On 20/03/2014 22:28, charles wrote:
In article , Harry
Bloomfield wrote:
Nightjar has brought this to us :
On 20/03/2014 21:19, Harry Bloomfield wrote:
on 20/03/2014, Nightjar supposed :
On 20/03/2014 18:42, Harry Bloomfield wrote:
After years of use, the 4 lamps in the oven needed replacement.
Ibought some from a local shop which were marked 230v and they
lasted just weeks, got another set from ebay listed as 220 - 240v
which each lasted only a week. all were marked as oven lamps, but I
wasn't conviced about that, due to the glass being very clear,
rather than toughened. Very annoying, because they are not that easy
to change.

Latest set have lasted a month and were 2 for a pound from
Poundland, marked 240v on the package and on the lamp base, the
glass was also discoulored suggesting they were toughened. Better
yet, they have lasted a month so far ;-)

Try explaining to numpty sales people that 220v is very different
from the 240v in the UK :'(

We harmonised with the rest of Europe many years ago, so UK voltage
is 230V +10% -6%. Anything sold within the EU for mains voltage use
should work on any voltage within that range.


Except filament lamps, which either under run at 220/230v, or are over
run and last no time at all on 240v.

There are no exceptions to the requirement. Filament lamps should be
designed to work at 253V, even if that means there is a slight loss of
light output at 216V.


The difference in light output between those to voltages is quite
considerable. In the days when the UK had various mains voltages, you
could buy lamps of 210, 220, 230, 240 and I think 250v ratings.

even 50v which one of the Cambridge colleges had in 1960 - the town having
a 200v supply. It was soldring irons that suffered really badly if you had
a 240v element on 200v.


25v and 50V are still common as working lights on machine tools,
although modern ones tend to use 12V H1 halogen lamps, presumably as
they are readily available for cars.

We used to have a wide variety of different voltage lamps in the
Electricity Museum. DC systems were often 100V or 110V, but could be
used to charge lead acid batteries in houses, with house voltages
anywhere between 12V and 96V. There were also traction lamps, for use on
trains at track voltages in the range 500-630V DC.

However, while early lamps were made to exactly match the supply
voltages, a necessity with the poor quality of early filaments,
latterly, if you looked closely at the markings on the lamps, one that
was sold for 220V could be exactly the same as one sold for 240V. People
were so used to buying lamps to match their supply that it was simpler
to put the same lamp in different packages than to try to educate them
to the fact that you could run a 240V rated lamp on 220V, but not
necessarily the reverse.

Colin Bignell