I haven't done this, but I recently saw a splitter/adapter that would let you run 2 600 Watt bulbs off a 1000 Watt ballast - not sure how the math works on that, but that's how the product was described.

Maybe they have the same type of thing for 400W bulbs.

Can a room be overlit? Love to know from some of the experts on here.
cannabis-seeds Reviewed by cannabis-seeds on . Multiple bulbs on a single ballast? Hey everyone.. Had a technical question posed to me today.. Just wondering if any of you electrical wizards could chime in on this! I have a friend growing in a 4ft crawlspace with 1000W bulbs.. needless to say... his room is WAY overlit.. and he was wondering if it is possible to wire 2 x 400W HPS bulbs to a single 1000W magnetic ballast? Seems to me that this might work as its still pulling less than the ballast rating.. but I dont know for sure and we want to be safe if we try Rating: 5