Specifically about your lumatek:
[FONT=Verdana,Arial,Helvetica]Why are there separate ballasts for 120v or 240v?
Lumatek ballasts are voltage specific and cannot be modified to change the input voltage. The 240v digital ballast is much more efficient, producing more light while generating less heat than its 120v counterpart. Other dual input voltage digital ballasts can never achieve the same efficiency as dedicated 240v versions.[/FONT]