how many lumens is enough?

doingfine · Mar 14, 2011

im ready for growing stage , can anyone tell me im growing 3 plants 18 inches high is too many lumens too much? is their a limit? how far should i keep these lights to the plants? im using 400 watt high pressure sodiums for the tops and was gonna use some t12s on the sides while i rotate the plants?
any help would be great

kevb123 · Mar 14, 2011

400 will be fine but 600 or 1000w would b better.
keep the light 6 ft above cuttings/seedlings and gradually lower it over a week to 2ft above cannopy.

Wetdog · Mar 14, 2011

General rule of thumb:
3000 lumens/sqft for vegging
5000 lumens/sqft for flower

While I think 6' is a bit high, do start well above and gradually lower the lights to just high enough to where they don't burn.

I don't think the T-12's will be of much benefit. Not if the plants are only 18".

Wet

Serapis · Mar 14, 2011

If you have T12's ALREADY, use them as side lighting as you planned. However, if you are going shopping, get at least T-8's. Wal*mart sells 4' T-8 lights and bulbs for under $10 each... I would not use 1000w on 3 plants. that is just overkill and will prsent new problems, such as getting rid of the heat generated. I've also never read or advised anyone to keep a light 6' from a plant top..... what's the guy got? 10' ceilings?

kevb123 · Mar 14, 2011

Serapis said:
If you have T12's ALREADY, use them as side lighting as you planned. However, if you are going shopping, get at least T-8's. Wal*mart sells 4' T-8 lights and bulbs for under $10 each... I would not use 1000w on 3 plants. that is just overkill and will prsent new problems, such as getting rid of the heat generated. I've also never read or advised anyone to keep a light 6' from a plant top..... what's the guy got? 10' ceilings?

6ft above cuttings or seedlings it said as you will burn them to death otherwise.

doingfine · Mar 14, 2011

do t8's produce more lumens?
and how do you know if your burning the plants?
so i would assume that 2 400 watt sodium is fine with the t8's for what i have?
thanks guys for all your help

Magnificient · Mar 14, 2011

I think 12 inches is the optimum distance from plants for a 400. Check out Tinker's post here: https://www.rollitup.org/hydroponics-aeroponics/9996-grow-light-height.html

Magnificient · Mar 14, 2011

doingfine said:
do t8's produce more lumens?
and how do you know if your burning the plants?
so i would assume that 2 400 watt sodium is fine with the t8's for what i have?
thanks guys for all your help

The only real difference between t5, t8, and t12 lights is the diameter of the bulb. The t5s are 5/8", t8s are 1", and t12s are 1 1/2". The t5s are better for growing because they put out more lumens per square inch.

how many lumens is enough?

doingfine

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Wetdog

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Serapis

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kevb123

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