magnetic (the ones with the big ass wire coils) get hot. the newer ones with the fancy cases don't heat up that bad.

give it a test run.

i have used 400wmh's for 24/7 in work environments, and it didn't hurt them at all. they are magnetic, and yeah, the ballasts get hot as hell. same with my grow lights, but my exhaust beat any heat issues.
Solosan Reviewed by Solosan on . Ballast And Light ?'s i have a 250 watt MH Conv. and i was wondering if its cool to keep it on the full 18 hrs or if u give it a small break? and is the ballast supposed to get super hot??:rastasmoke: Rating: 5