MH Ballast Wattage Specific?

[Kuzu]

If you have a high-bay fixture with a pulse start metal halide ballast and currently with a 400W metal halide lamp, can you just replace the 400W lamp with a different wattage lamp (with the same base) or does this require you to replace the ballast as well?

In short, are the MH ballasts one size fits all or specific to each wattage?

Thanks!

 

[LarryFine]

If you look on this page, it's evident that the ballast is sized to the bulb: http://www.elights.com/methalbal.html

 

[Kuzu]

Thanks chief!