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comments on "low-voltage" halogen incandescents/question about MH track lights

Tom wrote about his success with his MR-16 halogen lamps (a.k.a. low-voltage
halogens), and wondered about their lumens/watt ratings.  Dave responded
with a nice table of lumens/watt ratings and costs, which clearly show why
the MR-16 and its relatives are not economical in the long run.

I have a couple more comments:
Tom mentioned that he didn't notice a difference in the light between a new
lamp and a used lamp.  In terms of lumens, halogens maintain about 95% of
their initial lumens at 100% of their rated life, which is about as good as
the best T8s.

Tom also mentioned that 14 out of 15 of his lamps have been running for 4
yrs. @ 10 hrs./day, or 14,600 hrs total.  Tom has been pretty lucky since
the rated lives of the 50W MR-16 GE ConstantColor Precise lamps is 5000 hrs.
Normally, I would expect to see a few lamps surviving twice their rated
lives, based on the rating methodology, but not much more.

In terms of heat, for the equivalent amount of lumens, the halogen
incandescents will be _much_ hotter.  As Dave's table shows, they're not
very efficient.  And as I once heard in a lecture about lighting,
"incandescents are good electric heaters that happen to produce a little bit
of light."

For those concerned with color temp., the 50W MR-16 GE ConstantColor Precise
lamps have a color temp of 3050 K.

Finally, if the fixture doesn't incorporate a lens over the lamp, you might
want to consider the MR-16s with a cover glass to avoid shattering the bulb
due to splashing, and to keep the reflector clean.

As an alternative to halogen track lights, has anyone tried the MH track
lights that are now available?  The lamps look like incandescent floods and
some of them even come with electronic ballasts.

Wade Shimoda