Frequently asked questions

  • What does an LED driver do?

    A driver is used to output the necessary constant current or voltage required for our LED product operation. Our constant current drivers operate at 350mA or 700mA depending on the product and require the luminaries to be wired in series. Our constant voltage drivers operate at 24V CV and this is used to operate our Contour LED strip light.

    Unlike traditional transformers used with halogen or LED retrofit lamps which convert mains 230V down to 12V, LED drivers allow for multiple dimming platforms such as Phase, 0-10V and DALI dimming which provide a smoother dimming performance with the addition of a ‘DRINT’.

    What is a DRINT?
    A DRINT is used in conjunction with a Constant Voltage Driver to enable smooth dimming via a 1-10V or Dali control.


  • Can my lights be controlled via tablet or phone?

    All controls systems offered come with their own SMART phone/tablet standalone applications which allow for more flexibility in controlling the systems.

    Our controls team will go through how they operate in person and cover all the features that they offer.

  • Do you sell control systems?

    Yes at John Cullen Lighting we sell lighting controls in house and they are supported by our specialist controls and technical team.

    We offer controls for various scenarios in the home from Single room solutions to whole home systems.

    Working alongside respected brands Lutron, Helvar, Rako and Forbes & Lomax we have a solution that will suit your requirements.

    For any enquiries please contact the customer service centre on 020 7371 9000 or email

  • What are LEDs?

    An LED is a semiconductor device that emits a visible light of a certain colour when an electrical charge is applied. They provide a very low heat source with a very long lamp life – around 50,000 hours.

    What defines the colour of the chip?
    Different material composition of LED Chip materials allow for a single colour from a huge spectrum of colours.

    Can an LED chip emit white light?

    How do we get white light for lighting?
    LED Chip manufacturers combine either a blue or UV emitting LED with a yellow phosphor.
    They can be used to introduce accents of colour or are ideal in situations where no heat is a requirement such as uplighters and floor washers where little fingers could be burnt. Linear versions can now be used for shelf lighting such as the Contour. They are also more energy efficient than standard halogen fittings which help in our efforts to be greener consumers.

    What are dimming LEDs?
    LED’s can be easily dimmed but require slightly different equipment and wiring. Most LED’s are 0-10v, this dimming requires a 0-10v dimmer module (which can fit in the JCL wall plates and dimmer plates) rather than a regular dimmer. Secondly 0-10v dimming requires a pair of cable to be connected to the dimmer module.
    Some LED drivers allow for the product to be dimmed on regular dimmers, however compatibility with the particular module needs to be checked.
    A DALI dimmer is the recommended dimmer for best performance. Click here to view our DALI dimmers.

  • What is the difference between current rated LEDs and voltage rated LEDs?

    Current rated LED’s require a constant current such as 350mA or 700mA, these LED products will also require a forward voltage that is specific for the particular LED being used in the product. A current rated LED needs to be specified with these two factors taken into consideration i.e. 4 x LED’s rated at 700mA with a voltage of 3.2vDC each will require a driver that produces 700mA with a minimum voltage of 12.8v. Current LED’s also need to be wired in SERIES.

    Voltage rated LED’s require a constant voltage such as 24vDC, these LED products will also consume a power (wattage) that is specific for the particular LED product being used. A voltage rated LED can be specified much the same as regular low voltage products i.e. having the required voltage (24vDC) and having a wattage output suitable to the amount of wattage consumption. Voltage rated LED’s also need to be wired in PARALLEL.

  • What are fibre optics and would you use them?

    These are created by a single light source located remotely in what is known as a light box. A special reflector focuses the light down individual glass fibres, usually enveloped in black sheaths, which emit light at their ends. They emit no ultra-violet rays and no heat. If side emitting, they have no black sheath and their entire length is lit. They are best used where a cool source of light is required e.g. walk over uplighters, water features, where maintenance is an issue e.g. swimming pool or in assessable spaces where very small light sources are required e.g. in cabinets, water spouts etc. and for the introduction of colour – a colour wheel can be used for a changing array of colours.

  • What is an IP rating?

    The system is used provide a guide to the degree of protection that a luminaire has against the ingress of solids and liquids.

    The First Number relates to solids and ranges from 0 –6.
    The ratings offer a logical progression from larger to smaller objects, so the lowest number (zero) indicates that there is no protection against touching live parts within the equipment. The most common rating for a light fitting intended for general interior use is IP20, which tells you that nothing larger than 12.5mm diameter can reach a live part when the equipment is fully assembled.

    The Second Number relates to liquids and ranges from 0 –9.
    Unlike the natural progression assigned to the ingress of solids, the second number relates to styles of liquid ingress; drips, sprays, splashes, jets and immersion.

  • What is a PIR?

    A PIR is a presence detector that can turn on a light circuit through the detection of a moving object. This can be used within bathrooms, porch ways etc.

  • What is the Colour Rendering Index?

    Colour rendition is the ability of a light source to accurately illuminate a colour compared to a reference source.

    How is this measured?
    The current method uses a reference pallet of 8 colours (R1-R8) called the Colour Rendering Index (CRI) developed by the CIE. Latterly an additional 6 (R9-R14) more saturated colours have been added but do not have to be referenced. CRI is stated in terms of a factor of 100 e.g. CRI80 or CRI 90 and is an average of colours tested (Ra).


    What is the future of Colour Rendition?
    The Lighting Industry has taken steps to move away from the CRI method as it is too limited and not a true representation of colour, especially with White LEDs.

    What is TM-30?
    The new TM-30 standard offers two metrics Colour Fidelity (Rf) and Colour Gamut (Rg). Colour fidelity is similar to CRI however references 100 swatches rather than 8.
    Colour Gamut is the average level of saturation relative to a reference illuminate (measured between 60 and 140).


  • What does the Correlated Colour Temperature mean in regards to LEDs?

    Correlated Colour Temperature (CCT) is reference to the colour of light emitted by a reference solid object (Black Body) as it gets hotter from red through to white. It is expressed in degrees Kelvin. The sequence of colours describes a curve within a colour space. This is shown in the diagram on the right.

    What do John Cullen Lighting Offer?
    The standard JCL colour offering is 2700K. However in our flexible strip range we also offer 2400K (a warmer colour).

    Why do we offer 2700K?
    Traditionally residential properties were lit with incandescent lamps which emit light with a colour of roughly 2700K.

    LED Colour Temperature


  • What is Colour Consistency in terms of lighting?

    Colour consistency in an index related to the light sources range of variation in chromaticity (colour) that can be picked up by the human eye.

    Why is this an issue for LED?
    During the manufacture of LED the colour, luminous flux and forward voltage can all vary. An LED is essentially grown and although accuracy of this has improved over time consistency is still an issue.

    How is colour difference measured?
    Colour difference is defined by a steps of MacAdamellipse. The scale is set by ANSI Chromaticity Standard. In short though the smaller the ellipse value (size) the smaller the colour difference.

  • How do LED chip manufactures manage variation?

    As there is no method today that offers 100% replication of a set specification, so the LED manufacturer measures each LED chip and separates them in separate groups (or bins) which are defined by each manufactures own coding system. In the diagram to the right 8Cis an example bin. At John Cullen Lighting we specify LED chips with the smallest bin possible to allow for consistency among the range.

  • What are the beam angles available with LEDs?

    The beam angles available are: Narrow (Under 20°), Medium (20°-35°) and Wide (35°-65°).


  • What is a Lumen?

    Lumens measure how much light you are getting from a bulb. More lumens means it’s a brighter light; fewer lumens means it’s a dimmer light.

    Lumens let you buy the amount of light you want. So when buying your new bulbs, think lumens, not watts.


  • What is Thermal Management?

    A common misconception is that LEDs do not generate heat. Although the beam emitted is cool they do, like any other light source, convert electric power in radiant heat. Lifetime of the LED Chip is directly linked to the operating temperature of the LED Chip (often expressed as Tjor Junction Temperature). Poor thermal management where the LED is operating above manufacture guidelines can also lead to colour shift.

    How does John Cullen manage the operating temperature?
    There are various methods of doing this, at John Cullen we use the body of the luminaire to draw heat away from the LED chip. We do this by carful material selection, considered produce development and by working alongside our subcontract partners who are able to virtually assess designs and physically test prototypes.

    How does this benefit you (our clients)?
    By fully testing our luminaries we are able to offer our clients information such as maximum ambient temperature the luminaire can operate in, so our clients can be assured of life time and colour consistency of their investment in our lighting.

  • What are Part L Building Regulations?

    Since April 2010, at least three in four light fittings in new and refurbished homes must be energy efficient (Part L Building Regulations). John Cullen’s range of energy efficient fittings are not only practical but also decorative and well-designed. They are ideal green solutions for anyone renovating a house.

    Our designers will always discuss regulation requirements but ultimately it is the client’s responsibility to ensure contact with their local authorities building control service inspector as they do vary from region to region, inspector to inspector.

  • Will the European lamp ban affect my John Cullen Fittings?

    Currently all John Cullen products fall within the current guidelines on efficiency – tungsten halogen bulbs are not included in the directive until 2018. However we do recommend transferring all of your lights to LED before the 2018 ban to spread the cost over time. LED lights do cost more however their value and lifetime worth is far less than halogen lights.

  • Which lamps are affected by the European Commission lamp phase out?

    The European Commission has ruled to stop the sale of certain types of inefficient lamps for household use in a series of dates up to 2016.  The lamps that this currently affects are those most commonly found within decorative fittings such as table lamps and pendants.

  • Do I need a burial sleeve with my uplighter?

    Sometimes it is advisable to use a burial sleeve. These should only be used when the integrity of the installation surface is unstable such as old plaster board or loose uneven ground.

  • Are your Drivers and Transformers compatible with Lutron, Crestron, iLight etc?

    John Cullen power supplies are compatible with all of the above systems, for advice on any other compatibilities please contact Sales on 020 7371 9000.