David
Thanks for your input.

On Feb 26, 1:08 pm, David Hansen
wrote:
On 26 Feb 2007 03:36:31 -0800 someone who may be "gmw"
wrote this:-

I have just used a photographic exposure meter to compare the light
output of a CFL bulb with various pearl light bulbs.

A camera light meter. Not quite the right thing to measure the
output of light bulbs, though it will give some indication.

The light meter was a Gossen Sixtar hand held CdS meter, used in
incident light mode. As you say, it gives some indication.
To check that my results were not too wildly out, I also made an
extinction photometer that I placed between pairs of bulbs, which
gives similar results.

What sort of CFL were you measuring with the camera meter? Some
designs take a while to achieve full brightness.

The CFL is a Philips B22 BC 15000h 1200 lumen 140mA 230-240V order
code 544742xx
Our mains voltage is 230V nominal, during the test I measured 228V on
a basic DMM early evening. The afternoon voltage is 232V.
The voltage variations obviously affect the light outputs of both
types of lamp.

I took readings with the Sixtar set to 100ASA (so that EV = LV) at 5
minute intervals at the same distance of ~1.5m.
At switch on from room temp the LV was ~3.0.
After 5 minutes the LV was ~3.5
After 30 minutes the LV was ~3.7
A new 240V 60W 2000h pearl bulb (555 lumen) gave an EV of 3.9 and was
subjectively as bright as the CFL
A new 240V 100W 2000h pearl bulb (gave an EV of 4.9 and was
subjectively much brighter than the CFL
A new 240V 100W 1000h pearl bulb gave an EV of 5.0


The CFL is a 20W bulb claimed to be equivalent to a 100W bulb. It has
had about 1 year of evening use.
Its measured light output is a little LESS than a 60W 2000h pearl bulb
rated at 555 lumens, and ~40% of a 100W 2000hr bulb.

I note with interest the different conditions. From what you have
typed it appears that you compared the output of a one year old CFL,
measured with your meter, to the claimed output of two bulbs, the
age of which you don't state. Fascinating.

The pearl bulbs were fairly new. Pearl bulb outputs are less
susceptible to aging than CFLs, and pearls are statistically likely to
be younger than CFLs for most of their lives, if CFLs last as long as
claimed.

I think the problem could be due to supply voltages. I suspect that
CFL output is more sensitive to supply voltage than pearls, in which
case we need 230V rated CFLs if we are to get the claimed output.


Having replaced several 100W pearl light bulbs with "100W" CFLs

Where were these installed?

All the bulbs were for general illumination, fitted to ceiling light
fittings, mostly with open lampshades above them.

we have reverted to pearl in all but one room.

For what reason(s)?

In living rooms a single "100W" CFL room light was too dim to read
comfortably by etc even after fully warmed up, giving similar light to
a 60W bulb.
A single 100W pearl was adequate.
In rooms where lights are normally off, the CFL's slow warm up and
alleged reduced life caused by cycling could be a problem. CFLs would
be left on much longer than pearls, negating energy saving.


These misleading claims must be understood and ruled out.

Though earlier you typed that these claims were presumably accurate.
Why should accurate claims be ruled out?

The claims are no doubt accurate in the technical terms defined in the
small print. Those compare the CFL light output with "soft
colour" (low efficiency) type of bulb that is not used for general
illumination.
I suspect that they are both measured at 240V, but that CFLs may
produce much less light at 230V than do pearl bulbs. Is this so?
I presume that this is why the actual output of the bulbs in service
is way below the "headline" equivalent output, which is why I say the
claim is misleading.


CFLs are not yet ready to replace conventional bulbs.

Incorrect. In most cases there is now a suitable energy saving bulb.
The number of cases where such bulbs are not suitable has been and
is being reduced.

I would be delighted to fit CFL bulbs that, at 230V, give similar
light levels to 100W 2000h (long-life) pearl lightbulbs at the same
voltage, for most of their lives, and do not suffer infant mortality
or DOA.


At one time such bulbs were really only suitable for relatively
large fittings with lamps that were left on for long periods. This
was because of the size/weight of the bulbs, the length of time they
took to reach full output and a relative lack of robustness of the
starting mechanism. However, that was in the early 1980s. The
engineering of energy saving bulbs has progressed a long way since
then.

Re lack of robustness, I recently purchased 3 CFLs (in much heavier
packaging than pearl bulbs).
One had broken glass, one failed quickly, the third is still going
strong.
Filament bulbs are much more robust.
I have no financial interest except as a consumer.
I want CFLs to work. They have never yet worked as advertised for me,
or many others.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Giles Whittaker, Kirkliston. BAe Systems (Retired)