On Thu, 07 Jun 2018 07:07:50 +0100, Brian Reay wrote:

On 06/06/2018 23:27, Johnny B Good wrote:
On Wed, 06 Jun 2018 22:02:00 +0100, Brian Reay wrote:


I suspect the problem is that the fittings are old, T12, types and I'm
using T8 tubes- ARW's post provided the clue. Some other tubes, used
in a suspended ceiling, haven't given any trouble in 20 years (since
we bought the house). They've just been removed (part of a bathroom
replacement) and are the larger diameter, T12, style.

We have CFLs in several other places and they've been fine.

JOOI, did those tubes you've just decommissioned after 20 years of
faultless service, happen to light up with no flicker within a quarter
of a second of being switched on?


No, they didn't fail but where 'slow' sometimes with a flicker when
starting.

Interesting. I was wondering whether the fittings were using
"Quickstart"(tm) ballasts which would have neatly explained their long
life. Obviously not. In fact that seems more like the behaviour of my 5
foot T8 tube in my office fitting using a selected starter to get it fire
up at all (the Quickstart upgrade had to be downgraded since T8 tubes
just sit there like dummies in a QS ballasted fitting).

I've never seen the 5 foot tubes (both T12 and T8) do the classic flash,
flash, fla****y flash startup sequence of the switch start 4 foot
fittings, it just sits there with no indication it's been switched on for
4 to 6 seconds before it springs into life as if nothing was wrong. Since
this is rarely cycled on and off more than twice in an evening, it's just
not worth fretting over.


They had conventional starters. I have replaced a couple of the
starters in the garage with 'electronic' ones. I can't say I've noticed
any real difference. I put the new LED tube in the remaining garage
fitting with an old starter.

Those last four words had me confused. I'm guessing you really meant
"old fashioned switch start fitting" rather than the implied LED tube and
an old starter switch. :-)


I've not been impressed by LED lamps in the house until recently. The
new bathroom has LED lights which are good and now this tube. I've a few
'smart' LED bulbs (Philips and Ikea) controlled by Alexa- they aren't
bad. Previously I've always been disappointed by the output.

Until now, you had justification for not being impressed with *most* LED
GLS lamps being foisted on the all too trusting shopper. It's true you
could get genuinely "60W (the better American 810lm standard)
incandescent equivalent" LEDs which outshone the 20W CFL versions for a
mere 12W (claimed - it was more like 14W - still less than the dimmer CFL
version) when the 81LPW lamps first started to appear about 5 years ago.
This was about the limit until just over a year back when the 125LPW
"100W 1500lm equivalent" GLS lamps appeared in Home Bargains stores at
£2.99 a pop (still their current price).

The limiting factor regarding the incandescent wattage equivalency is
the much lower maximum temperature limit of the lamp (circa 80 deg C
versus the 200 or degrees of a classic tungsten filament lamp). The
better the LPW performance, the more light you can get for your watt and
the less of that energy input is turned into heat.

People had overheating issues trying to use the brightest available LED
lamps of the day if they overlooked the ventilation requirements in
fittings that restricted the free flow of air which wasn't an issue with
incandescents which could compensate by running 10 to 20 degrees hotter,
not something you could do with an LED which may already have been within
5 degrees of its limiting maximum temperature in a freely ventilated
fitting to begin with.

As LED lamp technology improvements approach the 303LPW figure reached
in Cree's Labs just over four years ago, this overheating will become
less of an issue and the lamps more likely to meet their promised 20 to
30 thousand hour lifetime ratings.

--
Johnny B Good