By Scott McMahan, Editor of Solid State Lighting Design
One year ago today, I moved into a new condo in the suburbs of Austin. The condo came equipped with a combination of LEDs and compact fluorescent bulbs. The master bathroom has a vanity mirror, two sinks, a shower, and bathtub. Two fixtures above the vanity each hold three LED bulbs.
The LED bulbs come from a reputable company that is well known in lighting. The dimmable bulbs above the vanity consume 14 watts and deliver 1100 lumens. I do not get to take advantage of the dimmability because the switches are merely on and off. The bulbs are ETL listed for wet locations, making them ideal for a bathroom installation. The lamps are also UL certified to be safe retrofit replacements for either incandescent or compact fluorescent bulbs.
Despite only a few thousand hours of use over the past year, four of the bulbs failed within a two-week period.
I am at a loss as to why. Each lamp’s point of failure was obviously not the LED die itself. The drive circuitry is apparently where the fault lies. Since four of them failed in a such a short time, I have to question whether or not it is the result of a manufacturing issue, or even a design problem.
Since I did not purchase the lamps myself, I wasn’t sure what recourse I would have to return them without any proof of purchase. I looked them up online. The listing showed that when purchased they had a 5-year warranty from the company. I called the company’s 800 number and explained the situation as best I could. When I mentioned that I did not buy the LED bulbs, but the condo’s builder did, they hung up on me! Despite the extremely poor treatment, I plan to send them the faulty lamps along with a letter explaining why I think there is a serious issue with them. I will await a reply to the letter and the package and will inform you of the outcome.
I looked at Wikipedia to find potential points of failure in an LED lamp. Apparently LEDs have numerous ways of failing. They include package related points of failure such as Epoxy degradation, thermal stress, and differentiated phosphor degradation (causing a color change). Other causes of failure can be related to metals or semiconductors including nucleation and growth of dislocations, electro migration, ionizing radiation, metal diffusion, and short circuits. Stress related failure methods include current crowding, thermal runaway, electrostatic discharge, reverse bias, and catastrophic optical damage.
After reading through an explanation of each, I decided that a short circuit caused by a corrosive (wet) environment was the most likely cause. In theory, a wet and corrosive environment could lead to multiple lamps short circuiting in a relatively short period, but not all at once. While this seems the likely cause, it does not excuse the extremely short lifetime of the bulbs in what I assume is to be relatively normal bathroom use.
Perhaps if they had a moisture sensitivity rating of MSL-1, their lifetimes would essentially be unaffected by a wet environment, and they may not have failed the way they did. In any case, I will never buy any LEDs products from that company in the future. This is more because of the way the person treated me on the phone than the LED bulbs themselves. I have chosen not to mention the company’s name. I am sure that they make some good products, but the LED bulb that my builder selected was apparently not the right one for the job.
