400w MH question

[mockery]

So friend of mine bought a used setup and it came with a MH setup. On the bulb it says 400W 14,000k, the brand is SPS I believe, and the ballast that came with it says 250W. Well he plugged it in and the bulb fired and ran just fine. But I thought 400 watt bulbs had to have 400 watt ballasts and 250 watt bulbs and 250 watt ballast? I' I wrong? Could someone enlighten me on this situation?

Thanks,
Colin

 

[porpoiseaquatics]

As far as I know...a 250w ballast will not fire a 400w bulb.

 

[haninja]

My 175w ballasts fires a 250w bulb...

 

[ga_daisy]

Maybe it fires but doesn't give the full wattage?

Dunno....tagging along.

 

[brianjfinn]

I've heard that it's possible, but it's definitely not running the bulb the way it should. He'd better get a bulb that matches the ballast. I'm pretty sure it's the same as running a bulb on a dimmer switch, which most HID bulbs are not designed for. You'll loose a lot of the spectrum and I think it can actually shorten the bulb life. I could be wrong on that last part, though.