As far as overdriving T-5 off an IC 660, all you have to do blow lots of air across the bulbs. Many people have gotten 12 months or better overdriving off a 660 as long as you blow the heat away. I'm not sure where the 50% loss of light in 7 months came from, unless it was an absolute cheapo bulb with no ventalation. The testing I have seen done on -- showed about 80% output after a year off a 660. Pretty darn good in my opion. On my 55g I currently run 2 250 MH's along with 2 110w superactinics off a 660. In another two months I am changing the VHO's out with T-5's for my actinics on the 660. Then I'll get to see for my self the difference.
Here is what the President of IC wrote me concerning overdriving T-5's off a 660. Also a 54w bulb will actually use around 74w off an IC 660.
"Conventional ballasts are made to run a specific lamp load and apply a specific milliamp output to the lamp's filaments. That charge goes from one end of the lamp to the other filament, aided by mercury in the gasified mixture. That bolt of energy while traveling the length of the lamp, excites the gases enough to cause them to strike the phosphorus lamp coating. If you apply too much output to the filament, it doesn't last very long. It's made to fail.
We don't do that. We send a signal more like a radio transmitter, from one filament to the other at a specific high frequency that excites the gases enough to cause them to strike the phosphorus lamp coating. As we use less voltage, our high frequency output can travel 100 feet or more vs. the usual 8 feet max a conventional ballast can tackle in distance from the ballast to the lamp. We don't over tax the filaments so all types work fine. Coincidentally, our method of lighting a fluorescent lamp, produces light more evenly across the length of the lamp. Lamp end blackening over time is diminished as we don't constantly deplete the filaments with charged particles trying to make it to the other filament only to fall short and adhere to the lamp's sides. Sudden blackening is the result of a poor connection (lamp to lamp holder or a splice between wires) and/or lamps running in an unvented fixture.
Wiring must be to the wiring diagrams we provide. Unused lamp wires must be independently capped of for possible future use. ANY perceived open circuit will cause the ballast to immediately shut down, not just off.
Our VHO ballasts, after confirming continuity exists, measure the lamp load and provide power accordingly. As the lamps heat up the load changes and the ballasts constantly adjusts to the load. Even as lamps age they change. If you re-wire from 3 to 4 lamps the ballast will produce more output to adjust to the new lamp load.
NO (normal output) lamps when overdriven per their specifications will not last 4 years on our VHO ballasts but if lamp heat is vented, they can provide reef required output for 12 to 24 months depending on the application's heat venting and brand of lamps used. Longer lamps last longer. With T5HO lamps active venting is required for maximum light output and lamp life. So there is some trade off of lamp life but not much. When it comes to Actinic lamps I recommend running them till they stop or you aren't happy with the visual effect they produce. As far as the tank's needs, if they're lit the tank is getting more than enough.
Re MH overdriving; the Kelvin (color temperature) the lamp was made to produce will change with too much power applied, there's a potential for an arc-tube to explode, and most likely the lamp will prematurely age and stop working. We once upon a time did this with 175-MH bulbs w/o a problem but we found in hindsight it was a very specific solution that worked with a few select lamps. We compensated for the overdriving by lighting the lamps at 1KV vs. 5KV conventional ballasts used and running them at >20KHz vs. 60 Hz. (or 60 on/offs per second). We now believe that with better fixtures that are more efficient and positioned lower to the water there's no need to overdrive MH bulbs. The sweeping high frequency we now use if a huge leap forward in eliminating flickering, bulb noise and being almost universally compatible.
Andy"
