On Tue, 05 Jun 2018 19:52:52 +0100, Dave Liquorice wrote:

On Tue, 05 Jun 2018 16:13:49 GMT, Johnny B Good wrote:

You can buy 125LPW LED GLS lamps in Asda and Home Bargains stores (8
quid a pair of 1522Lm bulbs in Asda or 3 quid for a single 1500Lm bulb
in Home Bargain).

What type of "LED GLS"? filament or individual LEDs on a big lump of ali
heat sink?

The latter with around a 260 deg throw from a translucent envelope. The
former filament type are also a bunch of individual LEDs strung along the
filaments. Not being mounted onto a BFO heatsink limits them to 810 Lm
using the 125LPW LEDs but it does have the charm of a wider 300 deg throw
of light similar to a tungsten filament lamp.


If you're looking for a more economic to run LED replacement, don't
waste your money on Aldi and Lidl's offerings. Up to now, checking out
the specifications of such tat has only made my lip curl in disgust at
the results of my LPW calculations.

Simple lm/W isn't the whole picture. Aldi 5' LED tubes are 2000 lm and
22 W - 91 lm/W. Not so shabby. 2000 lm is numerically less than half
that of 58W 5' florry but I find in practice that it's not noticeable so
I'm getting the same percieved light level for less than half the watts.
At least two are on for 18 hours a day, that's 1.3 kWHr/day not consumed
or 473 kWHr/year @ 12p/kWHr = nearly £60 and I bought them when Aldi
were floggin' em off at £4.99 each.

The ones I was looking at were only 81LPW at best. It does depend on how
you're intending to use them. If it's for a reflector type fitting
intended to concentrate the illumination in mainly one direction, then
they'll reduce the running costs for no reduction in useful illumination.

However, if it's for use in a ceiling fitting intended to take advantage
of all the light output of a fluorescent tube to provide diffuse
shadowless room illumination in, say a kitchen for example, then they're
not such a good alternative.

A better way to emulate the diffuse illumination properties of a linear
fluorescent tube with LEDs would be to use them in ceiling mounted
lighting panels which can also neatly solve the cooling issue that arises
when the LEDs have to packed pretty close together in a narrow "tube" or
GLS lamp format.

Way back in March 2014, Cree announced a record breaking 303LPW
laboratory achievement in LED lamp technology. Since the record of such
milestone achievements indicates a typical lead time to marketable
product of a decade, we just might see 250 to 280 LPW product going on
sale, some time around 2024.

This is something to look forward to, not only for the sake of the
relatively marginal savings on household electricity bills but mainly for
the fact that we'll be able to fit LED GLS equivalents of 150 and 200
watt tungsten filament lamps into existing lamp sockets without risk of
premature failure from overheating.

The recent introduction of a practical GLS LED substitute to the 100W
incandescent was only made possible with the advent of the current
generation of 125LPW LEDs. The older 81LPW LED lamps were limited to the
(American standard) "60W 810Lm" GLS light bulb primarily on account of
the waste heat dissipation temperature limitations of semiconductor based
devices (external lamp surface temperature limited to little more than 80
deg C maximum versus the 200 or so deg C limit of tungsten filament
lamps).

Unless you're in a real hurry to upgrade to "Instant On, Full
Brightness" lighting, you'd be better off putting up with your
electronically ballasted T8 tubes with their barely sufficient dosing of
mercury which makes them emulate the mercury amalgam dosed CFL run up
delay and the need for the fancy micro-processor controlled HF ballasts
to preheat the tube cathodes for an unconscionable 900ms before allowing
them to turn on[1], and wait a little longer for even better and cheaper
LED GLS lamps or ceiling panels to materialise.

[1] Sadly, the price of reducing energy consumption of a 52W 4 foot
Quickstart fitting with a T12 full fat mercury dosed fluorescent tube
that could provide flicker free "instant on" (250 to 300ms) startup
without sacrificing the 16,000 hour life to the brutality of a cheap 'n'
nasty switch starter cursed fitting.

The 16W saving is some consolation but I'm going to miss the utter
simplicity of the half century old Quickstart technology used in my last
Quickstart fitting in the basement when my last functioning T12 Quickstart
compatible[2] tube finally expires.

[2] There was a time when *all* T12 fluorescent tubes sold in the UK were
Quickstart compatible until about 10 or 15 years ago when replacement
tubes started to appear that wouldn't start up in such fittings,
necessitating a return trip to the electrical factor to try a different
brand of tube. Now we're stuck with crappy under-dosed T8 tubes with
their minutes long run up times and the one second delay from switch on
that modern electronic ballasts are forced to use to avoid premature tube
failure. It's lucky that higher efficiency LED lamps are only just round
the corner. Nice timing!

--
Johnny B Good