Metal Halide - Choices

[plutoniumJoe]

Originally Posted by lastlight

How is 2x400 less power than 3x250?

The 400s are going to burn 800 watts and the 250s 750 watts?

I'd stick with 250s myself. I know it's a dying breed but I've finally tracked down another hqi ballast for my tank. I can run my radiums as they were intended and down the road I can run a lower kelvin bulb and get super sweet par numbers.

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