how high to hang lighting?

my current dilemna is figuring out the optimum height to hang a 1000 watt hps to cover a 4x4 footprint with a 7.5 foot tall ceiling after subtracting 6 or so inches for framework etc. i would like to have the plants rest on the floor instead of having to construct a series of tables and so on however the hood is aircooled, which means that unless i am going to leave several feet of slack in the duct and shit on the cfm rating as a result i wont be able to raise/lower the light much without having a lot of slack in the duct.

i have seen numerous videos of professional setups where they have their plants on the floor and they typically have their lights as far up to the ceiling as they can get them, but then again they also have many lights with cross coverage not a single one.

should i just adjust the height of the light so that it optimally covers the 4x4 area and leave it at that height throughout? that would be my choice but i have read numerous statements that ideally you want a 1000w light 18 inches from the canopy for best results (or as close as possible without burning the tops) this means i would have to lower the light to about two feet off of the floor (which doesn't seem right) and raise it as things progress.

i suppose this is why folks have separate vegging and flowering rooms where they have the vegetating lights at one given height and the flowering lights at another but unfortunately that is not currently doable and i will be running both cycles in the same room off the same light.

suggestions highly appreciated as i like to do things correctly.

unless you are planning on doing 12/12 from seed you cant veg and bloom in the same room because plants in veg need 16-18 hours of light and flowering plants need to be on 12/12 so u need like a veg cabinet and then flower outside the cabinet

as for your actual question i use cfl's so i really dont know the answer, i just thaught i point out that the reason for seperate rooms is not the spectrum of lights but the light cycle

your plants being real young or weak is the the only reason i would put that light so far away(to the ceiling) and just cause its a 1,000 watt. Just get that light as close are you can with out burning the plants like you said. Hold you hand under the light, above the plants, and put it too a level that doesnt feel too hot. That 1,000 wt will cover a 4x4 no problem.

yeah i know about light cycles and what not but i will ony have one grow going at a time not a perpetual setup initially so i will be runing 18/6 for a few weeks under the hps and then flipping it to 12/12 i realize this will add a few weeks to each cycle instead of having pre vegged plants ready to kick into 12/12 but as i said an extra veg room isnt an option right now. i will have a separate mother/clone room that i intend to stabilize clones under flourescents in until their stout enough to put under the HPS but it is only 3x4 so im not sure if it is big enough to both fit a few healthy mothers in AND veg plants for a few weeks without getting crowded but will certainly try it out.

have to take the first step though and hang my light =P

You don't build a series of tables don't know were this came from but its bogus.4x4 rm cut a cheap peice of plywood in half trim edges legs large hole in center.Your lights should be far enough away to not burn.And this grow is on you slack and there will most likely be 0 buds worth smoking .Do it right bro!

Put em as close an the heat will allow, an raise the light to cover the 4x4 area as they get bigger.

The closer the light the more intinse it is. The deeper it will penaterate the canopy
More light = more photosynthasis= more growth= more yeild.

Becarefull cause youll bleach the cloroplasts of chloraphil if the light it to intense. 18 in from a 1000 sounds realy close to me.

I ran some Numbers through the Yeild O ramma site I love for lighting questions an crop yeld analasis they are pretty good for SOG guesstomates.

http://www.angelfire.com/cantina/fourtwenty/yor/yieldcalcadvanced.htm

hps lumens=135000 (nice) x 8500 footcandels (witch gives you 16sq ft 4x4) x 9 in experience x non hydo medieum x 3week veg time=

555 grams or 19 oz or 1.22 lbs! This is 39 grams/sqft! 4 grams per kilolumen.

Snickelfrits said:

unless you are planning on doing 12/12 from seed you cant veg and bloom in the same room because plants in veg need 16-18 hours of light and flowering plants need to be on 12/12 so u need like a veg cabinet and then flower outside the cabinet

as for your actual question i use cfl's so i really dont know the answer, i just thaught i point out that the reason for seperate rooms is not the spectrum of lights but the light cycle

Click to expand...

yeah i was going to have the plants stabilize a bit under flourescents in the mother room initially and then leave the HPS at a comfortable height from them, my question is even once the plants are a foot tall and able to handle the HPS being close i would still only have my light a few feet off the ground and would have to raise/lower it several feet over the course of the flowering cycle, this is what im trying to avoid as the hood is air cooled and will be prone to tangling/tearing the ductwork on each adjustment as well as adding 3 feet or so of slack duct that will rob CFMs from my fan which id like to avoid.

perhaps i am overthinking this and should just go ahead and incorporate the slack into my duct for a heavy range of adjustment, is that what those of you that use aircooled hoods do? or do you construct tables to take up some of the adjustment and only run maybe a foot and a half od duct slack?

thanks for the replies thus far fellas.

so the general consensus is that there is no way around the raising/lowering of the light and to just go ahead and work enough slack into my ducting for all future adjustment?

perhaps i can dig up some rubber padding to pad the contact corners where the duct will come into contact with clamps and so on in order to reduce fatigure as i am moving things around.

https://www.rollitup.org/attachments/grow-room-design-setup/1025624d1278246207-good-info-lighting-hps-light-distance-chart.jpg

Great distance chart! 18 in = 20000 ftcandels.

Or you could leave bulb fixed an lower the plants away from the light as they get to close.
I use stacked up styrafoam to keep em close, this way in my lil grow cabnet.
But my top of my box (3sqr ft) sealed with glass to keep heat up top an its vented with a 50 cfm bathroom fan