Compact Florescents burn out at the same time

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snipped-for-privacy@invalid.com wrote:

I have had more bad experience with GE than with Philips and Sylvania, but less than with Lights of America.
My biggest GE gripes for compact fluorescents are for a couple specific ones probably obsoleted or discontinued.
My biggest gripe with GE now is they are outsourcing the F8T5 (not an actual CFL but a smaller one of the "standard" fluorescents to China and the label only claims 5,000 hours life. The F8T5 used to be claimed to last 7500 hours. The 5,000 hour version costs no less than these ever did.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Fri, 29 Jul 2005 01:12:24 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

And what does that 5000 or 7500 hours really mean? No one really times them. However, lets just make a rough estimate. I would guess that I average 30 minutes per day of lights in the bathroom. That figure is probably a little high for actual usage, but I do occasionally forget to shut the light off. So, 1/2 hour per day times 365 days in a year would be approximately 183 hours. So, lets just round this off to 200 hours, since they were left on overnight a couple times. I installed the bulbs about 1 1/2 years ago. (2 years at most). That means I got at most 400 hours of usage out of these GE CFL bulbs which are rated at 5000 hours. At this rate, I did not even get 10% of their rated life.
At my rate of usage, they SHOULD have lasted 12.5 years.
These bulbs were NOT enclosed in glass, and the base was DOWN.
I don't think I'd complain if I got even half the rated life, but I didn't even get 10%.
That 5000 hour rating means nothing as far as I am concerned. And how is that measured? Is it supposed to be continuous use, or ON/OFF total use? I heard that turning an indecesant bulb on and off shortens their life. Is that also true with CFL bulbs?
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An article in papers several year ago discussed the bulb high in the far reaches of the NY Opera House that had been burning for 40 years and nobody had any idea where the switch was for it if there was one.
On Mon, 01 Aug 2005 02:21:26 -0500, snipped-for-privacy@invalid.com wrote:

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Every once in a while I hear about this lightbulb somewhere or that one somewhere else that has been running for many decades or about a century.
Now for the kicker: How much electricity is being consumed and how much light is the bulb producing? Answer: These super long life bulbs produce about or less than half as much light as that produced by "standard" incandescents of the same power consumption.
If you double your power consumption to get the same amount of light and avoid changing lightbulbs, chances are you increase your electricity cost more than you spent on lightbulbs.
Heck, incandescent traffic signal bulbs are only designed to last 8,000 hours. And surely labor cost of changing lightbulbs is high there.
If you have some special need for a lightbulb to last a century, get a 230 or 240 volt lightbulb and run it at 120V. At half voltage, power consumption will be about 28-29% of rated, life will be a few thousand times rated, and light output will be somewhere around 9% of rated.
- Don Klipstein ( snipped-for-privacy@misty.com)
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snipped-for-privacy@invalid.com wrote:

<I snip>

The "Big Three" makers actualy test their fluorescent lamps in aging tests, turning them off and restarting them every 3 hours. At least they did and do this for ones made in their own plants.

Usually the rating is for total "on" time with an average of 3 hours "on" time per start.

Most incandescents do not lose much life from this, despite incandescents usually burning out during a cold start, and despite cold starts even visibly shaking the filament or causing the filament to produce a "ping" sound audible at close range in a quiet room. (Some incandescents do suffer significant filament fatigue from cold starts, but most don't.) What happens is that an aging filament becomes unable to survive a cold start a little before it becomes unable to survive continuous operation.
Filament failure from a cold start is usually from a filament with a thin spot from uneven evaporation experiencing a temperature overshoot of the thin spot. The thin spot melts during a cold start. However, these thin spots will only survive continuous operation for a limited amount of time if they are already unable to survive a cold start, since once they get that bad they are worsening at a rate that accelerates worse than exponentially.

Yes, that is true, and much more true than with incandescents. The filaments in fluorescents do suffer actual extra wear from starting.
Some are worse than others for use in bathrooms used mainly for short trips, although I doubt any are really good if they average only a couple minutes runtime per start.
Worse ones for this start in these ways:
1. Blink a few times before staying on. 2. Start truly instantly. 3. Start truly instantly, although with a minor sudden jump of brightness 1/4-1/2 second later.
Better ones start in these ways:
1. Delay of a fraction of a second to a second before turning on, and then it's on without blinking.
2. The ends glow first and then the whole thing is on, without blinking.
3. The lamp fades on in a smooth, steady but rapid process taking a fraction of a second to maybe as long as a second.
=================== I have seen in some commercial buildings restrooms with fluorescent lights controlled by occupancy sensors. Here this makes sense since a 4-foot fluorescent only costs about a dollar when purchased several cases at a time, and electricity savings per bulb are greater than with lower wattages.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Mon, 1 Aug 2005 15:13:33 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

Don
Since you seem to have much knowledge about bulbs, I got another question. When I drop a trouble light using a standard indecescant bulb (or even a heavy useage bulb made for trouble lights), the bulb often gets much brighter than it was originally, but usually they burn out shortly after. Is this extra brightness because particles fall off the filament and it gets thinner, or is there another reason?
Thanks
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snipped-for-privacy@invalid.com wrote:

It is because part of the filament has shorted across itself and reduced the resistance and increased the current flow. As they get older the filament may sag and with a trouble light it may be moved into different positions so the filament can cross over itself easier than in a fixed light.
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Joseph Meehan

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snipped-for-privacy@invalid.com wrote:

I have seen lightbulbs do this, although not yet seen a trouble light do this (I am not around trouble lights in use enough to see this).
If the filament has any sharp turns, part of the filament can get shorted by mechanical shock. This results in the remainder of the filament getting full line voltage. I have seen this happen with nightlight bulbs and christmas bulbs with multiple-support filaments with sharp turns at the supports, and also with chandelier bulbs with V-shaped filaments.
I give a possibility that other styles of filament could become partially shorted if stretched out of shape from an impact.
I do consider it possible that if a portion of a filament gets severely stretched with the remainder of the filament unstretched, then the stretched portion will run cooler, have reduced resistance, and allow the filament to get excessive current and possibly total light output could increase. I have seen filaments unevenly stretched by impacts/shock that were obviously very uneven in temperature.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Mon, 1 Aug 2005 19:54:23 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

So, if the filament shorts or overlaps itself or any of these things, then when the light gets brighter, I would assume the wattage also increases, and thus the amount of electricity being used. Is this correct? This leads to yet another point. If the wattage does increase, and it was a 100 watt bulb in a fixture rated at maximum wattage 100w. Then the fixture is really overloaded, right? I suppose this could actually become a safety issue, even though the bulbs generally burn out soon.
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snipped-for-privacy@invalid.com wrote:

Yes, and the lamp becomes more efficient so the amount of increased light is more than the increased energy used. Of course you pay with shorter lamp life.

Usually not. Fixtures are rated for temporary overloads.

It could, but I would believe that the actual number where it becomes a safety issue is very very small.
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snipped-for-privacy@invalid.com wrote:

This is correct. Most lightbulbs that I see brightened by mechanical shock have enough filament shorted to increase power consumption 10-20%. If the filament is partially shorted but not stretched, it's roughly a square root thing. Unstretched filament with more than roughly 40% overcurrent will melt instantly.

If the fixture barely does not overheat with an undamaged bulb and cannot handle the extra heat from bulbs damaged this way, then it is a safety issue. I would think that trouble lights would be made to take into account stretched filaments consuming extra power, whether or not more light resulted. Now I wonder if that's wishful thinking...
- Don Klipstein ( snipped-for-privacy@misty.com)
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