I wonder if any of you knowledgeable folks out there know why compact
fluorescent lamps take time to get up to full brilliance?, in my
kitchen I have a conventional 5" linear fluorescent and it is at full
brilliance as soon as you switch it on.
Trevor Smith

Trevor Smith wrote:
I wonder if any of you knowledgeable folks out there know why compact
fluorescent lamps take time to get up to full brilliance?, in my
kitchen I have a conventional 5" linear fluorescent and it is at full
brilliance as soon as you switch it on.

Basically, the operating temperature of the linear tube - I assume you
mean 5' - is much closer to room temperature.
With CF, they run at 100C or so.
In order to get the optimum pressure of mercury when running, the 'off'
pressure is rather lower.

It's also a compromise between electrode life and turn-on speed.
If it takes 1-2 s to start, then it allows the electrodes to warm up
before the tube is started.

This causes less wear of the electrodes and blackening at the ends than
'instant on'.
(this is completely seperate from the tubes taking time to warm up once
on)

Ian Stirling wrote:
Trevor Smith wrote:
I wonder if any of you knowledgeable folks out there know why compact
fluorescent lamps take time to get up to full brilliance?, in my
kitchen I have a conventional 5" linear fluorescent and it is at full
brilliance as soon as you switch it on.

Basically, the operating temperature of the linear tube - I assume you
mean 5' - is much closer to room temperature.
With CF, they run at 100C or so.
In order to get the optimum pressure of mercury when running, the 'off'
pressure is rather lower.

It's also a compromise between electrode life and turn-on speed.
If it takes 1-2 s to start, then it allows the electrodes to warm up
before the tube is started.

This causes less wear of the electrodes and blackening at the ends than
'instant on'.
(this is completely seperate from the tubes taking time to warm up once
on)

Sorry I meant 5', when you say they run at 100C I take it you don't
mean the operating temperature as I have just touched the tube of a 15
watt CF and it is warm but definitely not 100C
Trevor Smith

The message
from Ian Stirling contains these words:

It's also a compromise between electrode life and turn-on speed.
If it takes 1-2 s to start, then it allows the electrodes to warm up
before the tube is started.

Doesn't it also increase the output per unit area? A more important
consideration in CFLs than in linear units.

--
Skipweasel
Pay no attention to that man behind the curtain.

In article . com,
"Trevor Smith" writes:

Ian Stirling wrote:
Trevor Smith wrote:
I wonder if any of you knowledgeable folks out there know why compact
fluorescent lamps take time to get up to full brilliance?, in my
kitchen I have a conventional 5" linear fluorescent and it is at full
brilliance as soon as you switch it on.

Actually, it's not. Initial output is nearer the final brightness
than is the case with compact fluorescents, but long linear tubes
still have a run-up time, and it's actually much longer than a
compact fluorescent (20 minutes is quite typical).

Basically, the operating temperature of the linear tube - I assume you
mean 5' - is much closer to room temperature.
With CF, they run at 100C or so.
In order to get the optimum pressure of mercury when running, the 'off'
pressure is rather lower.

Conversely, long linear tubes are designed to run at 40C
in a ambient of 25C. (Actually, that's T12 tubes -- I don't
have the figure for T8 tubes, but it's probably not a lot
higher.)

Another factor is that most compact fluorescent tubes use a
mercury amalgam pellet to control the mercury vapour pressure
over the range of operating temperatures the tube might find
itself in. It takes time for this pellet to warm up and for
the mercury to diffuse out of it. This is not necessary in
T12 and most T8 tubes, although all the new T5HE and T5HO
linear tubes use it.

Sorry I meant 5', when you say they run at 100C I take it you don't
mean the operating temperature as I have just touched the tube of a 15
watt CF and it is warm but definitely not 100C

It will depend on the enclosure, but they are designed to
run with the tube up to 100C.

--
Andrew Gabriel