distance from plants? HPS 400w

Guys:

I bought a HPS (400 watt) and my questions is what is the correct distance to keep the HPS light from my plants?? Just starting flower stage.

Thanks for any input :)

I start off at about 12'' above the canopy, the let the plant grow up too 3'',4'' from top of plant. 400w , you can just about touch the plant with the bulb, they dont get real hot. but if you start to see heat stree , move them up a little. All plants differ. I had white russian last time, and i could bring the bulb 3'' from the top. now i have cali,mist going and they are more sensitive to heet

Scott,
I picked up an inexpensive laser thermometer on ebay (about $30). So I can spot around on individual colas to see exactly how hot they are. I havenâ??t had any heat stress keeping the max at 82â??84˚. Real handy for res temps and many other things too.

HMR

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Originally Posted by Horsemanrocks

Scott,
I picked up an inexpensive laser thermometer on ebay (about $30). So I can spot around on individual colas to see exactly how hot they are. I havenâ??t had any heat stress keeping the max at 82â??84˚. Real handy for res temps and many other things too.

HMR

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Thanks for the tip, I will check it out and pick one up. I have a few LED's and this is my first HPS, they run "hot". Going to do a side by side grow to see what is better. Right now I put it 18" from top of the plants, thanks again for info :)

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Originally Posted by drdettroilet

the let the plant grow up too 3'',4'' from top of plant. 400w , you can just about touch the plant with the bulb, they dont get real hot.

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And the Darwin award of the week goes to you my friend. I invite you to come touch my HPS's and tell me how hot they aren't.

The real answer is you have to play with it a little. Some people won't let their plants come within 12" some 16". Like Horseman said, don't let it get much over 84 degrees at the canopy or you will probably have some heat stress issues. With my current setup i'm in the 6" to 8" neighborhood, no pun intended. Obviously if you have an open reflector or an air cooled one it will also make a difference. 12" to 18" should be a decent safe zone for a relatively mature plant, seedlings should be stay about double that distance away. Let us know what you end up with:thumbsup:

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Originally Posted by irydyum

And the Darwin award of the week goes to you my friend. I invite you to come touch my HPS's and tell me how hot they aren't.

The real answer is you have to play with it a little. Some people won't let their plants come within 12" some 16". Like Horseman said, don't let it get much over 84 degrees at the canopy or you will probably have some heat stress issues. With my current setup i'm in the 6" to 8" neighborhood, no pun intended. Obviously if you have an open reflector or an air cooled one it will also make a difference. 12" to 18" should be a decent safe zone for a relatively mature plant, seedlings should be stay about double that distance away. Let us know what you end up with:thumbsup:

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Going with some auto flowers (AK 47, Hindo Kush) this grow and wanted to try out HPS light to see how yield vs. my LED's. Also got a couple of Super Lemon Haze going for mother plants. Will see how it goes and I will play around with heat/temp and get used to HPS light. Got a fan going as well as exhaust fan, so far grow tent is at 76 degrees :)

Aim the fan so it blows on the bulb and out towards the side the is not shielded with the light cover. It cools my temps about 8 degrees just by doing that with my 400w hps.

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Originally Posted by jtsik330

Aim the fan so it blows on the bulb and out towards the side the is not shielded with the light cover. It cools my temps about 8 degrees just by doing that with my 400w hps.

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Good idea, will do thanks.

just imagine your hand is a mj plant if its to hot for you ,its to hot for plant:jointsmile: