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I have a small grow box - 36x36x18" . I bought a large 125w 9600 lumens CFL with reflective hood. I also have two 42w CFL's and I cannot get the temperature below the 85-90 range (i want it around 80).
These are all CFL's but I'm thinking the large 125w (this is a rather large bulb - over 12" long) might put off too much heat in this area.
Would i be better off selling these 125w (I have one 6500k and one 2300k) and the hood and just hanging more 42w cfls?
best advice, don't remove lighting, just increase air circulation ... you need a fan to exhaust the hot air (cooler intake at bottom, heated exhaust at top) ... also, need to put in an oscillating fan, to remove moisture and strengthen stems :jointsmile:
Yep, you need to exhast that heat. i put my seedlings in front of a fan at about a week old, strengthens the stems real well, and gets the air moving. i am growing in a big room, so just the one fan moves air enough to keep it under 75. But You need to get some of that heat out the top somehow and bring in cooler air from the bottom.
good luck
and good growin'!
Thanks for the advice. Here's what I've done. I put a 2" passive intake in the bottom. I have a 6" oscillating fan right inside the passive intake and pushing air to the top where I have a 4" 80cfm cpu fan for exhaust.
I still have to install the 80cfm tonight. My total area is about 8.5 cubic feet - will the 80cfm's fan be enough to bring down heat?
I think you've got 13.5 cu. ft. (3'x3'x1.5')
Anyway, an 80 cfm should move enough air...I think the best estimate is that you should be able to recirculate your air 3 times a minute. 80 cfm will be 6 times a minute.
As for the heat...you'll just have to check and see. One thing I've noticed is that the bases/ballasts of the big CFLs generate quite a bit of heat, so I know what you're talking about with the heat concerns from a 125w CFL.
Here's what I ended up with. I put two 2 inch passive intakes on opposite ends of the bottom of the box. I put a 7 inch turbo power oscillating fan on the bottom of the box blowing directly at the lights. I cut a hole in the top and put a high rpm 6 inch oscillating fan blowing out.
I just bought a digital thermometer with a remote sensor and put the sensor at plant top level.
It now reads 77 degrees with all lights on. It almost seems impossible that the temp dropped that much and I almost think the thermometer might be wrong. Thanks for the help everyone!
Glad to hear you sorted it mate, amazing what a fan and a couple holes can do ;)
Unfortunately I'm back up to 90 degrees. I think keeping it at 20/4 schedule will give some reprieve for the plants.
Should I install another fan, or try to "air tight" what I have considering it is a bit loose, especially considering airflow could come from the small gap between, under, and above the doors.