T5's and overdriving them? Anyone?

I don't know of anyone who can or is driving a 24 watt lamp at 100 watts. The Ice Cap ballasts (according to Ice Cap) drives a 24 watt at 50~55, a 39 watt @60, 54 watt at 85 and the 80 watt at 100. The color shift in an overdriven lamp would be towards the blue spectrum which is also the first to deminish as the lamp ages anyway so it is no big deal, I can handle a little extra blue in my light As for output an overdriven 54 watt lamp running at 85 watts produces much more PAR than my 80 watt lamps overdriven to 100 watts, let alone running at 80 watts. Ice Cap has an article on their website about running a Normal output fluorescent on their ballast that claims the output is equal to a VHO.

I agree that overdriving is not a good substitution for the right number of lamps. The advantage of overdriving the lamps is deeper penetration into the tank. You can throw a dozen normal output T5's over a tank and have wonderful PAR within 6" of the surface but at 12" deep they wont do what 4 spaced out HO lamps will do. Same rule applies with overdriving lamps, a bit of a waste if you don't have 1 lamp for every 3 to 4 inches of aquarium depth front to back. But if you have more than 16" of water depth or so and want a clam or SPS on or near the bottom overdriving the lamps will give you a huge boost.

To the person with the 2 24 watt lamps, If you have a 660 ballast and have room grab yourself a couple more lamps, if it is a 430 one more lamp-don't run 4 T5's on the 430.

By the way, Reef geek sells T5 retrofit kits with the Ice Cap ballasts and reflectors. Seems a little odd the Gregg would warn against overdriving the lamps.

 

Just currious ... How are you measuring PAR?

 

Quantum PAR meter by Apogee Instuments. My comparisons of the 80 watt to 54 watt lamps are based on the readings taken by another reefer using the same meter to read the PAR on his 54 watt Ice Cap system. These are not perfect laboratory measurments but close enough. His readings were higher than mine both in and out of water so individual environmental conditions were not a determining factor, which is what I thought at first. But after digging into the numbers Ice Cap provided I discovered an interesting bit of info. When ran on the standard ballasts the T5's increase in efficiency with length. The easiest example is a 22.5" vs. 46.5" lamp, AKA 24 and 48 inch lamps. The 24" lamp is 24 watts but the 48" lamp is 54 watts. Double the length but more than double the watts.

However, when overdriven Ice Cap has measured as high as 55 watts from the 24" lamp which is over 2 watts per inch even if you use the 50 watt number and the 48" lamp is 85 watts, less than 2 watts per inch. In the case of my overdriven 80 watt T5's vs the 54's I calculated the watts per inch, About 1.72 watts per inch for mine and 1.84 for the 54 watt lamps if I remember right. Suddenly made sense that the 54 watt lamps were producing more PAR than the 80's. I havent measured them but I would bet 4 24" T5's would produce PAR equal to a good 250 watt halide at least to 24" of water. My 80 watt T5's blew away 150 watt halides in 18" of water. I wish I had a deeper tank

 

How would overdriven 80 watt t5's produce more par than 54's? If thats the case why would you use 80 when you can use 54.