On 16/09/2018 17:11, Cursitor Doom wrote:
Gentlemen,

Back in the 1960s, when tubes were coming into service more and more, it
was a widely held belief that they were more expensive to run than
tungsten filament bulbs if turned on for short periods. It was said that
most of the power they consumed was drawn during the 'strike-up' phase so
if they weren't on for at *least* an hour, you might as well be using TF
bulbs.

Yup, from an electrical point of view was a load of nonsense at the time
and still is...

If you think about it, say your tube draws 0.25A once lit, if you want
to draw an hours worth of energy in (say) 5 secs, you will need to pull
3600/5 or 720 times the current. That'a 180A - or enough to trip a 32A
circuit breaker instantly, let alone a 6A MCB or 5 amp fuse.

There is some truth in that there is extra cost to start the lamp but,
that is down to accelerated wear on the starting filaments which will
reduce the total lamp life (or at least the available number of
"starts"). Since they were quite expensive at the time, there was a
financial cost associated with that reduced life. So there was some
sense in not turning them off for very short durations.

Well, here we are 50+ years on and tubes are now very much old tech.
What, with the benefit of hindsight, have the Panel to say about those
old efficiency claims of the day?

Probably more wrong now than then since modern tubes are far cheaper,
and probably survive more starts anyway due to better control gear.

--
Cheers,

John.

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