The test results are in: ETC LEDs are built to last!
Date Posted: 4/21/2017
When evaluating a new technology such as LED fixtures, one of the primary concerns people often have is, “How long is my investment going to last?” Unlike traditional tungsten fixtures, LED fixtures consist of many electronic components that could potentially fail over time. While choosing a manufacturer that you trust will always be a recommended starting point, there are some metrics out there that can help with some of this analysis.
What is L70?
One such rating is called L70 and it is a measurement of LED lumen maintenance over time. LEDs lose output the more they are used. While ETC compensates for thermal droop that happens in our LED fixtures as they warm up (which allows our fixtures to maintain output and color consistency during use,) there are also lumen changes that happens over longer periods of time. This is what the L70 rating is for, it tells you how many hours of use - at full and at an ambient temp of 25C - an LED fixture can operate before it only outputs 70% of its original brightness.
How is L70 calculated?
Almost all fixtures on the market, including most of ETC’s LED fixtures, calculate their L70 rating based on information given to them by the LED manufacturers about how the LEDs can be powered and cooled and what ratings they will achieve based on those conditions. However, the LED manufacturers usually don’t have this information for all of the colors used because it is a lengthy and expensive test. That means they only test the LEDs that have really high volumes or LEDs used in illumination applications. It is often not typical for colors like cyan, PC-amber, etc. So many of the L70 ratings that you see are calculations based on partial data about the LEDs in use, not actual measurements of the fixtures themselves.
So, what’s with the new ratings on some of ETC’s fixtures?
The first generation of ETC LED fixtures operated well below maximum drive currents for the LEDs being used. Because of that, we were confident in setting an L70 rating of 50,000 hours. When we developed the Series 2 and ColorSource fixtures, we increased the drive current to improve output, though we were still under the manufacturer’s maximum ratings. In doing so, we changed the conditions for those LEDs. Because of the limited data available for the LEDs in use, ETC made calculations that were conservative as not to over promise and under perform.
At the time of release, those products carried an L70 rating of 20,000 hours. Since then, ETC decided to do what’s called an LM-84 test on the actual fixtures to determine an accurate rating. This test is run by an independent laboratory and consists of 10,000 hours of continuous output at 100%. The results of that test are used in a mathematical model to calculate the L70 rating. After this first round of testing, the results showed that the S4 LED Series 2 Lustr and the ColorSource Spot fixtures have a tested L70 rating of 54,000 hours. Tests for other ETC fixtures are currently under way.