the myth of cheap running lights

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Thunderchild

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ok so I remember everybody saying that a cheap running bulb must be on for three hours before you save anything. Is this possible. lets analyze this statement. say you have a 25 W fluorescent lamp to replace a 100 W bulb. now lets assume the best case that we can that the bulb uses 100 watts in the first three hours... thats four times the power going through it and surley enough to blow it, I know most components cannot take more than 50 % overload here we are talking 300 %
now lets say that we are talking about the first few minutes, so take 300 watts and put them all out in a few minutes say the first 5 minutes we are talking some kilowatts at this point and this theory seems even more ridicolous.

I think that it is all a load of rubish and that at most in the first 1-3 minute the bulb may use a bit more and therefore turning one on for 10 minutes is fine.

Is there something I have overlooked ?
 
Maybe they operate differently in Europe where the mains voltage is twice as high as my 120VAC.
Here a compact fluorescent light bulb uses a fairly high current in its filaments to start. You can calculate the tiny cost for filament current for a minute or two.

When the bulb fails it is usually because a filament has burned out. Then it would be cheaper to use the bulb for long durations instead of wearing out its filaments early by starting it too many times.
 
What are you talking about?

A compact fluroscent lamp uses 1/5 of the power of an incandescent lamp and doesn't have that much of a high starting current, though it does take awhile to warm up so it does apear dim for a few miniutes after starting.
 
yes well people told me unless you run one for 3 hours you will loose not save I was told that in the first three hours more current was used than by the incandescent bulb this is obviously false. you see hero999 I was told that there was a very high starting current only to realize years later that this must be false or there would be no fluorescent bulbs just fireworks
 

Like AudioGuru mentioned, you get a short higher current time during startup, as the tube heaters are on - but after that the current settles down to it's running current. But even this higher current isn't anything particularly high.

Interesting that AudioGuru always mentions heater failure on flourescent tubes, perhaps this is to do with the 120V mains in North America? - certainly in my experience with 240V (with a LOT of such fittings at work) such a failure would be extremely rare.
 
I do not recall the exact details but (Please do not hit me) the mythbusters did testing for the common types of lighting and concluded the startup cost is so small that you always save by turing off a light. That is to say even short off periods save money.

They also tested to see if the bulb life was shorted by frequent on/off cycles and that it was not a big factor.
 
240V fittings are just inductors, the larger 120V fittings are autotransformers which boost the voltage to start the tube.

Compact fluroscent lamps all have electronic ballasts and high qualitry new fittings also have electronic ballasts.
 
120VAC fluorescent tubes with an inductive ballast have the filaments fully heated for the entire lighted time. So the ends of the tubes turn black (due to the heat?) and a filament burns out and the tube doesn't light anymore.

The filaments and inductive ballasts waste a lot of power so they are not made anymore and are being replaced by ones with smart electronic ballasts that turn off the filaments when the tube has lighted, similar to a compact fluorescent bulb.
 
yes well I was told how huge the startup current was then realized later it can't be that much and that it can't be for that long hence turning the light on for only 10 minutes is fine after all the incandescent light also fails more quickly with frequent on off cycles.
 
audioguru said:
120VAC fluorescent tubes with an inductive ballast have the filaments fully heated for the entire lighted time. So the ends of the tubes turn black (due to the heat?) and a filament burns out and the tube doesn't light anymore.
Click to expand...

Another advantage of 240V mains!
 
well frankly I can't see the sense in 120 Volt mains it means that twice the amperage is needed for the same wattage and that twice the thickness cabling is needed a total waste of resources, I think we could use even up to 500 volts mains unless insulation was a problem
 
I have compact fluorescent light bulbs outside. Their minimum operating temperature is -15 degrees C and I turned them on when it was only -22 degrees C.
Boy oh boy they were dim for a few minutes!
I saw ultra-violet light coming out before visible light started to glow.

I had one fail and drip molten plastic on the table below it. Then it smoked. It was recalled and was replaced by the importer.
The Chinese manufacturer used a counterfeight tested/approval label.
 
The Chinese manufacturers will put any testing and approval label on that you want, for just the price of the label - no testing required!.
 
well people I learned this while working for a guy trying to import from china. the CE approval marking is CE our clever chinese friends instead have created the C E marking that they say means china export but is obviously meant to fool us, of course it is perfectly legal though.
 
They even have labels that say, "Made in the UK" and "Made in the USA".
UK and USA are the names of towns in China.

They spell the word Quality stating with the letter K.
 
I watched that episode not so long ago and remember some of the details.

From an incandescent to a CF bulb there were only a couple of seconds where the bulb took the higher current - it was more economical to turn them off when you left the room.

For the strip flourescent lights the break even point was 23 seconds off the top of my head it will still be economical to turn these off after you leave the room.
 
Put an analogue ammeter in series and see the results.
A 0 to 2 Amps schale is perfect for 240 Volts.
At start up for a 40 Watts CFL or TL, current may be 1.8 Amps for about 2 to 5 seconds when it tries to start up.
Then it settles quickly to around 250 mA's and drops slowly to about 220 mA's as the lamps warms up a little.
That's all,

Ok, for our 110 Volts users, double the values quoted above.

I used to believe too, that in the earlier days these lamps drew large currents and needed to be on for a long time to make it worth while.

It's just a fib
 
"They also tested to see if the bulb life was shorted by frequent on/off cycles and that it was not a big factor."

The mythbusters obviously haven't spent their time replacing incandescent lamps in a large electronic marquee. The on-off cycle stresses the filament. Although a new lamp may not seem to have a shorter lifetime with repeated on-off cycles, an older lamp will. As a filament erodes during operation, the ON cycles is what usually causes the burnout because of the high inrush current causing a high IR drop (and subsequent I²R burst) across a spot of high erosion.

Dean
 
Years ago when I worked with telephone systems, the switchboard used many incandescent bulbs that kept burning out due to the stress of blinking when a new call came in or a call was on hold.

I added a little DC current to the bulbs to keep them warm and then never had to replace another bulb.

There is a cabin in Alaska with an incandescent bulb that has been lighted continuously for over 60 years and it is still working today. It has had only one startup surge of current in its life.
 
Lightbulbs are an energy on demand device. Regardless of their wattage ratings, they still draw a designed amount of current and leaving them off when not needed is paramount to conserving power and money savings. Whoever recommends to leave them on as a power saving measure is blowing smoke. About the only time you save money is by leaving on the mercury vapor, metal halide, or high pressure sodium types since those will experience a shortened lifespan from too many unecessary on/off cycles. Even then it's more the lamp's engine that fails rather than the lamp. And since they require a lengthy amount of time to reach full output, it's a nuisance to have them cycling on and off for brief periods.
 
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