by, 08-20-2011 at 06:42 PM (780 Views)
My plan for passive temp control didn't work. The ambient temp in the house rose to 80F and 86 in the grow closet without the lamp on. I just finished installing a small AC unit which cramps things a bit but keeps the temps under control.
First pic shows the AC. Air intake is on the rt side and fed with exhaust air from the lamp. I found this unit for $99 at Lowes
5000 BTU 12x13x16 inches.
Simplest would have been to set it in a opening through the outside wall on the rt. But that faces onto the street and I just couldnt get comfortable with the idea of having any part of the grow setup visible to the street. AC units are installed this way all the time and there should be no reason anyone would pay attention to tha back side of an AC sticking through the wall, but I just couldnt relax about it.
Putting it entirely inside the closet means a. Things are tight and cramped. b. I have to evacuate the waste heat from the back. I sealed off all the air vents and fed a 4" duct in from the side for cooling air intake. For the exhaust, I am using the cavity in the wall as a plenum. This saves several inches of precious space. The back of the AC is against a hole in the sheet rock. The hot air is exhausted from the wall cavity by the vent above the AC unit and out to a roof vent.
It all seems to work very well. Holds a steady 75F with the lamp on. The unit is set on low cool medium cooling whch means it has plenty of reserve capacity. The exhaust vent does get a bit hot at times. I might insulate that to stop the heat from getting back into the room.
Things are very tight between the AC unit and the lamp ductwork. I will have to fiddle with things a bit to gain a couple of inches of space on the left of the lamp. Also, I mean to put a deflector infront of the AC to guide the air below the lamp. Ideally the AC would have been installed about 2' high but this robs a lot of grow space. Setting it 4' high allows a short plant to grow under it and still get plenty of light.