We try to keep our product descriptions as simple and straight forward as possible but from time to time those industry comments and words creep in, so we thought we would help you by adding this glossary of terms and any recurring questions we think you may have when choosing your lighting. We hope this helps but if you are unsure about ANYTHING Please, don’t hesitate to call us, we love talking to and helping our customers…


AC (~)

Alternating Current, as found in the mains power supply.

Accent Lighting

Also commonly called display or highlighting. Accent lighting is typically at a higher intensity to emphasise an object or area. A Ratio of 3:1 versus ambient lighting is recommended for accent lighting to be noticeable.

Ambient Temperature (Ta)

The air temperature surrounding the luminaire or component. LED luminaires are particularly temperature sensitive with excess temperature affecting performance and rated life. See also Junction Temperature.

Amenity Lighting

Decorative lighting intended to enhance the appearance of a building or an outdoor area. Can include Mood lighting of hotels, bars, restaurants and other leisure activities.

IT DOES NOT INCLUDE lighting to provide general illumination or circulation or building lighting.

Ampere (Amp)

The unit for measuring rate of flow of electrical current:

Current (Amps) = Power (Watts) / Voltage (Volts)

Asymmetric Light Distribution

Where the distribution of light from a luminaire is not even in one plane. Common in display luminaires such as ‘wall washers’ where light is directed intentionally in one direction.


The ‘swivel’ angle, as used in floodlighting or display lighting designs and installations.

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In a fluorescent lighting system, regulates the current to the lamp and provides sufficient voltage to start the lamp.

Ballast Lumen Factor (BLF)

The proportion of light emitted by a luminaire when in emergency mode, usually powered by batteries, compared to the normal mains powered output. BLF figures can be less than 10% or 0.1 as emergency lighting levels are far lower than those required for normal lighting.

Bathroom Zones

Bathroom lighting needs to be functional and safe. It is divided into zones where only suitable light fittings should be used.

·  ZONE 0 is inside the bath or shower. Any fitting used in this zone must be low voltage, max 12v) and rated at least IP67 which is immersion proof.

·  ZONE 1 is the area above the bath to a height of 25m from floor. In this zone a minimum rating of IP65 is required.

·  ZONE 2 is the area stretching 6m outside the perimeter of the bath and the area between zone 1 and the ceiling upto 3m. Also the area around the wash basin, within a 60cm radius of any tap. In this zone a minimum rating of IP44 is required.

Bayonet Cap

A common lamp cap found on many lamps in domestic use in the UK. The lamp cap has two small pins that protrude from the base, these are inserted into the lamp holder and lock the lamp in place as it is rotated. B15 and B22 are the most common types.

Beam Angle

Not, as commonly thought, the width or angle of light emitted from the lamp/luminaire. Instead, the point where intensity reaches 50% of the peak value.


The method used for sorting LED chips during manufacture, typically based on output and colour temperature. The latest manufacturing techniques employed by leading chip manufacturers are yielding chips that no longer require binning as the consistency and tolerance is greatly improved.


Whilst brightness is what people see and react to, luminance is the actual surface brightness of an object and is measured in candelas per metre2.

British Building Regulations

Various building regulations, usually referred to as the approved regulation document letter, exist not only to ensure that buildings are constructed safely but also that materials or equipment installed is of the current requirement. Various products comply with:

·  DOCUMENT B – Fire Safety

·  DOCUMENT C – Resistance to contaminants and moisture

·  DOCUMENT E – Resistance to sound

·  DOCUMENT L – Conservation of fuel and power

British Standards Institute (BSI)

The national standards organisation is responsible for publication of standards that ensure products are constructed and operated safely and efficiently. Standards are prefixed with BS for a British Standard, EN for a European Standard and BS EN where the European Standard has been adopted as a British Standard.

All BG Electrical products are conceived and produced to comply with the relevant standards, key standards for the LED range include:

·  EN 60598-1 – Luminaires – General requirements

·  EN 55015 – Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment

·  EN 61547 – Equipment for general lighting purposes – EMC immunity requirements

·  EN 61000-3-2 – Electromagnetic compatibility (EMC) – Part 3-2: Limits – Limits for Harmonic current emissions

·  EN 62471 – Photobiological safety of lamps and lamp systems

·  EN 62560 – Self-ballasted LED-lamps for general lighting services by voltage 50 V. Safety specifications

·  EN 61347-1 – Lamp control gear – Part 1: General and safety requirements

·  2002/96/EC – Waste Electrical & Electronic Equipment (WEEE)

·  2002/95/EC – Restriction of the use of certain Hazardous Substances in EEE (RoHS)

·  (EC) No 1907/2006 – The Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH)

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The SI unit for luminous intensity.


The European Community mark ‘Conformité Européenne’ signifying all relevant standards and directives have been complied with.


The European body responsible for the preparation of other (Non- Electrical) standards in Europe.


The European body responsible for the preparation of electrical standards in Europe.


Critical Fusion Frequency – 60-100Hz


Compact Fluorescent Lamp.


The LED Chip is the light source.

Chip on board

Is the latest generation of LED light source. Many small LED chips are incorporated in one packaged light source to provide a more efficient solution that can be combined with a lens and/or reflector to maximise the light distribution.

Class I

Class one luminaires require an Earth connection for electrical safety.

Class II

Colour Appearance

Term used to describe how “white” the emitted light looks. Commonly, warm, neutral, cool and daylight are used to categorise.

Colour Rendering Index (CRI)

A measure of the degree of colour shift objects undergo when illuminated by the light source as compared with those same objects when illuminated by a reference source of comparable colour temperature. The reference source has a CRI of 100. Natural light (daylight) would also be 100.

Correlated Colour Temperature (CCT)

The description used to describe the effect of heating an object until it glows incandescently, the emitted radiation, and apparent colour, changes proportional to the temperature; easily envisioned when considering hot metal in a forge that glows red, then orange, and then white as the temperature increases. Measured in degrees Kelvin.

Corridor Function

Refers to luminaires that when not required to emit 100% light output, switch to 10% output. This ‘standby mode’ allows the luminaire to provide a low level of illumination for a feeling of security so the area is not totally dark. Upon sensing movement the output automatically and instantly switches to 100%. This is particularly useful in circulation areas such as corridors and stairwells.

Cut Off Angle

Small downlights can appear too intense and very glary, so cut off angle illustrates the point where the light source can’t be seen.

Cut-out Dimension

Size of hole required to install luminaire.

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Stands for Digital Addressable Lighting Interface, where each driver and control component such as a sensor or switch has a unique address on the lighting installation. This allows for infinite configuration of the lighting installation and flexibility in the future.


Many Luceco luminaires are available as a dimmable version option. Generally this requires a different driver to the standard fixed output driver and also may require additional wiring on site to control the dimming function.

Direct Lighting

Luminous flux that reaches the working plane without being reflected from walls/ceiling or within the luminaire itself.

Display Lighting

Comprises lighting intended to highlight displays of exhibits, merchandise and other associated uses. Spot projector for shops, theatres, galleries and studios.


Light Output in a downward direction.


Downward Light Output Ratio is the percentage of luminous flux output from the lamp/luminaire that is emitted in the 180° angle below horizontal.

Double Insulation

Also known as Class II, where two levels of insulation (such as two cable coverings) protect live parts from exposure.


The driver is often the critical component in a LED luminaire or lamp, more so than the LED chip itself. The driver has to be matched to the power requirements of the LED chip and also have quality components. Drivers that use inferior components such as capacitors, will fail before the rated life of the LED chip, reducing the claimed life by as much as 50%.

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Edge Lit

This means that the LED chips are positioned vertically around the perimeter of the panel. This provides an excellent uniformly illuminated panel in a fixture as slim as 8mm.

Edison Screw

A lamp cap that features a screw thread for a positive fit in the lampholder, common sizes include E15 and E27.


Is the measure of how efficient a lamp or luminaire is. This can be expressed as (source) lumens per Watt, which is the normal measure for lamps. Or, as luminaire lumens per circuit Watt, which is common for luminaires. The figure for luminaires will also include the LOR of the luminaire in the calculation.

Efficient White Light Units

Products that are specifically designed to provide efficient, high quality illumination.


Extra Low Voltage.

Emergency Lighting

Allows the safe evacuation of an area in the event of a mains failure. The positioning and number of emergency lighting luminaires is detailed in British Standard BS5266. It is vital that emergency lighting is maintained correctly to ensure batteries are conditioned, so it operates when required.

Escape Route

Emergency lighting along a route such as a corridor or staircase to enable safe evacuation.


European Product Registration Database for Energy Labelling.

Exterior Area Lighting

Covers all exterior lighting which is intended to provide downward light onto horizontal or near horizontal surfaces, including roadways, carparks, paths, stairs, ramps, gardens and other open surfaces.

Exterior Floodlighting

Lighting that is intended to light vertical or near vertical surfaces including floodlighting of buildings, monuments and statues.


F Mark

Denotes luminaires that can be mounted on to flammable surfaces as the heat generated will not cause any combustion. Previously luminaires that were suitable had to be marked, but the most recent standard requires only luminaires that don’t comply to be marked.

Fire Rated

Where a luminaire is installed in a fire barrier such as into a ceiling, it must have the same resistance to fire rating as that barrier. For domestic installations there are ratings of 30, 60 and 90mins and each limit must be tested for. A 90min rated product does not automatically comply with 30 or 60mins due to the different ceiling constructions. Non-domestic applications usually have a fire-resistant barrier such as a concrete slab between floors and so do not have the requirement in many cases.

Flux/Luminous Flux

Luminous flux is the measure of the perceived power of light, adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light and is expressed in Lumens (lm).

Frequency (Hz)

Rate that the power supply wavelength fluctuates and is measured in Hertz.

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General Lighting

Lighting to illuminate the general area without supplementary task lighting.


Difficulty seeing in the presence of bright light such as direct or reflected sunlight or artificial light. Proportional to the background illuminance; a good example is a car headlight that creates glare at night time but not during the day.


A photometric device for testing the luminous intensity distribution, efficiency, and luminous flux of luminaires.


Heat Sink

A part of the thermal system that conducts or convects heat away from sensitive components, such as LEDs and electronics.


High Efficiency Lighting Unit.

Hertz (Hz)

The unit to measure frequency.

HID Lamp

High Intensity Discharge Lamp – type of electrical gas discharge lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube.

High Power LED

A high power LED, sometimes referred to as a power LED, is one that is driven at a current of 350mA or higher.

High Risk Area

A requirement in emergency lighting where a process may require safe shut down or an increased hazard. Higher emergency lighting levels are therefore required local to the risk.



International Electrotechnical Commission.


Illuminating Engineering Society, an American organisation that provides standards and recommendations. Photometric data files are commonly in .ies file format.


The intensity of light falling on a surface area. If the area is measured in square feet, the unit of illuminance is footcandles (fc). If measured in square meters, the unit of illuminance is lux (lx).

Indirect Lighting

Lighting that is reflected by room surfaces or within the luminaire before falling on to the working area. As a result of reflection it is often lower in intensity and glare.

Ingress Protection (IP) Rating

A system that identifies the protection that a lamp or luminaire has against solid objects and water. The first digit being solid object protection and the second one resistance to water.

Protection against solid foreign objects Protection against harmful ingress of water
IP Tests IP Tests
0 No Protection 0 No Protection
1 Full penetration of 50mm diameter of sphere not allowed. Contact with hazardous parts not permitted. 1 Protected against vertically falling drops of water.
2 Full penetration of 12.5mm diameter of sphere not allowed. The jointed test finger shall have adequate clearance from hazardous parts. 2 Protected against vertically falling drops of water with enclosure tilted 15° from the vertical.
3 The access probe of 2.5mm diameter shall not penetrate. 3 Protected against sprays to 60°from the vertical.
4 The access probe of 1mm diameter shall not penetrate. 4 Protected against water splashed from all directions – limited ingress permitted.
5 Limited ingress of dust permitted (no harmful deposit). 5 Protected against low pressure jets of water from all directions – limited ingress permitted.
6 No ingress of dust. 6 Protected against strong jets of water e.g. for use on ship decks – limited ingress permitted.
    7 Protected against the effects of immersion between 150mm and 1m.
    8 Protected against continuous submersion at a specified depth.

Initial Lumens

The output up to 100 hours use.

Inrush Current

Components such as drivers can have high inrush currents for milliseconds due to the use of capacitors; this should be considered when specifying switching and breaker ratings.

Integrating Sphere

A device used for a variety of optical, photometric, or radiometric measurements.


Internet of Things – a system of physical things embedded with sensors, software, electronics and connectivity to allow it to perform better by exchanging information with other connected devices.
e.g. NEST smart home device, smart fridge, DHL tracking and monitoring.

Isolux Diagram

A graphical representation of common illuminance levels to show lighting levels over a calculated area.



The point at which the positive and negative conductors meet in a LED.

Junction Temperature

A critical consideration in LED lamp or luminaire design. For every 10°C that the junction temperature exceeds the optimum figure, life of the LED chip is reduced by 50%. Overrunning LEDs by operating at higher amps will cause this to happen.



The SI unit used to measure and denote colour temperature, degrees Kelvin.


Kilo-Watt-hour is the typical billing unit for electricity costs and represents 1kW of power over a 1 hour duration.



A lamp converts electrical power into light and sometimes they are called “bulbs” due to the traditional lamp shape.


Light Emitting Diode. An LED is a solid-state semiconductor device that converts electrical energy directly into light. On its most basic level, the semiconductor is comprised of two regions. The p-region contains positive electrical charges while the n-region contains negative electrical charges. When voltage is applied and current begins to flow, the electrons move across the n-region into the p-region. The process of an electron moving through the p-n junction releases energy. The dispersion of this energy produces photons with visible wavelengths. Most LEDs emit a blue light as that is the most efficient format, a phosphor coating turns the blue light into the white light required.

LED Rated Life

LED chip figures are quoted by the chip manufacturer and in some cases these are not translated when the chip is used in a luminaire, where it can run hotter. As heat affects the LED chip, the life can be reduced dramatically.

Light Output Ratio (LOR)

Percentage difference between the luminous flux emitted by the light source and the amount emitted from the fixture it is housed in.


Luminaire lumens per circuit Watt is total lumens emitted from the luminaire (source lumens x LOR) / total luminaire wattage including control gear.


Light Output Ratio – ratio of the total light emitted by the unit to that emitted by the bare lamp(s).

Lumen Depreciation

Describes the percentage of light lost relative to the initial lumen output. LEDs depreciate at a far slower rate than other light sources, so a LED with a lower initial output can quickly provide more light than a faster depreciating light source.

Lumen Maintenance

The luminous flux at a given time in the life of the LED. This is expressed as a percentage of the intial luminous flux. This usually determines the rated life of a LED product as the point it should be replaced.

Lumens (lm)

The international (SI) unit of luminous flux. Lumens will become the measure of light output as Watts cannot be a reliable measure due to the different efficacy of light sources and the ongoing improvement in LED efficacy through development.


A lighting fixture complete with installed lamps or light source.

Luminaire Lumens (Llm)

The light emitted from a luminaire will typically differ from the source lumens. This can be from losses within the luminaire housing. Also it is common for LEDs to operate at a higher temperature in the luminaire; this can lead to the output increasing when compared to the source (chip) lumens. Luminaire lumens = source lumens x LOR

Luminaire Wattage

Total wattage of LED and any control gear included.


The surface brightness of an object measured in candelas/m².

Luminous Efficiency

The percentage of total lamp lumens that a lighting fixture, luminaire, or system emits, minus any blocked or wasted light.

Lux (lx)

The SI (International) unit of illuminance, or luminous flux incident on a unit area, frequently defined as one lumen per square metre (lm/m²).


Maintained Emergency

A Maintained emergency luminaire is able to be used for both general and emergency lighting, a second live cable allows it to be turned on/off as required and detect a mains power circuit failure.

Metal Halide (MH)

Lamps that produce light by an electric arc through gaseous mixtures of vaporized mercury and metal halides (compounds of metal with bromide and iodine).

Microwave Sensor

The sensor emits low power microwaves that form a pattern in the area covered. When movement disturbs the pattern, movement is detected and the sensor turns the light source on. Microwave sensors are only recommended for indoor use as they are sensitive to movement and not heat.

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Non-Maintained Emergency

A Non-Maintained emergency luminaire ONLY operates in emergency mode and is not for general lighting.


Open Area

Lighting also called ‘anti-panic’ area lighting is emergency lighting where not a high risk area or escape route.

Organic Light-Emitting Diodes (OLED)

Organic light-emitting diodes (OLEDs) are based on organic (carbon based) materials. In contrast to LEDs, which are small point sources, OLEDs are made in sheets which provide a diffuse area light source. OLED technology is developing rapidly and is increasingly used in display applications such as mobile phones and PDA screens. However, OLEDs are still some years away from becoming a practical general illumination source.



Protected Extra Low Voltage.


A coating of phosphorescent material which photons from a royal blue LED pass through, causing those photons to exit with a different colour property.

Photometric Data

A generic term for light output and distribution data for a lamp or luminaire and can be shown in many formats. Generally data is produced following the IES or ELUMDAT method to provide a .ies or .ldt computer file for use in a lighting design program such as Relux or Dialux. Photometric data is available for a wide selection of BG Electrical luminaires from our downloads page.


Passive Infra Red sensors detect movement by the change in background temperature as body heat moves into the area.

Power Factor

The active power divided by the apparent power (i.e., product of the rms input voltage and rms input current of a driver).

Power Factor Correction

In an electronic device, such as a LED lighting fixture, a system of inductors, capacitors, or voltage converters to adjust the power factor of electronic devices toward the ideal power factor of 1.0.


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Registration, Evaluation, Authorisation and restriction of CHemicals. The EU Directive covering the use of hazardous chemicals used in the maufacturing process and supply of products.

Remote LED Driver

Some LED lights in our range use a remote plug and play LED driver, that offers flexibility to select either a fixed output, dimmable driver or emergency versions, with all being interchangeable.

Remote Phosphor

A phosphor conversion technique in which photons from a royal blue LED pass through a phosphor material that is not attached to the LED chip.


Restriction of Hazardous Substances (2002/95/EC) is an article 95 directive, meaning it is across all European Union member states. Since July 1st 2006 the use of hazardous substances is restricted in products, to prevent environmental harm. The prohibited substances are Lead, Mercury, Cadmium, Hexavalent Chromium, Polybrominated Biphenyls and Polybrominated Diphenyl Ethers. All relevant Luceco products comply.



The most common type of Emergency lighting luminaire, where all of the components are within one Emergency luminaire. This can include gear boxes connected directly to individual luminaires but outside the main luminaire housing. If within 1m, it is classed as self-contained.


Safety Extra Low Voltage – less than or equal to 60VDC.


Surface-mount LEDs.

Source Lumens (lm)

Source or Chip lumens is the output of the LED array and does not allow for any reduction or increase from the luminaire.

Source Wattage

Could also be referred to as chip wattage – for the LED only and does not include any control gear.


Task Lighting

Localised lighting intended for a specific task.

Thermal Management

Controlling the operating temperature of the product through design, examples include heat sinks and improved airflow.


Temporal Light Artefact – Flickering light repeatedly brightened and dim.

Two types

Visible Flicker (low frequency)

Invisible (stroboscopic effect)

TLA Measurement

Flicker Index (FI)
Percent Flicker (MD) modulation depth


Fire Retardant Thermoplastic. Diffusers used on emergency lighting luminaires and also certain applications where the percentage of diffusers against the ceiling surface area is calculated must be of Tp(a) material.


Diffusers are acceptable for the majority of applications, following the 2013 revision of the building regulations. Approved Document B – Fire Safety: Volume: Building other than dwellinghouses, includes further detail.



Light Output in an upward direction.


Upward Light Output Ratio, the percentage of light emitted from a lamp or luminaire above the horizontal plane.

Ultraviolet (UV)

Electromagnetic radiation with wavelength shorter than that of visible light. LEDs emit minimal UV and therefore do not attract insects or potentially damage sensitive materials illuminated by them.

Utilisation Factor

In lighting design, the proportion of the luminous flux emitted by a light source, which reaches the working plane.



The term used to describe the electrical potential difference between oppositely charged conductors.



The power consumed by the LED.