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Distance from 400W HPS to plants

R

roadhouse

What is the optimal distance to keep my light from the tops of the plants? If it makes a difference my grow area is approximate 5.5'x3.5'. I figure there must be an optimal distance with the light centered directly in the area in which all the plants can get optimal coverage with dispersal being relatively even. Any formulas out there? TIA

edit: the reflector is 19" Wide x 16.5" Long x 6" Tall
 
Yes, it's a very scientific formula! Extend your arm straight out until it is in the middle of the light. Turn it (your hand) palm-down. If the back of you hand feels warm, the bulb is too close!

BTW, a 400 watt will not cover a 5.5' area. A 600 watt will have a hard time. With Mylar lined walls, I can pretty much do 4' length using a MH bulb.

Mike
 
wordwiz said:
Yes, it's a very scientific formula! Extend your arm straight out until it is in the middle of the light. Turn it (your hand) palm-down. If the back of you hand feels warm, the bulb is too close!

BTW, a 400 watt will not cover a 5.5' area. A 600 watt will have a hard time. With Mylar lined walls, I can pretty much do 4' length using a MH bulb.

Mike
Click to expand...


yeah man just like he said!!!
 
LOL fair enough. I ended up hanging it about 18-24 inches from the tops of the plants due to height variance. What would be a more typical distance for brand new seedlings (for future reference)? I figure it has to be fairly shorter, or maybe not?

You're making me worried about the coverage now though! The plants pots are in a 4 feet by 3 foot area but some of the branches extend past that area and make it more like 3.5x5.5. I hope that the parts that are exposed will end up getting enough coverage to keep growing then. I ordered a big white poly reflective sheet that I will be putting up so hopefully that will help as well.
 
roadhouse,

Shouldn't be a problem. I'm not an expert, but if the center of the plant is getting the light it needs, and the outside leaves are getting some light, you should be set to go.

Mike
 
I use 1000 watt HPS and keep the bulb about 8-10" above the plants and still get more than enough coverage so I'm sure you can put it a LOT closer which would give you better results.
 
Great to hear. I have to say it's been only 3 days now since I got the light set up and brought my plants inside, with it on for 16 hours per day, and the plants already have exploded with flowers and even have a few pods starting up along with new foliage as well.

Definitely not the best setup as far as space goes being in a corner in my crowded apartment though it will have to do. Anyone that walks in probably thinks I have a cannabis farm set up in here, should be interesting to hear what the landlord has to say when they first come in for some repairs LOL
 
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