How close is too close?

[bigjb]

Can anyone out there give me some advice as to how close your plants can get to the light before damaging itself or yield? I have an air cooled 1000w hps and some ladies I vegged too long. The temp currently in the flowering area is 78 (mid canopy) and when I hang the therm. 3 in. from the light it jumps to 88. I can raise the light up to about 7.5ft. so should I let the tops get real close to the light or should I raise the light farther?

 

[pcduck]

Place back of hand at canopy level. Lower light till back of hand feels some warmth then move light up an inch.

 

[Roddy]

Usually around 8" to a foot....but judge as duck has suggested!

 

[BackWoodsDrifter]

Yup what these good folk be tellin ya

BWD

 

[Red eyed gardener]

Yep get the light down just low enough to be close but still in that cool zone.Man i have been having good luck with mounting a large computer fan blowing on the bulb of my 400 w and i was blown away by the temp drop.Be suure to check them at least every other day if they are in stretch.You can also keep an eye out on them top hairs and make sure they look happy and not curled or showing signs of heat stress.if the temp rises in the room you will probably have to move the light away and if it cools you could probably move it closer.

 

[Hushpuppy]

Its hard to trust the thermometer placed directly in front of the light because you are getting radient heating of the thremometer as well as ambient heating. The two heat signatures are different. You want to maintain the temps in the air space around the plants in 75-80degree range but then you also don't want the radient heat to burn the tops of the plants. The trick is to do just what PC said. You place your hand over the highest plant top and feel the light on the back of your hand, then either lower the light or raise yer hand until you feel the radient heat start to get a bit uncomfortable. Just below your hand is the closest you want to let the girls get to the light.

They make a hot spot diffuser to put on the 1k bulbs which really reduces that problem and allows the bigger lights to be run closer to the plants. Most hydro/light stores carry them.