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on the links below for Terminology |
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Ballast:
A current limiting device that provides necessary circuit conditions to
start and operate an electric-discharge lamp |
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Ballast
Efficiency Factor:
The Ballast
Efficiency Factor (BEF) is the Ballast Factor (See Below) divided by
the input power of the ballast. The higher the BEF-within the same
lamp ballast type-the more efficient the ballast. |
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Ballast
Factor:
The Ballast
Factor (BF) for a specific lamp ballast combination represents the
percentage of the rated lamp lumens that will actually be produced
by the combination. |
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Candela
(CD):
A unit
of luminous intensity (strength) from a light source of lighting system
in a given direction. |
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Chromaticity:
The
whiteness of a light source expressed in Kelvin (K) Incandescent 2700K:
Warm
White Fluorescent 3000K: Cool White Fluorescent 4100K: Daylight Fluorescent
6500K. |
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Coefficient
Of Utilization (Cu):
The ratio
of lumens delivered from a luminaire to the work plane to the lumens
operated by the lminaires’s lamps alone. |
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Color
rendering index (CRI):
An evaluation
of how colors appear under a given light source. Expressed as a two-digit
number. The higher the number, the better the light source in rendering
colors naturally. |
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Color
Temperature:
The absolute
temperature at which a black-body radiator must be operated to have
chromaticity equal to that of the light source. |
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Compact
Fluorescent:
A small
fluorescent lamp that is often used as an alternative to incandescent
lighting. The lamp life is about 10 times longer than incandescent
lamps. Also referred to as PI, Twin-Tube, CFL or BIAX lamps. |
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Diffuse:
Term describing
dispersed light distribution. Refers to the scattering or softening
of light. |
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Diffuser:
A translucent
piece of glass or plastic sheet that shields the light source in a
fixture. The light transmitted throughout the diffuser will be redirected
and scattered. |
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Efficacy:
A measure
used to compare light output to energy consumption. Efficacy is measured
in lumens per watt. Efficacy is similar to the efficiency, but is expressed
in dissimilar units. For example, if a 100 watt source produces 9000
lumens, the efficacy is 90 lumens per watt. |
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Electronic
Ballast:
ballast
that uses semi-conductor components to increase the frequency of fluorescent
lamp operation – typically in the 20-40 kHz range. Smaller inductive
components are used to provide the lamp current control. Fluorescent
system efficiency is increased to high frequency lamp operation. |
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EMI:
Abbreviation
for Electromagnetic Interference. High frequency interference (electrical
noise) caused by electronic components of fluorescent lamps that interferes
with the operation of electrical equipment. |
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Energy
Saving Ballast:
A type
of magnetic ballast designed so that the components operate more efficiently,
cooler and longer than“standard magnetic” ballast. By U.S.
law, standard magnetic ballasts can no longer be manufactured. |
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Energy
Saving Lamp:
A Lower
wattage lamp – generally producing fewer lumens. |
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Fluorescent
Lamp:
A light
source consisting of a tube filled with argon, along with krypton or
other inert gas. When electrical current is applied, the resulting
arc emits ultraviolet radiation that excites the phosphors on the inside
of the lamp wall, causing them to radiate visible light. |
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Foot Candle:
The unit
of illuminance equal to 1 lumen, uniformly incident upon an area of
1 square foot; also, equal to the illuminance of a point 1 foot distant
from a 1 candela source. |
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Glare:
The effect
of brightness of differences in brightness within the visual field
sufficiently high to cause annoyance, discomfort or loss of visual
performance. |
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H.I.D.:
High Intensity
Discharge – A group of lamps generally consisting of mercury
vapor, metal halide, high pressure sodium and low pressure sodium. |
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High-Bay:
Pertains
to the type of lighting in an industrial application where the ceiling
is 20 feet or higher. Also describes the application itself. |
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High
Output (HO):
A lamp or ballast designed to operate at higher currents (800
mA) and produce more light. |
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High Power
Factor:
ballast with a .9 or higher rated power factor, which is achieved
by using a capacitor. |
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Illuminance
(E):
the “quantity” of light (foot-candles lux) at a point
on a surface.
Formula: Illuminance = Lumen/Square Foot |
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Instant
Start:
A fluorescent circuit that ignites the lamp instantly with a
very high starting voltage from the ballast. |
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Lamp –Lumen
Depreciation:
The fractional loss of lumen output over a period of
operating time. |
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Lens:
Transparent
or translucent medium that alters the directional characteristics of
light passing through it. Usually made of glass or acrylic. |
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Light-Loss
Factor (LLF):
The product of all considered factors that contribute
to a lighting system’s depreciated light output over a period
of time. |
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Louver:
Grid
type of optical assembly used to control light distribution from a
fixture. Can range from small-cell plastic to the large-cell anodized
aluminum louvers used in parabolic fluorescent fixtures. |
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Lumens/Watt
(L/W):
A ratios expressing the luminous efficacy of a light source. |
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Luminaire:
A
complete lighting unit consisting of a lamp (or lamps) together with
the parts designed to distribute the light to position and protect
lamps and connect them to the power supply |
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Luminaire
Dirt Depreciation (LDD):
The fractional loss of task illuminance because
of the accumulation of dirt on luminaire. |
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Luminaire
Efficiency:
The ratio of total lumen output of a luminaire and the
lumen output of the lamps, expressed as a percentage. For example,
if two luminaries use the same lamps, more light will be emitted from
the fixture with a higher efficiency. |
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Luminance
(L):
Practically, the brightness of an object, that which the eye perceives,
reflected, transmitted, generated.
Formula: Luminance = Illuminance
x Reflectance Factor. |
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Metal
Halide:
A type of high intensity discharge (HID) lamp in which the
major portion of the light is produced by radiation of metal halide
and mercury vapors in the arc tube. |
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Occupancy
Sensor:
Control device that turns lights off after the space becomes
unoccupied. May be ultrasonic, infrared or other type. |
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Optics:
A
term referring to the components of a light fixture (such as reflectors,
refractors, lenses, louvers, etc.) or to the light emitting or light
controlling performance of a fixture. |
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Radio
Frequency Interference (RFI):
Interference to the radio frequency band
caused by other high frequency equipment or devices in the immediate
area. Fluorescent lighting systems generate RFI. |
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Reflectance:
The
ratio of light reflected from a surface to that incident upon it. |
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Reflector:
The
part of a light fixture that shrouds the lamps and redirects some of
the light emitted from the lamp. |
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Retrofit:
Refers
to upgrading a fixture, room, building etc. by installing new parts
or equipment. |
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Room-Surface
Dirt Depreciation (RSDD):
The fractional loss of task illuminance because
of the accumulation of dirt on a room’s surface. |
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S/MHwp:
Spacing-To-Mounting
Height above Work Plane – the ration of the
distance between luminaire centers to the mounting height above the
work plane. |
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Specular:
Mirrored
or polished surface. The angle of reflection is equal to the angle
of incidence. This word is used to describe the finish of the
material used in some louvers and reflectors. |
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System
Efficiency:
System Lumens x LLF x CU
SE = ------------------------------------
System Watts
(LLF) Light Loss Factors:
Ballast factor – Thermal Factor – Lamp Lumen Depreciation – Luminaire
Dirt Depreciation – Room Surface Dirt Depreciation.
(CU) Coefficient of Utilization:
The ratio of lumens delivered from a luminaire vs. lamp lumens. |
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Tandem
Wiring:
A wiring option in which ballast is shared by two or more luminaries.
This reduces labor, materials and energy costs. Also called “master-slave” wiring |
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Underwriters
Laboratories (UL):
An independent organization whose responsibilities
include rigorous testing of electrical products. When products pass
these tests, they can be labeled (and advertised) as “UL Listed” UL
test for product safety only. |
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VCP:
Visual
Comport Probability – A rating of a lighting system expressed
as a percent of people who, occupying a specified location and looking
in a specified direction, will be expected to find it visually acceptable. |
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Watt (W):
The
unit for measuring electrical power. It defines the rate of energy
consumption by an electrical device when it is in operation. The energy
cost of operating on electrical device is determined by its wattage
time the hours of use. |
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Work Plane:
The level at which work is done and at which illuminance
is specified and measured. For office applications, this is typically
a horizontal plane 30 inches above the floor (desk height). |
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