I was comparing costs and percieved brightness of golfball type CFLs and LEDs the other day and the nice young lady in the shop warned me that a CFL cost 2p every time you switch it on.
Assumming electricery at 12p a unit, how big an MCB would I need for a circuit with 5 of these things??!! !:=))
Chris Holmes wrote in news:decc001a-0c31-40c1-81fa- snipped-for-privacy@r10g2000vby.googlegroups.com:
Unfortunately - perhaps repeating something she heard at home. My wife used to believe that cold water was best for rinsing stuff off plates. I realised it was because the hot water at her parent's was very low pressure and took ages to come through - so they used cold.
Is there a reason for believing this?
2.5A is the smallest I've seen, and would be fineNT
Am 04.10.2012 15:14, schrieb Chris Holmes:
If the CFL breaks after 3000 On/Off-Cycles and costs 6 Pounds, she is only by the factor of 10 away from the truth ;-)
63A on both sides of the ring should be fine. For a start.Disclaimer: Don't try this at home.
That used to be true of switch start fluorescents that took a life shortening hit on start up. IIRC, the rule of thumb was that the break even point was around 45 minutes.
CFLs, like all electronics, are most likely to fail on start up and the specs of some include minimum number of startup cycles. So, in a sense, this tale has some truth & it is better to leave them running rather than switch off for a short time.
It has nothing to do with the power consumed.
Chris K
And where is this 2p being used then, are we saying its that starter current or what?
Brian
It was never true for any type of fluorescent.
That's about the equivalent run time wear that a start uses up (although it depends heavily on control gear design). It doesn't use any extra power at all.
IME, CFLs most often fail whilst running, as the last bit of emission coating is sputtered off one of the electrodes.
Why was this "common knowledge"? (Note that I'm not disagreeing with you; I wonder why this idea is widespread.)
this is one of those myths that seems to have become accepted in many circles. It has almost nothing to do with fact. If you do the calculations it comes out as just seconds.
The myth dates from the early days of fluorescent lighting, and was never true. Obviously power consumed is part of the calculation, otherwise the calculation is wrong.
NT
My *guess*...
If you look at the total operating costs (tube replacement + electricity), I suspect the tube may have been the most significant part of this originally. This means that extra wear due to starts would have been more significant. It's easy to see how this expense could be misrepresented as extra power draw as the story gets passed on by those who don't fully understand it.
Nowadays, the electricity costs more than the tubes, so keeping tubes on when not required, just to reduce switching cycles, makes no sense.
Getting on for 1 kWh in about 2 secs then? 7.8kA - so you might get away with a D600 MCB ;-)
Fluorescent lighing wwa invented in '36, commercialised in '38 and was roll= ed out in factories during the war as much as limited resources allowed. Th= e equipment was beneficial to production and profits, ever in short supply = and expensive. Hence the greater than normal interest in minimising total r= un costs. The number of starts per tube was rather less than it is today, a= nd its true that the ballast takes more current during starting, even if le= ss power. Hence the situation was ripe for such things to spread.
NT
well its actually only 800Wh or 1800x800/240 amps so only 6KA.
out in factories during the war as much as limited resources allowed. The equipment was beneficial to production and profits, ever in short supply and expensive. Hence the greater than normal interest in minimising total run costs. The number of starts per tube was rather less than it is today, and its true that the ballast takes more current during starting, even if less power. Hence the situation was ripe for such things to spread.
My father put a fluorescent light in the garage in 1961. It was still there when my mother went into care in 2003 and we sold the house. So 42 years.
It was a bit dim I'll grant you. I THINK I had to put a new starter in, in the 80s some time.
That makes it easy then ;-)
out in factories during the war as much as limited resources allowed.
The first UK installation was one of the London Underground stations, in 1937. (I used to know which one, but I've forgotten.)
and expensive. Hence the greater than normal interest in minimising total run costs. The number of starts per tube was rather less than it is today, and its true that the ballast takes more current during starting, even if less power. Hence the situation was ripe for such things to spread.
My grandfather put fluorescent lighting in his factory during the war - it was encouraged to save power (don't know if it might also have been subsidised), and he was always fascinated by new things like that anyway.
When he retired and his factory closed (site was being demolished for redevelopment), we took some of the fluorescents to use as loft lights in my parents house, and they're still there. Unfortunately, these weren't the very originals as we were looking for the nicer looking ones (and the very originals couldn't be surface mounted as the ballast was in a bulbous box on the top). It would now be quite nice to have saved an original one or two, but that's not the sort of thing one thought of back in the 1969 when we took them.
The original tubes were designed to use existing products to run them, so there was little new tooling up required. The tubes were designed to run on 80W mercury vapour lamp ballasts, and the end caps were standard bayonet cap lampholders. Tubes came in 5' which ran at 80W, and later 6' which ran at slightly higher power on the same ballasts.
In the 1950's when more tube sizes had appeared, the 5' tube rating was reduced to 65W which was more efficient in that tube size, and we changed to the bi-pin lamp contacts, although most 5' tubes were dual rated 65/80W through to around 1980 for backwards compatibility, and BC to bi-pin adaptors were readily available.
The ones in my parents loft are the 5' 80W type with BC ends. Fortunately, I had a spare tube when a builder accidentally smashed one of them a couple of years ago.
Example extract from a spec sheet for Philips CFLs
?Lifetime of lamp: 8000 hour(s) ?Rated lifetime: 8000 hour(s) ?Number of switch cycles: 20,000 ?Lumen maintenance factor: 0.7 (at the end of the nominal lifetime)
etc
Others are similar
That is there is a spec for on-off cycles but it is so large as to not be worth worrying about. 2p for a £4 CFL suggests only 200 on-off cycles & it would never have been that small. 8000 hours divided by
20000 suggests that switching it on & off for less than 25 minutes hits the switching cycle spec first. So don't worry about it.Chris K
Or more precisely, each on/off cycle "costs" £4/20000 == 1/50p
At 10p/unit a 20W lamp costs 1p/5hours so each switching cycle is equivalent to about 6 minutes of operation so there is some rationale behind the story. All subject to wide variance though.
Still not worth bothering about - particularly since my pile of giveaways in storage are good for several lifetimes. They get replaced because of dim-ness rather than complete failure.
Chris K
Because it was going the rounds in the 60s after being mentioned in some publication that you'd expect to get their facts right.
Oops. Which one?
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.