>>Dave wrote:
>>> First time I've ever bought one of these LL lamps (sad,,, sad). Anyway, It's 20W
>>> equiv. light of 100W and has three long U shaped tubes. When switched on, only
>>> two of the tubes light up (takes about 1 minute to reach full brilliance). But
>>> it takes a few minutes longer before the third tube shows any light at all! Is
>>> this normal operation?
>>> tia

It's all one tube. What you describe is not uncommon if the lamp
hasn't been used for a while or is quite cold. There's no light
from part of the tube (the middle normally) as there's no mercury
vapour there. It will diffuse down as the tube warms up.

--
Andrew Gabriel

Andrew Gabriel wrote:
> >>Dave wrote:
> >>> First time I've ever bought one of these LL lamps (sad,,, sad).
Anyway, It's 20W
> >>> equiv. light of 100W and has three long U shaped tubes. When
switched on, only
> >>> two of the tubes light up (takes about 1 minute to reach full
brilliance). But
> >>> it takes a few minutes longer before the third tube shows any
light at all! Is
> >>> this normal operation?
> >>> tia
>
> It's all one tube. What you describe is not uncommon if the lamp
> hasn't been used for a while or is quite cold. There's no light
> from part of the tube (the middle normally) as there's no mercury
> vapour there. It will diffuse down as the tube warms up.
>
> --
> Andrew Gabriel

I'd say it's not acceptable for normal indoor temperatures. I bought a
3 pack of cheapo 11w bulbs from Ikea - 2 of them would start instantly
but the 3rd would sit for ages before the whole tube fired up and get
very hot, so they went back. I remember the older heavy, non electronic
ballast bulbs taking longer to start and reach full brightness, but
with modern ones a I think a much quicker start up is expected.

In article <(E-Mail Removed) .com>,
(E-Mail Removed) writes:
>
> I'd say it's not acceptable for normal indoor temperatures. I bought a
> 3 pack of cheapo 11w bulbs from Ikea - 2 of them would start instantly
> but the 3rd would sit for ages before the whole tube fired up and get
> very hot, so they went back. I remember the older heavy, non electronic
> ballast bulbs taking longer to start and reach full brightness, but
> with modern ones a I think a much quicker start up is expected.

There's a technology problem here which hasn't been solved.
These compact fluorscent lamps operate at a higher mercury vapour
pressure than did the old traditional large linear fluorescent tubes
in order to achieve the higher power output in their compact size.
The compact size also means they have to be designed to run hotter
than traditional fluorescent tubes (tube temperature of 100C is typical,
verses 40C for traditional fluorescent tubes). A third factor is the
concern about mercury in the environment, which has resulted in very
much more accurate dosing of mercury in tubes -- these tubes now have
pretty much just what they need whereas tubes used to have perhaps 10
times what they actually needed which meant there was still plenty
available in vapour form even when the tube was cold. All these
factors have combined to make the initial cold running lamp (in
particular the mercury vapour pressure) so very different from the
final running temperature/pressure that some form of run-up time is
pretty much unavoidable. Some manufacturers are working on minimising
this effect, but I suspect you're going to wait for a technology
change to something like xenon lamps with programmed power output
control gear (as used in HID headlamps) before the issue is solved
to everyone's satisfaction. (Then there will be a new set of things
to moan about such as uneven colour distribution from the xenon
arc, and noticable colour variations with lamp aging and between
identical lamps in multi-lamp fittings.)

--
Andrew Gabriel