Metal Halide - Choices

[lastlight]

Sorry I wasn't thinking specific ballast data you used generic numbers so I thought I was missing something. My radium is a 250w and burns at around 333w so I fully get that. I always thought the e-ballast would use a little less. For example my same Radium on icecap uses 244W. Not sure if this was the old or newer icecap but I didn't think any e-ballasts overdrove bulbs.

[sphelps]

Originally Posted by plutoniumJoe

That is what I always believed as well but you must take into account the power to drive the ballast as well as the amount of light they give off. So for instance a Vertex 400 watt ballast actually consumes 444watts with a ppfd of 121 so at 888watts you get 242 ppfd. Watts per ppfd 3.6

A vertex 250w consumes 263 and produces 52 ppfd for an output of 789watts at 156ppfd. Watts per ppfd 5

So for marginally more power consumption you are getting considerably more light. That is why I was questioning it. Maybe with 2 400 I can run the lights less consuming the same amount of electricity and get better results.

Does that make sense or do you loose out because your are not getting as equal of coverage with only two. I also think that I don't put much in the last 4-5" on the extreme sides of the tank so I can still clean the glass. Last consideration is that 2 400W bulbs are less expensive that 3 250s.

- Joe

Yes but that's just that one bulb, the same isn't true for all bulbs. Quite simply the 400W bulb in that brand produces a spectrum slightly more concentrated in the areas that add to ppfd. If you look at a different bulb like the Aquaconnect 14K it produces 83 ppfd @ 250 (e=33%) and 143 ppfd @ 418W (e=34%) on an electronic ballast (same as vertex). So basically the same efficiency which is more typical. And all this doesn't take reflectors and tank sizes into consideration. Even if you can get a little more efficiency from 400W bulbs how do you concentrate all that light over a 6 foot tank with only two bulbs? With 3 250W bulbs you can distribute the light better and make more use of it so realistically that is more efficient.
Like I said before it's more related to reflectors, bulb and ballast combinations over wattage.

[fkshiu]

Joe, it depends on what you want your tank to be. I get fine coverage and grow all sorts of high light stuff with 2x175W Vertex electronics running Iwasaki 15Ks under Lumenmax pendants. PPFD per watt, this is the most efficient set up according to Sanjay's figures using less electricity than 150W HQI system but putting out more PAR than some 250W systems:

http://www.canreef.com/vbulletin/showthread.php?t=59449

Understand that I have a mixed reef with lower light creatures too and my tank is on the shallow side for a 6-footer. Looks wise no one has ever noticed any dim spots. If you want a full out SPS garden, however, going with three 250W pendants is the better choice. You start getting diminshing rates of return once you hit 400W territory.

You can have a closer look when you come by for you macro later this week.

[Myka]

Those Iwasaki bulbs on electronic ballasts are a PAR breaker...not typical! You can't get the same PAR using different bulbs on that ballast. As long as someone is happy to commit to that one single bulb, that's a great choice! Pricey bulb though...

[lastlight]

That sums up my radium conundrum. You sorta gotta commit to run them proper. Unlike that 175w choice tho you're not quite as ltd as you will get awesome par out of a ton of 250w bulbs tho you may burn them out prematurely (unlike with the radium).

[daniella3d]

Gee wizz..how much do you pay per kilowatt per hour? Here it's 7 cents. Surely not 40$ per month and why do you have to run it 12 hours?

That'S way too much I think.

Originally Posted by sphelps

Fun fact, 3 400W halides running 12hours a day will cost close to $40 per month in electricity!

[sphelps]

Originally Posted by daniella3d

Gee wizz..how much do you pay per kilowatt per hour? Here it's 7 cents. Surely not 40$ per month and why do you have to run it 12 hours??!!!

That'S way too much I think.

Based on $0.08/kWh and that most 400W ballasts out there run closer to 500W a piece. So 1500W x 12hours = 18kWh x 30.4 (average days per month) = 547.2kWh x $0.08 = $43.78