150watt hps how low can they go

the lights now are 1' from the top of the plants. can i go closer or no?

how big is your box?

Put your hand under the light, when you start to feel heat, thats how close it can be.

Your plants shouldnt be feeling the direct heat of the light.

Yup do the back of the hand heat test like BC stated. Thats the best way to feel what your ladies are feeling.

I keep my plants 3" from my 150w hps without any heat problems. An inch higher and I start to feel the heat.

If you have a fan blowing directly on the bulb you can get it down to 2" in some cases but that will still make the plant sweat too much. I like to maintain around 4" with mine, up to 6" but I do have a little 6" el cheapo clip on fan blowing on the bulbs directly from about a foot away.

Under no circumstances would it be efficient further than 6" away, because then it's only giving the best light to the top few inches to the plant.

Don't try to force it too close though if you don't have a fan directly on the bulb or cooltube or something not that it will show physical signs of burn but just will slow or stall growth before actually showing signs of physical burn.

6" without any fan is probably still fine though as long as your ambient temp isn't too high or humidity incredibly low too. (not that anyone should be growing any plants without a fan blowing on the tops of them anyway)

well the room is 2' by 4' and 5' tall and as you can see in the pic there are 2 150wt hps i did put my hand over them and they where getting slight heat

i do have a fan blowing over the tops and one 4" can fan sucking air out into a large carbine filter

this might show it better

here are some more pics

sold me, im buying on instead of 6 23watt cfls