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Commercial Lighting Retrofits Part I: Glossary

Posted by CLS Admin on October 22, 2013


Several common terms in the realm of commercial lighting are used frequently. In this post, we’ll define these terms for you.

Average Rated Life: A rating (in hours) that indicates when 50% of a specific group of lamps have failed.

Ballast:  The device that provides power to the lamp in a luminaire.

Ballast Factor: There are varying types of ballasts (low, normal, high) that can be utilized in a luminaire. These different levels impact the amount of lumens a fixture produces, in addition to the energy it emits.

Color Rendering Index (CRI): The ability of a light source to accurately render all frequencies of its color spectrum when compared to a perfect reference light of a similar type. When analyzing CRI on a cut sheet, the higher the CRI, the more quality the light source.

Compact Fluorescent (CFL): A fluorescent lamp that has been compressed into the size of a standard incandescent one. CFLs generally last 5-10 longer than incandescent lamps, while utilizing less energy.

Cut Sheet: The sheet that displays statistics, data and performance characteristics of a lamp, ballast or luminaire. It is a good idea to ask for product cut sheets when analyzing a lighting retrofit project.

Daylight Sensor: A special sensor – often attached to a light fixture – that turns off the fixture when daylight is present. These sensors are commonly used on parking lot lighting, exterior wall packs, and also interior lighting near windows.

Efficacy: A measure displayed in lumens per watt, that judges the overall efficiency of a luminaire.

Environmental Protection Agency (EPA): A federal organization currently making a large impact on lighting, due to its phasing out of energy-deficient technologies, including T12 fluorescents and high-watt forms of halogen and HID lamps and ballasts.

Foot Candle (FC): A unit of measure for the density of light as it reaches the surface. (1) FC = (1) lumen per square foot.

High Bay Lighting: A fixture used in many warehouse, storage or industrial applications, generally recognized for use above a 20-foot mounting height.

High Intensity Discharge (HID): Lamps that typically require ballasts for operation, but give off large amounts of light. Many HID lamps are now being replaced by LED and Induction solutions that are more energy efficient and exhibit 5-10 times the life of an HID.

High-Pressure Sodium (HPS): Similar to a Metal Halide in energy consumption, but commonly being replaced (See HID). HPS lamps tend to give off an orange tint and fail to bring out the natural color of the spaces they illuminate; for this reason, Metal Halides, LEDs, and Induction technologies are preferred aesthetically as well.

Induction: A very energy-efficient lighting technology with 5-15 times the lifespan of HID, and 30-80% more energy efficient than HID. Induction lights are often compared to LED because they operate with a driver, not a ballast. 

Initial Lumens: A number that represents the initial amount of light (measured in lumens) that a lamp projects. Lumens will decline throughout the burn life of a lamp, though excellent lamp specs have strong ‘lumen retention’.

Input Watts: Also referred to as “system wattage”, this term stands for the total number of watts that a specific luminaire emits. It is important to remember that input watts include the lamp and the ballast.

Instant Start Ballast: These ballasts are used for “instant on” applications at the flick of a switch. Instant Start Ballasts will have a longer life when fixtures are turned on and off minimally, as too many on/off cycles shorten the ballast’s life.

Kelvin Temperature: Color temperature is a Kelvin measurement that indicates the hue of a specific type of light source. Kelvin temperatures can have a profound impact on the appearance of the items that light illuminates.

Kilowatt Hour (kWh): A unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour (1h) of time. When analyzing kWh savings, hours of operation and potential wattage reduction are large factors.

Lamp: In lighting terms, it is important to remember that the correct term is lamps and not bulbs.

Light Emitting Diode (LED): Energy efficient lighting systems whose technologies are ever changing. Referred to as LEDs because of the small diodes which produce light. LEDS operate without the use of a ballast.

Lens: The protective covering of a fixture or luminaire. A lens can be prismatic (plastic), parabolic (cubes), or even tinted. Keeping lenses clean is important, as dirty lenses can reduce light output.

Lo-Bay Lighting: A luminaire designed for applications generally below a 15 to 20-foot mount height.

Lumen: A measurement judging the total amount of visible light in a specific beam or angle.

Lumen Depreciation: This refers to the amount and rate of lumens (light output) that a lamp will lose over its lifespan.

Lumen Maintenance: The ability of a lamp to maintain its light levels throughout its lifespan.  High-quality lamps have better lumen maintenance, and their light levels will not drop off dramatically over time.

Luminaire: A common term for a complete light fixture (lamp, ballast/driver, housing, etc.).

Metal Halide (MH): A common form of HID lamp that provides high levels of light, but exhibits poor energy efficiency. Many metal halides are now being replaced by fluorescent, LED and Induction solutions.

Occupancy Sensor: A mechanism that senses movement in order to determine when a lamp/fixture will illuminate. Occupancy sensors can be mounted directly to sensors or mounted separately and control multiple fixtures simultaneously. These sensors are an excellent tool to help boost energy efficiency.

Phosphors: The substances which are utilized to coat the inside of fluorescent lamps. These substances are a natural resource, whose price continues to increase dramatically.

Return on Investment (ROI): When calculating ROI for lighting, it is imperative to evaluate the cost of the project and the energy savings, in addition to the maintenance and material savings that result from installing extended-life technologies.

Spread: Refers to the coverage of light that a fixture illuminates in a given area. New technologies offer dramatic increases in the overall spread of light, in addition to increased lumen levels.

System Wattage: The total watts that a given fixture emits. Wattage cannot be judged merely by the wattage of a lamp, but must also include the wattage of the ballast (or driver in an LED).  For example a 400-watt HID normally has a system wattage of 450-460 watts, after factoring in the ballast.

T5/T5/T12: Types of fluorescent lamp technologies. T stands for ‘tubular’, while the number refers to the diameter of the lamp. Generally speaking, the smaller the number, the more energy efficient the lamp, and the newer the technology. T12 lamps are currently being phased out by the EPA, due to poor energy efficiency and large levels of mercury.

Throw: Refers to the outward reach or ‘throw’ of light that a fixture emits. LED wall packs tend to have greater forward throw than HID fixtures.

Troffer: A recessed luminaire with a trough-like design that contains lighting to illuminate a room or office space.

Utility Rebates: Many areas of the country offer lucrative utility rebate opportunities that can help offset a portion of the cost of lighting retrofit projects.

U-Lamp: A common type of lamp utilized in troffers, usually 2’x2’ fixtures in office/hallway settings.

Voltage: Facilities have varying voltage, ranging from 120 to 277 to 480 volts. It is extremely important to know voltage when it comes to lighting, because various ballasts and technologies are constructed for specific voltages.

Wall Pack: A type of lighting commonly used to illuminate the exterior of building. Converting to from HID to LED or Induction wall packs can lead to massive energy and maintenance savings, along with a large boost in lighting output.

Wattage Reduction: A term referring to the total watts saved when converting to a more energy-efficient lighting system.

In our next post on lighting retrofits, we’ll talk about LED, and the effect that the green movement has had on lighting technology…and of course, what it all means to you.

If you want to learn more about CLS’s commercial lighting retrofits, or all other CLS services, please call us at 800-548-3542.


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