Probably A STUPID Quection

[OldSalty]

Was just wondering if I could put a 250 watt MH on a 400 ballast? :o After all, you can put any size bulb in your light sockets. I was thinking the 250 watt bulb would only draw thw current it needed from the ballast. This is a m59 magnetic ballast. It was FREE. Guess I could get a cheep 250 watt bulb from HD and try it. (and stand back if it explodes :-o)

[matt]

Nope, can't do it. Think about the word "ballast" it implies equalization or balance. The bulb will simply draw as much current as is available; the ballast "balances" or allows the bulb a specific amount of current. A 250W bulb will definitely burn out with a 400W ballast.

BTW, there are no stupid questions, only stupid answers.

[OldSalty]

Thanks Matt, for clearing that up, Even tho down inside I knew what the answer was, just thought Id ask in hopes I was wrong and could try it.

[adaminaustin]

Matt what happens?
Does it just not light at the correct spectrum? Or does the bulb burn out premature?

I have a 175W 20,000K on a 250W ballast for at least 3 months trouble free. It was given to me and had a new bulb. The last owner explained it Like Oldsalty did, he said that it was fine because the bulb pulled less current than the ballast?

Is my light going to burn out sometime soon?

Thanks,

[matt]

Probably your bulb is burning brighter, but as they say, the brightest bulb burns out the fastest... (or something like that) Maybe the difference betwen 175 and 250 isn't enough to blow out the bulb immediately, but I would expect your bulb to fail at some point. Actually, I'm hardly an expert at this; you could post something on reefs.org for Sanjay Joshi. That guy knows everything about lighting.

[Instar]

Unless your balast is specifically rated as a dual balast, the bulb should be expected to shift spectrum and loose its effectiveness. These MH bulbs have narrow operating ranges in temperature, watts and mounting angle. Fans blowing on them, the wrong balast or angle that is a couple degrees off horizontal (or verticle, depending on bulb specs) makes the bulbs fairly deficient and can get pretty far off your desired effect. Then bulb useful life is shortened significantly. Another reason not to buy used bulbs, IMO. Don't know where they've been. I believe that the differences people describe between their systems and results with the same bulb can often be attributed to these things combined with their shields if they use such a thing. Its not that done wrong it doesn't make light, it does. But, without some heavy duty equipment to measure it, there is no way to know the loss. The eye can't see it, so saying there is no "bad" effect is not a measurement of performance, draw that runs up your light bill a few extra dollars more than it should (all balasted lights that are out of balance increase your bill), or colortone in your corals.

[adaminaustin]

Thanks for the info guys. Looks like it is time to upgrade to a 250w bulb.