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 :'(

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

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.

Colin Bignell

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.

Colin Bignell

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

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

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.

Colin Bignell

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.

Colin Bignell

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.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

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.

Colin Bignell

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.

--
From KT24

Using a RISC OS computer running v5.18

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

On Fri, 21 Mar 2014 08:53:14 +0000, Nightjar
wrote:



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.


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.

After WW2 before Dad settled down he worked with an electrician in a
rural area. We ended up with a large box of SBC lamps of various
voltages rendered redundant by the coming of std AC mains replacing
home generators .
Too tempting for a youngster so experimentation was undertaken.
Some lamps just shattered others had a short but brilliant career.
24V was found to take out the circuit fuse but the filament remained
intact. Adding a 0 with a chinagraph pencil and replacing one of the
lamps in a school corridor ensured the caretaker would go from his
usaul mild mannered self to a swearing purple coloured monster over an
hour or so. Some of the 200V+ lamps were coloured so for years the
outside loo was bathed brightly in green/red, orange and blue as the
lamps were used up.

G.Harman

In article ,
Nightjar wrote:
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.

Low voltage filament lamps survive vibration (and knocks) rather better
than mains ones - and 12v car ones perhaps best of all.

--
*Isn't it a bit unnerving that doctors call what they do "practice?"

Dave Plowman London SW
To e-mail, change noise into sound.

On 21/03/2014 10:27, Dave Plowman (News) wrote:
In article ,
Nightjar wrote:
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.

Low voltage filament lamps survive vibration (and knocks) rather better
than mains ones - and 12v car ones perhaps best of all.


I think the main motivation, certainly with the exposed lamp types, is
that ELV won't kill you if the coolant stream goes in the wrong place.

Colin Bignell

In article ,
Nightjar wrote:
Low voltage filament lamps survive vibration (and knocks) rather better
than mains ones - and 12v car ones perhaps best of all.


I think the main motivation, certainly with the exposed lamp types, is
that ELV won't kill you if the coolant stream goes in the wrong place.

Certainly a consideration. But even rough service mains lamps have a short
life when subjected to vibration. So even on a tool where lubricant
wouldn't normally be used any built in lights are better if low voltage.

--
*What are the pink bits in my tyres? Cyclists & Joggers*

Dave Plowman London SW
To e-mail, change noise into sound.

On Fri, 21 Mar 2014 08:53:14 +0000, Nightjar
wrote:

====snip====

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.


I'm afraid to say this, but that last paragraph is basically a load
of bull****. Regardless of 'poor quality of early filaments' the
design criteria is still affected by the same physical laws that
determine the life versus luminous efficacy trade offs made with
today's high quality filaments.

The improved quality of filament just allows for an improved luminous
efficacy for a given lamp life (1000 hours being the standard lamp
life arrived at all those years ago as offering the best TCO between
the electricity and lamp replacement costs).

Once you've decided what the lamp life should be, the voltage is
pretty well determined within 1 or 2 percent for a given wattage and
lamp life.

Tungsten filament GLS lamps are very sensitive to voltage variations
that can readily be dismissed by most other domestic appliances.

For voltage variations within +/-25% of nominal, each 5% increase
will approximate to a halving of lamp life (and associated improvement
of efficacy). Conversely, a 5% reduction will double the lamp life and
reduce efficacy.

220v is just slightly shy of a 5% reduction on 'our harmonised 230v
mains' and similarly, 240v is just shy of a 5% increase. It should be
blindingly obvious why tungsten filament GLS lamps have _always_ been
marked with a singular votage rating to this day.

A tungsten filament GLS lamp designed for the notional harmonised
voltage of 230 cannot be sold in the UK and on the continent where
most supplies are using the 220v level since a lamp that lasts 2000
hours on the continent will only last 500 hours in the UK. We'd find
ourselves replacing lamps four times as frequently as our continental
neighbours.

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'.
--
Regards, J B Good

On 21/03/2014 17:41, Johny B Good wrote:
On Fri, 21 Mar 2014 08:53:14 +0000, Nightjar
wrote:

====snip====

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.


I'm afraid to say this, but that last paragraph is basically a load
of bull****...

I would pass that on to the curator of the Electricity Museum, who
showed me the markings and explained the situation, but he was a retiree
when I was in my 20s and he is now long gone.

Colin Bignell

on 21/03/2014, Nightjar supposed :
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.

That was not my experience at all - On say a 210v supply, in an awkward
to get to location, it was common to deliberately install say a 240v
lamp, to increase the life. It would be noticeably dimmer for a
comparable lamp of the correct voltage. Fit a 210 lamp, in a 240v
situation then you would be replacing it very soon.

The difference between the correct lamp for the voltage was not only
noticeable by its life, but by its brightness.

Local shops, would stock the local voltage, but for another voltage it
involved atrip to the wholesalers.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Friday, March 21, 2014 5:41:29 PM UTC, Johny B Good wrote:
On Fri, 21 Mar 2014 08:53:14 +0000, Nightjar
wrote:

====snip====

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.

I'm afraid to say this, but that last paragraph is basically a load
of bull****. Regardless of 'poor quality of early filaments' the
design criteria is still affected by the same physical laws that
determine the life versus luminous efficacy trade offs made with
today's high quality filaments.
The improved quality of filament just allows for an improved luminous
efficacy for a given lamp life (1000 hours being the standard lamp
life arrived at all those years ago as offering the best TCO between
the electricity and lamp replacement costs).
Once you've decided what the lamp life should be, the voltage is
pretty well determined within 1 or 2 percent for a given wattage and
lamp life.
Tungsten filament GLS lamps are very sensitive to voltage variations
that can readily be dismissed by most other domestic appliances.
For voltage variations within +/-25% of nominal, each 5% increase
will approximate to a halving of lamp life (and associated improvement
of efficacy). Conversely, a 5% reduction will double the lamp life and
reduce efficacy.
220v is just slightly shy of a 5% reduction on 'our harmonised 230v
mains' and similarly, 240v is just shy of a 5% increase. It should be
blindingly obvious why tungsten filament GLS lamps have _always_ been
marked with a singular votage rating to this day.
A tungsten filament GLS lamp designed for the notional harmonised
voltage of 230 cannot be sold in the UK and on the continent where
most supplies are using the 220v level since a lamp that lasts 2000
hours on the continent will only last 500 hours in the UK. We'd find
ourselves replacing lamps four times as frequently as our continental
neighbours.
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.


NT

After serious thinking Johny B Good wrote :
I'm afraid to say this, but that last paragraph is basically a load
of bull****. Regardless of 'poor quality of early filaments' the
design criteria is still affected by the same physical laws that
determine the life versus luminous efficacy trade offs made with
today's high quality filaments.

Is exactly right!

There has been little if any improvement or development in lamps and
filaments, since the 1950's maybe even back to the 1920's.


The improved quality of filament just allows for an improved luminous
efficacy for a given lamp life (1000 hours being the standard lamp
life arrived at all those years ago as offering the best TCO between
the electricity and lamp replacement costs).

They were quoting 1.00 hours back in the 1950's and coiled coils.


Once you've decided what the lamp life should be, the voltage is
pretty well determined within 1 or 2 percent for a given wattage and
lamp life.

Tungsten filament GLS lamps are very sensitive to voltage variations
that can readily be dismissed by most other domestic appliances.

For voltage variations within +/-25% of nominal, each 5% increase
will approximate to a halving of lamp life (and associated improvement
of efficacy). Conversely, a 5% reduction will double the lamp life and
reduce efficacy.

My experience suggests life is reduced by much more than 1/2 the life.
My problems with the oven lamps is not the first time I have been sold
220 -240v lamps and have them need to be replaced within a very short
time.

I would expect oven lamps to typically last for several years in a
domestic oven, rather than just a week or so.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Friday, March 21, 2014 7:29:09 PM UTC, Harry Bloomfield wrote:
After serious thinking Johny B Good wrote :
I'm afraid to say this, but that last paragraph is basically a load
of bull****. Regardless of 'poor quality of early filaments' the
design criteria is still affected by the same physical laws that
determine the life versus luminous efficacy trade offs made with
today's high quality filaments.
Is exactly right!
There has been little if any improvement or development in lamps and
filaments, since the 1950's maybe even back to the 1920's.

The improved quality of filament just allows for an improved luminous
efficacy for a given lamp life (1000 hours being the standard lamp
life arrived at all those years ago as offering the best TCO between
the electricity and lamp replacement costs).
They were quoting 1.00 hours back in the 1950's and coiled coils.

IIRC the last significant change was the coiled coil, introduced in the 1930s. If you buy vanilla GLS you're getting 1930s technology.

There have been other developments since, but either very minor (higher temp rated cement enabling smaller envelopes) or large enough to produce new lamp types, halogen & xenon.


NT

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

On Fri, 21 Mar 2014 19:29:09 GMT, Harry Bloomfield
wrote:

After serious thinking Johny B Good wrote :
I'm afraid to say this, but that last paragraph is basically a load
of bull****. Regardless of 'poor quality of early filaments' the
design criteria is still affected by the same physical laws that
determine the life versus luminous efficacy trade offs made with
today's high quality filaments.

Is exactly right!

There has been little if any improvement or development in lamps and
filaments, since the 1950's maybe even back to the 1920's.


The improved quality of filament just allows for an improved luminous
efficacy for a given lamp life (1000 hours being the standard lamp
life arrived at all those years ago as offering the best TCO between
the electricity and lamp replacement costs).

They were quoting 1.00 hours back in the 1950's and coiled coils.


Once you've decided what the lamp life should be, the voltage is
pretty well determined within 1 or 2 percent for a given wattage and
lamp life.

Tungsten filament GLS lamps are very sensitive to voltage variations
that can readily be dismissed by most other domestic appliances.

For voltage variations within +/-25% of nominal, each 5% increase
will approximate to a halving of lamp life (and associated improvement
of efficacy). Conversely, a 5% reduction will double the lamp life and
reduce efficacy.

My experience suggests life is reduced by much more than 1/2 the life.
My problems with the oven lamps is not the first time I have been sold
220 -240v lamps and have them need to be replaced within a very short
time.

I would expect oven lamps to typically last for several years in a
domestic oven, rather than just a week or so.

That's certainly the case with our Bosch double oven which we
acquired (2nd hand but hardly used) just two and half years ago.

Only one of the E14 40W Philips 300 deg C rated lamps was bought new
at the time, the other being an original lamp. Neither have needed to
be replaced so far but it's only the top smaller grille/oven that's
seen regular use and I can't undo the jamjar bottom pyrex glass cover
to take a closer look at the lamp itself without using some sort of
'Jar Lid Opening Tool' to get the extra purchase and leverage to
examine that lamp to see whether it was it was the new or the old
lamp.

Even when trying to undo the more accessible lamp glass in the lower
oven, I found it a bit of a struggle but I was able to verify that the
lamp rating was indeed a full 40W, as well as testing that the totally
ubiquitous 15W E14 300 deg C oven lamp (2 for a quid) would fit and at
least relieve the darkness of the oven's interior recesses 'in a
pinch'.

At somewhere in the region of a fiver a pop for the Bosch 40W oven
lamp, I'll happily make do with the standard 15W Pygmy oven lamp thank
you very much. I think the only reason I 'splashed the cash' in this
case was on account we needed a replacement jamjar bottom pyrex glass
lamp cover anyway so I added the 'special lamp' to the order.

The thing is with oven lamps, they have to be rated for for an
ambient temperature of 300 deg C as well as for the mains voltage in
use. Even if the standard glass envelope is still ok at that
temperature the filament could well land up running a good 200 deg C
higher than designed for if an ordinary lamp 'dressed up as mutton, so
to speak' were to be used.

Even a 15W pygmy oven lamp needs to specified precisely for the mains
supply voltage in use by the oven. In the UK, it should specify 240v,
definitely not 220-240v which makes me suspicious straight away as to
whether it would actually be rated for 300 deg C ambient.

Where are you buying your oven lamps from? Does your oven use the
readily (and only) available 15W E14 Pygmy oven lamp, or is it
something a little more inconveniently exotic like the ones used in
our Bosch oven?
--
Regards, J B Good

Johny B Good wrote on 22/03/2014 :
Where are you buying your oven lamps from? Does your oven use the
readily (and only) available 15W E14 Pygmy oven lamp, or is it
something a little more inconveniently exotic like the ones used in
our Bosch oven?

They came from an ebay seller, listed as 240v oven lamps by the seller,
6 for £5 6 months ago and standard 15w E14.

When they turned up, they were marked 220-240v and a month later, they
had all 6 blown. Since when, it did without any lamps until recently.
None of the 2 for a £1 Poundland lamps have failed yet, which suggests
they are the pukka item.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On 21/03/2014 19:29, Harry Bloomfield wrote:
....
There has been little if any improvement or development in lamps and
filaments, since the 1950's maybe even back to the 1920's....

Hint: It was a museum.

Colin Bignell

On Sat, 22 Mar 2014 09:06:30 GMT, Harry Bloomfield
wrote:

Johny B Good wrote on 22/03/2014 :
Where are you buying your oven lamps from? Does your oven use the
readily (and only) available 15W E14 Pygmy oven lamp, or is it
something a little more inconveniently exotic like the ones used in
our Bosch oven?

They came from an ebay seller, listed as 240v oven lamps by the seller,
6 for £5 6 months ago and standard 15w E14.

When they turned up, they were marked 220-240v and a month later, they
had all 6 blown. Since when, it did without any lamps until recently.
None of the 2 for a £1 Poundland lamps have failed yet, which suggests
they are the pukka item.

Ah, that's good news then (selfishly thinking of me with my
'poundland' spares). Well, at least you know where to get the next set
of replacements from (if you ever need any more, that is!).
--
Regards, J B Good

On Saturday, March 22, 2014 1:36:09 AM UTC, Johny B Good wrote:
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.

life/LIFE = (VOLTS/volts)^13
&
efficacy/EFFICACY = (volts/VOLTS)^1.9


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 assume it dates back to the 1930s or earlier. Back then people used to repair tungsten lamps. The 30s was the era of (illegal?) price fixing for lamps. Then again electricity was eyewateringly expensive too at 5p a unit.

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.

750 gets you better TCO. OTOH no-one appreciates short lamp life.

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.

http://wiki.diyfaq.org.uk/index.php?title=Filament_lamp
also has ways to increase lamp life or efficacy.


NT

On Saturday, March 22, 2014 2:55:34 AM UTC, Johny B Good wrote:
On Fri, 21 Mar 2014 19:29:09 GMT, Harry Bloomfield
tiscali.co.uk wrote:
After serious thinking Johny B Good wrote :
I'm afraid to say this, but that last paragraph is basically a load
of bull****. Regardless of 'poor quality of early filaments' the
design criteria is still affected by the same physical laws that
determine the life versus luminous efficacy trade offs made with
today's high quality filaments.

Is exactly right!

There has been little if any improvement or development in lamps and
filaments, since the 1950's maybe even back to the 1920's.


The improved quality of filament just allows for an improved luminous
efficacy for a given lamp life (1000 hours being the standard lamp
life arrived at all those years ago as offering the best TCO between
the electricity and lamp replacement costs).

They were quoting 1.00 hours back in the 1950's and coiled coils.


Once you've decided what the lamp life should be, the voltage is
pretty well determined within 1 or 2 percent for a given wattage and
lamp life.

Tungsten filament GLS lamps are very sensitive to voltage variations
that can readily be dismissed by most other domestic appliances.

For voltage variations within +/-25% of nominal, each 5% increase
will approximate to a halving of lamp life (and associated improvement
of efficacy). Conversely, a 5% reduction will double the lamp life and
reduce efficacy.

My experience suggests life is reduced by much more than 1/2 the life.
My problems with the oven lamps is not the first time I have been sold
220 -240v lamps and have them need to be replaced within a very short
time.

I would expect oven lamps to typically last for several years in a
domestic oven, rather than just a week or so.
That's certainly the case with our Bosch double oven which we
acquired (2nd hand but hardly used) just two and half years ago.
Only one of the E14 40W Philips 300 deg C rated lamps was bought new
at the time, the other being an original lamp. Neither have needed to
be replaced so far but it's only the top smaller grille/oven that's
seen regular use and I can't undo the jamjar bottom pyrex glass cover
to take a closer look at the lamp itself without using some sort of
'Jar Lid Opening Tool' to get the extra purchase and leverage to
examine that lamp to see whether it was it was the new or the old
lamp.
Even when trying to undo the more accessible lamp glass in the lower
oven, I found it a bit of a struggle but I was able to verify that the
lamp rating was indeed a full 40W, as well as testing that the totally
ubiquitous 15W E14 300 deg C oven lamp (2 for a quid) would fit and at
least relieve the darkness of the oven's interior recesses 'in a
pinch'.
At somewhere in the region of a fiver a pop for the Bosch 40W oven
lamp, I'll happily make do with the standard 15W Pygmy oven lamp thank
you very much. I think the only reason I 'splashed the cash' in this
case was on account we needed a replacement jamjar bottom pyrex glass
lamp cover anyway so I added the 'special lamp' to the order.
The thing is with oven lamps, they have to be rated for for an
ambient temperature of 300 deg C as well as for the mains voltage in
use. Even if the standard glass envelope is still ok at that
temperature the filament could well land up running a good 200 deg C
higher than designed for if an ordinary lamp 'dressed up as mutton, so
to speak' were to be used.
Even a 15W pygmy oven lamp needs to specified precisely for the mains
supply voltage in use by the oven. In the UK, it should specify 240v,
definitely not 220-240v which makes me suspicious straight away as to
whether it would actually be rated for 300 deg C ambient.
Where are you buying your oven lamps from? Does your oven use the
readily (and only) available 15W E14 Pygmy oven lamp, or is it
something a little more inconveniently exotic like the ones used in
our Bosch oven?

The 300C rating is the standard, but unnecessary. You have a lamp enclosure with upto 220C one side, 20-40C the other, so the rise in operating temp is 100-110C. This does push filament temp up, but that's of minor consequence given how little ovens are used. The big difference is the cement in the bulb base, which is definitely not rated for the temp rise. You thus get a higher failure rate there, with glass parting from base sometimes. Some appliance lamps also have hardened glass to resist shattering into food, I forget whether that includes oven rated lamps. In practice though theyre behind a glass cover.


NT

Bob Henson explained on 22/03/2014 :
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 :'(

You did get ones that were specifically marked as oven lamps for 300°C use?

Yes I did!

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

In article ,
writes:
750 gets you better TCO. OTOH no-one appreciates short lamp life.

TCO also includes the relamping costs.

Streetlamps (back in the days of filament ones) usually used
double life and sometimes triple life lamps, because
a) The relamping costs were high, and
b) They paid a rate which worked out typically only 1/4 of
the standard domestic electricity rate.

There's no one right value.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Harry Bloomfield writes:
After serious thinking Johny B Good wrote :
I'm afraid to say this, but that last paragraph is basically a load
of bull****. Regardless of 'poor quality of early filaments' the
design criteria is still affected by the same physical laws that
determine the life versus luminous efficacy trade offs made with
today's high quality filaments.

Is exactly right!

There has been little if any improvement or development in lamps and
filaments, since the 1950's maybe even back to the 1920's.

That's not true.

There have been deployments of better gas fills, which reduce
filament evaporation, and reduce heat loss by convection cooling
of the filament.

Tungsten Halogen lamp.

Move to low voltage filament lamps (more efficient).

Infra-red reflective coatings to reflect the IR emission back
onto the filament.

Most recently, there has been the development of tungsten filament
surfaces with an interference pattern to prevent emission of IR
wavelengths. (This has been demonstrated, but abandoned due to
many countries banning filament lamps, rather than banning lamps
below certain efficiences).


The improved quality of filament just allows for an improved luminous
efficacy for a given lamp life (1000 hours being the standard lamp
life arrived at all those years ago as offering the best TCO between
the electricity and lamp replacement costs).

They were quoting 1.00 hours back in the 1950's and coiled coils.

Coiled-coil is just to get around that 240V is a long way from
the most efficient filament lamp voltage for lamps below a few
hundred watts - it needs the filament to be so thin it has too much
surface area, which the coiled-coil counteracts to some extent.
(The most efficient design voltage for 100W filament lamp is
about 55V.)

My experience suggests life is reduced by much more than 1/2 the life.
My problems with the oven lamps is not the first time I have been sold
220 -240v lamps and have them need to be replaced within a very short
time.

I would expect oven lamps to typically last for several years in a
domestic oven, rather than just a week or so.

Oven lamps are heavily under-run. If yours have short life, it's
for some other reason - vibration of a fan or slamming the oven door,
stress on the lamp, overheating, etc.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

(Andrew Gabriel) writes:

In article ,
writes:
750 gets you better TCO. OTOH no-one appreciates short lamp life.

TCO also includes the relamping costs.

Streetlamps (back in the days of filament ones) usually used
double life and sometimes triple life lamps, because
a) The relamping costs were high, and
b) They paid a rate which worked out typically only 1/4 of
the standard domestic electricity rate.

If that's correct, it tells us something about the true cost of
generating electricity.
While they might sell it at cost for such purposes, I doubt they'd sell
it at a loss.

--
Windmill, Use t m i l l
J.R.R. Tolkien:- @ S c o t s h o m e . c o m
All that is gold does not glister / Not all who wander are lost

In article ,
lid (Windmill) writes:
(Andrew Gabriel) writes:

In article ,
writes:
750 gets you better TCO. OTOH no-one appreciates short lamp life.

TCO also includes the relamping costs.

Streetlamps (back in the days of filament ones) usually used
double life and sometimes triple life lamps, because
a) The relamping costs were high, and
b) They paid a rate which worked out typically only 1/4 of
the standard domestic electricity rate.

If that's correct, it tells us something about the true cost of
generating electricity.
While they might sell it at cost for such purposes, I doubt they'd sell
it at a loss.

There was a surpless at night, which was also the driver for
economy 7 and similar dual rate tarrifs - to try and use up
the power generated by plant which can't wind up and down as
quickly as once a day.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]