Don't do it! You could at the very least shorten the life of your bulb and/or ballast, and at worst, end up with the bulb actually breaking.
Please don't give this sort of advice: "in theory it would work" when you don't actually have a good concept of the 'theory'. In theory, you should NEVER mismatch electrical components!
stinkyattic Reviewed by stinkyattic on . 600w bulb with 400w ballast? Hi All I have a couple of 400 watt ballasts and 400 watt bulbs. I was wanting to nkow if i can use 600 watt bulbs with the 400 watt ballast or will this blow the bulb? Thanks Rating: 5