Quote:
Originally Posted by Delphinus
I guess the real question is what are the real watts out of a 400W? It's like the 250W M80 is more like a "real" 400W. Looking at Sanjay's site ( http://www.manhattanreefs.com/lighting ) I note that switching to an electronic ballast for 250W the XM lamps drops to 115.
Assuming an electronic ballast really uses 250W (might be a stretch, I don't know), and we get 115 ppfd, that's like saying 0.46 ppfd per watt. If the HQI uses 405W but nets 182 ppfd, that's also 0.45 ppfd per watt, but we just "get more".  So I guess it's not a real question of who's more efficient, but a question of how much PPFD do you want.
Wow, my head is swimming just trying to digest this. I knew that a 175W wasn't really 175 and 250W wasn't really 250 and 400W not 400W but I thought the "real versus rated" differences would be less than this.
Dang maybe T5's really are the way to go in the future.  |
I think your conclusion is quite correct if you look at Sanjay's results across the board - the more juice you put in, the more light you get out of it. Of course the law of diminishing returns kicks in at some point where the extra PPFD isn't worth the added electrical cost. What concerns me is that my M80 ballast seems to be pulling quite a bit more than what Sanjay's M80 was pulling with the same bulb. I don't have a PAR meter to see how much useable light it is putting out, but sphelp's and speerider's concerns are well taken. The bulbs are CRAZY bright, for the record. I had a friend comment that you can't look directly AT THE TANK (not the lights) for a extended period of time without having to squint.
As far as T5s are concerned, putting them on an Icecap 660 ballast will overdrive them resulting in more PPFD, but at the expense of reduced lifespan.
I chose this particular MH combo because of the crazy PAR. My next set of bulbs (assuming that I don't change ballasts) will be Radium 20Ks which are spec'd to be driven by an HQI ballast. I'm curious as to what wattage results I'll get from them.