Glossary of Terms

A

• Amps - Units used to measure electrical current flow.
• Average Rated Life - How long it takes to burn out the light. Average rated life is the expected time when approximately 50% of the lamps in a given group remain burning.

B

• Ballast - A power-regulating device used to control fluorescent lamps.
• Ballast Factor - A ratio of the light produced by a lamp operated by a given ballast to the light produced by a lamp operated by reference ballast. Expressed as a percentage. Also called light output. For example, a ballast having a ballast factor of 0.93 will result in the lamp emitting 93% of its rated lumen output.
• Ballast Efficiency Factor (BEF) - A measure of light output per watt consumed by a given lighting system. BEF= % light output / input power (watts).

C

• Candela (CD) - The international unit (SI) of luminous intensity. The term has evolved from considering a standard candle, similar to a plumber's candle, as the basis of evaluating the intensity of other light sources. Sometimes the term "candlepower" is used to describe the relative intensity of a source. (See Lumen.)
• Candle Power - A measure of intensity mathematically related to lumens. Candlepower is often used to measure the intensity of lamps that project light.
• Class B Ballast - A ballast that has an operating temperature classification for electrical components establishes by Underwriters Laboratories. Class B allows operation up to 130° C. This type of ballast is not allowed for indoor use.
• Class P Ballast - The UL classification for thermally protected ballast. The incorporation of a temperature-sensing device that switches the ballast off if excessive internal temperature develops. The switch closes and re-energizes the ballast once the temperature is tolerable.
• Coefficient of Utilization - A percent of initial lamp lumens that reaches the work plane as determined by surface reflectances, room shape (RCR), and fixture efficiency.
• Color Rendering Index - Measure of the degree of color shift objects undergo when illuminated by the light source as compared with the color of those same objects when illuminated by a reference source of comparable color temperature. Color rendering is measured on an index from 0-100, with natural daylight and incandescent lighting both equal to 100. Objects and people viewed under lamps with a high color-rendering index (CRI) generally appear more true to life.
• Color Temperature (Chromaticity) - A scientific measurement of the balance of wavelengths making up any "white" light. The unit of measurement is the Kelvin, abbreviated K. Although it may not seem sensible, a higher color temperature means a cooler, bluer light source. Typical color temperatures are 2800K (incandescent), and 5000K (daylight-simulating fluorescent).
• Compact Fluorescent Lamp (CFL) - An industry term for small diameter (T4-T5), single ended energy efficient fluorescent lamps. These lamps are used to replace inefficient incandescent lamps and consume approximately one-forth of the wattage of incandescent lamps with similar lumen output. CFL lamps are available in 2700K, 3000K, 3500K, 4100K and 5000K color temperatures and have high CRI ratings. The use of rare earth phosphors create a warm and inviting mood, with colors so rich and natural that you won't believe they're fluorescent. Ballasts regulate CFL lamps.

 

D

• Damp Location Listing - Denotes a lighting product that has been listed by UL to be used in damp locations. These are defined as locations where the lighting fixture is shielded from direct contact with rain or water, such as exterior locations which are protected by an overhang or protective roof.

E

• Efficiency - The ratio of lumens emitted by the light source to the wattage consumed expressed as lumens-per-watt. (See lumens-per-watt.)
• Electronic Ballast - (a.k.a. High Frequency or Solid State Ballast) - A power-regulating device that consumes approximately 25% less energy than magnetic ballasts and controls lamps by means of electronic components. Lamp operation must be above 1000 Hz and is typically about 25 kHz (25,000 cycles per second) which eliminates flicker.
• Emergency Ballast - Commonly referred to as fluorescent battery packs, emergency ballasts provide instant backup lighting when normal power fails. When AC power fails, the emergency ballast automatically switches to the emergency mode, illuminating one lamp for a minimum of 90 minutes. When AC power is restored, the emergency ballast automatically returns to the charging mode.

F

• Footcandle - The unit to measure how much total light is reaching a surface, such as a wall or table. One lumen falling on one square foot of surface produces illumination of one footcandle.
• Fluorescent Lamp - One in which electric discharge of ultraviolet energy excites a fluorescing coating (Phosphor) and transforms some of that energy to visible light.

G

• Grounding - The connection of an electrical conductor with the earth, so that the electricity passes off into it. All Brownlee Lighting models must be grounded.

H

• Hertz (Hz) - The electrical unit of frequency. One cycle per second = one hertz.
• High Frequency - All fluorescent lamps operate more efficiently when driven at frequencies greater than 15 kHz. This efficiency improvement is one reason for the popularity of electronic ballasts, which operate at high frequencies.
• High Intensity Discharge Lamp (HID) - General term for a mercury, metal halide or high-pressure sodium lamp.
• High Pressure Sodium Lamp (HPS) - A high-intensity discharge light source in which the light is primarily produced by the radiation from sodium vapor. Produces a slightly yellow light but has a very high energy efficiency.

I

• Instant Start - A circuit used to start specially designed fluorescent lamps without the aid of a starter. To strike the arc instantly, the circuit utilizes higher open-circuit voltage than is required for the same length preheat lamp.

K

• Kilowatt (kw) - A larger unit of power; a thousand watts (watts x 1000 = kilowatts).
• Kilowatt Hour (kwh) - The measure of electrical usage from which electricity billing is determined. For example, a 100-watt bulb operated for 1000 hours would consume 100-kilowatt hours, (100 watts x 1000 hours = 100 kwh). At a billing rate of $0.10 / kwh, this bulb would cost $10.00 (100 kwh x $0.10 / kwh) to operate.

L

• Light - The term generally applied to the visible energy from a source. Light is usually measured in lumens or candlepower. When light strikes a surface, it is absorbed, reflected or transmitted. Light is said to travel in straight lines.
• Lumen - The basic unit of measurement for light. One lumen per square foot equals one foot candle.
• Lumen Maintenance - How a lamp maintains its original brightness over its life.
• Lumens Per Watt (lpw) - A measure of the efficacy of a light source in terms of the light produced for the power consumed. For example, a 100-watt lamp producing 1750 lumens gives 17.5 lumens per watt.

  • Examples
    Incandescent lamps	10 - 40 lpw
    Fluorescent lamps	35 - 100 lpw
    Halogen lamps	20 - 45 lpw
    Mercury lamps	50 - 60 lpw
    Metal halide lamps	80 - 125 lpw
    High-pressure sodium lamps	100 - 140 lpw

• Luminaire - A complete lighting unit consisting of a lamp (or lamps), together with the parts designed to distribute the light, position and protect lamps and connect them to the power supply.
• Luminaire Efficiency - The ratio of lumens emitted by a luminaire to those emitted by the lamp or lamps used.
• Luminance Efficacy - The light output of a light source divided by the total power input to that source. It is expressed in lumens per watt.
• Lux - The SI (International System) unit of illumination: one lumen uniformly distributed over an area of one square meter.

M

• Metal Halide Lamp - A high-intensity discharge light source in which the light is produced by the radiation from mercury, together with halides of metals such as sodium and scandium. Produces a very efficient white light output.
• Mean Lumens - The average light output of a lamp over its rated life. For fluorescent and metal halide lamps, mean lumen ratings are measured at 40% of rated lamp life. For mercury, high-pressure sodium and incandescent lamps, mean lumen ratings are measured at 50% of rated lamp life.

P

• Phosphor - An inorganic chemical compound processed into a powder and deposited on the inner glass surface of fluorescent tubes and some mercury and metal halide lamp bulbs. Phosphors are designed to absorb short wavelength ultra-violet radiation and to transform and emit a visible light.
• Power Factor (PF) - A measure of the phase difference between voltage and current on alternating current circuits. Power factors can range from 0 to 1.0 with 1.0 being ideal. Power factor is sometimes expressed as a percent. A high power factor means that an electrical system or device is utilizing power efficiently. Incandescent lamps always have power factors close to 1.0 because they are simple "resistive" loads. The power factor of a discharge lamp system is determined by the ballast used. "High" power factor usually means a rating of 0.9 or greater. The power factor of core and coil "electromagnetic ballasts may be as low as 0.5 - 0.6.
• Preheat - A circuit used on fluorescent lamps wherein the electrodes are heated or warmed to a glow stage by an auxiliary switch or starter (can be a glow switch, thermal type, or a mechanical device like a push button) before the lamps are lighted. This system was used on the original fluorescent lamps and is still in use today.

R

• Rapid Start - A circuit designed to start lamps by continually heating or preheating the electrodes. This circuit is a modern version of the trigger start system and requires lamps designed for this circuit. In the rapid start two-lamp circuit, one end of each lamp is connected to a separate starting winding. The other end of each lamp is connected to a common winding.

S

• Switching - The life of a fluorescent lamp is affected by the number of times the lamp is started. Frequent switching results in shorter lamp life, while continuous operation will provide the longest lamp life. Most fluorescent lamps have a life ratings based on 3 hours per start.

U

• Underwriters Laboratories (UL) - A private organization which tests and lists electrical (and other) equipment for electrical and fire safety according to recognized UL and other standards. A UL listing is not an identification of overall performance. Lamps are not UL listed except for compact fluorescent lamp assemblies - those with screw bases and built-in ballasts.

V

• Voltage - A measurement of electromotive force or the pressure of electricity. This is analogous to the pressure in a waterline; i.e., pounds per square inch. The voltage of a circuit is the electrical pressure it gives. In an incandescent lamp, "voltage" designates the supply voltage to which the lamp should be connected. In other lamp types, it may refer to "operating voltage" of a lighted arc discharge lamp.

W

• Watt - Unit used to measure power consumption.