Does a ballast with a 1000 watt lamp dimmed to 600 watts put out the same light as a regular 600 watt lamp and ballast?
This is a very popular question lately. We have not done a direct shootout like you mentioned. Due to potentially different THD% output ratings of a native 600w ballast/lamp vs a dimmed 1000w ballast/lamp, the results will only be estimates because of the different hardware, but they will be close as long as you use the same manufacturer of ballast and lamps. Sunlight Supply’s Galaxy 1000w dimmable ballast is the only manufacture that states that you can use a 600w lamp when the ballast is set to the 600w dimmed setting. Therefore, this ballast will probably provide the most accurate results since you are not changing ballast hardware, only the lamps, for the output comparison. As soon as we get a galaxy ballast we will do this test.
In the meantime, we have done some performance tests measuring the lux output of a dimmable ballast at 1100w, 1000w, 750w, and 600w settings. For the test we used the following equipment:
We placed our tablet light sensor 19 inches off the floor. The lamp and reflector were hung 46 inches above the tablet. We turned the ballast on at its default 1000w setting and let everything warm up for 30 minutes before taking any readings. For each of the wattage settings/tests, we adjusted the wattage on the ballast and then waited 20 minutes before taking any readings. We initially saw that it took about 5 minutes for the lamp to adjust to the new wattage settings and then an additional 10 minutes for the light output to stabilize enough to take readings. Here are the results:
1100w = 39,000 lux
1000w = 34,900 lux
750w = 21,250 lux
600w = 16,900 lux
In theory you would expect the 600w setting to output around 60% of what the 1000w setting is outputting (600 ÷ 1000 = .6 or 60%). But in our test we found that running a 1000w lamp at 600w gave us an output that is lower than 50% (16,900 ÷ 34,900 = .48 or 48%) of what the 1000w setting gave us. That’s not very good and it’s pretty inefficient. Not only that, but we became concerned about the lamp when doing the test at the 600w setting. After 15 minutes on the 600w setting our meter reported a lux of 17,800. Over the next 20 minutes, the lux meter kept dropping and never seemed to stabilize. When we hit a lux of 16,900 we decided to end the test since we were already well below the anticipated 60% output and we didn’t want to kill the lamp. We did not see this unstable behavior at the 750w, 1000w, or 1100w settings.
We did not measure the lamps Kelvin Temperature at any of the settings. However, with the naked eye, it is easy to see the difference between an HPS lamps 2000K and our test lamps 3200K. None of us could see any change in the light spectrum between any of the settings.
I hope that helped a little. As soon as we can source a Galaxy ballast to test against the different lamp outputs, we will post that info.
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