Incidentally, I make many of my T8 fluorescent fixtures
about twice as bright by overdriving them. I learned about overdriving fluorescent fixtures many years ago by reading a message thread in Garden Web, started by a user named Zink. The original thread seems to be lost, but a continuation of it occurs here:
http://forums.gardenweb.com/di...
The basic idea behind overdriving is to modify the fixture to concentrate the ballast power usually supplied to two bulbs onto a single bulb. That means you add a second ballast to a two bulb fixture, so that each bulb gets all the power from a two-bulb ballast. That just about doubles the brightness of the bulb. The bulb burns noticeably warmer, but not super hot, and that probably shortens the bulb life. But fluorescent bulbs usually last for years anyway, so the bulb life has not been a problem for me. There are some expensive ballasts that get roughly the same result from a single ballast, but those are not standard in readily available fluorescent fixtures. And they are brighter, but not as much as you get from overdriving.
A new thing that I started doing a couple of years ago is to install a four-bulb ballast in a two-bulb fixture. The four wires go to two bulbs, nicely overdriving them very brightly. And another advantage of that is weight. A four-bulb ballast weighs somewhat more than a two-bulb ballast, but not twice as much, so that you get a lighter fixture using a single four-bulb ballast versus two two-bulb ballasts. The wiring scheme on some ballasts does prevent them from being used in overdriving. But many ballasts can be connected for overdriving.
Overdriving isn't for everybody, because you do purchase and install additional ballasts. But it does make your bulbs burn
way brighter. My zinnias really respond to overdriven T8 bulbs. I learned to overdrive from Zink's original message thread, so I have been doing it for about 9 years, and learning more as I go. (Do
not stick your tongue on a cold pipe or refrigerator cooling coil, and do not stick your tongue on a hot wire.)
If you have the ballast go bad in a fluorescent fixture, it is much more economical to replace the ballast than to replace the fixture. And that could give you the opportunity to buy two two-bulb ballasts or one four-bulb ballast for a standard two-bulb fixture and enjoy the extra bright light of an overdriven fixture.
ZM
