I have a 250Watt HPS light with 4 plants underneath it. What distance is good to keep between the plants and the light? Right now its about 19 from the tallest and 22 from the shortest.
you wannna get that thing as close as possible without making temps to hot. Pretty much the closer it is, the more lumens you plants gonna get so the faster it will grow check out this chart, i though it was useful
30 cm / 12 inches / 1 ft is ideal distance if you can get away with it. All depends on how your venting your light hood.
I have a oscillating fan which blows over the plants and hits the bottom of the light (would hit the light even more if I lower more, so I am going to try to lower it down to about 14 inches for now and see how that works. Thanks for the help. Do any of you by chance know which metal halide bulb is best for vegetative? I dont know what ___k after the wattage to get ie, 4200k, 10k/20k etc.
Hold the back of your hand under the light level with the plant tops. If you can keep it there comfortably for 30 seconds or so it's fine.
i have mine at less than a foot away, inside sun 250w hps no problems yet you just have to be careful and it helps alot to have a fan blowing on the area, or heat will build up.
I am running 2 x 250watt hps in a 2.5ft square tent over a 4 plant scrogg I have my light 2ft away from my plants don't want to risk drying the heads out