Don’t be fooled by dubious marketing!
Purchasing an LED fitting is fraught with pitfalls to unwitting buyers. LED brochures can be confusing and sometimes deliberately misleading in how they disclose lumen output. Without a thorough knowledge of the difference between effective lumens, nominal lumens and system lumens you may very well be caught out by technical specifications which are meaningless in the actual performance of a lighting fixture.
The difference between nominal lumens and system lumens in LED lighting refers to the amount of light that is produced by the LED light source (nominal lumens), and the amount of light that is available for use after taking into account various losses and factors (System lumens).
Nominal lumens refer to the amount of light that is produced by the LED light source when operated under ideal conditions, such as at a specific current and temperature. This number is usually specified by the manufacturer and is based on laboratory testing.
System lumens, on the other hand, take into account the various losses and factors that can reduce the amount of light available for use in a real-world lighting application. These losses can include things like
- Optical efficiency
- Thermal losses
- Electrical losses
- Manufacturing variables
System lumens provide a more accurate representation of the amount of light that is available for use in a specific lighting application and is a useful metric for comparing different LED lighting options and determining the appropriate light level for a given space.
When comparing luminaires, it is essential that a consumer understands the concept of nominal vs system lumens together with the way in which the driver is delivering power to the LED Chips. An overdriven LED Chipset may produce more lumens but at a reduced lifetime of the LEDs if the thermal increases aren’t managed.
You will have noticed how TV’s in the shop always look better than your home TV. This is purely related to the fact that the LED’s are being driven on a demo mode at higher power in the shop.
Effective Lumens are by far the most important aspect of a purchasing decision. Effective lumens are the lumens that will be delivered to the desired area of an application via the use of reflectors or directional optics.
A basic LED chip is manufactured with a standard 120-degree beam angle and hence if the light is not harnessed via an optic or reflector, a substantial loss of light may be wasted.
In summary, what this means is that the nominal lumens are of little benefit to the purchasers buying decision, while the system lumens, while more informative, should not be relied upon without analysing the effective lumens.
The challenge with most luminaires is that are commonly available at retail stores is that this detail is not provided and cannot be obtained.
Purchasing products without proper analysis is almost certainly going to result in a significantly higher operational costs and poor lighting.
