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An auxiliary device consisting of starter and induction windings and sometimes a capacitor for power correction. It is used in fluorescent and HID luminaries to provide the necessary starting voltage and to limit the current during operation. (see also “Power Factor”). Dimmer ballasts are special ballasts which have used together with a dimmer control (supplied by others) will vary the light output of a lamp.
Glass formed by exerting outward pressure on the inside of a mass of molten glass at the end of a blow pipe, this forcing the glass into contact with a metal mold. Hand tools are sometimes used to form the glass before or after it comes out of the mold.
A saucer below the candle cup originally designed to catch the molten wax drippings of the candle.
A glass with high resistance to thermal shock often used where concentrated high temperatures are encountered and for outdoor applications.
A shallow metal shade with sloping sides used on French lamps of Empire Directoire Periods.
That part of the building wiring system to which a luminaire is connected for electrical power supply.
The degree of apparent lightness of a surface; its brilliancy; concentration of candlepower. Brightness is produced by either a self-luminous object, by light energy transmitted through objects, or by reflection. Unit of measurement of brightness is a footlambert (f1).
A cable comprised of a flexible metallic covering inside of which are two to more insulated wires for carrying electrical current.
Fibre tube, usually white, which covers the sockets of a chandelier and simulates a candle
Metal piece between bobeche and candle which represents the candle holder that was used in candle burning chandeliers.
Luminous intensity expresses in candelas.
A graphic presentation of the distribution of light intensity in a given plane of a lamp or luminaire. It is determined by photometric tests.
A covering, usually metal or wood, used to conceal that junction box and wiring at the ceiling line.
An electric energy storage which when built into or wired to a ballast changes it from low to high power factor. It decreases the current required per ballast, permitting more fixtures to be installed on a given electrical circuit. (See also Power Factor).
Two or more layers of glass of different colours, such as clear and white, fused into a single piece and used to improve the diffusing properties of the glassware, its light transmission and to give a finger appearance.
Metal housing mounted directly to the ceiling. A diffusing element, such as a glass bowl, is usually supported from it to shield the lamps.
A series of links or rings, usually of metal, fitted together to support a fixture between the ceiling and the body of the fixtures.
In a chandelier, that portion which extends from the body outwards to provide the wireway and hold the lighting element. It is also a part of the decorative element of the chandelier and comes in a variety of shapes and sizes.
The reflecting enclosure housing the ballast and lampholders in a fluorescent luminaire.
A blown glass tube of various shapes placed around the flame to protect against wind. In today’s usage, it is for ornamentation and light diffusion.
The closed path of an electric current including the electric source, the wiring and the electric load.
Tube or pipe, often used in an enclosure to protect electrical wires.
Generally used to refer to Task Contrast. The difference between the luminance (brightness) of the detail in a visual task and the luminance of its immediate background (e.g between the print and the paper).
Electrical outlet provided on some fixtures (e.g. bathroom lighting) for plugging in an electric shaver or other electrical device. A grounded convenience outlet accommodates 3-prong cord plugs.
A combination of two or more insulated conductors in an outer jacket or covering.
A system comprising light sources shielded by a panel parallel to the wall and attached to the ceiling and distributing light over the wall; down light only.
A system comprising light sources shielded by a ledge or horizontal recess, and distributing light over the ceiling and upper wall; up light only.
The top ornament on a chandelier.
Colourless glass of high brilliance and clarity used in making chandelier parts such as prisms, bodies, bobeches and arms.
The angle from the vertical at which a reflector, louver, or other shielding devices cuts off direct visibility of a light source. It is the complementary angle of the shielding angle.
A translucent glass or plastic that shields the light source and spreads light evenly in all directions.
The scattering of light rays so that they are emitted or reflected from all directions. Light that comes from a larger source of uniform brightness is more diffused because it is coming from more directions.
See ballast.
Flow of electricity continuously in one direction from positive to negative. Rarely used in today’s lighting circuits.
A system in which the work plane or an object is illuminated predominately from a preferred direction.
Luminaries may be classified according to the percentage of light emitted above and below the horizontal.
Classifications include the following:
Direct: 0 to 10% up’ 90 to 100% down.
Semi-direct: 10 to 40% up; 60 to 90% down.
General diffuse: 40 to 60% up; 40 to 60% down.
Semi-indirect: 60 to 90% up; 10 to 40% down.
Indirect: 90 to 100% up; 0 to 10% down.
Distribution of light may also be defined in terms of angular array or distribution of the individual rays:
Directional – If all rays of light are aligned essentially parallel with each other, a definite beam is determined and a directional distribution of light is obtained.
Spread - Actually all light distributions fall between two idealized limits of directional and diffuse. Those of high directional quality are those characterized by the beams from automobile headlights, floodlighting projectors, and high=bay industrial units. Distribution of a more diffused character are those from indirect lighting systems. Between these idealized and practical limits are the spread types of distribution. There are no sharp lines of demarcation between directionally, spread and diffuse classifications.
A reflector shaped, in cross section, like an ellipse. The reflected rays of light from a light source at one focal point will converge at the other focal point, making it possible to send a large amount of light through a small opening.
A system designed to supply illumination essential to the safety of life and property in event of failure of normal supply of light.
Glass of which the surface has been frosted by acid etching to product a satin or velvet appearance.
Crystal beads of jewels linked in a chain used to adorn a chandelier. The chain is usually draped from one part of the chandelier to another.
The finished ornament at the top of a lamp or, in some cases, at the bottom of the fixture
The melting of surface of crystal or other lighting glassware to achieve high lustre and smoothness.
Luminaries, as distinguished from a portable lamp inn that it is permanently wired into the building wiring system.
In a chandelier, that portion of fixture which extends from the body outwards to provide the wire way and hold the lighting element. It is also a part of the decorative element of the fixture and comes in a variety of shapes and sizes.
The central portion of fixture which coordinates the design and mechanical elements.
In a chandelier, that portion of the fixture which extends from the body outwards to provide the wire way and hold the lighting element. It is also a part of the decorative element of the fixture and comes in a variety of shapes and sizes.
The central portion of the fixture which coordinates the design and mechanical elements.
Loop which connects the chain to the main body of the fixture.
Overlapping metal portion of a recessed luminaires at the ceiling line. It serves to cover the ceiling opening around the luminaries.
A container at the bottom of an oil lamp used to store the fuel. In today’s usage, it is any bottom ornament shaped like a font.
The unit of measurement of the illumination of a surface. One footcandle is equal to one lumen per square foot. It is the illumination produced by a standard candle at a distance of one foot.
The unit of measurement of brightness. A footlambert equals a candela per square feet. The brightness of a reflecting surface in the footlamberts is equal to the incident illumination in footcandles times the reflectance of the surface.
See Alternating Current.
A metal line of low melting point which melts when the current exceeds the prescribed limit. When placed in an electrical circuit, it will prevent fire and damage to electrical equipment on the circuit under abnormal operating conditions such as excessive voltage or short circuits.
The application of small particles of glass to a glass surface by heat in a kiln. They are fused to the glass and are a permanent part of the glass.
A open work or pierced metal border or frame, usually decorative in appearance.
Small rectangular type of junction box, used principally for wall installations. Commonly measures 3” x 2” x 1-7/8” deep.
Brightness or brightness contrast which causes annoyance, discomfort, or reduced seeing efficiency.
Direct Glare - Glare resulting from high brightness or insufficiently shielded light sources in field of view.
Reflected glare - Glare resulting from specular reflections of high brightness sources in polished surfaces in the field of view.
A transparent or diffusing material intended to produce a lamp, to diffuse and redirect its light or to change the colour of its light.
Flexible metallic tubing for the protective enclosure of electric wires.
A rounded loop attached to either the canopy or the outlet box from which the chain is hung.
“U” bracket with two threaded holes, used to connect threaded centre pipes in fixture body.
See power factor.
The metal body of a luminaire.
A metal socket cover – usually on portable lamp.
A method of forming sheet metal in which the metal is placed on a flexible rubber diaphragm which is supported by oil under pressure. The metal is formed around a male punch as the diaphragm is raised. The resultant part is generally of uniform thickness and quite strong.
Metal part which joins or overlaps the ends of fluorescent luminaries when installed in continuous runs.
A metal housing, commonly 3” or 4” square or octagonal with removable cover. Building wire is brought into the junction box so that splices can be made leading to other points in the circuit or to the lighting fixtures. Also used frequently to support a lighting fixture from ceiling (up to 50 lbs).
Any socket which does not have a built-in switch.
1000 watts (see watt)
A unit for measuring the consumption of electrical energy. Electric power is sold by the “kilowatt-hour” (KWH).
A portion of a metal enclosure which has been partially cut out be remains in place. It can be easily removed to permit an electrician to attach switches, convenience outlets, conduit connectors, etc. Often referred as a KO.
An artificial source of light. also a portable luminaries equipped with cord and plug. lamps are divided into the following major classifications:
Incandescent Lamp (also know as a Filament Lamp or “bulb”) to incandescence by the flow of electric current through it. The filament is usually of tungsten wire and operates in the range for 4000 degrees F. Incandescent lamps come in many sizes, wattages and shapes, in clear, frosted or white coated bulbs, and are available in many special types for particular applications such as reflectorized lamps (R and PAR types), or solved bowl lamps (SB).
The tungsten-halogen lamp is a special type of incandescent lamp that has its filament in a quartz enclosure which is filled with halogen gas. Due to the regenerative cycle the evaporated tungsten is removed from the bulb wall and redeposit on the filament. As a result lamp blackening is eliminated and lamp life is roughly doubled compared to standard incandescent lamps.
Fluorescent Lamp - A lamp generally in tubular form in which light is produced by the excitation of phosphors which emit light (fluoresce) when subjected to ultra-violet radiation. The ultra-violet radiation results from an electric discharge, i.e. the flow of current through a metallic vapour or gas (usually a combination of mercury and argon). The phosphors form a coating on the inside of the fluorescent tube, surrounding the electric discharge within. Fluorescent lamps come in varying colours, diameters, lengths and wattages in are made for various starting and ballasting systems.
High Intensity Discharge (HID) Lamp - A lamp usually in a bulb shape in which light is produced by the flow of electric current (electric discharge) through vaporized metal, exciting it and causing it to give off light. Three types of HID lamps are available: mercury, metal halide and high-pressure sodium. In the current types of HID lamps the bulb wall is coated with a phosphor to improve the colour characteristics.
Crystal with a high lead content. This adds clarity and brilliance to the glass.
Small pieces of glass, usually of different colors, joined at the edges into a larger surface by strips of lead.
A glass or plastic element used in incandescent and fluorescent luminaries to change the direction of and control the distribution of light rays. A fresnel lens, commonly used with incandescent luminaries, has concentric rings, each of prism section.
A mount of light produced by a light source such as a lamp. The unit most commonly used to measure light in the lumen.
A series of vertical baffles designed to cut off light traveling in undesirable directions.
See power factor
The unit of luminous flux; a measure of light output; equal to the flux emitted through a unit solid angle (one steradian) from a uniform point source one candle.
A complete lighting unit comprising bare lamp and means of controlling its light output; a lighting fixture, wall bracket, portable lamp.
Totally lumen output of luminaries (as determined by photometric tests) divided by the total lumen output of bare lamps, expressed in percent.
Technically, any plane of brightness; usually a translucent glass or plastic sheet used to diffuse light from an array of lamps.
A numerical value which provides a depreciation allowance for design purposes, relating the initial illumination to the illumination at the time at which it is anticipated that maintenance procedures will be instituted.
A non-glossy dull surface, as opposed to a shiny (specular)surface. Light reflected from a matte surface is diffused.
A threaded coupling for attaching a fixture to an outlet box.
Glass with a uniform diffusing texture which is a milky white colour.
Another term for junction box.
One of more layers of glass of different colour applied over another and cut through the outer layer to show the inner colours.
A reflector shaped, in cross-section, like a parabola. A small light source at the focal point of the parabola produces an essentially parallel ray beam.
A metal frame attached to the lathing or furring in a plaster ceiling to support a recessed luminaire to provide a definite stop for the plasterer to work to. Normally the luminaire trim overlaps the plaster frame.
China clay fired at high temperature to make it translucent.
Glass formed by pressing molten glass into a metal mold.
P.F. is primarily applicable to ballasts. Since volts and watts are usually fixed, amperes (or current) will go up as power factor goes down. This necessitates the use of larger wire sizes to carry the increased amount of current needed with Lower Power Factor (L.P.F.) ballasts. The internal addition of a capacitor to a L.P.F. ballast converts into a H.P.F. ballast.
A piece of crystal with faceted surfaces used as a decoration on chandeliers.
Type of fluorescent ballast circuit not using a separate starter, which permits a rapid start fluorescent lamp to start almost instantaneously. Used on 30W and 40W lamps. Requires use of lamps marked “RAPID START” or “PRE-HEAT REAPID START”. This is the most popular type of fluorescent circuit.
Another term for convenience outlet.
A luminaire installed complete above the ceiling line so that only the shielding element (and trim flanges) are visible.
The mechanical device around which the wiring coils and uncoils in a pull-down fixture.
Sometimes called reflectance factor. The ratio of incident light (light falling on a surface) to reflected light (see reflection). Reflectance is generally expressed in percent.
A surface which redirects the light striking it.
The change of direction a ray of light undergoes in passing obliquely from one medium to another in which its velocity is different. For example, light is refracted when it passes through a piece of glass at an oblique angle, also when it passes through water.
A device used to redirect the light from a light source.
Transparent quartz. This is mined and cut to shape, and is used for bodies, bobesches, prisms and other decorative parts in place of crystal.
Plastic-sheathed electric conductors; frequently used instead of metal-sheathed BX cable.
Metal strips formed into the shape of an “S”, “C” or “J”.
An opaque or translucent covering added to fixtures and lamps to enhance the decoration, shield the light source and/or direct the light.
The metal covering for the reel in a pull-down fixture.
A general term including all elements used to block, diffuse or redirect light rays. This includes baffles, louvers, shades, diffusers and lenses. Also “Light shield”.
The angle from the horizontal at which a light source first becomes visible. It is the complementary angle of the cut-off angle.
The ratio of the distance between fixtures to the height above the work plane. The maximum spacing ratio for a particular fixture is determined from the candlepower distribution curve for that fixture and when multiple by the mounting height above the work plane, gives the maximum spacing of fixtures at which even illumination will be provided.
A shiny, highly polished surface which reflects light at an angle equal to that of the incident light. See reflection.
A turned center body or arm on a fixture.
A device used to make a grouping of pendant type fixtures into a chandelier form with the use of one electrical source.
A small clamp of metal or plastic used to hold cord mounted fixture in place.
A universal joint or linkage used to permit rotation in almost any direction.
That which is to be seen. The visible function to be performed.
A length of metal rod affixed to the ceiling along with a fixture, such as a pull-down fixture, can be moved on rollers.
Type of ballast circuit for 15w and 20w pre-heat fluorescent lamps which permits the lamp to start almost instantaneously without a starter. There are not lamps marked “trigger start”; Trigger Start circuits used Pre-Heat fluorescent lamps.
The outer frame of a recessed luminaire which engages the ceiling. Lay-in trim lays over exposed ceiling runners. Fit-in trim butts up against ceiling tile or panels. Overlap trim extends past bottom edge of ceiling tile or ceiling opening (see “Flange”).
A recessed fluorescent luminaire (see “Recessed Luminaire”) generally designed to fit into modules of suspended mechanical ceilings. Many troffers are designed to be installed in continuous runs.
A system comprising light sources shielded by a panel parallel to the wall at the top of a window; both down and up light.
The unit for measuring electric potential. It defines the force or pressure of electricity which is required for satisfactory operation of an electrical devise.
The unit for measuring electric power. It defies the power or energy consumed by an electrical device with it is in operation. The cost of operating an electrical device is determined by the watts it consumes times the hours of use. It is related to volts and amps by the following formula: watts – volts X amps.
Insulating plastic or porcelain cap with internal threads to permit it to be screwed over splices of two or more electric wires. Widely used instead of soldering and taping.
The plane at which work is done, and at which illumination is specified and measured. Unless otherwise indicated, this is assumed to be horizontal plane 20 inches above the floor.
The finishing of crystal by polishing it on a rotating wood wheel. This achieves both permanent high lustre and sharp faceting. The finest crystal parts are polished in this fashion.
A “U” shaped metal channel used to support a recessed luminaire. A yoke clamps to supporting structure of mechanical ceiling system or is fastened to plaster frame, and spans the opening where a recessed luminaire is to be installed.