Are mains and low volatge halogen bulbs the same size? If one has a fitting
which takes a mains bulb (by a spring clip around the outside of the conical
section) would a LV one fit?

(I know the connectors are different. The reason I ask is a client wants a
particular rather nice looking light fitting which seems to be available
only in mains, but wants them for a bathroom, so I'm thinking of chucking
out the mains lamps and fitting LVs.)

John Stumbles wrote:
Are mains and low volatge halogen bulbs the same size? If one has a fitting
which takes a mains bulb (by a spring clip around the outside of the conical
section) would a LV one fit?

(I know the connectors are different. The reason I ask is a client wants a
particular rather nice looking light fitting which seems to be available
only in mains, but wants them for a bathroom, so I'm thinking of chucking
out the mains lamps and fitting LVs.)

Probably not a good idea.
The current for a LV fitting will be some 20 times that of a mains one,
and the heating for a given contact resistance 400 times.

On Mon, 28 Jun 2004 00:24:06 +0100, "John Stumbles"
strung together this:

Are mains and low volatge halogen bulbs the same size?

Yep, the lamps are the same physical size around the front edge.
--

SJW
A.C.S. Ltd

On 28 Jun 2004 07:21:37 GMT, Ian Stirling
strung together this:

Probably not a good idea.

Oh really.

The current for a LV fitting will be some 20 times that of a mains one,
and the heating for a given contact resistance 400 times.

What significance would the current draw be then?
--

SJW
A.C.S. Ltd

Lurch wrote:
On 28 Jun 2004 07:21:37 GMT, Ian Stirling
strung together this:

Probably not a good idea.

Oh really.

Yes, really.

The current for a LV fitting will be some 20 times that of a mains one,
and the heating for a given contact resistance 400 times.

What significance would the current draw be then?

The contacts of the mains lamp may have been designed for a much, much
lower current (lower pressures, smaller contact area) than the LV ones.
If you exceed the designed current by a factor of 20, then the sockets
can just die.
Much as if you tried to pull 260A from a mains plug.

In article ,
Lurch writes:
On Mon, 28 Jun 2004 00:24:06 +0100, "John Stumbles"
strung together this:

Are mains and low volatge halogen bulbs the same size?

Yep, the lamps are the same physical size around the front edge.

Also note that it's pretty impossible now to buy anything
other than dichroic LV lamps. The mains ones are easily
available in both types, and if the fitting is designed
for mains full reflector type and you fit LV dichroic,
the fitting will get hotter than designed for.

--
Andrew Gabriel

In article ,
Ian Stirling wrote:
Probably not a good idea.
The current for a LV fitting will be some 20 times that of a mains one,
and the heating for a given contact resistance 400 times.

Whilst this is true, are you sure the socket is indeed different? They
might just use the same one for both - economies of scale.

--
*Starfishes have no brains *

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

"Andrew Gabriel" wrote in message
...
In article ,
Lurch writes:
On Mon, 28 Jun 2004 00:24:06 +0100, "John Stumbles"
strung together this:

Are mains and low volatge halogen bulbs the same size?

Yep, the lamps are the same physical size around the front edge.

Also note that it's pretty impossible now to buy anything
other than dichroic LV lamps. The mains ones are easily
available in both types, and if the fitting is designed
for mains full reflector type and you fit LV dichroic,
the fitting will get hotter than designed for.



Hmm, that's interesting - are the GU10 mains halogens not generally dichroic
then?

The packet of a spare that I have in stock gives no more information on this
than "Aluminiumised Reflector" - I had always assumed that they would have
been dichroic just as the LV ones are, but from what you say perhaps this is
not the case.

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

"Ian Stirling" wrote in message
...
Lurch wrote:
On 28 Jun 2004 07:21:37 GMT, Ian Stirling
strung together this:

Probably not a good idea.

Oh really.

Yes, really.

The current for a LV fitting will be some 20 times that of a mains one,
and the heating for a given contact resistance 400 times.

What significance would the current draw be then?

The contacts of the mains lamp may have been designed for a much, much
lower current (lower pressures, smaller contact area) than the LV ones.
If you exceed the designed current by a factor of 20, then the sockets
can just die.
Much as if you tried to pull 260A from a mains plug.

Yes, but the contacts are irrelevant here - they will have to be binned and
replaced with the standard LV connector (completely incompatible).

Dichroic/non-dichroic may be an issue, but not connectors.

This is in the assumption that the tails of the LV connector are connected
directly to the feeding LV cable or mini-"transformer", and that there is no
built in switch or other intermediate connectors (which should not be used
for LV).

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

"Dave Plowman (News)" wrote:
In article ,
Ian Stirling wrote:
Probably not a good idea.
The current for a LV fitting will be some 20 times that of a mains one,
and the heating for a given contact resistance 400 times.

Whilst this is true, are you sure the socket is indeed different? They
might just use the same one for both - economies of scale.

They might.
But they also might not, and it's very hard to tell on inspection if this is
the case.

RichardS noaccess@invalid wrote:
"Ian Stirling" wrote in message
...
Lurch wrote:
On 28 Jun 2004 07:21:37 GMT, Ian Stirling
strung together this:

Probably not a good idea.

Oh really.

Yes, really.

The current for a LV fitting will be some 20 times that of a mains one,
and the heating for a given contact resistance 400 times.

What significance would the current draw be then?

The contacts of the mains lamp may have been designed for a much, much
lower current (lower pressures, smaller contact area) than the LV ones.
If you exceed the designed current by a factor of 20, then the sockets
can just die.
Much as if you tried to pull 260A from a mains plug.

Yes, but the contacts are irrelevant here - they will have to be binned and
replaced with the standard LV connector (completely incompatible).

Oh well.
Sorry, I haven't dealt much with HV bulbs, and the one that I thought
I saw had an identical connector.

"RichardS" noaccess@invalid wrote in message
.. .

"Andrew Gabriel" wrote in message
...
In article ,
Lurch writes:
On Mon, 28 Jun 2004 00:24:06 +0100, "John Stumbles"
strung together this:

Are mains and low volatge halogen bulbs the same size?

Yep, the lamps are the same physical size around the front edge.

Also note that it's pretty impossible now to buy anything
other than dichroic LV lamps. The mains ones are easily
available in both types, and if the fitting is designed
for mains full reflector type and you fit LV dichroic,
the fitting will get hotter than designed for.



Hmm, that's interesting - are the GU10 mains halogens not generally
dichroic
then?

The packet of a spare that I have in stock gives no more information on
this
than "Aluminiumised Reflector" - I had always assumed that they would have
been dichroic just as the LV ones are, but from what you say perhaps this
is
not the case.

Unfortunately the supplier's web site (John Lewis - you'd think they'd know
better) doesn't even say if the fittings are mains or LV. I'm guessing
mains.
http://www.johnlewis.com/stores/prod...rsid=1558&m=-1

I'm also planning to fit 20W LV bulbs rather than the original 50s (the
client wants lighting, not roasting :-) so even if the fitting is intended
for reflectors the heat back into it from dichroics shouldn't be too much (I
hope!).

On Mon, 28 Jun 2004 10:02:27 +0100, (Steve
Firth) strung together this:

The ^2 is significant.

You mean you've no idea either? ;-)
--

SJW
A.C.S. Ltd

In article ,
"RichardS" noaccess@invalid writes:

Hmm, that's interesting - are the GU10 mains halogens not generally dichroic
then?

GU10 aren't, and GZ10 are (if I remember the right way round).
You can put the aluminium reflector one in the dichroic lampholder,
but not the other way round. Aluminium reflector lamps have a bevel
around the base, and the dichroic lamps have a square edged base
to stop them fitting in the Aluminium reflector lampholder.

--
Andrew Gabriel

"John Stumbles" wrote in message
news:cPUDc.84$UA2.39@newsfe5-win...
"RichardS" noaccess@invalid wrote in message
.. .

"Andrew Gabriel" wrote in message
...
In article ,
Lurch writes:
On Mon, 28 Jun 2004 00:24:06 +0100, "John Stumbles"
strung together this:

Are mains and low volatge halogen bulbs the same size?

Yep, the lamps are the same physical size around the front edge.

Also note that it's pretty impossible now to buy anything
other than dichroic LV lamps. The mains ones are easily
available in both types, and if the fitting is designed
for mains full reflector type and you fit LV dichroic,
the fitting will get hotter than designed for.



Hmm, that's interesting - are the GU10 mains halogens not generally
dichroic
then?

The packet of a spare that I have in stock gives no more information on
this
than "Aluminiumised Reflector" - I had always assumed that they would
have
been dichroic just as the LV ones are, but from what you say perhaps
this
is
not the case.

Unfortunately the supplier's web site (John Lewis - you'd think they'd
know
better) doesn't even say if the fittings are mains or LV. I'm guessing
mains.

http://www.johnlewis.com/stores/prod...921&trsid=1558
&m=-1

I'm also planning to fit 20W LV bulbs rather than the original 50s (the
client wants lighting, not roasting :-) so even if the fitting is intended
for reflectors the heat back into it from dichroics shouldn't be too much
(I
hope!).


yep, spec a bit vague on that front! I'd have expected them to at least
state whether it is mains or ELV as a "feature" if nothing else.

From the looks of it I can't see why ELV 20W would be a problem, but as you
could be essentially installing something out-of-spec for a customer then
I'd be a little cautious in your circumstance.

JL ought to be able to answer a specific technical question or put you in
touch with the manufacturer's technical department to clear the issue once
and for all - with a positive answer you should be able to demonstrate that
there has been due diligence when making the mod.

"with the appropriate 12v connector, is there any reason why this fitting
should not be used to house a 20W 12v lamp" kind of thing.


(BTW, many thanks for helping out Pearl & Emma a while ago, they were most
impressed.)

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

"RichardS" noaccess@invalid wrote in message
...
"John Stumbles" wrote in message
news:cPUDc.84$UA2.39@newsfe5-win...
"RichardS" noaccess@invalid wrote in message
.. .

"Andrew Gabriel" wrote in message
...
In article ,
Lurch writes:
On Mon, 28 Jun 2004 00:24:06 +0100, "John Stumbles"
strung together this:

Are mains and low volatge halogen bulbs the same size?

Yep, the lamps are the same physical size around the front edge.

Also note that it's pretty impossible now to buy anything
other than dichroic LV lamps. The mains ones are easily
available in both types, and if the fitting is designed
for mains full reflector type and you fit LV dichroic,
the fitting will get hotter than designed for.



Hmm, that's interesting - are the GU10 mains halogens not generally
dichroic
then?

The packet of a spare that I have in stock gives no more information
on
this
than "Aluminiumised Reflector" - I had always assumed that they would
have
been dichroic just as the LV ones are, but from what you say perhaps
this
is
not the case.

Unfortunately the supplier's web site (John Lewis - you'd think they'd
know
better) doesn't even say if the fittings are mains or LV. I'm guessing
mains.


http://www.johnlewis.com/stores/prod...921&trsid=1558
&m=-1

I'm also planning to fit 20W LV bulbs rather than the original 50s (the
client wants lighting, not roasting :-) so even if the fitting is
intended
for reflectors the heat back into it from dichroics shouldn't be too
much
(I
hope!).


yep, spec a bit vague on that front! I'd have expected them to at least
state whether it is mains or ELV as a "feature" if nothing else.

From the looks of it I can't see why ELV 20W would be a problem, but as
you
could be essentially installing something out-of-spec for a customer then
I'd be a little cautious in your circumstance.

JL ought to be able to answer a specific technical question or put you in
touch with the manufacturer's technical department to clear the issue once
and for all - with a positive answer you should be able to demonstrate
that
there has been due diligence when making the mod.

"with the appropriate 12v connector, is there any reason why this fitting
should not be used to house a 20W 12v lamp" kind of thing.

Call me cynical & jaded if you will but I'll bet you a pint to a packet of
crisps that (a) the manufacturer operates in a different character set (b)
JL under influence of their legal mafia would say something non-committal
and arse-covering. :-)

Basically I'll see if it looks like a good engineering proposition, if not
they can always get their money back from JL and choose something else. (I
did look around for soemthing similar in LV but can't find anything in
brushed steel, let alone what looks like a sort of wedge-section shape that
the JL units seem to have.


(BTW, many thanks for helping out Pearl & Emma a while ago, they were most
impressed.)

You - and they - are welcome, thanks for putting me in touch. Must say I'm
not heartbroken they got it done by someone else: it was going to be a right
challenge redoing the gas in 22mm from the meter. If you're ever down there
with a digicam I'd be interested to see how it was done :-)