CFLs - switching on and off

[Don Klipstein]

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.

1. 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 ( [e-mail])

[Don Klipstein]

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 ( [e-mail])

[Don Klipstein]

Many dimmers don't let you achieve full brightness. The bulb may randomly have longer-than-average life. Some "ordinary" bulbs are long-life versions (with slightly less light output).

So I am not surprised.

- Don Klipstein ( [e-mail])

[colinstone]

Many thanks for all your informative and illuminating inputs - the way ahead is much brighter now. I amazed that this thread has not degenerated into the usual flaming after a few posts - I can only assume that a better class of person inhabits the a.h.r and uk.diy threads. Best regards.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember John Rumm saying something like:

Ding!

The first time I read about this was nearly 30 years ago in New Scientist, where the article made the point it was about overall lifetime of the lamp and fittings, rather than electricity consumption. In that original article there was bare mention at all of the start-up energy cost, probably because it was insignificant. The piece illustrated how the lifetime of a lamp was reduced by multiple starts, and showed that it was more economical *at that time* to reduce the number of starts, or once started, leave the lamp on for a while.

At that time, with the fluorescent lamps and fittings available and the energy cost of the day, the break-even point was 20 minutes.

It's usenet, so it's not unknown for the ill-informed start an argument without knowing the full story.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember [e-mail] (Don Klipstein) saying something like:

Good for you. Have a coconut.

[Andrew Gabriel]

Actually, regular mains filament lamps don't care about switching, and it doesn't shorten their lives. (This might not apply to high current and halogen lamps, for which I haven't seen figures.)

That's why people think that switching shortens their life, but it's a misunderstanding of what's happening. At the end of life, lamps can continue operating for a few hours past the point where they won't survive another switch-on. If you switch them off during this period, they will blow at next switch-on, and in the case of a lamp which isn't normally switched on for an hour or more, it's pretty certain to blow at a switchon rather than whilst running. However, this is independant of the number of times the lamp has been switched on in the past and depends only on burning hours. There are a number of applications where this effect can be measured, such as continuously flashing signs which use regular lamps, where life can be seen to depend on total burning hours and not frequency of switching.

Assuming the most common fluorescent tube failure mode (electrode emission mix all sputtered off), it depends on the design of the control gear, and not much on the type of tube.

[meow2222]

But the 2 situations arent comparable afaics. Filament failure vs oxdide contamination on a filament heater running only red hot.

NT

[meow2222]

Perhaps if we'd been discussing gas lamps it might have done...

NT

[meow2222]

CFL candle lamps will fit chandeliers etc, but imho they dont come anywhere near being a replacement in visual terms. The appearance is bulkier, ungainly, and they have no sparkle at all, unlike clear filament candles. Also with chandeliers the splitting of colours depends on a small light source, so use of CFLs does this no favours either. Chandeliers are one app where filaments still rule. LV filaments can at least gain a bit more efficiency over mains.

NT

[meow2222]

I would think it would make quite a big difference, but havent calced it yet.

NT

[Fred]

Many thanks for your support. I was trying to make the point, admittedly badly, that in the 70's that there was the misapprehension that starting a fluorescent tube took an inordinate amount of energy. I think we both agree that this is very untrue.

[Dan_Musicant]

:Nowadays domestic users of fluorescent tubes need not concern :themselves too much, but "Best Practice" is "Best Practice". If you :have a fitting that requires a lot of effort to get at (above the :stairs say) it makes sense to get the most out of the tube. : :DG

Yes, DG has it right. The issue is NOT energy usage here but the life of the bulb. Turning a CF on and off a lot DOES shorten the life. It may have 10,000 hours MTBF, say, but if you turn it on and off 10,000 times the life isn't apt to be 10,000 hours! I don't know if the bulbs have gotten better that way, but what HAS been getting better is the cost of the bulbs. They still aren't nearly as cheap as incandescents, but the economy of the situation has incandescents out of the picture. I haven't bought one in quite a few years.

If I only need a CF on for a few seconds, in my workroom, say, I generally use a flashlight rather than turn on the overhead light for

10-15 seconds in order to find what I need. At the ceiling are two CF's, and I don't want to wear them out. I've heard that nowadays the life is only shortened maybe 5 minutes, but I suspect that's quite inaccurate. I have had several CF's fail way before they were supposed to. There's a circular one in my kitchen that would probably cost me over $10 to place, and the one it replaced lasted maybe 10-15% of the supposed life expectancy.

Dan

[Dan_Musicant]

:"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

[Don Klipstein]

My suspicions:

1. Heat - see if it gets unduly warm where that light is. Rated life is with ambient temperature 25 degrees C (77 degrees F). Better ones should have only slight incidence of early failures if it gets a fair amount warmer. But if you have an enclodure around it, try removing the enclosure.
2. Was it a brand other than GE, Sylvania or Philips? Most "circline" lamps that I have seen to go into screw sockets have been by Lights of America so far, and I have had a disproportionate share of LOAs die young. (However, I have only bought one LOA since 2001 so they may have improved.) I have also generally experienced LOAs (as well as Maxlites) to be a little dimmer than others of same claimed light output.

- Don Klipstein ( [e-mail])

[David Hansen]

On Mon, 20 Aug 2007 11:38:55 -0700 someone who may be [e-mail] wrote this:-

The comparison is one of whether leaving on equipment involving hot bits of metal has advantages in terms of reliability. It does in many fields, but this has to be weighed against the energy consumption of doing so.