How far should 400 HPS be from Plants

How far should I keep my 400 watt HPS for my plants. I just started 12/12 two days ago. Its about 2 and 1/2 feet from them now.

Put your hand over your largest plant, when you start to feel heat, move the light up a few inches.. Do you have a air cooled reflector? How about a oscillating fan?

12-24in from the plants start at 2ft then lower it in a 2 weeks time slowly lower it to 1ft
make sure you got good ventilation or else you plants are gonna get burnt.so keep it at 2ft to be safe.


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i have a 400watter and keep it 12-18 inches away with an ocilating fan blowing across just below the light werks great go with 18" and you will be growin

12-24in from the plants start at 2ft then lower it in a 2 weeks time slowly lower it to 1ft
make sure you got good ventilation or else you plants are gonna get burnt.so keep it at 2ft to be safe.
This is a good book knowledge answer...


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i have a 400watter and keep it 12-18 inches away with an ocilating fan blowing across just below the light werks great go with 18" and you will be growin \

I have know idea what is really going on in this room...


If you feel heat on the back of your hand after holding it there for 5 sec. then it is a little to close...Just use basic reasoning....You can even hold up a thermometer next to a top and if it goes over 80 deg, then you should raise the light up...There are alot of variables, so I would suggest this method...GL

I got the same setup a 400 watt hps now for my flowering babies, u dont wanna burn them , but look at this pic my plant is 3 inch away and its been like that for 3 weeks now , just keep that fan on em works for me might work for u what kinda plants do u have ? INdica or sative , mine are sativa mostly, how far in are u ?