HPS Distance From Young Plants

OK...I know this is one of the perennial questions, but here goes...I have a 400W HPS in a PL Midi reflector. Not air-cooled, other than a fan that blows in the space in between the light in the plant tops. At this point, the light is probably about 14" from the tops...using the hand test, everything is cool. In fact, it seems as if I could drop the light a bit more, actually. What I'm not clear about is whether the fan breeze is actually making the light cooler. If so, should I drop the light even closer? Also, where is the best place to measure the heat of the cabinet? The plant level? In the shade? Etc. etc. There does seem to be a fairly large spread of temperature depending upon where the thermometer is kept.

Anyhow, as always, thanks!!!!

mine is 30" and the soil still seems to dry up fast, but thats the furthest i can get it away, id prolly put it about 35" if i could.

YETTT, i only have it that far because my grow space is small (growing lowryders), and at 30C/85F in heat. whats the temp in your grow space?

Hey, thanks for the reply. The temp depends upon where I have the thermometer. If it's lower than the plant level and out of the light, it's generally in the low 70sF. If it's in near the plant level and exposed, it tends to get closer to the upper 70sF.

Put your hand under the light. If you hand feels uncomfortable after a whle move the light. I have had temps up to 90 and the plant still thrived with no stress. just don't burn the babes

mine is 30" away from the tops of the plants the whole Veg and Bloom...