L70: What causes some LED lights to reach L70 faster than others?

By Wade Johnson     24 Jul 2019     Reading Time: 3 minutes


This is Part 2 in a 4-part series.

The major cause of LED fixtures losing light output faster than others is low-quality components. As with any engineered product, manufacturers of LED fixtures must make choices – and compromises – on the level of quality of materials and components to be used for the finished product in order hit the cost targets.

The largest percentage of LED fixtures manufactured for commercial applications go through a bid process where the lowest bid receives the order. This drives most manufacturers to cut corners and select the lowest cost of materials and components that can be used without the end user noticing or complaining. In the LED lighting industry, the biggest competition in the race to lower costs at the expense of quality has come from companies based in China.

Chinese companies are partially owned by the Chinese government, which gives them liability protection from lawsuits. A company that knows it cannot be sued is likely to cut corners more aggressively. In addition, since China is a Communist country, the labor and raw materials used to manufacture LED lights are subsidized by the government. This creates a situation that results in a higher risk for end users than most people realize.

The second major factor influencing loss of light output or lumen depreciation, is heat. As most people have experienced when leaving their phone in the sun, electronics do not like heat. In unconditioned spaces, heat builds up fast and rises, exactly where the light fixtures are installed. Keeping the electronic components cool inside LED fixtures that are exposed to high heat requires engineering know-how and the use of higher-grade components and materials with higher thermal conductivity, which increases the bill of materials.

The most cost-effective material to build LED fixtures that can withstand the high heat existing in most industrial settings, is aluminum. Sheet metal is the number one choice by manufacturers wishing to win low bid processes because it is cheaper than aluminum, but not nearly as effective at dissipating heat.

Typically, if the temperature on a factory floor is 80 degrees Fahrenheit, the temperature at the light fixture will be 1 degree hotter for every foot above the floor. Most LED light fixtures are only tested at 77ºF (25ºC) so the end user may have a difficult time determining the lumen output of their LED fixture during the hottest season of the year. Will it be enough to meet the recommended light levels for employee safety and productivity? If that is unknown for day one, what would happen in year 5 or beyond?

The engineering design of LED fixtures is also important. Heat sinks designed with vertical fins that are perpendicular to LED boards are a crucial element. Since heat sinks will only work if they are attached to the LED boards, the attachment method is equally important. The least expensive way to attach LED boards is to use screws. While this method is cheap and simple for the manufacturer, it is detrimental to the owner in the long run. Over time the LED boards will soften and begin to sag between the screws, separating the LED board from the heat sink. Even the best designed vertical heat sink made from the highest quality aluminum will be ineffective if it cannot maintain contact with the LED board.

Air flow is also important in the design of an LED light fixture. If the design allows the air to flow from underneath the fixture and pass through the fixture itself, and not just around it, the fixture will run significantly cooler.

In addition to looking for quality materials and good design parameters, the best advice for purchasing LED light fixtures that can last in industrial environments, is to choose the ones rated for the highest ambient temperature, not just the temperature you believe your facility will ever reach.


Next, we need to consider two other questions

  • Can we accurately predict L70? (Part 3)
    Available end of August
  • When LED lights reach L70, what do we do with them? (Part 4)
    Available end of September

Wade Johnson
Wade Johnson
Sr. Business Development Manager
Flex Lighting Solutions