48" LED Array - Up and Running...Mostly

[Canadian]

Originally Posted by StirCrazy

Andrew, you have to go do some reading in this thread, he is getting higher par at 5 times the distance. T5 was at 3.5" and he is still getting higher PAR at 17" above the tank, which he did becasue he didn't have his dimming setup done yet. At 8" he was over 500 PAR where at 3.5 with the T5 he was at 300 PAR, Also this is with 60 and 80 degree optics, no one ever said thoes optics will give you 250 - 400 MH levels, it is 40 degree optics you need to get that, the best you will get with 60's is around a 150 watt MH which he is pretty close to as a 150watt mh isn't much higher than a good T5 set up. if you want a good comparason maybe Ron will take a PAR reading at 3.5" with the LEDs then you can see how much more punch he is realy getting, I am going to guess that he will be around 700 at the surface and probably close to or over 400 at the bottom, but thats a guess.

now as for the PAR output, you are thinking along the lines of a gas filled cathode tube. you can't think that way with LED as there is no gas to break down and change the spectrum. it has been showen there is absolutly no shift in spectrum in a LED over its life, only a 15% decrease in intensity, so there is no reason to think other than a 15% decrees in PAR as there will be no spectrum shift to compound the drop as it does in MH, PC, CF, ect. so if we look at that the average MH has a 20% drop by the time it is changed, and most of that drop occures int he first 6 months, floressents have a even steaper drop off, so going with LEDs after 5000 days (10 hours per day) you will have 15% less intensity with no spectral shift so you should not get nusence algae ect..

Steve

Steve,

You'll have to read Ron's post after yours. The PAR measured with the low quality T5 fixture was on more than 1 year old T5 lamps and therefore a very poor comparator - forget about the height of the fixture comparison. Additionally, I'm less concerned about the comparison to T5s than I am to MH (the only reason I commented on T5s was because the comparison was hugely favorable to the LEDs based on the manner in which it was performed). Various qualities of LEDs make them favorable to T5s IMO. With that said, comparisons are being made all over the place to MH by retailers, manufacturers, and hobbyists. When you were standing on your soap box about MH a few months ago you pounded your chest about getting over 1000 PAR at the surface and 500 on the bottom of the tank. Clearly, the numbers being reported here don't fall in line with what you've purported constitutes adequate PAR for your SPS tanks.

And as far as the theory behind intensity drop in LEDs goes - it's just that: a nice theoretical expectation based on presumed qualities. Until there is some long term data for PAR the theoretical musings can carry on but with a healthy dose of skepticism.