On Thu, 11 Jan 2007 22:20:45 +0000, David Hansen
wrote:


That depends on the particular model of lamp.

But to fit an existing fitting the choice can be very restricted.

Some start very quickly

Yes

and are at full brightness in a second or two.

The devil is in the detail.

That is not my experience with the lamps I have by a very long chalk.

This morning before we switched the lighs on I brought my Luxmeter in
from the car and made some measurements with the lamps starting from
cold (20c).

I checked 3 types of lamp we had installed, all in good condition
about 1 year old except the Genura (But that is supposed to last 18
(?) years !). Starting from cold I made measurements at 5 seconds, 3
minutes, and when fully warmed up 15 minutes later. I expressed the
reults as a percentage of this ultimate maximum reached.

Fixed pitch font

IKEA 11W "Bulb" Feit 13W Spiral GE Genura

5 Sec. 16.6% 47.5% 20.0%

3 Mins. 80.5% 95.8% 80.0%

In general the light output appeared to increase linearly with time
from the 5 second point when all lamps had actually started to the 80%
output point and then approached the maximum asymptotically.

Others take longer to start.

It's not the time to start that concerns me it's the time taken to
reach say 80% of full output. One can surmount this problem to some
extent by oversizing the lamps if they'll go in the fitting, but ISTM
about 50% of max output can still take about a minute to reach.

Modern models for some time have generally started very quickly.

But they take a long time to warm up. The Feit Spiral was better than
the others (But very ugly in an exposed fitting) but would still
involve a tiresome wait to each say 80% output, very noticeable on
returning to a house in darkness and switching on hall, landing,
living room and kitchen lights.

ICBW, but I have a feeling that the amount of mercury in the lamps has
been reduced recently for environmental reasons, full output is not
achieved 'till all the mercury has been vapourised and distributed
around the tube.

Like all green initiatives there are two sides to the coin, viz it can
lead to users fitting bigger higher consumption lamps using more
energy, and disposing of lamps sooner thereby wasting raw materials
(including mercury !) and energy.

Le Chatelier's Principle in action.

I'll make some light output comparisons sometime soon between CF's and
GLS tungsten lamps, and post the results here. Trouble is I'll have to
remember to buy one, we don't have a single GLS tungsten lamp in the
house.

DG