Or if yours are dimmable just turn them down.
Lots of folks I know run 600w mh at 750 and swear they are brighter. I figure that's the same as my ballast doing 1150 on my 1000w de bulbs.
I hate to say it but lets see in most cases with using lights.
Were growing in our own homes , or apartments, or rental properties ballasts light bulbs are engineerred to work a certain way with proper things attached to it Right.
Now i do not know about you but i would hate explaining to police or insurance company or even land lord that you read it on the internet how to nigger rig a light ..
Its all about Safety and well being seriously when i leave my place with grow lights on i am comfortable its not going to burn my place to the ground .
Or when my kids and family go to bed at night
i sleep better ..
Its not about hey i got a 1000 watt ballast but will plug in a 600 watt bulb and dim it down to 600 or 650 watts that is just plain stupid
Use the right tools for the job were adults here lets use our brains instead of cutting corners that will probably bite you in the ass in the end ..
SAFETY FIRST if a person cannot get a a ballast right now oh well wait till next payday or save plan do it right and life will be better
So the ops quetion was can he plug in a 600 watt into same mogel socket that 1000's were in and the answer is yes.
Aslong as his buddy gets the right ballast and plug in's doing it right
Which i am confident his buddy will do
