[noktommaster]

how far from the plant tops should a 400 watt MH or HPS be?

 

[jansjukebox]

That all depends. Are they seedlings or full grown plants? Is it an air cooled light or not? You need to keep lights farther away from seedlings untill they harden from the light. Usually start at about 3 feet from seedling ans bring it down a couple of inches a day untill you get it 12-24 inches if it's not air cooled and if it's air-cooled, you can bring it right down to within a couple of inches. best test is to put your hand directly above the plants palm down. Lower the light untill it a tolerable level when leaving your hand under for one minute. If it's too hot for your hand, it's too hot for the plants

 

[red southwest]

hey happy 4:20...i got my 400/hps in a 4x4 room my light is like 12.inchs from my tops with a fan

 

[aphid]

With seedlings or clones I start them about 3 ft. and work my way down to about 14-18 in. eventually.

 

[dooobster]

That all depends. Are they seedlings or full grown plants? Is it an air cooled light or not? You need to keep lights farther away from seedlings untill they harden from the light. Usually start at about 3 feet from seedling ans bring it down a couple of inches a day untill you get it 12-24 inches if it's not air cooled and if it's air-cooled, you can bring it right down to within a couple of inches. best test is to put your hand directly above the plants palm down. Lower the light untill it a tolerable level when leaving your hand under for one minute. If it's too hot for your hand, it's too hot for the plants

Exactly. :)