In case any of you have used these GU10 8W MasterLED retrofit spotlamps...

http://luxmagazine.co.uk/news/23/phi...gu10-led-lamps

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

On Fri, 21 Dec 2012 13:50:49 +0000 (UTC),
(Andrew Gabriel) wrote:

In case any of you have used these GU10 8W MasterLED retrofit spotlamps...

http://luxmagazine.co.uk/news/23/phi...gu10-led-lamps

One of those modern "hunt the scroll bar" Web sites. Much like the
"new " Google Groups interface, and very annoying.





--
Graham.
%Profound_observation%

On 21/12/2012 13:50, Andrew Gabriel wrote:
In case any of you have used these GU10 8W MasterLED retrofit spotlamps...

http://luxmagazine.co.uk/news/23/phi...gu10-led-lamps


Noticed a few LED spots on the RAPEX website over the last couple of
months - inherent issue with this type of design?

In article ,
Lee writes:
On 21/12/2012 13:50, Andrew Gabriel wrote:
In case any of you have used these GU10 8W MasterLED retrofit spotlamps...

http://luxmagazine.co.uk/news/23/phi...gu10-led-lamps


Noticed a few LED spots on the RAPEX website over the last couple of
months - inherent issue with this type of design?

Yes.

These are made by companies which previously made CFLs.
CFLs have no exposed metalic parts, except the lamp cap.
Now they're making LEDs where the most difficult part is
the thermal design, and this generally requires a significant
proportion of exposed aluminium to dissipate the heat.
They don't seem to have the experience required to do this
safely, i.e. keeping the mains potential a safe distance
from the exposed aluminium whilst still having a good thermal
contact between it and the LED junction (often at mains
potential). I was a bit surprised at Philips falling into
this trap though.

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

On 2012-12-21, Andrew Gabriel wrote:

These are made by companies which previously made CFLs.
CFLs have no exposed metalic parts, except the lamp cap.
Now they're making LEDs where the most difficult part is
the thermal design, and this generally requires a significant
proportion of exposed aluminium to dissipate the heat.
They don't seem to have the experience required to do this
safely, i.e. keeping the mains potential a safe distance
from the exposed aluminium whilst still having a good thermal
contact between it and the LED junction (often at mains
potential). I was a bit surprised at Philips falling into
this trap though.

(I'll take the risk of asking a stupid question here.) Isn't that
problem --- keeping the mains potential a safe distance from the
exposed [metal] whilst still having a good thermal contact --- rather
like designing kettle & immersion heater elements?

On 21/12/2012 19:24, Andrew Gabriel wrote:

I was a bit surprised at Philips falling into
this trap though.


Do Philips make anything these days or are they just re-branding
electronics purchased from the cheapest source?


--
mailto:news{at}admac(dot}myzen{dot}co{dot}uk

In article ,
Adam Funk writes:
On 2012-12-21, Andrew Gabriel wrote:

These are made by companies which previously made CFLs.
CFLs have no exposed metalic parts, except the lamp cap.
Now they're making LEDs where the most difficult part is
the thermal design, and this generally requires a significant
proportion of exposed aluminium to dissipate the heat.
They don't seem to have the experience required to do this
safely, i.e. keeping the mains potential a safe distance
from the exposed aluminium whilst still having a good thermal
contact between it and the LED junction (often at mains
potential). I was a bit surprised at Philips falling into
this trap though.

(I'll take the risk of asking a stupid question here.)

It's not a stupid question at all - it's the essence of the
problem.

Isn't that
problem --- keeping the mains potential a safe distance from the
exposed [metal] whilst still having a good thermal contact --- rather
like designing kettle & immersion heater elements?

Yes and no.

It's like trying to make a kettle or immersion heater which
requires no earth, i.e. it's double insulated, as there's no
earth connection to a light bulb. This is not the case with
immersion heaters and kettles, which are normally earthed.

Also, there's no requirement for good thermal contact between
the resistance wire and the element casing. The wire gives off
3kW, and it will simply get hot enough to pass that 3kW across
the electrical insulator, regardless of how thermally insulating
it is (as long as the resistance wire remains below its melting
point). It might well be running at 800C+ above the casing at 100C.
That won't work with an LED where the challenge is to keep the
junction at as low a temperature as possible, and the thermal
conductivity must therefore be as good as possible, or both the
efficiency and the life of the LED drops rapidly.

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

In article , Andrew Gabriel
writes
In article ,
Lee writes:
On 21/12/2012 13:50, Andrew Gabriel wrote:
In case any of you have used these GU10 8W MasterLED retrofit spotlamps...

http://luxmagazine.co.uk/news/23/phi...lly-dangerous-
gu10-led-lamps


Noticed a few LED spots on the RAPEX website over the last couple of
months - inherent issue with this type of design?

Yes.

These are made by companies which previously made CFLs.
CFLs have no exposed metalic parts, except the lamp cap.
Now they're making LEDs where the most difficult part is
the thermal design, and this generally requires a significant
proportion of exposed aluminium to dissipate the heat.
They don't seem to have the experience required to do this
safely, i.e. keeping the mains potential a safe distance
from the exposed aluminium whilst still having a good thermal
contact between it and the LED junction (often at mains
potential). I was a bit surprised at Philips falling into
this trap though.

Spot on analysis IMV, a serious and surprising failure on Philips' part.
Even if they self certify on safety I would expect the analysis and
testing to have been carried out by a totally separate branch of the
group who would dissect the design very carefully. I've certainly gained
no favours in the past from in-house testers.

Given the compact dimensions perhaps we can assume reinforced rather
than double insulation but that, in itself, should have called for more
stringent analysis and testing. Manufacturing defect?
--
fred
it's a ba-na-na . . . .

Completely impossible to navigate as bits are permanently hidden.

Brian

--
From the Sofa of Brian Gaff Reply address is active
"Graham." wrote in message
...
On Fri, 21 Dec 2012 13:50:49 +0000 (UTC),
(Andrew Gabriel) wrote:

In case any of you have used these GU10 8W MasterLED retrofit spotlamps...

http://luxmagazine.co.uk/news/23/phi...gu10-led-lamps

One of those modern "hunt the scroll bar" Web sites. Much like the
"new " Google Groups interface, and very annoying.





--
Graham.
%Profound_observation%

On 2012-12-21, Andrew Gabriel wrote:

In article ,
Adam Funk writes:
On 2012-12-21, Andrew Gabriel wrote:

These are made by companies which previously made CFLs.
CFLs have no exposed metalic parts, except the lamp cap.
Now they're making LEDs where the most difficult part is
the thermal design, and this generally requires a significant
proportion of exposed aluminium to dissipate the heat.
They don't seem to have the experience required to do this
safely, i.e. keeping the mains potential a safe distance
from the exposed aluminium whilst still having a good thermal
contact between it and the LED junction (often at mains
potential). I was a bit surprised at Philips falling into
this trap though.

(I'll take the risk of asking a stupid question here.)

It's not a stupid question at all - it's the essence of the
problem.

:-)

Isn't that
problem --- keeping the mains potential a safe distance from the
exposed [metal] whilst still having a good thermal contact --- rather
like designing kettle & immersion heater elements?

Yes and no.

It's like trying to make a kettle or immersion heater which
requires no earth, i.e. it's double insulated, as there's no
earth connection to a light bulb. This is not the case with
immersion heaters and kettles, which are normally earthed.

Also, there's no requirement for good thermal contact between
the resistance wire and the element casing. The wire gives off
3kW, and it will simply get hot enough to pass that 3kW across
the electrical insulator, regardless of how thermally insulating
it is (as long as the resistance wire remains below its melting
point). It might well be running at 800C+ above the casing at 100C.
That won't work with an LED where the challenge is to keep the
junction at as low a temperature as possible, and the thermal
conductivity must therefore be as good as possible, or both the
efficiency and the life of the LED drops rapidly.

Interesting, thanks. Out of curiosity, what is the stuff they use
between the resistance wire & the casing of a water-heating element?

On Friday, December 21, 2012 9:52:24 PM UTC, fred wrote:
In article , Andrew Gabriel
writes
In article ,
Lee writes:
On 21/12/2012 13:50, Andrew Gabriel wrote:

In case any of you have used these GU10 8W MasterLED retrofit spotlamps...

http://luxmagazine.co.uk/news/23/phi...lly-dangerous-
gu10-led-lamps

snip

Spot on analysis IMV, a serious and surprising failure on Philips' part.
Even if they self certify on safety I would expect the analysis and
testing to have been carried out by a totally separate branch of the
group who would dissect the design very carefully. I've certainly gained
no favours in the past from in-house testers.
Given the compact dimensions perhaps we can assume reinforced rather
than double insulation but that, in itself, should have called for more
stringent analysis and testing. Manufacturing defect?

I expect the design and samples passed, but the manufacturer cut corners later, and got away with it for a while.


NT

In article ,
Adam Funk writes:

Interesting, thanks. Out of curiosity, what is the stuff they use
between the resistance wire & the casing of a water-heating element?

Magnesium oxide is the traditional material for many decades,
highly compressed as the element casing is rolled down to its
final diameter though multiple pressure rollers.

Its downside is that it is hygroscopic (likes to absorb water),
and if the outer casing is not perfectly sealed, moisture will
get in and generate earth leakage, and eventually failure (even
if the heater is not a submerged type).

It would not surprise me if some other suitable non-hygroscopic
material had been found more recently, but I haven't heard of
any such.

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

On 2013-01-01, Andrew Gabriel wrote:

In article ,
Adam Funk writes:

Interesting, thanks. Out of curiosity, what is the stuff they use
between the resistance wire & the casing of a water-heating element?

Magnesium oxide is the traditional material for many decades,
highly compressed as the element casing is rolled down to its
final diameter though multiple pressure rollers.

Its downside is that it is hygroscopic (likes to absorb water),
and if the outer casing is not perfectly sealed, moisture will
get in and generate earth leakage, and eventually failure (even
if the heater is not a submerged type).

Right, I remember that now.

It would not surprise me if some other suitable non-hygroscopic
material had been found more recently, but I haven't heard of
any such.

Probably too expensive!

Adam Funk wrote:
On 2013-01-01, Andrew Gabriel wrote:

In article ,
Adam Funk writes:
Interesting, thanks. Out of curiosity, what is the stuff they use
between the resistance wire & the casing of a water-heating element?
Magnesium oxide is the traditional material for many decades,
highly compressed as the element casing is rolled down to its
final diameter though multiple pressure rollers.

Its downside is that it is hygroscopic (likes to absorb water),
and if the outer casing is not perfectly sealed, moisture will
get in and generate earth leakage, and eventually failure (even
if the heater is not a submerged type).

Right, I remember that now.

It would not surprise me if some other suitable non-hygroscopic
material had been found more recently, but I haven't heard of
any such.

Probably too expensive!

As long as it outlasts the guarantee, there's no incentive for the
makers to find anything better. I've heard of very few elements failing
within the guarantee period, so the technology used must be "good enough".

--
Tciao for Now!

John.