My grow room setup is as follows: the room is 2.5 x 3.3 x 1.8 meters. I have 3, 1000w HP sodium lamps, 3 fans and a good big extraction fan set up to draw air out my 1.8-meter Mountain Air filter. I have a hydro drip system set up where the table is about 40 cm high. This leaves about 90 cm from the table to the lights. Not much space but I’m trying to grow 40 plants, but the temp is hard to control.
I was thinking of getting an air unit set up on a thermostat to help better control the temperature. My reservoir is only 75 liters. Why do some plants need more water than others when they are all the same strain? Is the size of the room and setup OK to grow 40 plants or do you think I should make the lights flush with the ceiling to give me another foot of grow space?
Heat will be a constant problem and the lights are too close to plants. Three 1000w lamps produce a hell of a lot of heat and should be at least two feet above plants to avoid burning foliage. Remember when the inside of the plant will be about 30 percent warmer than the room temperature. At 30 degrees C the interior of the leaf is about 40 degrees E The plant will transpire more and more water to lower the internal temperature of the leaf. This sets the stage for increased water consumption, higher humidity and more problems that are easily avoided. A 75-liter reservoir will need to be filled every day without fail. Definitely attach the fan to a thermostat and possibly a humidistat to control both temperature and humidity. You will find that the temperature lowers a little but humidity will rise substantially after the lights go out. This excess humidity will set the stage for powdery mildew and bud mold (botrytis).
You should give plants more space to grow and to stay cool. You should consider using 400 or 600w lamps that generate less heat and cost less to operate. Either wattage will provide adequate light to form thick dense buds. You can also place these lamps closer to foliage without fear of burning it. Also, set up a heat shield such as a sheet of aluminum or other metal to deflect heat from the ceiling and place lamps as close to the ceiling as possible.