I remember thirty years ago, you wouldn=92t even think about breaking a flu= orescent lamp while replacing it. In fact you hardly ever had to replace th= em. Now they make the class thinner than an eggshell and if you=92re not VE= RY careful it breaks before you even finish putting it on, and even if you = manage to put it on, the glass doesn=92t last long once it gets hot. Glass = is mostly made of silica which is cheap, so it=92s not that the Chinese are= saving money by making it thinner and if it=92s not to save money then the= only reason they would have to do so would be so you keep having to replac= e them and buy more.
I believe incandescents fail because tungsten evaporates (the bulb blackens somewhat) and hot spots develop. Small lamps are under vacuum. At about 40W they are gas filled (not including oxygen). The gas reduces evaporation of the filament.
In halogen lamps, the halogen transports the evaporated tungsten back to the filament. As a result the filament can run hotter, producing a smaller percentage of heat.
I suspect in a significant percentage it is the ballast electronics that fail.
In general, flourescents have a filament, or cold cathode, at each end that produces electrons. The electron emitting surface slowly fails and when it gets too low the lamp won't start. Sometimes the filaments open.
I would guess cumulative damage from heat. Semiconductors (and electronics in general) don't like heat.
One of the problems in LED lamp design is removing the heat from the LED.
In my experience CFLs fail so rarely that I was never interested in why and never investigated - always looked like a random event anyhow.
LEDs, on the other hand, failed so frequently that I did look and, basically, the reason is two-fold. They require bringing the voltage across each individual LED to 3.5-3.6V Given that you start out with 120V power, they string 20+ of them together so the power supply of the LED bulb does not have to lower it down too much and they also very frequently skimp on the design and the components of the power supply. I can't say for the higher-end LED bulbs which I've not yet gotten any due to costs and my general skepticism about their life expectancy, but the lower-end ones I've opened often even lack some component that are clearly labeled on the PCB inside. For example, an inductor that's intended to limit the inrush current through the string of the diodes, is often labeled on the board but missing (replaced by a wire short) because it's kinda expensive (about $1). I'm also pretty sure the LEDs themselves and every other component inside were picked from the lowest cost (lowest quality) bins.
One other intrinsic issue with LEDs due to their low voltage and consequent stringing of a couple of dozen together is that life expectancy of such serial circuit drops dramatically. It's pretty much false advertising when they print on the box "30,000 hours life" because even if one LED might really last 30,000 hours, the probability of the string of 24 failing in the first 1000 hours or less is much higher - the probabilities of each LED failing compound and bring the entire circuit's way down.
Failure of incandescents is complex but mostly due to sublimation and thinning of the tungsten filament with time. When I bought my house over 35 years ago we had bulbs filled with krypton rather than the usual argon which slows sublimation and several of these bulbs are still in use.
As others point out there is a lot or circuitry in these new bulbs that can fail before the actual light source itself.
suddenly than the lamps themselves. Both LED and CFL loose output slowly with age - both use phosphours to create the visible white light, and those phosphours deteriorate with use (photon production)
I remember back in the 70s seeing a tour of Thomas Edison's Florida home and they had a bulb of his burn so many hours a day since he left. I guess it was like 50+ years then and still burning well. So I got to believe what most people say in this thread as true.
I used to use a 300 watt incandescent bulb on a dimmer for my grandma who couldnt see well....
bulb life was forever however the inside of the bulbs turned black over time, eventually so little light even at full dimmer output i couldnt read a paper. grandma was bothered i replaced the bulb before it burned out
i have had a copuple CFLs die while i used spray wax in their vicinity. fire came out of one... it appears the spray wax vapor causes a short of some sort..
dont use a lot of wax but these days if i do i make certain the lights are off and cold, then i wrap a rag around the CFLs do my waxing, and remove the rags before powering the lamps back on.
sometimes i just remove the bulbs if they are dsty and spray the glass part with water, then let it dry a long time
It is easy to get an incandescent lamp that has very long life. Just get a 240V bulb and use it on 120V. It will last nearly forever. But you won't get much light out of it. That is what "long life" bulbs do. There is a trade off of bulb life and light output. What is the light output of the Centennial and other long lived bulbs in this thread?
It's an efficiency thing though... say you have a 120W, 240V incandescent running on 120V. The light out of that bulb will be dimmer than a 60W, 120V bulb running on 120V, as the filament won't be as hot and therefore won't glow as brightly. You're trading life for efficiency...
The graph I have goes to 90% voltage. At that point the life is increased 50% (and rising fast). The lumens are 70%. At half voltage the lumens would be a rather low percentage (far lower than 60W equivalent).
As you lower the voltage the spectrum shifts toward red and infrared (as you more or less said) That means a much higher percentage is heat.
With higher voltage the spectrum moves toward blue and a higher percentage is in the visible spectrum. Photographers used to run bulbs at overvoltage. Stadiums sometimes did the same thing.
Last time I was in Menards they had some long life bulbs with appalling low lumen ratings for the wattage.
That reminds me of a street light that was about a block from where I grew up at. This light was over the middle of an intersection in town. The road was not used much at night as this was about 50 years ago. We would get in the street and throw and kick a football around. Once or twice every year one of us would kick the football and hit the light and break it by accident.
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