I just got a growzilla hood. I have a 1000w HPS and a 1000w MH in it. I know the rule of thumb with 1000w is 30" away from top of plant. what is it for my light?
That's awesome! I want to add a MH to my HPS and was also thinking of getting the Growzilla. Anyways 30" is too far imo. I keep my 1000 15-20" away from the glass on my reflector. Basically you want to push it down as far as you can while still achieving acceptable light spread for your area, and not exceeding 80 degrees or so at the canopy level. How big of an area are you going to be covering?
I do not think there is a rule. If you can manage the heat you can have your light as low as 1" away from from the top of the plant.... the only reason people keep the light high is because they can not control heat.... Currently I have 600W only 6" away from the canopy and there is not much heat at the canopy level....
Heres a excellent light guide. http://forum.grasscity.com/attachme...-lights-plants-light_distance_chart_1__1_.jpg