Everything you need to know about LED lighting

This time we focus on the topic of LED lighting, luminaire power, luminous efficiency and color temperature. 

  1. LUMINAIRE RATED POWER
    This is the total power of the luminaire that we can measure on the power cord, including the light source and power supply. Fluorescent, sodium, metal-halide and other luminaires made in non-LED technology always have the power of the light source indicated, not the entire housing. A typical office raster had the power of 4 fluorescent lamps 18W (72W) plus a power supply (ballast) with a power of about 18W, which gave the rated power of the luminaire 90W. A typical LED panel that is a replacement for such a raster has a rated power (including the power supply) of 35-40W.

    It should be noted whether the supplier uses the rated power of the luminaire or only the light source itself. Moreover, there are many power supplies available on the market with a variable power configuration
    (you can easily turn up the LEDs to give more light while consuming more energy), so the supplier should inform us about the real rated power of the equipment ultimately ordered.

  2. RATED LUMINOUS FLUX
    Rated luminous flux: determines how much light the LED luminaire gives. It is worth distinguishing between the luminous flux of the diode (light source) and the entire luminaire after losses, which result from the efficiency of the diode, diffuser, housing and power supply.

    The range of losses that can be expected from the individual elements of the housing:

    – diffuser: 10 – 50%,
    – housing: 5 – 20%, – power supply: 6 – 20%.

  3. LIGHT EFFECTIVENESS
    It is the ratio of the rated luminous flux to the rated power of the luminaire, simplifying: flux after loss, compared to real power. If the diode itself has a luminous efficacy of 160lm / W with the nominal luminous flux of the light source 5280lm, we can expect that the rated luminous flux of the luminaire will be 4000lm with an efficiency of 121lm / W.
    No. Quantity Label Luminaire (lm)
    Industrial: LED; 5.0; Max; Version
    1 86 surface mounted; 5000K; 185

    The best way to verify the results is to check the results in a lighting design made in the Dialux / Relux program (example above: lamp flux 5000lm / lamp power 66W = efficiency 185lm / W) and a document confirming the correct performance of lighting measurements.

  4. CRI/RA INDICATOR
    Color Rendering Index – in short, it is a value on a scale of 0-100 describing the quality of colors perceived by the human eye in the case of lighting any scene with a given light source. The closer this value is to 100, the more natural a person perceives colors. The maximum CRI has incandescent sources and the sun. Fluorescent lamps can be in the range of 65-90. LEDs from renowned manufacturers currently used in lighting have a CRI between 70-95. In practice, the difference in CRI between LEDs of the second and third type is insignificant today. Diodes with a two-component phosphor achieve CRI values ​​of 90-95, classic diodes with one phosphor achieve a CRI of 80-85. It is worth mentioning that for human perception, the CRI value of at least 80 is a value that is completely sufficient for most lighting applications.It is worth mentioning that for human perception, the CRI value of at least 80 is a value that is completely sufficient for most lighting applications.A CRI above 95 is needed where the highest accuracy in color reproduction is needed (museums, art galleries, surgery rooms).

  5. COMPARISON OF SOURCE WITH THE SAME COLOR TEMPERATURE BUT DIFFERENT CRI VALUES
    Ideal for industrial and heavy-duty applications such as LEDs and lenses, they are selected at 3 SDCM, which gives us a guarantee of uniform light throughout the warranty period.
    Due to the participation of different wavelengths in the radiation spectrum, we can get the impression that the luminaires with the same CRI and color temperature have a different shade or even the color of light.

  6. CORRELATED COLOR TEMPERATURE (CCT) 
    The shade of the light emitted from a given source is described by the color temperature, the value of which results from the blackbody theory. This theory describes an object that, when heated to an appropriate temperature, expressed in Kelvin, emits light that can be perceived as a warm color (<3300 K), a neutral color (between 3300 K and 5000 K) or a cold color (> 5000 K).A perfect example is an ordinary light bulb, which has a color temperature of around 2700K (warm white) because its filament is heated to this temperature. As in the case of power, it is not enough to specify the temperature of the diode itself (which is a popular practice), and the color temperature should also take into account the influence of the diffuser, optics (lenses) or reflector on its final value.

    Payback Period: This is by far the most important measure.
    Instead of using a simple price measure that tells us little in the context of the next years of using LED lighting, it is worth using a parameter that tells about the scale of savings that we will achieve.

    In addition to the price, the payback period also includes the cost of energy (kWh / PLN), the time of using the lighting (number of hours per day, number of days in a year) as well as the number and power of luminaires. To get the correct payback period, you should:

  • make an audit of the current lighting (can be performed as part of an energy audit)
  • prepare a project (based on clearly defined, predetermined guidelines regarding: uniformity, mounting height, intensity in a room, detailed specification)
  • prepare an offer and finally calculate the payback period

    Only after completing the above steps can a reliable return on investment be calculated. Any attempt to shorten this process will give us results that are far from the real thing. The most common mistake is to compare the energy consumption based on a new project with the current energy consumption, which in many buildings deviates (in minus) from the norm. You can then come to the wrong conclusions that LED lighting will give us little savings.

On the topic of luminaires, see our offer of lighting poles!