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Dimming - Help! How do I choose dimmable LED lighting?

If you are looking for LED lighting and want to be able to dim the light intensity, do verify a few items before or during the purchase. Use the tips below to make the best choice of LED lamps or lighting.

  1. Choose a dimmable light source. On the packaging, a dimmable LED lamp or lighting is indicated by an icon. Only dimmable lamps can be dimmed with a phase control dimmer. A few examples of icons are given below.

  2. Select the desired colour temperature. The colour temperature defines the colour components that are dominant within the light that is radiated by the lamp or luminaire. Colour temperature is usually expressed in Kelvin (K) and is typically represented on the package as T[Kelvin]. Light that has a low colour temperature value is usually considered to be warmer. Light with a high colour temperature value is generally considered to be cooler. Warm light is ideal to create a cosy atmosphere during evenings or for relaxing. Cool light is useful to maintain or elevate concentration levels during an activity or, for example, to reduce mid-afternoon tiredness.

    If you wish to improve your well-being or performance levels, opt for the Human Centric Lighting (HCL) concept. In its most simple form, you can achieve this via LED lamps or luminaires with the tuneable white function. With the right controls, you can simulate the solar cycle; warm light in the morning, cool light with blue colours during the afternoon and then again, a warmer colour temperature with shades of orange and red as the afternoon transitions into the evening. The table below provides descriptions of a few colour temperature ranges. 

     Colour temperature range Feeling 
     2200 K to 3200 K  Very warm white, comparable to sunrise or sunset
     3500 K to 4500 K  Warm white, like one hour after sunrise
     5000 K to 6000 K  Daylight, midday sun, 5600 K is standard daylight
     6500 K to 8000 K  Cool white
     8000 K to 20000 K

     Very cool white - the blue colour component is very clear

  3. The electric wattage of the lamp. A phase control dimmer requires a minimum wattage (electric load) to work effectively. Ensure that the overall load is above the minimum electric load threshold. The wattage of a LED lamp is indicated on the pack.

    Note: Do not use the indication of the equivalent wattage for an incandescent lamp. This value is a way to guide people in the decision-process when replacing an incandescent lamp with a LED lamp. The equivalent wattage is not the effective electrical power of a LED lamp.


  4. Luminous flux This is the quantity of light that is emitted by a light source per time unit. It is expressed in lumen (lm). The greater the lumen value, the more light the lamp or luminaire emits.

    You can define the efficiency of a LED lamp by dividing the light current by its electric power. This is known as the luminous efficacy. A standard LED lamp, based on phosphorous technology, realises over 100 lumen per watt. The luminous efficacy of LED technology will become better over time.


  5. Choose the right fitting for the lamp base. If you wish to replace a traditional light source with a LED lamp, install the replacement lamp in a lamp base. You must select the right lamp fitting. There are a few variants, most of which are set out below:

    1. E27 is a large fitting with an Edison Screw thread, which allows you to screw the LED lamp into the lamp base. It is the most common lamp base in Europe. This fitting is also suitable for 230V AC.
    2. E14 is a narrower or smaller variant of the E27 fitting. A LED lamp with this fitting is screwed into a lamp base and is also suitable for 230V AC.
    3. G4 or GU4 lamp bases are usually used for decorative lighting. The G4 or GU4 lamp bases are characterised by two protruding contacts which are set 4 mm apart. The diameter of the contacts with the GU4 variant is slightly bigger. The lamp base is suitable for 12V DC.
    4. GU5.3 or MR16 fittings are usually used in environments which can be damp. The contacts are set 5.3 mm apart. The lamp base is suitable for a voltage of 12 V DC.
    5. GU10 is a fitting with a twist-lock connection. Light sources with this lamp base are usually used for spotlights. The contacts are set 10 mm apart. This lamp base is also suitable for 230V AC.

    Note: with LED luminaires, you can't usually replace the individual LED lamps. This is called integrated lighting.


  6. Colour Rendering Index. When the correct colour representation is important, select LED lamps with a colour rendering index (CRI or Ra) >80, or even better >90. The colour rendering index is a figure which indicates how colours are reproduced under the light from a specific lamp, compared with the light from a reference lamp. This metric is based on 14 colours and the maximum value of the index is 100. The colour red is the most difficult to reproduce naturally with a LED lamp. Halogen lamps have a CRI value of 100.


  7. European Union energy label. This label determines the efficiency, economy and how friendly LED lighting is towards the environment. Energy-efficiency for lighting is expressed on a scale of A++ (most efficient) to F (least efficient). LED lamps always fall into category A or better. Halogen lamps usually fall into categories C or D while incandescent lamps fall into E or F.