12 to 14 inches but it really depends on whether the hood is vented or not. If it's vented,then you can go 6 or so.Still need to place your hand under the light.The back of your hand will tell the tale.

Ga Grown!
GaGrown Reviewed by GaGrown on . 400 W distance question Spent quite a lot of time looking through the posts and must be a pest and ask a question that has probably been answered before. I am only 8 days in and I have 1 400W sodium light. How far do I keep the light from the top of the plants? Thanks so much in advance! Peace from Praha! Rating: 5