"David Nebenzahl" wrote in message
.com...
Client wants to install some low-voltage halogens with a dimmer. Is this
OK? I know the dimmer will work, since the lamps are a resistive load, but
I'm not sure the halogens want to work on reduced voltage. Anyone know for
sure?
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Not a problem. There are a couple of things to know, however:
- Use the proper dimmer. Low voltage halogens require either a transformer
or electronic voltage reducer. Use a dimmer that's compatible with what
you're using.
- Halogens don't care if they are dimmed. At full power halogen lamps are
designed to utilize a tungsten recycling process which keeps the inside of
the bulb clean. The gas chemistry inside the bulb recycles the tungsten
that would ordinarily deposit on the bulb surface back onto the filament.
If you dim the lamp, the halogen cycle stops; but that's O.K. The filament
is operating at a lower temperature and not throwing off much tungsten
anyway. Some wonder if there is some kind of "forbidden zone" of
operation -- a dimmer setting where there is still filament evaporation, but
where the halogen cycle is not operating so the bulb darkens and perhaps
fails. According to the lamp engineers that I've talked to, that's
possible, but not likely in general lighting lamps. But if it should
happen, (you will be able to see the filament tube with a black deposit on
the inside surface) simply operate the lamp at full power for a few minutes
to restart the halogen cycle.
I have a house with several dimmer-controlled track lighting systems which
use numerous 120 volt PAR20 and 12 volt MR16 halogen lamps for downlighting,
accent lighting, etc. These systems are operated 6-10 hours/day at various
dimmer settings. I used transformer-powered fixtures for the MR16 lamps.
There is no noticeable noise, even when the dimmers are at the lowest
setting, unless the house is absolutely quiet (not a normal situation).
I've not had any 12 volt MR16 lamps fail during the 3+ years that the system
has been installed. The lamps have a life rating of 5000 or 6000 hours, so
I'm starting to expect a few failures.
The 120 volt PAR20 halogen lamps are very sensitive to physical shock. I've
had those fail when I simply adjust the fixture and happen to shake the
fixture. What happens is that some filament coils short together and put
too much voltage on the rest of the filament. (you can see the filament
move when you look at the light beam). Now, I dim the lamp and move the
fixture very carefully and replace lamps with the power off.
TKM