Re: Fwd: Wall switch dimmers work with 12v halogen?

[Nigel Orr <nigel.orr@xxxxxxx>]

I'm not sure who wrote what, but anyway...

At 11:09 15/03/99 EST, you wrote:

> Trevor (at AHA) has been advised by Home Control plc (the UK
distributors of
> X10Pro) that the wall switch dimmers will work with low voltage
halogens up
> to a total load of 300W per switch. We are both slightly dubious about
this.

Why?  As long as the 'transformer' is marked as suitable for dimmers, it
should work, with only two problems... halogen lights are designed to run
at full power- at slightly reduced power,
1) Their life will be shortened, and
2) light output will fall off much faster than expected with applied power.

I may have some of the 'technicals' mixed up, but the basic reason for 1)
is that halogens need to run at full power to avoid the vapour from the
element being deposited on the glass envelope.  If they are run at lower
power, the temperature is so low that the vapour from the element condenses
on the glass.  Over time, if they are never run at full power, the element
will break prematurely.  This can be avoided by running them at full power
every so often.

I guess both these problems occur exactly the same with mains powered
halogens, but I've never used them so I couldn't be sure...

>I am not aware of the operational characteristics of the international
>devices. However I copied this to our Technical VP, and here is his
response.
>"The operative word here is Dimmer. The LW10U is a dimmer and as
such cannot
>control low voltage lights."

Someone's Technical VP seems to have a bit of technical confusion... note
that the dimmer would have to go on the 240V side of the lighting, not the
12V side (maybe he meant LW10U is a _mains_ dimmer, with the operative word
being mains?), but it should work, with a dimmable transformer, for
suitable values of 'work' as explained above...

Nigel

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