DIYbanter - View Single Post - 220-240v lamps

Johny B Good[_2_]

On Fri, 21 Mar 2014 12:24:18 -0700 (PDT), wrote:

On Friday, March 21, 2014 5:41:29 PM UTC, Johny B Good wrote:

====snip====

There's a very good reason why lamps sold in the uk with 240v printed
on the envelope are _really_ 240v filamented lamps (and similarly in
the case of 220v lamps sold in most of continental Europe).
Modern electronically ballasted fluorescent lamps (both linear and
CFLs) and mains voltage LED lamps can be readily designed to cope with
such variations so can be sold with 220-240v voltage ratings. The good
old fashoined tungsten filament GLS lamp however, still has to work
within the constraints of 'Physical laws'.

230v is a politician's description rather than a real physical one. UK still has a
240v target voltage, and France etc 220v. What has changed is
a) what the voltages are called
b) appliance specs, which are now specced - where possible - to cope with both
supplies.
c) and the outer limits of what's permitted for supplies, which is of small
significance in practice.

FWIW 1000 hours is not minimum TCO for GLS, but I expect it was when the
standard was decided. US uses 750 hours, which is closer. Long life lamps are
even further from minimum TCO, and even more so when overpriced.

That's exactly why ordinary tungsten filament GLS lamps have to have
their voltage so closely matched to the mains supply voltage local to
the regions they're sold in.

The "Thousand Hour" lamp life does have its origins in the early
days. My reference for this figure comes from the "Lamps and Lighting"
(second edition) published in 1972, reprinted 1979. This must have
been when lamps cost relatively more compared to the unit price of
electricity than is the case today.

I suspect the reason for sticking with the 1000 hour rating was more
to do with satisfying established expectations by the general public
in the matter of 'lamp quality'.

The yanks seem to have really gone overboard in the matter of
rejigging the lamp life hour rating down to a mere 750 when you
consider that the lower voltage filaments will straight away offer a
superior TCO compared to 220 and 240 volt filaments even at the 1000
hour life rating.

There's a very good reason why 12v halogen downlighters have such
endurance when powered via a modern current limiting electronic
ballast compared to their cheap 'n' cheerful 240v counterparts.

The wikipedia article on tungsten lamps, whilst pretty good, is a bit
skimpy on the detail (but still worth a look if you want to check your
basic facts). Particulary informative in this case, is the link to
"lamp rerating" that can be found there towards the end of the
article.
--
Regards, J B Good