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lighting 11-07-2011 06:03 PM

Do newer dusk to dawn lights cover more area?
So, some roofers broke my mother's dusk to dawn light and I need to get her another. The problem is, it was made/installed back in 1985. It used a 175 watt metal halide bulb (or mercury vapor.. I can't exactly tell for sure.). Anyhow, all the newer dusk to dawn lights use either a 65 watt CFL bulb or a 100 watt metal halide. Do these newer light cover around the same amount of lighting area as the old 1985 lights? I've found one 175 watt mercury vapor fixture, but it's much bigger in diameter (15-18 inches for the new one vs 10-12 for the old one). Is there a way of knowing if the newer fixtures can cover more area with less wattage? Also, are the bulbs just as reliable? Do lumens determine the lighting area coverage? I just want to make things right for my mother. I also had a few other questions..

Can I use a higher wattage bulb in a lower watt fixture? What are the effects of that?

Also, can I use a metal halide bulb in a mercury vapor fixture or any other fixture (the 175 watt bulb bother have the wider diameter screw in base)?

Any contributions would be appreciated.
Thanks in advance.

Here are a few links to the dusk to dawn lights I'm looking at:





gregzoll 11-07-2011 07:48 PM

No, they are all the same. Just buy one that fits her budget and color choice and be done with it.

mpoulton 11-07-2011 10:46 PM

Mercury vapor is considerably less efficient than metal halide or sodium. Sodium is more efficient than metal halide, but not by much, and the yellow light is less attractive. CFL may be somewhat more efficient than the others, on par with sodium. Energy cost will greatly outweigh the cost of the fixture within a couple years, so I'd probably go with the most efficient and lowest wattage fixture available. That would be the CFL. Metal halide would be my next best choice. Do not buy a "new" mercury vapor fixture. As of 2008, the manufacture or importation of mercury vapor fixtures and ballasts is prohibited as an energy saving measure. Any mercury vapor fixture you buy now has been sitting around for awhile.

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