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Posted by Fred on August 18, 2007, 7:16 pm
>
>>
>>> On 18/08/2007 18:59, Marsbar wrote:
>>>
>>>> Switch on only when required. What made you think that switching a
>>>> fluorescent light on and off wasn't a good idea?
>>>
>>> It was either a common misapprehension, or used to be different with
>>> older
>>> tubes. I certainly remember an "order" going around school in the early
>>> 70's to NOT switch off lights during break-times as it took more
>>> electricity to re-start them, than to leave them on for 20 minutes.
>>
>>It was a complete redherring then
>
> When, and with fittings of what vintage? Tubes and control gear have
> been improved continuously, changing out of all recognition since the
> end of the war.
>
>>and still is.
>
> Sorry not the case, there is still an optimum way of operating the
> tube.
>
> This sort of advice was originally intended for industrial users who
> had a machine shop or a weaving shed etc lighted with hundreds of
> fluorescent fittings mounted on the ceiling over the machines. These
> tubes were replaced on a planned preventative maintenance basis whilst
> the plant was shut down for (annual ?) holidays. To have tubes fail
> between times was very expensive, the electrician would have to work
> above the machines (which would have to be stopped) and there was the
> possibility that a tube would be dropped or broken contaminating the
> workplace with broken glass, and if that was a loom would include
> hundreds of feet of very expensive cloth.
>
>>Yes the current is higher in order to ignite the tub,
>
> That's not the issue (even if it's true, I've not seen it mentioned
> elsewhere), shortening of the tube life is the issue. Modern control
> gear can be a lot better than old stuff, but as always the best
> equipment is more expensive and not always used.
>
It's very much the issue! I recall stories as the poster had where the
starting of a fluorescent tube was equivalent to 1/2 hour running.
>>but given it lasts for a second or so. As long as the tube is
>>switched off for over, say 5 seconds, there'll still be a net saving.
>
> No.
>
> http://en.wikipedia.org/wiki/Fluorescent_lamp
>
> 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.
>
I have read the article and it confirms what I know. I was answering a post
outlining a supposition put forward in the 70's. At that time the ballast
would be an inductor and the starter would be gas filled device.
It's a great shame that the article doesn't qualify "Lamps operated for
typically less than 3 hours each switch-on will normally run out of the
emission mix before other parts of the lamp fail". That is the most common
failure mechanism for lamps. I recall figures which suggested that whilst
the lamp lifetime when "on" was shorter, the act of switching it off when
not needed actually increased the "real" life time of the lamp as well as
saving energy!
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