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Things you need to know in the world of Lighting

Published: November 24, 2010

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The meaning of IP rating

IP stands for Ingress Protection; the code refers to the resistance of a luminaire to the ingress of solid particle and water. The IP rating code has the format of: “IPxy”, where x and y are numbers varying from 0 to 8 which ultimately define the resistance to solid particles and water. Basically, the higher the number, the higher the protection rate, e.g. a luminaire in a bathroom in a bathroom which is close to a bath or shower has a typical rating of IP44; an outdoor up light has a typical minimum rating of IP65, while a swimming pool luminaire will have an IP Rating of IP68. Sometimes a third number may be included in the ingress protection code, indicating the resistance to impact, this is essential when luminaires are installed in areas where the resistance against accidental or vandalism or is of high importance (e.g. prisons, sport halls, certain schools and public areas etc.).

The difference between Dichroic and reflector bulbs

Every tungsten and tungsten halogen bulbs that are used in downlights, spotlights and similar luminaires use a reflector at the back of the light source that allows it to concentrate the light on a beam as opposed to diffuse it in all directions. Originally this reflector was created by coating the back of the lamp with an aluminium layer. However, because the tungsten and halogen lamps generate a lot of heat, aluminium reflectors focus and project this heat in the light beam. In most cases this would be seen as a disadvantage as the heat could potentially damage the illuminated surfaces in the long run. To get past this problem, dichroic reflectors were developed; these are designed with special material filters that reflect light but only a small percentage of the heat is generated, most of this is transmitted through the reflector to the back of the lamp. The result is that the heat generated in the beam of light is considerably lower and the side effects are contained. Make sure to allow enough clearance around the fitting in the void because the heat is dissipated in the void at the back of the luminaire. If this space is somewhat unavailable because of the proximity to a timber joist or insulation materials, the dichroic lamps should not be specified as the surfaces near the luminaire would be exposed to a serious fire risk.

The difference between transformers and ballasts

A transformer is an electrical or electronic component needed for low voltage bulbs in order for these to operate correctly. A common transformer for lighting applications converts the supply voltage from 230v (mains voltage in residential buildings throughout Europe) to 12v, which is the typical voltage required by tungsten halogen bulbs. A ballast or control gear performs a similar function of a transformer, but it also incorporates additional electrical and electronic components required by other types of bulbs in order for these to work properly. An element that is required by the linear, compact fluorescent lamps, metal halide lamps, cold cathode lamps and LEDs is a control gear. In terms of LEDs the control gear is more commonly called driver. The secondary or output voltage of the ballast varies depending on the specific type of lamp it is serving.

How to dim LED lights

LED lights can be dimmed providing the correct driver is installed and it is compatible with the lighting control system dimming the related circuit. Like with fluorescent lamps, there are various ways of dimming LEDs, the most common methods for dimming LEDs are 1-10v and DMX. Any dimming method requires an extra set of cables from the lighting control system to the LED driver in addition to the cables for the power supply (230v). Another requirement is a cable for the control signal (extra low voltage e.g. 1-10v, DMX bus, etc.). You must make sure that the correct wiring is provided before completing the installation works. Due to LED technology constantly evolving, new drivers are being developed that are capable of dimming via standard dimmers that are adopted for the incandescent or low voltage bulbs.

The correct way to wire LEDs

There is a right way and a wrong way to wire LEDs, it all depends on the type of LED you have. With the exception of LED replacement bulbs for halogen downlights (GU10 and GU5.3 lamp holders), which have been recently introduced into the market, all LEDs need a driver for their correct operation. A driver can feed either one LED luminaire or multiple LEDs. The vast majority of LEDs currently commercially available will have to be wired in series from the driver. This means that the “+” (red wire) of the driver will have to be connected to the “+” terminal (red wire) of the first LED, while the “-” terminal (black wire) of the first LED will have to be wired to the “+” (red wire) of the following LED, and so on until the last LED, which will have the “-” connected to the black wire of the driver. A series connection ensures that the current is kept constant across all LEDs. Remember that there are many different currents and loads, some of them are dimmable, but some are not. Always check that the driver adopted is compatible with the number and types of LEDs installed. Also, make sure that you check the product sheets for technical details of the LEDs.

A fire rated downlight

A fire rated downlight is a recessed luminaire that integrates a fire resistant can or ring of intumescent material in the portion of the luminaire concealed in the ceiling void. In case of fire in the space below the luminaire, the high temperature will cause the intumescent material of the can or ring to expand and fully seal the installation hole of the downlight (ceiling cut-out), thereby assuring the original fire resistance characteristics of the ceiling. An alternative to standard downlights and fire hoods (where these are required) is fire rated downlights, and although they may be more expensive than standard downlights, they generate a saving in the installation cost.

Make sure that you select good quality fire rated downlights as there are many cheap alternatives out there which should only be fitted with open bulbs or bulbs with a maximum rating of 35w. These can be a bad choice due to the fact that they not only limit the flexibility in the choice of the bulb, but may also cause a fire risk if you insert the wrong type of bulb. Do not assume that you can replace the bulb with a standard 50w version available from all retail shops. If you do this then it will cause the downlight to overheat, therefore creating a potential hazard in the years that follow when the bulb needs replacing.

The meaning of EE lighting

Energy Efficient Lighting is dictated by the light emission versus power consumption of various light bulbs.

In residential applications, a bulb is considered energy efficient when its luminous efficacy** is higher than 40 lumens per circuit watt*.

  • *A circuit-watt is the power consumed in lighting circuits by bulbs, their associated control gear and power correction equipment.
  • **Luminous efficacy is a measure of how effective a bulb is in transforming electricity into light. It is measured in lumens per watt and often referred to as “lamp efficacy”.

This has become more relevant to the domestic user due to Part L of the Building Regulations which came into force in April 2006. It states:

“Para 43: Reasonable provision would be to provide in the areas affected by the building work, fixed energy efficient light fittings that number not less than;

  • a) one per 25m² of dwelling floor area (excluding garages) or part there of OR
  • b) one per four fixed light fittings. Typical energy efficient lamps are linear and compact fluorescents, cold cathode, metal halide, sodium and some LEDs.”

For more useful information and advice please take a look at our Lighting Advice section.