quick question?

[Zandor]

The lack of CO² is by the plants using it. Warmer temperatures make it easer for the plants to process the extra CO².

The only part light plays is you need to have HID lights, fluorescent lights don't have enough lumens for the plant to process the extra amount of CO².

You can get fresh CO² by changing out the air but you will only end up with normal amount around 300 PPM. Enhanced CO² is more like 1500 PPM extra so that raises the level to 1800 PPM to feed your plants.

So cool temperature is great but if you use enhanced CO² then you need to push the envelope and raise the temperature to around 85-88f or even into the low 90. Yes you run some risk of hermie but I have found the plants respond to enhanced CO² and do not turn hermie. It takes temperatures over 100 for extended periods to do that. It's all about the environment they live in. You can push the limit but being in control is the key.

[Zandor]

The math formula for light calculations. You can do the math your self and see it's different for each light wattage and bulb type. The only thing that is the same is 0-12" the lumens are the same you start with. From 12" to ? is how fast you loose the lumens and it's different from wattage to wattage.

I=L/D²

Light output divided by the distance squared FYI.

[Trichome Creator]

If it's to hot for your hand at the top of the canopy then it's to hot for your plants. 75ºF is the optimal tempature for cannabis. If you use CO2 then your plants can endure tempatures up to 90ºF for short durations of time if your CO2 is dispersed at 1500 ppm. Hope this was of help to you.

[BOYZNUS]

I FOUND OUT THE HARD WAY,,, WHEN YOUR LIGHT BRACKET BREAKS,,,, YOUR LIGHT FALLS ON YOUR PLANTS,,, AND YOU HAVE TO CUT OFF 6 OF THE BUD TIPS. BURNT TO SHIT. I HOPE SHE SURVIVES OK. WILL POST A PIC TOMORROW

[JohnnyPotGrower]

cash4hash,

i am growing with a 400W HPS and my seedling started about 24" away from the light and i saw great growth despite the distance. it has since grown and is now only about 12" from the light and its starting to get to the point where i may have to raise the light. What I would recomend (if you are still taking suggestions) is to leave your young seedling a good distance away (at least 18-24") from the light b/c while young it is suceptable to being burned if too close. It will still grow just as well (at least mine did). Then, if you really want to get it as close as possible, I would lower the light to 12" from the top once you have at least the 2nd-3rd set of leaves. You really dont need to, as i have seen in my grow, but i think the closest it should be is 12" and the furthest 24".

Hopes that advice helps.

-JPG

[Zandor]

If it's to hot for your hand at the top of the canopy then it's to hot for your plants. 75ºF is the optimal tempature for cannabis. If you use CO2 then your plants can endure tempatures up to 90ºF for short durations of time if your CO2 is dispersed at 1500 ppm. Hope this was of help to you.

Well that's not really a good indicator. Normal body temperature is around 98.6f. So for the heat to be felt you need to build up temperature above 90f and that is to hot for plants. A good remote temperature probe is a better way to know the temperature. You check it when the door closed and the room up to normal operating temperature. You can't do that with the door open and you standing there with your hand out. The room cools and the temperature changes.
You need to know real world temperature.

[Sentinel]

so would a thermometer placed at the top of the canopy give you an accurate temp.?

[Zandor]

Well a wireless version that monitors temperature and Humidity is what you really want. But you can use one of the remote indoor / outdoor ones that have a wire to a remote probe.

Like this FAQ

http://boards.cannabis.com/showthread.php?t=40868