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:
Yep, the lamps are the same physical size around the front edge.
On 28 Jun 2004 07:21:37 GMT, Ian Stirling strung together this:
Oh really.
What significance would the current draw be then?
Yes, really.
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.
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.
I^2*R
The ^2 is significant.
Whilst this is true, are you sure the socket is indeed different? They might just use the same one for both - economies of scale.
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
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
They might. But they also might not, and it's very hard to tell on inspection if this is the case.
Sorry, I haven't dealt much with HV bulbs, and the one that I thought I saw had an identical connector.
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.
On Mon, 28 Jun 2004 10:02:27 +0100, snipped-for-privacy@malloc.co.uk (Steve Firth) strung together this:
You mean you've no idea either? ;-)
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.
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
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.
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 :-)
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