The heat is on—and we’re doing something about it..

All electronic components generate heat, and all depend on effective heat dissipation technologies to insure proper operation and fully-rated life. As shown on the charts below, both lumen output (or “relative luminous flux”) and long LED life are directly related to the LED junction temperature (T_J).

Concept #1:  LM-80 (manufacturer reported longevity)

The IESNA recently published the inaugural edition of LM-80—the Approved Method for Measuring Lumen Maintenance of LED Light Sources—which specifies the precise methods LED manufacturers must use to reliably evaluate the lumen depreciation of LEDs over a fixed time period.

Cree, the LED supplier for the DuraStreet Series LED Light Engine, uses LM-80 methodology to verify that their products will provide 70% of initial lumens for at least 50,000 hours (L₇₀), providing that LED junction temperature (T_J) remains within specified guidelines.

However, as shown below, recent LM-80 testing performed by Cree predicts L₇₀ LED lifetimes much longer than 50,000 hours. For example, when T_J = 65°C, lumen maintenance of 95% or higher is expected at 40,000 hours. This translates to L₇₀ lifetimes of 100,000 hours or more, especially when T_J is maintained at levels below 65°C. To see how the DuraStreet LED light engine performs at a variety of outdoor and LED junction temperatures, download the Advanced Manufacturing Institute report.

Data courtesy of Cree.

Concept #2: Lumen output decreases as LED junction temperature (T_J) increases

As the chart below shows, cooler LEDs produce more light than hotter LEDs. Since the power (as measured in watts) consumed by LEDs remains relatively constant as T_J increases, the efficiency (as measured in lumens per watt) also decreases.

Concept #3: LED lifetime is lengthened as T_J decreases

Achieving 50,000 hours of LED life with 70% of the initial lumens (or 70% lumen maintenance, sometimes designated as L₇₀) is dependent on keeping T_J within a specified range.   L₇₀ lifetimes are lengthened as LED junction temperature decreases. 

Concept #4: Ambient vs. Outdoor Temperature 

There is a common misnomer in the LED lighting space regarding temperature measurements.  “Ambient temperature” is measured in the space immediately surrounding the LEDs, and is a critical factor for determining LED lifetime (L₇₀).  "Outdoor temperature" refers to the temperature surrounding the luminaire, and only indirectly influences LED life based on how it impacts the ambient and junction temperatures of the LED.  For example, if the outdoor temperature is 10°C, the ambient and junction temperatures of the LEDs may be 25°C and 45°C , respectively.   A common mistake is to use the outdoor temperature, instead of ambient temperature, when determining LED lifetime (L₇₀) from a LED manufacturer’s data sheets.

EcoFit lighting has measured the ambient and junction temperatures for the DuraStreet LED light engines in a variety of outdoor temperatures.  These data are then used to determine the resulting LED lifetime (L₇₀) of the LEDs using LM-80 certified testing data performance provided by the LED manufacturers.

The bottom line: When it comes to LEDs, the cooler the better.

At EcoFit, we specialize in the design and manufacturing of effective, high-quality heat dissipation technologies that, when combined together as a system, ensure that our products will operate within LED suppliers’ temperature ranges for many years to come.

But don’t take our word for it. We had an independent test laboratory, the Advanced Manufacturing Institute, test the performance of our product under a variety of ambient conditions. View the Advanced Manufacturing Institute report, which shows that the DuraStreet Series LED Light Engine maintains T_J—the most critical measure of LED performance and long life—at or below the recommendations published by our LED suppliers, Cree, at all levels of outdoor temperature likely to be encountered in North America.