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Glossary of Lighting TermsAC (Alternating Current)Current which flows alternately in one direction and then the other.Accent LightingSimilar to task lighting but more directional focusing on particular subject matter.Acoustic ratedMaintains the ceiling acoustic properties in compliance with the Building Regulations Approved Document E – Resistance to the Passage of Sound.Aluminium ReflectorA reflective aluminium coating which reflects the heat from the lamp forward.Ambient LightingMost often called general lighting.BallastDevices used with fluorescent or high intensity discharge (HID) lamps. They provide sufficient voltage to ignite and operate the lamp. Once the lamp is ignited the ballast will limit the current.Candela (CD)The measure of luminous intensity of a source in a given direction.Colour RenderingThe ability of a light source to reveal the colours of an object. Measured on the colour rendering index (CRI), and measured in Ra. Ranges from 0 to 100 with the higher the number the better the result.Colour TemperatureThe temperature of lamps measured in degrees Kelvin and defines the shade of white light. It is a simplified way to characterise properties of differing light sources.
Constant CurrentA circuit in which the current remains constant but the voltage may vary.Constant VoltageA circuit in which the voltage remains constant but the current may vary.Control GearUsed to start most fluorescent or HID lamps. Control gear may include a ballast, igniters or transformers.DC (Direct Current)An electric current that moves in one direction with constant strength.Dichroic ReflectorA reflective lamp that allows most of the heat from the lamp to pass through the reflector. These are considered ‘cool beam’.DimmerA device in an installation used for varying the brightness of lamps.Direct LightingLuminaires with a light distribution which achieves 90 – 100% of luminous flux and reaches the working plane directly.Discharge LampsLight is produced either directly or by the excitation of phosphors by electric discharge through a mixture of gas and metal vapour, i.e. fluorescent tubes.DownlightA ceiling fitting which projects the illumination forward (down).FilamentA tungsten wire which emits light and heat once a current runs through it.Fire RatedMaintains the ceiling fire barrier integrity in compliance with the Building Regulations B – Fire Safety.HID LampHigh intensity discharge lamps have a longer life and provide more light (lumens) per watt than most other light sources.High frequency electronic control gear (HF)Device used to generally operate fl uorescent tubes at a high frequency 30-60 KHz compared to mains supply 50 Hz. This results in a higher quality of light and reduces running costs. These may also be used in conjunction with HID lamps.IgnitorRequired when mains supply voltage cannot directly start a lamp. Commonly found within fittings which use the following lamps, metal halide and high-pressure discharge lamps.IlluminanceRefers to the amount of light falling onto an area (lux). 500 lux is required within an office environment. The sun produces 1,200,000 lux and the moon reflects from the sun 3 lux.Indirect LightingLight which is reflected onto a secondary source, generally ceilings and walls are the primary source.Ingress Protection (IP)This denotes the amount of protection a product has against moisture, and or foreign bodies, tools etc. It uses 2 digits to denote the rating.Intumescent materialMaterial used within Fire Rated Downlights and Gaskets, it expands to form a fire rated barrier once exposed to fire.Kilowatt (kW)Measure of electrical power which equals 1000 Watts.LampAn artificial light source used in conjunction with appropriate fittings to create a light effect.Lamp LifeThis is an average measurement of lamp life. E.g., if 20 lamps are tested, the average lamp life is when the 10th fails.LED (Light-emitting diode)Small semiconductor device that emits light. The advantages of LED’s include, low operation costs, compact size and long life.Light Output Ratio (LOR)The ratio of light emitted by a luminaire to the total light output of the lamps it contains. This will always be less than 1.Extra Low VoltageVoltages under 50V AC.LumenRefer to Luminous Flux.Lumens per Watt (lm/W)A term relating to the efficiency of light output Vs Wattage used.Below are some basic results, this will vary due to different lamps used and also the combination of Lamp and Ballast.
LuminaireA fitting which emits light by use of connecting a lamp to the required power supplyLuminaire-lumens per circuit wattLuminaire efficiency factor given by LOR x (total bare lamp flux in the luminaire/circuit Watts).Luminous FluxThe total light output emitted by a light source or received by a surface. Commonly known as lumens.Unit: lumens lm. LuxUnit of luminance, equal to one lumen per square metre.Mains VoltageFittings/Lamps which can be powered directly from mains power supply, generally this is 240V AC.TransformerSteps voltage up or down. They are available as Magnetic and Electronic versions.WattageA measure of electrical power consumed by a lamp or lighting fixture.Watts = Volts x Amps, (P = V x I). Working planeA surface where tasks are performed. |