metal halide question

[rugar20]

I have acess to a 400 watt metal halide ballast but i only want to run at the max 250w lights on my tank will it hurt to use the 400 watt ballast but only have a 250w bulb?

[ckusnierek]

cant be done the bulb will explode!

[ckusnierek]

you could sell the 400W and probally get enough to buy a 250w

[monkeyreefer]

just run a 20k bulb

[rugar20]

so you are saying use the 400w ballast with a 20k bulb for my 55 gallon tank

[twincitiesreefer]

ya,the 20k will turn the temp down a lil,anyways i would keep the 400,u know u can keep anything under their

[ckusnierek]

even @ 20K 400w may be too much in a 55. mount it high then bring it down slowly

[grallster]

Yeah, just mount it high.

[monkeyreefer]

Originally Posted by rugar20

so you are saying use the 400w ballast with a 20k bulb for my 55 gallon tank

been done before, as already stated, keep it high and slowly move it down, plus you'll have less of an issue with the 20k because the par is lower than with a 10-15k bulb. plenty of light, and enough spectrum so you dont have to run actinics. if i had to do it over, id run all 400 watt 20k's over my tank, as its about the same par as my 250w 15k setup, with more blue. then again those led lights are nice too, but pricey

[Loverotties]

Buy a bigger tank!

[digitalis]

I would think a 400 watt ballast should be able to run a 250W light. My opinion, it's only CAPABLE of 400W but doesn't necessarily have to RUN at 400W. The light only pulls the power it needs, and won't pull the extra power. I would try it if I had a bulb, but I don't... do it at your own risk. I called MWC and Gordon and Jim say you can't.
FWIW

[Junkzoo]

You can't run a bulb not matched to the correct ballast.

[digitalis]

that's what gordon said, too. I guess I don't understand how hid lamps work. maybe the 400W ballast would force 400W through the 250W bulb.... Someone else said a 400W will work on a 200W ballast, but will just be dim... No idea.

[ckusnierek]

light bulbs DO NOT just pull the power that they need They are given the wattage forced from the ballast. they are designed to be able to handle the designated wattage they are made for.

[Junkzoo]

Chris said it better than i was trying to word it.
I'm not so sure on the igniter part(voltage needed) being the same for 250/400 bulbs, since start up pull more current than when the bulb has fired and is "running".
I'm gonna try and find out the common sense side of this and post what i find out. But i do know from personal experience, and the basics of what i've been told , that the ballast HAS to match the bulb.Blow up/not work/or even burn dimmer are all things that could happen (really doubt the burn dimmer part) I just know right now, you don't mismatch ballasts n bulbs.