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Hi Chuck,

We have moved into their use extensively and LOVE them. It's true that they cannot be dimmed and it's also true that they will take about 5 minute to re-start after a power failure. However, the results are spectacular if they are deployed correctly. Add to the mix that Phillips has just introduced a "ballast-free" 25 watt version for use in PAR fixtures that puts out the same lumens as a 90 watt halogen and you get the drift. 

We recently changed all the lamps but two in one section of one of our galleries to 39 watt track fixtures with PAR floods. The result was that our energy use dropped by 50 % and our light levels went up by 50 %! Not only that, the bulbs last 10,000 hours and the color was more cheerful and whiter.

Presently you can get floods or narrow spots but I expect to see this change. Track fixtures are made by Capri and Indy Lighting. The 25 watt flood was somewhat less satisfying in that it seems to be a narrow flood (more like a wide-angle spot) and the efficiency is not nearly as good as the regular 39 watt versions with ballasted fixtures, especially the electronic ballast versions of the fixtures. 

The color rendition (for Phillips lamps) is about 85 CRI. I find the color to be a bit cooler than halogen but very white and pleasant. We hope to ultimately re-lamp most of the museum. I might add for the historical folks out there that these are fade-blocked lamps and UV shouldn't be a problem.

Of course there are down sides. The fixtures are expensive if you go for the 39 watt lamps (about $250. for the fixture and lamp) and are "clunckier" than regular ones due to the ballasts. While the 25 watt lamps are convenient they are not as efficient as the 39 watt, they only save about 50 percent off  a regular halogen lamp. The 39 watt (which need special fixtures) is about 4 times better. We pay $ 42.00 for the 39 watt lamps and the 25 watt self-ballasted lamps are about $ 50.00. Of course the lamps last about 4 times as long so when you figure in the cost of lamp replacement the high initial cost isn't so bad. This is especially true for those fixture we all have that are in inaccessible places.

I might also mention that Phillips also makes a special HPS lamp called the "White SON" in 50 and 100 watt sizes. These also have an excellent CRI (believe it or not!) and give a much warmer "incandescent" feel. Track and other fixtures for these lamps are made by Indy Lighting. We have several of these which have been running for years. They are also cheap to run with energy efficiency that rivals the metal halides. The major problem with these lamps is that they are very expensive (about $ 100.00 per bulb) and are an exclusive Phillips product which always makes me a bit edgy (what if they stop making them?) Nevertheless, these lamps are a very effective light source. By the way, we had one of these with over 15,000 hours on the bulb before I changed it because the color began to get sort of orange. So the life expectancy is very good for these lamps.

--
John Bowditch
Exhibits Director
Ann Arbor Hands-On Museum
220 East Ann Street
Ann Arbor, MI 48104
734.995.5439
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pager: (734) 670-4555

The views and representations stated in this e-mail are the individual's. They do not bind the Ann Arbor Hands-On Museum or its Board, staff or volunteers, and they do not necessarily reflect the Museum's institutionally-held viewpoints, opinions or policies.

> ----------
> From: 	Informal Science Education Network on behalf of chuck howarth
> Reply To: 	Informal Science Education Network
> Sent: 	Wednesday, November 23, 2005 3:32 PM
> To: 	[log in to unmask]
> Subject: 	Metal halide
> 
> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related institutions.> 
> *****************************************************************************
> 
> Does anyone have experience with metal halide track fixtures in exhibit 
> galleries?  The metal halides are said to be "green"  because they use 
> a lot less energy than conventional incandescent fixtures, but they are 
> not dimmable, which means the only way to change light levels is to 
> relamp the gallery.  Have any of you guys got opinions positive or 
> negative about thhis issue?  Thanks for the advice,
> Chuck Howarth/Gyroscope
> 
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> 

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