How Far Should Lights be from Tops?

hey guys, i have a t5 system going now and the light is not getting to the bottom of the plants with any strength to it. I have a 320w MH i will be switching to, found it while cleaning the shop out

long story short how far do they have to be from the tops? how far is too far? i would rather be too far to start than to close and burn them.

the light will be in a basement in a corner no real ventilation just a few fans for when it stinks to air it out. its a 900sq ft basement all open.

well you could make your t5 work if you hang some reflective material around it.Ive found that with a setup like yours, all open,that unless you have only 1 or 2 plants growing under your light it is hard to get light down below the canopy top.Yes it does cut down on the size of the buds that are lower,but you always could pull the top half at harvest and let the bottom half ripen a little more.this will increase the size of lower buds.As for the distance of the metal halide should be away from your plants,Metal halide burn hot so id start off about 2 foot away and lower as neccesary.Your ventilation might be a problem,but in 900 sq ft. there is a lot of room for the heat to mix with cooler air

thanks, i just rewired the fixture with a new ballast other one was not working. the heat should not be an issue as the ac will be running in the house as its getting hotter here in canada and should mix fine with the heat output of the fixture. although i will give the reflective thing a try too first as the mh takes up more power. what is a good reflector? tinfoil?

I use celotex,you can buy it here at home depot,dont know if canada has home depot.It is an insulation board from 1/2-1 inch thick.It has a shiny side and a white side.Its not the best as compared to mylar but will do the job for a couple grows,but will need to be replaced after a while cause the HID lights deteriorate the foil.

You can also use black and white poly or mylar. Don't use kitchen foil. On a low budget I've used space blankets which are cheap mylar that work fine and at walmart here they cost $1.50 usd each. A couple of those hanging from the joists will help alot I suspect. The T5's you can get very close to the plants. If you can hold your hand at the top of the canopy without it getting uncomfortably hot, the light is not too close.

Dowd1 said:

dont know if canada has home depot.

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That's funny stuff, made my afternoon

thanks for the info, will try one of these methods out

lwells2000 said:

You can also use black and white poly or mylar. Don't use kitchen foil. On a low budget I've used space blankets which are cheap mylar that work fine and at walmart here they cost $1.50 usd each. A couple of those hanging from the joists will help alot I suspect. The T5's you can get very close to the plants. If you can hold your hand at the top of the canopy without it getting uncomfortably hot, the light is not too close.

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I did not know about the space blankets.Probably a better suit than the celotex.I assume the are for keeping the heat in.Down in the tropical parts where im at i dont think wally world carries anything like that and i did most of my equipment buying from there.Will see if i can order some.
Thanks for the info.See you do learn something everyday

Without adding more lights I'd use the T5 for side light and the MH should be as close as possible probably 6-8" to verify just put you hand at the tops of the plant and see how it feels. I fit is too hot for you it is too hot for the girls. Make you plans now for your flowering light needs!

i just re worked my set up and have the 320w mh for top lighting and the t5's for side. the mh is red and t5's are blue spectrum (the mh is coated) the mh is about 16" from the top is that too far? It feels warm under there but not too warm, i just had knee surgery so i hate going to the basement to check on them and adjust things any help here would be great.

ok so in the middle of dropping the light i actually dropped it on ta few plats and busted up a few smaller branches off the main trunk. just wondering what to do should i cut them off or wait and see what happens, they are still attached and dont tear off but are a little limp, now i am sad it was my best looking plant too it landed on. rookie mistake.