Re: MR16 LEDs for Landscape Lights

["Jeff Volp" <JeffVolp@xxxxxxx>]

The DOE CALiPER program summary reports have some very interesting data in
this regard.  While I agree that many LED replacement lamps are not
competition for MR16 halogens, there are some that are.

A table listed 8 lm/W for a 20W halogen, and gave a range up to 13 lm/W for
a 60W incandescent.  So, illumination efficiency increases as incandescent
bulb wattage increases.  Reading throughout the latest report, I saw LEDs
range from 9 lm/W up to 59 lm/W.  So, it would seem that it is certainly
possible for LEDs to do much better than halogens.

I have received two samples so far.  One is a 4W 120V version of a MR16 with
3 high-intensity LEDs.  We now have that in a hallway fixture that did have
a 25W incandescent.  Color temperature is similar (warm white).  While
incredibly bright, the LED doesn't do quite as well as the incandescent in
this wall sconce application because its beam must first bounce off the
ceiling, providing indirect lighting.  Most of the incandescent light came
directly out the side of the sconce.  However, for 4W, it certainly does an
adequate job in that application.  The only real downside is its lack of
dimming.  That wall sconce lights an otherwise very dark interior hallway.
While on 24/7, we normally dim that bulb down to nightlight level at night.
Even set to the Leviton minimum 1.6% preset dim level, the LED is still
about half its normal intensity.

The other sample is a 12V 4W wide-angle 48-bulb MR16.  I installed that in a
landscape light.  While the lighting level is adequate, it is clearly not as
bright as the 20W halogen in that application.  Its color doesn't do as good
a job at bringing out the warm red tones in the crushed red rock we have in
our yard.  However, considering it uses only 1/5 the energy, I am impressed
by how well it works.

The CALiPER reports do question the estimated life for LED bulbs.  They
reported a couple of early failures.  And some of the bulbs only make it a
small fraction of their projected lifetime.  While it is clear to me that
some LED bulbs can provide adequate illumination levels for much less energy
consumption, the big question is whether their lifespan will be sufficient
to actually provide the payback promised.

Jeff

"amakyonin" <amakyonin-u1@xxxxxxxxx> wrote in message
news:ead98bf0-df7b-4401-b2d3-8af8e77a6ea6@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> LEDs are all less efficient than halogen lights (of the MR16 type). If
> you research them you will find that they all have fewer lumens per
> watt than any comparable halogen. They are getting close to parity
> nowadays but they still aren't there yet. Also be aware that some high-
> output LEDs like the Luxeon-V have a significantly reduced halflife of
> only 1000 hours. This is much worse than any halogen. When you add in
> the factor of the price premium for these more exotic lighting systems
> it doesn't make sense to use them in any application where a halogen
> will work. The newer Luxeon K2 is the first with a useable lifetime
> that is long enough to justify the higher cost. If you're still set on
> going with LEDs, the only option worth considering right now is a lamp
> with a K2 emitter. Don't buy any lamp that you don't know for certain
> what type of emitter is used in it. Otherwise, you can't look up its
> performance on a datasheet.
>
> I think that a lot of the misconception that LEDs are more efficient
> comes from the fact that they don't put out any infrared light that
> can be felt when you put your hand in front of them. All of the high-
> output LEDs, however, require significant heat sinking and this is
> where they dump all of their waste heat to.