuminated by a reference source of comparable color temperature; The measure of a light source is its ability to render the color of objects “correctly”, as compared with a reference source with comparable color temperature; It, along with chromaticity coordinates, expresses the degree to which colors will appear “familiar” or “natural” under the light source selected. In general, the higher the CRI number, the better the color rendering properties of the light source being measured.


Color temperature
The “whiteness” of a light source indicated in degree Kelvin, typically between 0-6000 degrees K; The correlated color temperature of a light source, expressed in Kelvin (K), is a means of describing the appearance or chromaticity of the source. The correlated color temperature of the light source contributes to the visual appearance of the lighted space. Color temperature evaluation for HID lamps should be made at 100 hours of operation to allow lamps stabilize; Sources having a low correlated color temperature (2700K to 3400K) are said to be “warm” in color. Most incandescent lamps have a color temperature “between” 2700K to 3000K. Fluorescent sources having higher correlated color temperature (4100K to 6300K) are said to be “cool” in color. Lamps having a correlated color temperature of 3500K are considered “mid-range” and provide excellent color rendition while not being wither “warm” or “cool”


Compact fluorescent lamp (CFL)
The general term applied to families of smaller diameter fluorescent lamps(T4 and T5), some of which have built in ballasts and medium screw bases for replacement of incandescent lamps. Fluorescent bulbs use approximately 2/3 to 4/5 less electricity than regular incandescent bulbs with comparable lumen rating and also last 20 times longer. They produce warm white tones that closely duplicate incandescent light


Compact fluorescent light (CFL)
A modern light bulb with integral ballast using a fraction of the electricity used by a regular incandescent light bulb


Cone
A retinal receptor that dominates the retinal response when the luminance level is high and provides the basis for the perception of color


Contrast
The ratio of luminance of an object or detail to that of its immediate background


Cornice lighting
It is a term that applies to light sources that are shielded by a panel that is mounted parallel to a wall and attached to the ceiling. It distributes light all over the wall below.


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


Cosine law
The law that the illuminance on any surface varies as the cosine of the angle of incidence (The angle of incidence is the angle between the normal to the surface and the direction of the incident light.)


Cove lighting
It is an expression for the effect of a light source that are mounted above a ledge or some form of recess that hides the light source from view and distributes the light over the ceiling and upper wall


CSA
Canadian Standards Association


Current
The flow of electricity, measured in amperes (A)


Current crest factor
Is the ratio of peaks to RMS value, The crest factor of a true sine wave is 1.41, input voltage to a ballast may be close to a sine wave, but the secondary voltage wave shape in the inductive and capacitive type ballast is distorted, and their crest factors are higher than 1.41. the most commonly used ballasts (CW, CWA) have crest factors of 1.8. some metal halide and HPS ballasts approach 1.65. Lamp manufacturers’ published lumen maintenance data is based on lamps operated on standard reactor (1.41CF) ballast in the laboratory. Tests indicate that ballast with higher crest factor may result in depreciation of lumen output, typically due to electrode degradation.


Current rise time
A dimmer performance characteristic which indicated the degree of filtering provided within the dimmer


Current type (AC/DC)
Whether the operational voltage is based on alternating current or direct current


Cut sheet
Also called submittal sheet, specification sheet and spec sheet, A data sheet that shows fixture dimensions, descriptions, options, and photometric, These sheets are submitted by dmf LIGHTING through contractors, engineer and architect to obtain final approval on the specific equipment to be furnished


Cut-off and shielding angle
The critical viewing angle beyond which a source can no longer be seen because of an obstruction, angle from the vertical 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 angle (of a luminaire)
Is the angle, measured up from nadir, between the vertical axis and the first line of sight at which the bare source is not visible


Cutoff luminaire
Outdoor lighting accomplished by means of “cut off “ fixture which essentially cuts off light output above 70 degree nadir. This generally results in better glare control


CW
Constant-wattage ballast, A type of HID ballast in which the primary and secondary coil are magnetically, not electrically, connected. Considered a higher-performance, higher cost ballast featuring excellent regulation


CWA
Constant wattage autotransformer, A type of HID ballast in which the primary and secondary coils are electrically connected. Consider on appropriate balance between cost and performance, it combines the best features of high reactance and magnetic regulator ballasts. Regulation is good, power factor is high, and losses are not excessive. A variation of the CWA called the peak lead auto regulator ballast is used exclusively for metal halide lamps. Advantages; 1- high power factor (over 90%) and low operating current 2- good regulation, permits and responds favorably to line voltage variations of up to +5% or -10% 3- starting current is even lower than operating current 4- costs less than magnetic regulator 5- provides good regulation of lamp wattage, especially in nominal and below normal systems 6- ballast losses are less than magnetic regulator 7- available for all standard voltages Disadvantages; 1- more expensive than reactor type ballast 2- slightly larger in size and weight than reactor ballast


Damp location (DL)
Refers to fixtures suitable for installation in locations protected from weather, but subject to moderate degrees of moisture, such as in cold storage warehouses or under partially protected canopies, Damp location is standards on all fixtures except when using emergency lighting equipment and then all DL is added of the description


Dark adaptation
The process by which the retina becomes adapted to a luminance of less than 0.01 footlamberts


Daylight compensation
A technique used to maintain a set light level; It utilizes a dimmer controlled by a photocell such that the intensity of the lamps tracks with the daylight level detected by photocell. A daylight levels increase, lamp intensity decreased, and consuming less energy


Daylight factor (DF)
The ratio of daylight illumination at a given point on a given plane due to the light received directly or indirectly from a sky of assumed or known luminance distribution, to the illumination on a horizontal plane due to an unobstructed hemisphere of this sky, expressed as a percentage. Direct sunlight is excluded for both values of illumination. The daylight factor is the sum of the sky component. The interior plane is usually horizontal. If the sky condition is the C.I.E. standard overcast condition, then the DF will remain constant, regardless of absolute exterior illuminance. If used in conjunction with other than standard overcast conditions, the sky conditions should be specified. The term is also informally applied to sky conditions; the DF remains constant only if the fenestration is completely diffusing (such as an ideal opalescent glass).


Depth of lamps
Referenced by IEC as dimension B


Diffused lighting
It is light that falls on a surface that does not appear to come primarily from a single given direction


Diffuser
It is a device that spreads, redirects or scatters light in a rather even manner, usually by means of rough surface or translucent material


Diffusing (surfaces)
Those surfaces and glazing that redistribute some of the incident flux by scattering in all directions.


Dimmable
Whether or not the lamp lumens can be varied while maintaining reliability


Direct current (DC)
The complement of AC, or alternating current, presents one unvarying voltage to a load. This is standard in automobiles


Disability glare
Glare resulting in reduced visual performance and visibility. Often accompanied by discomfort glare


Discomfort glare
Is a glare producing discomfort, it does not necessary interfere with visual performance or visibility


Distance between legs
For U-shaped fluorescent lamps, this is the average distance between the inner walls of the legs


Distance between legs center
For U-shaped fluorescent lamps, this measurement is the average distance between the centers of each leg


DOT type
The US department of transportation lamp number stamped in the glass lens or on the base of lamp heads


Eccentricity (Maximum)
In high intensity discharge lamps the bulb to arc angle is the angle off of center between electrodes and bulb. The bulb to base angle is the angle off of center that the bulb is from the base


Effective projected area (EPA)
It is the exposed surface of an outdoor fixture, multiplied by a shape factor which varies depending on the shape of the fixture; for example a cylindrical or round fixture will have less resistance to the wind than a rectangular fixture


Efficacy
A measure of the luminous efficiency of a radiant flux, expressed in lumens per watts(LPW or lm/W)as the quotient of the total luminous flux by the total radiant flux. For daylighting, this is the quotient of visible flux incident on a surface to radiant flux on that surface. For electric sources, this is the quotient of the total luminous flux emitted by the total lamp power input. The ratio of light from lamp lumens to the electrical power (watts) consumed, system efficacy includes ballast losses


Electric-discharge lamp
Is a lamp in which light (or radiant energy near the visible spectrum) is produced by the passage of an electric current through a vapor gas. Electric-discharge lamps may be named after the filling gas or vapor that is responsible for the major portion of the radiation; e.g., mercury lamps, sodium lamps, neon lamps, argon lamps, etc. A second method of designating the electric-discharge lamps is by the physical dimensions or operating parameters, e.g., short-arc lamps, high pressure sodium lamps, low pressure sodium lamps, etc. These lamps have become popular primarily for three reasons: 1- high efficiency, more lumen per watt of electricity consumed 2- long lamp life and good lumen maintenance, reduces operating expenses 3- compact source-permits good light control by use of reflectors, resulting in higher efficiency


Electromagnetic spectrum
A continuum of electric and magnetic radiation that can be characterized by wavelength or frequency, Visible light encompasses a small part of the electromagnetic in the region from about 380 nanometers (violet) to 770 nanometers (red) by wavelength


Electronic Ballast
An improvement over core/coil ballasts used to drive fluorescent lamps, a short name for fluorescent high frequency electronic ballast, electronic ballasts use solid state electronic components and typically operate fluorescent lamps.


Elliptical reflector(ER)
A lamp with an elliptical-shaped reflector designed to focus light in front of the lamp, used in deeply shielded downlights


Embodied energy
Literally the amount of energy required to produce an object in its present form; an inflated balloon’s embodied energy includes the energy require to manufacture it and inflate it


EMI
Electromagnetic interference


EMI/RFI
Ballasts contain circuits that limit electrical noise conducted onto the power line or radiated through the air, other-wise referred to as EMI/RFI


Emissivity/ Emittance
The ratio of radiance (for directional Emissivity) or radiant exitance (for hemispherical Emissivity) of an element of surface on a temperature radiator to that of a blackbody at the same temperature By Kirchoff’s Law, for a given wavelength of the electromagnetic spectrum, Emissivity of a surface equals its absorptivity (and is the reciprocal of its reflectivity)


EMT
Electric metallic tubing


Energy
A measure of work done by an electrical system over a given period of time, often expressed in kilowatt-hours (kWh)


ENT
Electrical non-metallic tubing


ESCO
Energy Service Company


Exitance
The density of light reflecting from a surface at appoint, measured in lumens per square foot (formerly “footlamberts”). It is determined by multiplying the footcandels striking a diffuse reflecting surface times the reflectance of that surface.


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 surrounding flammable atmosphere will not be ignited


FA
Fire alarm


Fenestration
Any opening or arrangement of openings (normally filled with glazing media) for the admission of daylight, including any devices in the immediate proximity of the opening that affect distribution (such as baffles, louvers, draperies, overhangs, light-shelves, jambs. Sills, and other light-diffusing materials)


Field angle (formerly beam spread)
It is the number of degrees in the horizontal and vertical planes at which 10% of the maximum candlepower occurs; It is the vertical and horizontal displacement of the beam in degrees, bounded by the angle at which 10% of the maximum candlepower occurs. Maximum candlepower is the highest intensity in the beam


Filaments
A filament designation consists of a prefix letter to indicate whether the wire is straight or coiled, and a number to indicate the arrangement of the filament on the supports. Prefix letters include: CC (coiled coil),wire is wound into a helical coil and this coiled wire again wound into a helical coil


Fire rated ceilings
Fire resistance rating provide a measure of the ability of a ceiling assembly to act as a heat barrier between a fire below and the building support structure above, fire resistance rating apply only to ceiling assemblies in their entirety. Individual’s components are not assigned a fire resistance rating, and are not intended to be interchanged between assemblies; rather they are designated for use in a specific ceiling /structural design in order that its rating may be achieved Generally, fluorescent fixtures bearing the UL listing mark can be utilized in most floor-ceiling designs as long as the fixture area ratio and the fixtures are installed as required by the specific construction details of the UL Design no. being considered. Specific construction details will vary but, if considering an exposed “T” ceiling grid system, most designs require additional hanger wires at the midpoint of ceiling grid tees along each 4’ side of nominal 2’ x 4’ and 1’ x 4’ luminaires as well as hanger wires at each of the four corners of the fixtures. In addition to hanger wire requirements, most designs also require the use of fixture protection which is usually fabricated from available ceiling acoustical material bearing the Ul classification marking with Design no. The extent of the fixture protection may range from as little as a single piece of material, to the use of a complete five-sided box enclosing the sides and the back of the fixture. Care should be taken in the application of fire rated assemblies to ensure that ballast do not overheat, thereby resulting in shortened ballast life and/or nuisance tripping of the ballast thermal protector. The use of low loss ballasts and reduced wattage lamps will reduce potential thermal problems in most applications involving elevated plenum temperatures. The final approving authority is the local code enforcements official and such should be consulted for local requirements and code interpretation. These requirements should be determined before construction, preferably during the specification period. Check the latest edition of UL “fire resistance Directory” for specific assembly hour rating and design constrains


Fixture
Informal substitute term for luminarie


Fixture watts
The input wattage shown in the ballast specifications is measured as per ANSI specification (ballast and lamps are measured while placed on bench top at room temperature) Actual operation in an enclosed fixture, due to the ambient heating of the lamps, is approximately 1.5 watts less per lamp than the ANSI input specification


FLA
Full load amperes


FLC
Full load current


Floodlight
It is a projector designed for lighting a scene or object to a luminance considerably greater than it’s surrounding. It usually is capable of being pointed in any direction and is of weatherproof construction


Fluorescent dimming
Single-lamp and two-lamp electronic dimming ballasts are available for variety light output of standard fluorescent lamps, straight or U shaped. Dimming ballast computability should be verified from the specific dimming control manufacturer manufacturing


Fluorescent lamp
A discharge lamp in which a phosphor coating transforms ultraviolet energy into visible light, the bulb shape and size of a fluorescent lamp are expressed by means of a code consisting of the letter ”T” (which designates that the bulb is “tubular” in shape) followed by a number which expresses the diameter of the bulb in eights of an inch. They vary in diameter from T-2 (1/4”) to T-12(1 ½”). In nominal overall length, fluorescent lamps range from 6” to 96”, which is always measured from back of Lampholder to back of Lampholder. Circuline lamps, which are circular, are available in 6 ½”, 8”, 12” and 16” outside diameter. There are also U-shaped fluorescent types with t-8 and T-12 bulbs. The width of U-shaped types is measured for the distance between the ends. The overall length is measured from the face of the bases to the outside of the glass bend


Fluorescent lamp base
They come either in 2pin or 4pin, the 2 pin lamps are designed for preheat operation, with lamps having an internal starter. The 4 pin lamps are dimmable and are designed for electronic ballast operation; these lamps have no internal starter


Flux (Luminous Flux)
For example, volume per hour is the flux of a fluid.


Footcandle (fc)
A standard measurement of illuminance, representing the amount of illuminance on a surface one-foot square on which there is uniformly distributed flux of one lumen. One footcandle is equal to 10.76 lux


Footcandle ratio
The ratio between average footcandle and minimum footcandles (such as 3:1) or maximum and minimum footcandles (such as 6:1), the maximum/minimum ratio generally preferred. (the lower the ratio, the more uniform is the lighting.


Footlambert (fl)
A unit of luminance equal to 0.3183010 candela per square foot, or to the uniform luminance of a perfectly diffusing surface emitting or reflecting light at a rate of one lumen per square foot, or to the average luminance of a surface emitting or reflecting light at that rate. An unobstructed sky of one footlambert uniform luminance contributes one footcandle of illuminance on a horizontal plane.


Fovea
A small region at the center of the retina, subtending about two degrees and forming the site of the most distinct vision and greatest color discrimination


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)


General purpose floodlighting (GP)
A weatherproof unit so constructed that the housing forms the reflecting surface. The assembly is usually enclosed by a glass cover


Generator
Any device that produces electricity


GFCI
Ground fault circuit interrupter


Glare
The sensation produced by illuminance within the visual field that is significantly greater than the luminance to which the eyes are adapted; excessive brightness that may be caused by either direct or indirect viewing of a light source


Glare Index
A method of predicting the presence of discomfort glare due to daylighting Factors affecting the glare index including the size and relative position of fenestration, sky luminance, and interior luminance. Most widely used in Europe, the glare index is similar to the index of sensation and the discomfort glare rating, which are used in North America for electric lighting applications.


Globe
A transparent or diffusing enclosure intended to protect a lamp, to diffuse and redirect its light, or to change the color of the light


Glow to arc transition
In order to achieve full rated lamp life, a ballast should start a lamp so that the time from when the lamp begins to glow to the time the lamp arc strikes should be short as possible.


Grid
A utility term for network of wires that distribute electricity from a variety of sources across a large area, the grid powers most homes and offices across the country


Grid (lay-in)
A type of ceiling construction where each supporting member is generally shaped like an inverted T, and the ceiling tiles and lighting fixtures are laid-in on the flanges of the Ts


Grounding
The ballast case and fixture must always be grounded. The grounding helps assure safety, proper lamp starting, and acceptable EMI/RFI performance


Halogen lamp (Tungsten Halogen lamp)
An incandescent lamp containing a halogen gas which recycles tungsten back onto the filament surface, which ordinarily be deposited in the bulb wall Advantages; 1- makes the color look natural 2- good lumen maintenance/light output remains almost the same throughout life Disadvantages 1- low light output/lumens per watt 2- elongated source limits beam control 3- medium lamp life/ 2000-4000 hours 4- high operating cost


Harmonic
An electrical frequency that is an integer multiple of 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
An area where ignitable vapors or dust may cause a fire or explosion created by energy emitted from lighting or other electrical equipment


Heat exchanger
Device that passes heat from one substance to another, in a solar hot water heater, for example, the heat exchanger takes heat harvested by a fluid circulating through the solar panel and transfers it to domestic hot water


Heat tempered borosilicate glass
Heat tempered (not chemically tempered) glass; it acts as an ultraviolet (UV) screen. It dices when broken (safety glass), and is not susceptible to thermal shock (shockproof)


Heavy duty floodlighting (HD)
A weatherproof unit having a substantially constructed metal housing, into which is placed a separate and removable reflector, and a weatherproof hinged door with cover glass that encloses the assembly but provides an unobstructed light opening at least equal to the effective diameter of the reflector


HID (High intensity discharge)
High intensity discharge lighting, including mercury vapor, metal halide and high pressure sodium light sources, although low pressure sodium’s are not HID sources, they often are included in the HID category


High mast 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 65 feet or higher


High power factor (HPF)
Type of ballast with a 0.9 or higher rating power factor, which is achieved by using capacitor


High pressure sodium (HPS)
Type of high intensity discharge lamp in which light is produced by radiation from sodium vapor


High Pressure sodium lamp
High pressure sodium lamps are used where efficiency is the most important factor and color is not as important. HPS lamps contain xenon as a starting gas to initial the arc tube which vaporizes a sodium mercury amalgam. This lamp has high efficiency of approximately 125 lumens per watt. Other characteristics of this lamp are a golden color, long lamp life, and excellent lumen depreciation. It takes 3-4 minutes for lamp to reach 80% light output. The hot restrike time for high pressure sodium lamps is 1-3 minutes for Special ballasting circuitry is usually required to produce high voltage pulses to start these lamps. Advantages; 1- long lamp life/24000hrs 2- exceptionally high efficiency/lumens per watt 3- lowest operating cost Disadvantages; 1- high initial cost 2- does not restart immediately after power failure with normal auxiliary equipment, but restarts one minute quicker than mercury and metal halide 3- fair color condition


High reactance autotransformer (HX)
A simple reactor ballast design with an extra coil attached to step down the line voltage as required. Similar in characteristics and function to reactor ballast except that the added function of voltage transformation can be performed. The standard id HPF models although they are available without capacitors as normal power factor ballast. The power factor correction is achieved on reactor and high reactance ballasts by placing the proper capacitor vaue across the incoming line. However, this does not provide regulation to the lamp, and may draw a higher current during open circuit operation Advantages; 1- slightly higher in cost than reactors, but less than regulated type ballasts 2- lower ballast losses than regulator types 3- provides good wattage regulation when line voltage is controlled 4- can be used with 120v, 208v, 240v, 277v, and 480v supply Disadvantages; 1- high operating current 2- higher starting current 3- poor regulation


High voltage integrated circuit (HVIC)
Proprietary microprocessor control that id featured in selected Quicktronic ballasts. Replaces over one-third of the components used in conventional ballasts while providing enhanced features such as higher efficiency, improved lamp starting, end-of-lamp-life sensing, circuitry to limit in-rush current, and constant light output over a wide range of input voltages


Highbay
Generally refers to the industrial lighting where high mounting heights may be encountered, many industrial HID type fixtures are called highbay


Horizontal footcandles
The footcandles falling on a horizontal surface, all horizontal footcandles are in the same plane for the same surface, they can be added together arithmetically when more than one source provides light to the same surface


Hot restrike
The phenomenon of reinstating or restriking the arc in an HID light source after a momentary power loss, hot restrike occurs when the arc tube has cooled a sufficient amount


Housing
Body of fixture


Hue
The attribute of a color that allows it to be classified as red, yellow, blue, and so on


HVAC
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 meal is formed around a male punch as diaphragm is raised. The result part is generally of uniform thickness and quite strong


Hydronic
Contraction of hydro and electronic, usually applied to radiant in-floor heating systems and their sensors and pumps


HZ
Hertz (cycles per second)


IALD
International Association of Lighting Designers


IEEE
Institute of electrical and electronics engineers


IESNA
Illumination Engineering Society of North America


Ignitor
A device that generates a voltage pulse to start discharge lamps without having to preheat the electrodes, predominantly used with HPS lamps as well as some MH sources. May provide uo to 4000 volt spikes


Illuminance
The density of incident luminous flux on a surface; illuminance is the standard metric for lighting levels, and is measured in lux (lx) or footcandels (fc); light arriving at a surface, expressed in lumens per unit area; 1 lumen per square foot equals 1 footcandle, while 1 lumen per square meter equals 1 lux


Illuminance (footcandle or LUX) meter
An instrument for measuring illuminance on a plane; instruments which accurately respond to more than one spectral distribution are color corrected. Instruments which accurately respond to more than one spatial distribution or incident flux are cosine corrected, i.e., the response to a source of unit luminous intensity, illuminating the detector from fixed distance and from different directions decreases as the cosine of the angle between the incident direction and the normal to the detector surface. The instrument is comprised of some form of photo-detector, with or without a filter, driving a digital or analog readout through appropriate circuitry


In-rush current
When a lighting system is energized, a momentary surge of current occurs called “in-rush”. This current must be limited so that it does not harm auxiliary lighting controls. Most electronic ballasts rated at <20% THD contain a passive front end inductor that typically results in lower levels of in-rush. Ballasts that have <10% THD typically use active power factor correction and unless limiting circuitry is included, can have 40 amps or more of in-rush current. This may damage mechanical switches and contacts. In-rush current should be considered when designing or retrofitting a lighting system


Incandescence
The emission of visible electromagnetic radiation due to the thermal excitation of atoms or molecules


Incandescent lamp
A lamp in which light is produced by a filament heated to incandescence by an electric start


Indirect Sources
Surfaces which, after being illuminated by the other sources (direct sources such as the sun, sky, Or electric light, or other indirect sources), have measurable luminance and, in turn, become sources themselves.


Infrared interference
Some infrared controls may be susceptible to interaction with fluorescent systems. This is due to infrared energy from lamps. Either increasing the distance between the fluorescent lamp and the infrared receiver, or shielding the infrared receiver from the lamp, can alleviate this interaction


Infrared radiation
Radiation with wavelengths too long to be perceived by the human eye (that is, longer than 0.77 microns) and less than 1,000 microns Room IR is infrared radiation in the 7.7-8.0 micron region and typical of that radiation from surfaces near room temperature.


Initial footcandle
The footcandles (minimum, maximum, or average) produced when luminaires and lamps are new


Injection molding
Process for manufacturing plastics lenses whereby hot liquid plastic is injected into a lens mold of desired shape and size


Insolation
Or incident solar-radiation; the amount of sunlight failing on a place


Instant start
A fluorescent lamp designed for starting by a high voltage without preheating of electrodes, also known as a cold-start lamp in some countries; instant start (high voltage is applied across the lamp with no preheating of the cathode) is the most energy efficient starting methods for fluorescent lamp ballasting. IS ballasts use 1.5 to 2 watts less per lamp than rapid start ballasts (low voltage is applied to the cathodes prior to lamp ignition and is maintained throughout operation) Other IS ballast benefits typically include parallel lamp circuitry, longer remote wiring distance, easier installation due to less complied wiring, and capability to start lamps at 0 degree F (versus 50 Degree F)


Insulation
A material that keeps energy from crossing from one place to another; on electrical wire, it is the plastic or rubber that covers the conductor; in a building, insulation makes the walls, floor, and roof more resistant to the outside (ambient) temperature


Inverse-Square Law
The law stating that the illuminance at a point on a surface varies directly with the intensity of a point source, and inversely as the square of a distance between that source and that surface. If the surface at the point is perpendicular to the direction of the incident light, the law is expressed by E=I/d2. It is applicable for point or near point light sources.


Inverter
The electrical device that changes direct current (DC) into alternating current (AC)


IOU
Investor-owned utility


Irradiance (E)
The density of radiant flux incident on a surface


ISO
International Organization for Standardization


Iso-footcandle curve (iso-plot)
Used to illustrate points of equal illuminance on planes perpendicular to the lamp axis


Isocandela line
A line potted on any appropriate set of coordinates to show location in space, about a source of light, in which the intensity is the same. A series of such curves, usually for equal increments of intensity, is called an isocandela diagram


Isolated regulator ballast (CWI)
Similar to the auto regulator ballast in performance, the isolated regulator ballast electrically isolates the lamp socket and capacitor from the line. The magnetic regulator ballast also isolates the lamp circuit from the line and additionally improves lamp wattage regulation, but may cause an increase in input watts. Advantages; 1- provides good wattage control up to +-10% line voltage shift, excellent wattage control in lines that operate near normal 2- cost less than magnetic regulator ballast, but slightly more than CWA 3- ballast losses are less than magnetic regulator ballast, but slightly more than CWA


Isolux (Isofootcandle) line
A line plotted on any appropriate set of coordinates to show all of the points on a surface where the illuminance is the same


Isolux (Isofootcandle) Line
A line plotted on any appropriate set of coordinates to show all the points on a surface where the daylight illuminance is the same. A series of such lines for various illuminance values is called an Isolux (Isofootcandle) diagram.


ITL
Independent Testing Laboratories, this independent laboratory is located in Bouler, CO. lighting manufacturers use this laboratory to control photometric or environmental test for luminaires


J-box
Junction box, A code-approved steel or plastic enclosure in which several wires come together for connection, such as the taps for the fixtures


K-factor
A measurement that qualifies the effect of non-linear equipment, such as lighting ballasts, on an electrical system. Lighting systems should be designed so that the transformer rating is sufficient for the ballasts used (typically K-factor<4)


kHz
Kilohertz


Kilowatt (kW)
A measure of electric power, a thousand watts


Kilowatt hour (kWh)
The measure of electrical energy usage from which electricity billing is determined, for example, a 100-watt bulb operated for 1000 hours would consume 100 kilowatt hours, (100watts x 1 kw/1000 watts x 1000 hours =100 kwh) At a billing rate of $0.10/kwh, the electric energy to operate this bulb would cost $10.00 (100 kwh x $0.10/kwh) to operate for 1000 hours


Knockout (KO)
A portion of a metal enclosure which has been partially cut out but remains in place, it can easily removed or “knocked out” to permit an electrician to attach switches, convenience outlets, conduit connectors, often referred to as a “KO”


Kv
Kilovolt


kVA
Kilovolt-ampere


Lag circuit ballast
The lamp current control element of a lag circuit ballast consists of an inductive reactqnce in series with the lamp.


Lamp (LP)
Manufactured light source, an electrically energized source of light, commonly called a bulb or tube. The source of light in fixture, Fluorescent lamps are often called “tubes”. Incandescent lamps are often called “light bulbs”


Lamp Current crest factor (LCCF)
The ratio of peak lamp current to RMS (average) lamp current, Lamp manufacturers require a LCCF of less than 1.70in order to achieve full lamp life. Values less than 1.70 do not achieve higher than rated lamp life


Lamp flicker
High frequency electronic ballasts provide a minimal level of lamp flicker, lamp flicker from magnetic ballasts can cause eye fatigue for some people


Lamp Lumen Depreciation (LLD)
The decrease over time of lamp lumen output, caused by bulb wall blackening, phosphor exhaustion, filament depreciation and other factors


Lamp position (Tilt) factor
It is not a consideration for incandescent or fluorescent, however it is significant for mercury vapor and metal halide HID lamps.


Lampholder
The bracket that holds a lamp in place


Lay-in troffer
A fluorescent that “lays” into a grid tee suspended ceiling


LCD
Liquid crystal display


Lead circuit ballast
The lamp current control element of a lead circuit ballast consists of both inductive and capacitive reactance in series with the lamp; however the net reactance of such a circuit is capacitive in mercury and metal halide ballasts, and inductive in high pressure sodium ballasts an inductive reactqnce in series with the lamp.


LED
Light-emitting diode, small circuit lamp used extensively in exit lights: an efficient source of electrical lighting, typically lasting 50000 to 100000 hours


Lens
Diffuser or refractor for a light fixture; prismatic shielding of a fixture, made of plastic or glass, through which the light passes, lenses change the direction and control the distribution of light ray


Lens frame
The retainer (usually metal) to hold the lens in place in a fixture


LER
Luminaires Efficiency Rating developed by the National Electrical Manufacturers Association (NEMA) and approved by the National Lighting Collaborative to fulfill the requirements of the Energy Policy Act of 1992. The result is a lumens per watt rating that can be used to compare the energy efficiency of various products. NEMA documents LE5 describes the calculation of LER as; LER= EFF x TLL x BF/ Input Watts where EFF= luminaire efficiency, TLL= number of lamps per luminaire x rated lumens per lamp, BF= ballast factor, and Input Watts= total system watts of the luminaire


Lexan
A polycarbonate material made by General Electric and used in the construction of many dmf LIGHTING products because of its inherent qualities of electrical insulation, Long life and durability


Life Safety Code
A code written by NFPA to ensure that building owners place equipment that will help save lives in an emergency, For example: emergency lighting equipment meets Life Safety Code requirements by placing a footcandle of light on “path of egress” or exit path in a building


Light
Radiant energy that is capable of exciting the retina and producing a visual sensation, when light strikes a surface; it is absorbed, reflected or transmitted. It is not visible until it is reflected into your eyes. Light is said to travel in straight lines. The visible portion of the electromagnetic spectrum (light) extends from about 0.38 to 0.77 microns ( 380 to 700 nanometers). Light is usually measured in lumens or candlepower.


Light center length (LCL)
The distance from a specified reference point on a lamp base to its light center, typically expressed in inches


Light level
Light output from a system is a function of rated lamp lumens, ballast factor, fixture efficiency, and ambient temperature. All of these factors must be considered when designing or retrofitting a lighting system


Light Loss Factor (LLF)
A factor used in calculating the illuminance after a given period of time and under given conditions. It takes into account temperature and voltage variations, lamp depreciation (of electric luminaries), and dirt accumulation on luminaire and room surfaces, maintenance procedures and atmosphere conditions. Formerly called maintenance factor, generally light loss factors are divided into two groups, classed as “recoverable” (with cleaning and relamping) and “non-recoverable” The product of the: Lamp lumen depreciation(LLD), luminaire dirt depreciation (LDD), Ballast Factor(BF) LLF=LLD x LDD x BF


Light pollution
Light distributed in outdoor areas where light is not desired. Light pollution is typically caused by outdoor lighting fixtures which may emit a substantial amount of light in an upward direction. This creates “haze” of light in the atmosphere that can not be efficiently utilized


Light Shelf
A horizontal shelf positioned (usually above eye level) to reflect daylight into the ceiling and t shield direct flare from the sky.


Light trespass
Light that goes beyond the planned area, a situation which occurs when light from a source is distributed onto areas where the illumination is not wanted


Lighting distribution
It is how luminaires are classified according to the manner in which they control or distribute the luminous flux


Load
An electrical device, or the amount of power required by such a device


Louver
A series of baffles used to shield a source from view at certain angles or absorb unwanted light, Grid type assembly used instead of a lens fixture, Can range from small-cell plastic to large cell anodized louvers used in parabolic fluorescent fixtures


Low power factor
An uncorrected power factor of less than 0.90


Low Pressure sodium (LPS)
Type of high intensity discharge lamp in which light is produced by radiation from sodium vapor, considered a monochromatic light source that renders most color as grey


Low temperature starting
Standard ballasts for standard bipin-base, 2 lamp Slimline and high output fluorescent lamps are designed to provide reliable starting at ambient temperatures down to 50 degrees F, all reduced wattage lamps will start reliably with standard ballasts down to 60 degrees F. Special ballasts are available for applications where standard lamps must be started at lower temperatures. Most low temperature ballasts will start standard lamps down to 0 degree F, with low-temperature HO ballasts good for -20 degrees F. High pressure sodium ill start lamps down to -40 degrees F and metal halide lamps down to -40 degrees F.


Lowbay
Pertains to an application and / or the type of lighting in a manufacturing area or warehouse where the ceiling is 25 feet or lower


Lucalox
Trademarked General Electric brand name for high pressure sodium lamp


Lumalux
Trademarked Sylvania brand name for high-pressure sodium lamp


Lumen (lm)
A basic unit of measurement for light, the quantity of luminous flux emitted within a unit solid angle (one steradian) by a point source with one candela intensity in all directions; the overall light output of a luminous source is measured in lumens. A dinner candle puts out about 12 lumens, and one 60 watt soft white bulb puts out 855 lumens. If a uniform point source of 1 candela is at the center of a sphere of 1-foot radius which has an opening of 1 square foot at its surface, the quantity of light that passes through is called a lumen. The sphere has a total surface area of 12.57 square feet. Since, by definition, a lumen flows to each square foot of a surface area, a uniform point of 1 candela produces 12.57 lumens


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 Method
A method of estimating the interior illuminance due to window daylighting at three locations within a room. Based on empirical studies, the use of this method is primarily limited to North America.


Lumens per watt (lpw)
A measure of the efficiency of a light source in terms of the light produced for the power consumed. For example, a 100watt lamp producing 1750 lumens give 17.5 lumens per watt. Edison’s first lamp 1.41 lpw Incandescent lamp 10-40 lpw Fluorescent lamps 35-104 lpw Halogen lamps 20-45 lpw Mercury lamps 37-63 lpw Metal halide lamps 80-125 lpw High pressure sodium lamps 54-153 lpw


Luminaire
A complete lighting unit, consisting of a lamp or lamps together with the components required distributing the light (housing), position the lamps, and any necessary starting components (ballast) and connecting the lamps to a power supply. Often referred to as a “fixture”


Luminaire dirt depreciation (LDD)
A multiplier used in lighting calculations to account for the reduction in illuminance produced by the accumulation of dirt on a luminaire.


Luminaire Efficiency
Total Lumen output of a luminaire expressed as a percent of rated bare lamp lumens, as determined by photometric tests


Luminance
The luminous intensity of a surface in a given direction per unit area of that surface as viewed from that direction; often incorrectly referred to as “brightness”. The luminous intensity of any surface in a given direction per unit area of that surface as viewed from that direction. All units; candelas per unit area and measured in candelas/ square meter


Luminance
It is luminous intensity of any surface in a given direction per unit of area of the surface as viewed from that direction. It is measured in candelas per square meter. All visible objects have some luminance


Luminance (L)
Light reflected in a particular direction; the photometric quantity most closely associated with brightness perception, measured in units of luminous intensity (candelas) per unit area (square feet or square meters). The average luminance of any reflecting surface in footlambert is; footcandels x surface reflectance


Luminance efficiency rating (LER)
The energy Policy Act of 1992 requires that the lighting industry develop a rating for luminaires that allows designers to compare the energy efficiency of lighting products. LER for some type of illumination have been developed by NEMA and approved by the National Lighting Collaborative to fulfill the requirements for the energy Policy Act.


Luminous efficiency
Total lumens emitted by a lamp divided by total input power


Luminous Flux
It is the measure of the total light producing power of the light source, it is the amount of light leaving the source without regard to direction. A typical 100 watt incandescent lamp has about 1700 lamp lumen and a 400watt HPS lamp has 50000 lumens


Luminous intensity
It is the strength or intensity of the light produced in a specific direction


Lux (lx)
The SI unit of illuminance equal to one lumen per square meter, the light on a surface of one meter square on which there is a uniformly distributed flux of one lumen; 10.76 lux equal 1 footcandle. One lux equal to .0929 footcandle, dacalux= 10 lux; Lux= lumens per square meter reaching a surface


Magnetic regulator ballast-regulator (isolated secondary)ballast (reg-lag)
Also known as constant wattage ballast (CW), is a three winding ballast similar in design to the older mercury design, but provides regulation with line voltage variation of + or – 10% from nominal. It has an isolated primary and secondary which transforms voltage and feeds power to the lamp through a reactor section (3rd winding). It also has a capacitor in the circuit for wattage control and is a HPF device. It provides better lamp wattage control than the other designs, but with the disadvantage of the highest ballast losses, the highest operation costs, and the highest manufacturing costs. This ballast id generally not necessary for systems operating at near normal line voltage Advantages; 1- high power factor over 90% 2- excellent line voltage regulation, it is responsive to systems that operate normally in extremely high or extremely low line voltage situations-in the “near to +-10range 3- low operating current and lower starting current 4- isolated secondary reduces danger of electrical shock 5- at nominal voltage, its volts/watts trace is quite like the performance of a reactor ballast 6- provides better lamp regulation Disadvantages; 1- heavier and longer than other ballasts 2- most expensive of all types of ballasts


Maintained footcandle
The footcandle (minimum, maximum or average) calculated through application of a light loss factor, which takes into account such factors as lamp lumen depreciation, dirt depreciation, ballast factor, etc.


Matte Surface
Surfaces from which the reflection is predominantly diffuse, with or without a negligible specular component


Maximum footcandle
The maximum amount of light falling on a surface or anywhere on the area being lighted


Maximum overall length (MOL)
The total length of a lamp, from top of bulb to bottom of base, typically expressed in inches; the maximum overall length of a single end lamp is the maximum distance, measured in inches, from the top of the bulb to the bottom of the base. For double ended lamps, it is the maximum distance from end-to-end


Mean lumens
The average lumen output of a lamp throughout its economic life


Mean time between failures (MTBF)
A calculation of ballast life based on thermal conditions, component values, and circuit characteristics used to develop relative predictions of ballast life.


Medium Base
The familiar metal screw base used on standard household incandescent lamps, Medium base sockets accept lower-wattage lamps of this base size


Megawatt (Mw)
1,000,000 watts


Mercury Vapor lamp (MV)
A type of high intensity discharge lamp in which the major portion of the light is produced by radiation from mercury, Emits a greenish cast of light, but phosphor coated mercury lamps have better color rendering. Mercury lamps are known for their long life, their efficiency is better than incandescent lamps but not as good as the other HID or fluorescent sources. Clear mercury gives a slight bluish green tint to a white surface, accents red, yellow, blue and green, and tends to gray deep reds. Advantages; 1- long lamp life/ 16000-24000 hrs or more 2- high light output/lumens per watt 3- low operating cost Disadvantages; 1- high initial cost 2- large light source 3- limited beam control especially with phosphor coated lamps 4- low efficacy compared to MH or HPS 5- poor color rendition 6- does not start immediately after power failure, but quicker than metal halide(3-6 minutes)


Metal eggcrate
Metal louvers of various cell sizes typically used in fluorescent troffers


Metal Halide (MH)
A type of high intensity discharge lamp in which the major portion of the light is produced by radiation of metal halide and mercury vapors in the arc tube, Includes clear and phosphor-coated lamps that differ in their color-rendering characteristics, metal halide lamps have an efficiency –approximately 100% higher than mercury vapor lamps. Metal halide lamps are used where efficiency and color are important and dusk to dawn applications where initial cost is important. Lamp life is approximately half that of mercury lamps. Metal halide gives a slight blue to a white surface, accents yellow, green and blue, and tends to gray reds. It takes 2-4 minutes for the almp to reach 80% light output. The hot-restrike time is 10.15 minutes. Advantages; 1- moderately long lamp life/ 7500-20000 hrs 2- higher light output than mercury for a given wattage 3- good color rendition, makes colors look close to natural 4- good beam control 5- low operating cost Disadvantages; 1- higher initial cost 2- does not restart immediately after power failure 3- slowest to restrike/ 10-15 minutes


Miltered
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


Minimum footcandle
The least amount of light (illuminance) falling on that point of a surface or anywhere on the area being lighted


Modules
The manufacturing panels of photovoltaic cells; a module typically houses thirty-six cells in an aluminum frame covered with a glass or acrylic cover and provides a junction box for connection between itself, other modules in the array, ant the solar electric system


Mogul base
A type of metal halide screw base used on larger lamps, primarily HID and some incandescent, Mogul-base sockets accept higher wattage lamps of this base size


Mogul base restricted
Mogul bases for metal halide lamps used in open fixtures


Monitor
A raised section of roof that includes a vertically (or near-vertically) glazed aperture for the purpose of daylighting illumination


Mounting height (MH)
In given applications, the distance from the luminous area of the luminaire (typically the bottom) to the floor or work plane; the vertical distance between the luminaire and the surface to be lighted. It includes both the pole length and the base (above grade) to which the pole is affixed


Multi tapped ballast
A ballast with tapped leads (wires) on the primary side which enables the ballast to function on more than one supply voltage


Nadir
The point of direction directly below the luminaire (0 degree angle)


NAED
Abbreviation for National Association of Electrical Distributors


Near Infrared (solar infrared)
The region of the electromagnetic spectrum between 0.77 to 1.4 microns, which most of the infrared solar radiation falls into this region. This near infrared (or solar IR) region is transmitted, absorbed, and reflected in a similar manner to visible light by most glazing and nonmetallic building materials.


NEC
National Electric Code, complied by the NFPA to provide guidelines for installation and application of electric equipment


NECA
National Electrical Contractors Association, professional society for electrical contractors, most whom are union members


NEMA
National Electrical Manufacturer’s Association


NEMRA
National electrical Manufacturer’s Representatives Association


Net metering
A desirable form of buy-back agreement in which the line-tied house’s electric meter turns in the utility’s favor when grid power is being drawn, and in the system owner’s favor when the house generation exceeds its needs and electricity is flowing into the grid. At the end of the payment period, when the meter is read, the system owner pays the utility the difference between what was used and what was produced


NFPA
National Fire Protection Association, the organization that publishes the National Electrical code* and Life Safety Code*


NPF
Normal Power Factor, a ballast/ lamp combination in which not components have been added to correct the power factor; hence, normal power factor


NRTL
Nationally Recognized Testing Laboratory (UL, CSA, ETL…)


Occupancy sensor
Control device that acts as light switch upon sensing that a person has entered a space, maybe ultrasonic, infrared, or other type


OEM
Original equipment manufacturer


Off- the-grid
Not connected to the power lines; electric self-sufficiency


Opaque
It does not let light pass through, not being transparent, not translucent


Operating current
It is the rated current flow under normal conditions once the lamp arc has been established and it is performing at rate levels. Most ballast types have starting current less than operating currents. Care should be taken when loading circuits to base load calculations on the higher of the two current ratings. Normal power factor ballasts have higher starting current than operating currents. Fuses, circuit breakers, and photoelectric control switches must be sized to accommodate the highest current.


Operating positions
The designated operating positions assure maximum lamp performance, where it is not specified, the lamp is suitable for operation in any position


Operating voltage
Mercury and metal halide lamp operating voltage remains relatively constant throughout rated life, although lamp manufacturing tolerances can allow for as much as plus/minus 10% variance from nominal. Depending on the type of ballast being used, lamp wattage may vary considerably. High pressure sodium lamps operating voltage rises continually, from initial installation unit end of life. HPS ballasts are designed to satisfy the increased voltage requirements of the lamp through-out rated life. As an example, a 400W HPS lamp nominally starts at 100 volts and increases to 140 volts at end of life.


Operating wattage
HID lamps operate at rated wattage only if the lamp voltage and supply voltage is nominal. Lamp wattage and lamp life will be affected if either of these vary from nominal


Optical system
The light control portion of the luminaire including reflectors, lenses, diffusers, baffles and louvers, the lamp cavity or environment is considered as part of the fixture for the purpose of controlling the light output


Optics
The light-emitting or light-controlling components of a light fixture (reflector, refractor, lens, louvers, etc)


Overcast Sky
A sky luminance distribution three times brighter near (C.I.E. Standard Condition) the zenith than at the horizon, as defined by a formula proposed by Moon and Spencer in 1942 and adopted by the Commission International de l’Eclairage in 1955;


Overhang
A horizontal building projection, usually above a window, for the purpose of shading; in roadway lighting, the distance between a vertical line passing through the luminaire and the curb or edge of the roadway:


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 lamp
Parabolic Aluminized Reflector lamp, an incandescent or low voltage lamp used to redirect light the filament in a manner resembling a parabolic reflector


Parabolic
Term applied to certain louvers and reflectors shapes derived from the geometric shape called a parabola where, if a light source is placed at the focal point of the parabola, the resultant emitted light will be redirected parallel to the parabola’s geometric axis


Parabolic aluminized reflector lamp (PAR)
A type of sealed beam lamp that controls its light beam by an internal reflector coating and sometimes a prismatic lens


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, they are also used in rooms with computer screens because of their glare reducing qualities


Parallel lamp circuitry
Parallel vs. series; ballasts with parallel lamp circuitry have the benefit of companion lamps remaining lit, even if one of the lamps operated by the ballast should fail. Systems with series lamp wiring (magnetic ballasts and some electronic ballast) result in lamp


Passively heated
A shelter that has its space heated by the sun without using any other energy


Path of egress
Quickest way out of a facility, usually under emergency conditions


Peripheral Vision
The seeing of objects displaced from primary line of site and outside of the central visual field point method, or a method of estimating the illuminance at various locations in a building using photometric data


Petroleum
An oily, flammable liquid composed of a complex mixture of hydrocarbons occurring in many places in the upper strata of the earth, a fossil fuel


Phantom loads
Appliances that draw power 24 hours a day, even when you turn them off, TV, VCRs, and microwave ovens with clocks, and plugs with integrated little black box all contain phantom loads


Photocell
A device that measures the amount of incident light present in a space


Photoelectric cell
A device used to convert radiant or light energy into the electrical energy, often used to control outdoor light fixtures


Photometrics
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 test conducted in a photometric laboratory. A photometric curve is a two dimensional drawing illustrating the intensity of the light emitted from a luminaire


Photovoltaic (PVs)
A technology for using semiconductors to directly converts light into electricity


Plenum
That space between the structural ceiling and the finished ceiling, this space may contain air ducts, electrical wiring, etc. It’s the area which conceals the housing part of a recessed fixture


Polar coordinates
Converts a selection from its rectangular to polar coordinates, and vice versa, according to selected options, You can use this filter to create a cylinder anamorphosis- art popular in 18th century- in which the distorted image appears normal when viewed in mirrored cylinder.


Polychlorinated biphenyls (PCBs)
This material formerly used in ballast capacitors, is now considered hazardous and disposal is regulated. A ballast should be assumed to contain PCBs unless stated otherwise on the ballast label


Polyester powder paint
A type of plastic paint in a powder form that is sprayed on fixture parts, the paint and the metal fixture parts are given opposite electrostatic charges, which caused the powder to adhere to the surface. It then goes through a baking process which melts the paint to form a durable finish


POMB
Position oriented mogul base


Power
The rate at which energy is taken from an electrical system or dissipated by a load, Expressed in watts; power that is generally by a utility is typically expressed in volt-amperes


Power Factor
A measure of the effectiveness with which an electrical device converts volt-amperes to watts; the phase between voltage and current; it is the ratio of line watts to line volts x line amps, expressed in a percentage; devices with power factors (0.90) are “high power factor” devices, usually as the lamp and capacitors age, the power factor will drop below 90%


Power surge
A sudden surge of high voltage on a power distribution circuit, usually caused by lighting or the switching on/off of heavy loads, especially motors


Powerline carriers
Schools, institutions and some industrial installations utilize Powerline carrier control systems (to control time clocks, alarms, etc.) on the same circuit panel as the lighting system. Some of electronic ballasts are incompatible with these Powerline carriers and inhibit their performance (the electronic circuitry blocks or alters the carrier signal characteristics)


Preheat
A circuit used on fluorescent lamps wherein the electrodes are heated or warmed to a glow stage by an auxiliary switch or starter before the lamps are lighted. This system was used on the original fluorescent lamps and is still sometimes used today


Primary dropout regulation
All power distribution systems experience dips and peaks in line voltage as well as other transient conditions. Well-regulated systems seldom see voltage fluctuations of 20% or more. Be sure to check the primary dropout voltage rating of the ballast if the voltage variations are of concern. Voltage dips in excess of this rating may cause the lamps to extinguish and recycle


Primary playing area (PPA)
The total area within the playing boundary in which the illuminance level must be maintained


Probe start lamp
A traditional or probe start metal halide lamp has an internal starting electrode or probe. A high open circuit voltage from the ballast initiates an arc between the two starting electrodes at one end of the arc tube. Once the lamp reaches full output, a bi-metal switch closes to short out the probe and discontinues the starting arc.


Prostart ballast
A method of starting fluorescent lamps where cathode heat is applied prior to lamp ignition, then removed once the lamp has ignited. Prostart maximizes the number of lamps starting cycles while maintaining energy efficiency. This is the preferred mode of lamp starting for applications with occupancy sensors and several on/off cycles per day


Pulse start ballast
The pulse start system uses dedicated ballast that includes an ignitor. This eliminates the need for the starting probe and bi-metal switch in lamp. There are three designs of pulse start ballasts, each has it’s own characteristics. As in all ballast designs, the ballast must match the electrical requirement of each specific lamp. The ANSI has applied specific codes to each pulse start system. 1- SCWA- super constant wattage autotransformer, the pulse start version of the CWA ballast, offers good ballast regulation and moderate ballast losses. For pulse start metal halide lamp only 2- LLRPSL- linear reactor, designed as an energy saving system, 277- volt only, is used in area with very little line voltage variation. Auxiliary quartz options are not available. For pulse start metal halide lamp only 3- RLB- Regulated lag ballast (LAG- type regulator, “reg-lag”), exhibits the best ballast regulation, is used in areas where excellent line dip tolerance is critical. For pulse start metal halide lamps only


Pulse start lamp
It has an improved arc tube design and an increased fill pressure. An ignitor in the pulse start system delivers a high voltage pulse directly across the lamp’s operating electrodes to start the lamp, eliminating the probe and bi-metal switch needed in probe start lamps. It takes 1-2 montes for lamp to reach 80% light output. The hot restrike time for pulse start metal halide lamp is 4-6 minutes


Pupil
The opening is the iris of the eye that admits light


Quartz Restrike
A system using quartz 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


Quick 60+
The first and most comprehensive system warranty in the industry, it offers the end user coverage for both lamp and ballast. This eliminates the common occurrence of “finger pointing” between lamp and ballast manufacturers over whose product failed and which party is responsible


Quicksense
Patented technology that utilizes “dynamic power sensing” to detect end-of-life lamps of T5 and less diameter,. Dynamic sensing minimizes incidence of false shut-downs and ensures maximum system safety even in low and high line input voltage conditions. If gone unchecked, the heat generated by small diameter lamps at end of lamp life can melt lamp sockets and cause the lamp glass wall to crack and break


R-value
Resistance value, used specially for materials used for insulating structures, three inches of fiberglass insulation has an R-value of 11


Radiant Energy (radiation)
Energy traveling in the form of electromagnetic waves, which is measured in units of energy such as joules, ergs, or kilowatt-hours


Rapid start
A circuit designed to start fluorescent lamps by continuously heating or preheating the electrodes. This circuit is modern version of the trigger start system and requires lamps designed for this circuit. In the rapid start as well as the preheat circuit, each end of each lamp has two separate contacts


Reactor ballast (R) 120V only
One kind of HID ballasts, it provides limited regulation by way of an air gap in the coil. Depending on the light source used, it may require a starter to supply the high voltage pulse necessary to start the lamp. The standard is NPF but it is available in HPF Advantages; 1- least costly to manufacturer 2- lowest ballast losses-least wasted energy 3- least costly to operate and maintain 4- light weight 5- provides good wattage regulation on systems that contact the voltage within+-5%


Recessed
The term used for a fixture mounted in a ceiling opening so that the housing of the fixture is hidden from view. The fixture’s lens/door assembly may be slightly protruding. Flush or slightly regressed relative to the ceiling surface


Reflectance
The percentage of light reflected back from a surface, the difference having been absorbed or transmitted by the surface; The ratio of reflected flux to incident flux, types of surface reflectance range from specular (mirror like) to the diffuse (non glossy), with many objects exhibiting combinations. Typically, reflectance becomes more specular with larger incident angles. Reflectances of room surfaces are important consideration when calculating illuminance using the “lumen method”; measure of the ratio of light that is reflected by a surface as compared with the light which falls on it


Reflection
Describes a process by which light bounces from a surface without a change in frequency


Reflector
The portion of a light fixture that shrouds the lamps and directs the light emitted from the lamps; a device used to direct the light from a source by the process of reflection


Refraction
The process by which the direction of light changes as it passes obliquely from one medium to transmitting material to another in which its speed is different.


Refractor
A device used to redirect the light the light flow from a source, primarily by bending the waves of light; redirects the light from a source by the process of refraction, that is a ray of light changes paths, as it passes obliquely from one medium to another.


Regressed
Describe the troffer doorframe in which lens or louver is positioned above the ceiling plane


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 in input


Regulator (isolated secondary)ballast (reg-lag)
Also known as constant wattage ballast (CW), is a three winding ballast similar in design to the older mercury design, but provides regulation with line voltage variation of + or – 10% from nominal. It has an isolated primary and secondary which transforms voltage and feeds power to the lamp through a reactor section (3rd winding). It also has a capacitor in the circuit for wattage control and is a HPF device. It provides better lamp wattage control than the other designs, but with the disadvantage of the highest ballast losses, the highest operation costs, and the highest manufacturing costs. This ballast id generally not necessary for systems operating at near normal line voltage Advantages; 7- high power factor over 90% 8- excellent line voltage regulation, it is responsive to systems that operate normally in extremely high or extremely low line voltage situations-in the “near to +-10range 9- low operating current and lower starting current 10- isolated secondary reduces danger of electrical shock 11- at nominal voltage, its volts/watts trace is quite like the performance of a reactor ballast 12- provides better lamp regulation Disadvantages; 3- heavier and longer than other ballasts 4- most expensive of all types of ballasts


Remote head
A lamp head that is wired to an emergency lighting unit, but is mounted away from the unit itself, if a power outage occurs, the parent unit supplies emergency power to the remote head


Remote wiring capability
Quicktronic T8 instant start systems can be mounted remotely from the lamp sockets at a distance up to 18 feet, while rapid start systems can be typically remote wired up to 12 feet


Renewable energy
An energy source that renews itself without, effort; fossil fuels, once consumed, are gone forever, while solar energy is renewable in that the sun we harvest today has no effect on the sun we can harvest tomorrow


Renewables
Shorthand for renewable energy or material source


Resistance ®
A measure of resistance to flow of current, expressed in ohms


Retina
A light-sensitive membrane lining the posterior part of the inside of the eye


Retrofit
Refers to upgrading a fixture, room, building, etc. by furnishing new parts or equipment, also, to change a fixture out in the field


RFI
Radio frequency interference


Ripple
Creates an undulating pattern on a selection, like ripples on the surface of a pond, for greater control, use the Wave filter, Options include the amount and size of ripples.


Rods
Retinal receptors that respond to low levels of luminance but cannot distinguish hues. Not present in the center of the fovea region


Room surface dirt depreciation factor
It is not generally applicable in outdoor lighting calculations; this should be evaluated for interior calculations and is a significant recoverable loss for “indirect” lighting systems


Rooms Cavity Ratio (RCR)
In lighting calculations, a measure of room proportion as determined by dimensions of length, width, and height, the room cavity is the portion of the space from bottom of the luminaire to the work plane


Screw-slot
Type of ceiling system, and type of fixture mounting trim, in which room partitions are screwed directly into ceiling-mounted metal screw slot grids, making it easy to move the partition around


Secondary playing area (SPA)
The area extending beyond the primary playing area and the physical barrier such as fence


Setback
The distance that the center of the luminaire is behind the area to be lighted by that luminaire


Shear
Distorts an image along a curve, Specify the curve by dragging the line in the box to from a curve for the distortion, you can adjust any point along the curve. Click default to return to a straight line. In addition, you choose how to treat undistorted areas.


Shielding angle
The angle measured from the ceiling plane to the line of sight where the bare lamps in a luminaire becomes visible, the shielded angle affects direct glare, it is the complementary angle of the cutoff angle; it is the angle between a horizontal line through the light center and the line of sight at which the bare source first becomes visible


Sine wave
Wave form that represents periodic oscillations, electrical voltage and current is transmitted in the form of these waves


Skylight
A relatively horizontal glazed roof aperture for the admission of daylight


Slipfitter
Metal connector that attaches a floodlight to a pole


Socket
Component that holds the lamp base and supplies electrical power


Socket wiring/ lamp connections
Proper connection to good quality sockets, wired according to the diagram shown on the product label is essential. As some applications may not require the use of all the ballast output leads, unconnected leads should be capped individually and insulated to at least 600 volts


Spacing
In roadway lighting, it is the distance between successive luminaires measured along the center line of the street. In interiors, it is the distance between luminaire centers


Spacing criterion (S/MH)
Spacing-to- Mounting Height Ratio, also called spacing criterion, indicates the ratio of the maximum spacing between luminaires to the mounting height above the work plane to achieve uniform illuminance. Calculated from the photometric data, this ratio is multiplied by the application mounting height to determine the recommended maximum luminaire spacing. This ratio should not be greatly exceeded if uniformity of the illumination is desired


Spacing Criterion (SC)
The ratio of the distance between luminaire centers to the mounting height above a reference plane, usually the work plane


Spec sheet
Also called specification sheet, submittal sheet and cut sheet, a data sheet that shows fixture dimensions, descriptions, options, and Photometrics. These sheets are submitted by dmf LIGHTING through the contractor, engineer and architects to obtain final approval on the specific equipment to be furnished Spectral power distribution (SPD) A curve illustrating the distribution of power produced by the lamp, at each wavelength across the spectrum


Specification
The precise written detail of the building contract which accompanies the building plans, normally includes all requirements of the general contractor and subcontractors to furnish and install the specified material and equipment using prescribed method and workmanship


Spectral power distribution (SPD)
A curve illustrating the distribution of power produced by the lamp, at each wavelength across the spectrum


Spectrum
Refers to the regions of the electromagnetic spectrum, it has been arbitrarily divided into wavelengths as follows; Vacuum ultraviolet <10 nanometers Extreme ultraviolet 10-100 nanometers Far ultraviolet 100-200 nanometers Middle ultraviolet 200-300 nanometers Near ultraviolet 300-380 nanometers Visible light 380-700 nanometer Near infrared 770-1400 nanometer Intermediate infrared 1450-5000 nanometers Far infrared 5000-1000000 nanometers Spectrum also is used in reference to color quantities of visible light within the 380-700 nanometers range, which we usually refer to as “ the color spectrum”


Specular Angle
The angle of mirror reflection (angle of incidence equals angle of reflectance)


Specular Reflection
The process by which incident flux passes through a surface or medium without scattering


Specular Surface
Shiny or glossy surfaces that reflect incident light


Spherize
Gives objects a 3-D effect by wrapping a selection around a spherical shape, distorting the image and stretching it to fit the selected curve.


Spill light
Lumens distributed by the luminaire which are outside the beam spread


Spotlight
Any of the several types of luminaires with relatively narrow beam angle designated to illuminate a specially defined area


Starting current
Is the initial current available to the lamp during warm-up. If the current is incorrect, the lamp may never come up to rated operating performance and/or lamp life may be affected.


Starting voltage
Mercury vapor and most metal halide lamps incorporate integral starting electrodes which allow the lamps to start at relatively low voltages in ambient temperatures ranging above -20F(-29C). high pressure sodium lamps require separate electronic starting device (ignitor) which deliver a high voltage pulse to establish the arc. The pulse repeats each cycle with a maximum pulse width of 15 microseconds. Once the lamp arc is established, the ignitor drops out of circuit


Stroboscopic 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; HID lamps output tends to follow the alternating current waveform. This can cause small moving objects to flicker or appear motionless. To avoid this annoyance, three phase power is suggested for high pressure sodium and mercury lamps. Split phase ballasting can also be used with mercury lamps. Single phase power can be used with metal halide lamps.


Subjective brightness
The subjective attribute of any light sensation giving rise to te perception of luminous intensity, including the whole scale of qualities of being bright, light, brilliant, dim or dark. Brightness refers to the subjective sensation of people


Submittal sheet
Also called specification sheet, submittal sheet and cut sheet, a data sheet that shows fixture dimensions, descriptions, options, and Photometrics. These sheets are submitted by dmf LIGHTING through the contractor, engineer and architects to obtain final approval on the specific equipment to be furnished


Surface mounted fixture
Any fixture mounted directly on a ceiling or wall


Suspended or pendant mounted fixture
Any fixture hung by supports


Sustainable
Material or energy sources that, if managed carefully, will provide at current levels indefinitely


Switch level dimming (SLD)
Switch level dimming of HID sources provides HI_LOW control for significant energy saving, it is useful when full output is not required, in unoccupied areas, it is also applicable for utility demand power reduction requirement


Tapped ballast
A ballast with tapped leads (wires) on the primary side which enables the ballast to function on more than one supply voltage


Task Light
Light that is directed to a specific surface or area to provide illumination for visual tasks


Temperature factor
It has a significant effect on HID and incandescent lamps; however, it is a major factor affecting fluorescent lamp lumen output


Tempered glass
Type of glass used for light fixtures owing to its higher resistance to breakage than normal glass


Tenon
A metal device that enables an outdoor luminaire to be mounted to a pole


Thermal protector
A device that protects a ballast from overheating, the class P thermal protector used in most ballast is a bi-metal switch that opens a circuit when the ballast becomes overheated and closes the circuit when the ballast cools down


THHN
A type of heat-resistant thermoplastic conductor insulation used in some fixture wiring


Threshold
Used for a variety of conditions generally to indicate the point at which they become visually perceived, the threshold may be one which simply enables the detection of he presence of an object; it could refer to determination of certain details of that object


Tilt angle (metal halide lamps)
Operating metal halide lamps designated as base down at angles away from vertical can significantly decrease initial lumen output. This decrease in output must be considered in design computation when a position other than vertical is used such as in floodlighting luminaires. Operating lamps at angles away from vertical can also adversely affect lamp life


Total harmonic distortion (THD)
Excessive THD (defined by ANSI as greater than 32%) may cause adverse effects to the electrical system. THD levels below 20% provide optimal system compatibility, but levels below 10% may not add any practical benefits. 10% THD types may also introduce excessive in-rush current unless circuitry is added that limits in-rush levels


Translucent
Letting light pass but diffusing it so that objects on the other side cannot be distinguished; partially transparent, or frosted glass


Transmission
Transmitting light rays so that object on the other side may be distinctly seen; as window glass is transparent; opposed to opaque and distinguished from translucent


Twirl
Rotates a selection more sharply in the center than at the edges, specifying an angle produces a twirl pattern.


UL
Underwriters’ laboratories, an independent organization whose responsibilities include rigorous testing of electrical products, when products pass tests, they can be labeled and advertised and “UL Listed”


Ultraviolet Radiation (UV)
A radiant energy within the wavelength range of 0.001 to 0.38 microns


UPS
Un-interruptible power supply


VA
Volt-ampere


Vac
Volts AC


Vapor-tight luminaire
A luminaire designed for installation in damp or wet locations, also described as “enclosed and gasketed” it is not designed to keep out vapors


Vdc
Volts DC


Veiling Reflection
Specular reflection superimposed upon diffuse reflection from an object that partially or totally obscures the details to be seen by reducing the contrast. Controlled by distributing the source over a larger area, relocating the source out of the reflected field of view, changing the task surface specular reflectance or tilt. Or relocating the observer


Vertical footcandles
The footcandles falling on a vertical surface, such as a wall, vertical footcandles may not be in the same plane; depending on the direction of light rays, vertical footcandles from different sources may not be additive


Visibility
Describes the state of being perceived by the eye, outdoors, we often use visibility in terms of the distance at which an object can be seen by the eye


Visor
A shield that can be mounted on top or sides of outdoor fixtures, the top visor provides horizontal cutoff when a fixture is aimed 30 degree below horizontal, the independent side visors provide 45 degree horizontal cutoffs


Visual acuity
A measure of the ability to distinguish fine details


Visual comfort probability (VCP)
The rating of lighting system expressed as a percentage of the people who, when viewing from a specified location and in a specified direction, will be expected to find it comfortable in terms of discomfort glare


Visual field
Represents the location of objects or points which can be seen when the head and the eyes are in a fixed position


Visual surround
Represents all portions that lie within the visual field except a given task itself


Visual task
Represents objects or details which must be seen in the performance of a given activity, it would include the immediate background of these things, but not the “surround”


Volt (V)
The unit of measuring electrical potential, it defines the force of pressure of electricity for the satisfactory operation of an electrical device


Voltage (E)
The electrical potential between two points, it is analogous to hydraulic system pressure (pounds per square inch), the voltage of a circuit is the electrical “pressure” available to push current through the circuit, in an incandescent lamp, “voltage” designates the supply voltage to which the lamp should be connected


Voltmeter
Device used to measure in volts the differences of potential between points in an electrical circuit


Wall bracket
A type of wall mounted fluorescent fixture for commercial and residential markets, often used in corridors, lavatories and hospital rooms


Wall Pack-wall pak
A wall mounted light fixture, often used for outdoor security lighting and small general area lighting


Wallwash
Term used to describe lighting to illuminate vertical surfaces, usually from ceiling to floor without shadows or hot spots, fixtures used to accomplish these areas 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 cost of operating and 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


Wave
Works in a similar way to the ripple filter, But with greater control, Options include number of wave generators, the wave-length (distance from a wave crest to the next), the height of the wave, and the wave type: Since (rolling), Triangle, or Square. The randomized option applies random values. You can also define undistorted areas.


Wavelength
Distance between two successive points of a periodic wave; the wavelengths of light are typically expressed in nanometers (nm), or billionths of a meter


Wet location
Installation


Wind chart
A chart showing the average annual wind velocities of various regions in US


Wind load
Wind speed in miles per hour to which an outdoor lighting pole will be subjected. Wind load vary geographically and are listed in an AASHTO publication, “Standard Specification for Structural Supports for Highway Signs, Luminaires, and Traffic Signals”.


Wireguard
Assembly made of wire and usually mounted over the face of a fixture to protect the lamps or housing


Work plane
The level at which work is done, and at which illuminance is specified and measured, for office application this is typically a horizontal plane 30 inches above the floor. This measurement is important in all calculations determining footcandle levels


Wraparound
A surface mounted commercial fluorescent fixture that has a curved plastic lens that wraps around the fluorescent lamp


Zigzag
Distorts a selection radically, depending on the radius of pixels in your selection, the ridges option sets the number of direction reversals of the zigzag from center of selection to its edge. You also choose how to displace the pixels: a Pond ripple displaces pixels to the upper left or lower right; out from center of the selection, and around center rotates pixels around the center.


Zonal cavity
The most common method used by the lighting industry to calculate coefficient of utilization for indoor luminaire