I hadn't thought much about this before but today I started wondering what percentage of light output is typically lost as a large (100-250 watt) incandescent bulb ages, before it's filament finally fails.
It seems to me that the noticeable deposits on the inside of the glass bulb must block some light, and as the filament boils off some of it's tungsten its resistance must increase, so the power dissipated in it will drop, reducing the light output.
Or, maybe it's just my aging eyes.
Jeff
Not trying to hijack your thread, but... That's another advantage to compact fluorescent. I've almost forgotten what it's like to change a lightbulb.
How many people does it take to change a compact fluorescent light bulb? None!
2) I've changed a bunch of them.
Christopher A. Young Learn more about Jesus
Not trying to hijack your thread, but...
How many people does it take to change a compact fluorescent light bulb? None!
as to the original question if the filament doesnt fail light output will be cut dramatically.
I had a 300 watt indandescent bulb in a living room light for grandma, on a dimmer so she could set the light output she needed, more for reading etc.
Since the lamp rarely ran at full brightness the filament nearly never burned out but the inside of the glass would turn nearly all black, and I would replace the bulb....
Incidently newer name brand CFs last nearly forever, the first dollar store type failed fast.
CFs are well worth their cost, and are saving me big bucks on electric
Thinning filament might get hotter and actually burn brighter but at some point fails because of higher heat essentially melting, I would guess. Grandma's never sees these high temps and bulb lasts longer.
I don't like cfl's in places where they are turned on and off frequently like a bathroom. I've noticed these tend to fail faster.
CFL's do loose output as they age.
It's easy to measure output. Use light meter.
I actually have that function on my HF vom.
Greg
Dont leave us in suspense. Which brands last forever? I've used the cheap dollar store ones, as well as Sylvania and GE. None seem to last long.
I dont use them in the bathroom either, turning them on and off definately does shorten their life and when I enter the bathroom in a rush, I may need FULL brightness so I dont miss the toilet :)
The CFLs marked "Energy Star" last the longest in my experience probably because they have to be life tested and the data submitted to receive E* listing. Lamps that I've tracked last 10 years or longer in residential service. But, starting a fluorescent lamp (of any kind) does shorten the lamp life.
Tomsic
Besides the shorter lifetime due to multiple starts, placing them in a socket-up position will overheat the electronics in the base drastically shortening lifetimes.
My grand parents had a light bulb that lasted from 1929 (house built) till they moved out in the late 1980's. It was a ceiling mounted 20 watt incandescent in an indoor small foyer.
I've purchased quite a few CFL's. Just about all of them were sylvania. Some last for years, others last for weeks. The ones that last the longest either are rarely used or turned on and left on most of the day. My wife does not care for the CFL failure mode of pop, spark, stinky burnt electrical parts smoke wafting thru the house. My solution is to switch over to halogen's encased in a traditional incandescent glass envelope. The halogen seem to be compatable with my built in intermatic light timers.
Steve
73 de N2UBP
All energy star checks is power consumption. And they don't check every one. The advantage is cheapassed manufacturers won't pay for the certification. The downside is the chinese will put any label on any turd and pass it off as "energy star" - and you don't know the difference.
VAST majority of lamps are socket up in actual usage. Should be designed for that use.
I have never bought a CFL--Feit, GE, Sylvania--that didn't say either five-year or seven-year warranty on it.
I have also never seen one last three months, although the ones currently in my dining room are getting close.
Oops, retraction. The one in my bedroom is about six months. But it is only on five or ten minutes a day, while the fine print on the warranty is three hours a day.
The warranties are just a marketing gimmick anyway. We'll replace the bulb if you don't lose your receipt AND you ship it at your expense to our headquarters.
In Mexico or China
Well, actually the only one I complained to was in California. Postage was slightly less than the cost of the bulb--but the difference didn't make up for the irritation of having the replacement garbage crap out the same way.
I've got a chrome bathroom light fixture with 8 of those clear round stylish incandescent bulbs in it. They came with the house over 12 years ago and don't even show any black. I wonder what makes them last so long?
Exactly true. Except for the ones that sit in a horizontal position such as typical bedroom fixtures, nearly every bulb in my house and out buildings sit with the base up. Table lamps and a few outdoor fixtures are the only exception. I dont fully understand why this would be true anyhow. The spiral glass part dont get real hot, it's the electronics in the base that generate heat. In some ways, you'd think that heat from the base would dissipate into the fixture.
Now the sealed globes over some lights could hold in the heat, and that makes more sense.
I still have two CFLs that Con Ed gave me probably 20 years ago. In their current position they probably get turned on about once a day for 5-30 minutes. But most of the others from back then are gone.
I had a CFL with a warranty and when I filled out the info on their website (it took two tries before they responded) they mailed me a $10 Home Depot gift card- I didn't have to send in the bulb.
My experience is that the dollar store ones don't last but the better ones mostly do, generally around 5-7 years is my best guess. And since they're no longer expensive they do save money.
Besides the shorter lifetime due to multiple starts, placing them in a socket-up position will overheat the electronics in the base drastically shortening lifetimes.
Yes, I agee. And putting CFLs in small enclosing fixtures, no matter what the socket position, can do the same thing. CFLs made well and operated base down in fixtures with good air circulation will give maximum life -- probably beyond the usual 10,000 hour ratings.
Tomsic
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