CFLs - switching on and off

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Joseph Meehan wrote:

I seem to recall, and emphasise seem, that Which back in the year dot when I started to subscribe, then suggested that a tube was best left on for 45 mins., if you were likely to re-enter that room. I still have that habit, but have reduced it to about 15 - 20 minutes.
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Joseph Meehan wrote:

AIUI this old advice was based on an elementary error, as it overloooked the fact that although the tubes may last more hours if left on, they will in fact last less days.
This whole subject is filled with myth and bad advice. Today for domestic installs, the only sensible thing to do is turn off when not wanted, however long or short that may be.
NT
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snipped-for-privacy@care2.com wrote:

Unless you have one of those pesky CFLs that take 10 mins to achieve a worthwhile light output! ;-)
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Cheers,

John.

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On Sun, 19 Aug 2007 18:09:51 UTC, John Rumm

Nah, don't have that problem...they *never* achieve a worthwhile light output!
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I see few taking that long, and they tend to be outdoor types in colder conditions.
If you want ones that warm up faster, I have found in general that ones without outer bulbs start brighter and warm up faster than ones with outer bulbs. Ones with outer bulbs have the tubing getting hotter, and are designed to work optimally at such a higher tubing temperature.
- Don Klipstein ( snipped-for-privacy@misty.com)
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That is a common myth. Any extra power consumption surge during starting amounts to the amount of energy consumed in a second or two of steady operation - or less.
However, the cost of bulb wear from an extra start could require several minutes of off-time in order for electricity savings to outweigh that.
How many minutes? This depends on the bulb cost, electricity cost, starting method, and when the bulbs were made.
Modern fluorescents suffer less starting wear than older ones.
The "break even time" is less for ones 4 feet and longer than smaller ones. Lower wattage bulbs cost even more than 4-footers, and lower ratio of power consumption to bulb cost increases the "break even time".
The "break even time" varies with starting method because different starting methods cause different amounts of starting-related wear:
"Program Start" - this is used in some CFLs. The bulb does not come on at all until a fraction of a second to about a second after power is applied, then turns on without blinking. It may have a "rapid fade-on" during a fraction of a second. This causes the least wear, and is often used in CFLs of Philips and Sylvania brands (and some others but I can't remember who and I have not tried them all).
"Rapid Start" - bulbs come on instantly very dim, usually slightly flickery, stay dim for about half a second to a second, then quickly brighten over a fraction of a second. This is next-best to "Program Start" for minimizing wear from starting. "Trigger Start" refers to a variation of "rapid start" used on bulbs designed for "Preheat Start".
"Instant Start" - The bulbs are on instantly. Sometimes the brightness makes a sudden slight upward jump a fraction of a second after starting when the filaments achieve normal operating temperature. This is worse than "program start" and "rapid start" for starting-related-wear.
"Preheat Start" - usually has a "glow switch starter" or "glow bottle starter", rarely an electronic alternative. Bulbs usually blink a few times before they start and stay started. Since each blink causes starting-related-wear, this method is worst for starting-related-wear. Fluorescent lamps using this starting method, especially with bulbs 22 watts or less, are likely to have break-even times in/near the 15 minute to 1 hour ballpark, and should be left on rather than being turned off and back on shortly later. Electronic versions of starters that make the first starting attempt successful greatly reduce the starting-related-wear. Electronic schemes that make some determination when the filaments are properly preheated as well as making the first starting attempt successful are at least arghuably "program start" schemes.
========================== Now, how bad is it to turn off and back on a fluorescent lamp?
Case 1: 4-footer, 32 watt T8, instant start costing $2. I am guessing that a start with an instant start ballast takes 20 minutes off its 20,000 hour life. I am assuming also that this is with an electronic ballast that improves energy efficiency and also mildly underpowers the lamp/bulb (expect about 90% of "catalog" light output from the lamp/bulb), and per-bulb power consumption could be about 30 watts, usually not exceeding 32 watts. Another assumption - electricity cost 11 cents per KWH, which I believe is close to current USA average residential rate.
Starting wear taking 20 minutes off the life of a $2 20,000 hour bulb costs .003333 cent. (Actually slightly less, since these bulbs are rated to last 20,000 hours with one start using rapid-start-method every 3 hours, and will last slightly longer than 20,000 hours if used continuously.)
To consume .003333 cent worth of electricity at 30 watts and 11 cents per KWH (.33 cent per hour) only takes .0101 hour, about 36 seconds.
Case 2: 15 watt spiral CFL purchased at a higher-side price of $7, instant-start. Assuming that the filament here is optimized a bit more for enduring starts, so I guess 15 minutes of life lost per start. (It could easily be 10 minutes or less.) Also, rated life expectancy 6,000 hours. (I know, now they make ones rated 7500 or 10,000 hours. But I want to be a little conservative here!) The life rating is with a start every 3 hours. So if it lasts 6,000 hours with a start every 3 hours and a start costs 15 minutes, then continuous operation avoids 2,000 starts over 6,000 hours and would add 500 hours to the 6,000 hour figure and make it 6,500 hours. Assuming that all my numbers here are good including ones that I am halfway pulling out of a hat, a start costs about .027 cent. If you get these bulbs in a $10 4-pack, then a start costs about .0096 cent. If you get these bulbs in a promotional $10 6-pack, then a start costs about .0063 cent. Now, to balance against 15 watts of power consumption at 11 cents per KWH (.165 cent per hour): .027 cent per start ($7 bulb) means "break-even" at 10 minutes .0096 cent per start ($2.50 bulb) breaks-even at about 3.5 minutes .0063 cent per start ($1.67 bulb) breaks-even at about 2.35 minutes
Lower wattage CFLs will tend to have longer "break-even" times, higher wattage ones will tend to have shorter "break-even" times.
Break-even time is also inversely proportional to electricity cost. It will be a little shorter in the metro areas of Chicago, Philadelphia and NYC.
================================================== Where starting wear on lower wattage CFLs is a big issue, consider cold cathode ones. Those do not suffer any significant starting wear, and are often even rated for heavy blinking duty. They also have longer life expectancy than hot cathode ones of same wattage even without starting wear.
Downsides:
1. Ones over 3 watts are mostly available from online lightbulb sellers such as bulbs.com. Even there, they are largely limited to about 8 watts or so as of last time I checked. (A 3 watt cold-cathode model I have seen at Home Depot - of the N:Vision brand. Look for it being rated for dimming, probably also blinking, and life expectancy 20,000 or 24,000 hours or so.)
2. Cold cathode ones produce somewhat less light than hot cathode ones of same wattage. An 8 watt cold-cathode one only slightly outshines a 25 watt incandescent, while a 9 watt hot cathode one is about as bright as most 40 watt incandescents.
- Don Klipstein ( snipped-for-privacy@misty.com)
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Don Klipstein wrote:
Don is a lighting expert with a very informative and detailed site last time I looked. However readers should bear in mind that tube types, starting types, costs, common practices and terminology are all different here in UK to the US.
Also I think somehting was missed in your calculations of switch off break even time. If keeping the tube on for 20 minutes gains you 20 minutes extra tube life, you have in fact gained absolutely nothing. The only difference is that 20 minutes of electricity have been wasted. You wont get a single extra day of service time out of the tube this way. I dont know why but this is so often overlooked in these calculations.
NT
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snipped-for-privacy@care2.com wrote:

Oops, I was only calculating break-even points in whether cost of operating the lamp is increased or decreased, without regard to considering leaving-the-lamp-on causes some of the lamp's life to be wasted in addition to the electricity being wasted.
I expect that adding consideration of wasting lamp operating life will change break-even-time calculations and make break-even times shorter.
I expect this correction will only make break-even times slightly shorter if electricity consumption during the life of the lamp (bulb) costs a lot more than the lamp (bulb) does, which is often the case. With lower wattage lamps, lamp cost becomes a more significant fraction of the total cost, so this correction gets less minor.
- Don Klipstein ( snipped-for-privacy@misty.com)
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Don Klipstein wrote:

I would think it would make quite a big difference, but havent calced it yet.
NT
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On Sun, 19 Aug 2007 00:40:40 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:
:"Program Start" - this is used in some CFLs. The bulb does not come on :at all until a fraction of a second to about a second after power is :applied, then turns on without blinking. It may have a "rapid fade-on" :during a fraction of a second. : This causes the least wear, and is often used in CFLs of Philips and :Sylvania brands (and some others but I can't remember who and I have not :tried them all).
Yes, IIRC Philips and Sylvania are among the handful of brands that I have seen recommended, and consequently I have bought several. I have had very spotty luck with off-brand CFL's lasting anything near the advertized MTBF. In recent years I have seen some pretty good deals on CFL's and bought some off brands anyway.
Dan
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There are a lot of "fools" about that believe anything they are told/hear and lack any sort of understanding to know its rubbish. Just look at Lenny in uk.t.b and you will know what I mean.
I bet there are loads of people about that think you should leave the CH on at night as it takes more energy to warm the house up in the morning than it does to keep it warm.. another common misconception doing the rounds.. again!!
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snipped-for-privacy@hotmail.com wrote:

a popular myth http://www.wiki.diyfaq.org.uk/index.php?title=Fluorescent_Lighting
NT
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On Sat, 18 Aug 2007 13:46:15 -0700, snipped-for-privacy@care2.com wrote:

Which one?
Could you point out please the particular myth you refer to?

Could you expand on that? It's a rather large webpage but all it says on lamp life is :
"Tube life depends on type of ballast (& starter where used), and how often the tube is switched on and off."
Which is correct but not specially helpful.
BTW Mr. Meow. we had another CFL fail yesterday after 6 months service in a cap down open fitting. It was a Feit electric 23 watt spiral offered for sale promising a 5 year life. The phosphor is quite significantly darkened and the top of the plastic end cap containing the electronic ballast has been toasted brown, what happened to the cheap Chi/Taiwa-nese pcb assy inside is anyone's guess.
DG
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wrote:

A five year life would be 5*365*24E,800 hours I_don't_think_so.
Why do GLS lamp manufacturers give an honest average lifetime in hours (say 2,000) but with longer lived CFL lamps, you have to find the small print that qualifies the headline figure.
One for the ASA IMHO.
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Graham
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You have to read the fine print. Under that bit Five Years is the small print that bases the life on X number of hours per day.
Feit states 8,000 hours. From my experience with a few of them, I'd say they are close and have even exceeded that. I use them in some places in our warehouses for night lights and security lights that burn 24/7. Not a bad deal for a bulb that sells for 74.
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Derek Geldard wrote:

I've noted the same, and that later models have a breather hole in them.
Classic case of insulated electronics failing after prolonged 'on' periods.
I remember having this issue once with some gear I designed: A probe inside showed the unit took nearly ten hours to reach equilibrium - or would have. It generally failed after 7..;-) ten holes.. 5 in the top and 5 in the base made it totally reliable.
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I've just had a Pro-life 25W spiral bulb fail in a spectacular way (very loud bang followed by lingering burnt smell). It's been fitted approximately 6 months.
Photos http://www.amac.f2s.com/bulb/index.htm
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Alan
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I avoid 25 watt spirals, especially of brands that are neither "Big 3" nor home center mainstays.
It appears to me that a big run of bad 25 watt spirals was made around 2000-2001 or so. I bought one of the Lights of America brand (and that brand I often had trouble with) and 2 of the GE brand (GE is one of the "Big 3" and normally does well). All 3 burned out in only a few hundred operating hours, but quietly.
I have seen only a year or two ago 25 watt spirals at Walgreens, of a brand that I cannot remember, that appeared to me to be of similar vintage. So I am suspicious that there are businesses that bought some of that boatload of 2000-2001 or whatever garbage and hope to make money reselling it under different brands.
======================= As for CFLs failing with a bang: Sadly, that was somewhat normal.
Two ways for a CFL to make a loud pop and what the manufacturers have done about it (or should be doing):
1. A usual screw base CFL with internal electronic ballast has a filter capacitor after the rectifier. This capacitor has limited life expectancy, especialy at elevated temperatures. It also contains a water solution of electrolyte, since it is an electrlytic capacitor.
If this capacitor gets too hot, the electrolyte can boil and make the capacitor burst. The capacitor's housing is normally designed to break without producing shrapnel of the housing.
A few years ago, quite a few people were disturbed by CFLs going POW and occaisionally dripping electrolyte. Usually, at least one of the following is usually the case:
* The CFL was an off-brand one * The CFL was operated in a higher temperature environment than the manufacturer anticipated, often in a downlight or a small enclosed fixture * The capacitor was not as good as the CFL manufacturer thought
What manufacturers have done about this: They have gotten better at using capacitors that are up to the task of CFL duty. I'm sure there will still be some capacitors popping in the future, but I am already hearing less about capacitors popping than I heard earlier this decade.
2. The electronic ballast shorts and a wire or a part acts as a fuse, sometimes with a loud pop or bang. Sometimes part of the ballast gets scorched or discolored by smoke.
If the CFL is UL listed and production units conform to units tested by UL, then the ballast and ballast housing materials are sufficiently flame retardant for the CFL to be reasonably safe from starting a fire.
However, I hope the manufacturers are aware that a light bulb going out with a bang, smoke output or getting a visible scorch mark in the process appears scary and does not make good press. I would hope they now put in fuses to make semiconductor failures/malfunctions leading to the CFL dying less spectacularly.
I expect less scary failures from manufacturers that hope to still be in the CFL business 10 years from now. I think "Big 3" (Philips, GE, Sylvania) would want to avoid bad press, so I think they mostly make better CFLs.
- Don Klipstein ( snipped-for-privacy@misty.com)
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wrote:

In my small smapling of Feit Electric, specifically a 23 watt spiral, I had better luck than that. I replaced it with a 3500K one of a different brand while the Feit was still working, because I wanted the whiter-but-still-warm color of 3500K.
Meanwhile, there is some tendency for longer life for ones of the "Big 3" brands: GE, Philips and Osram-Sylvania. Among others, there is at least some chance of better performance if the CFL has the Energy Star "seal of aproval" (my words).
- Don Klipstein ( snipped-for-privacy@rcn.com, snipped-for-privacy@misty.com)
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