NattyFido2, on Aug 31 2010, 12:16 PM, said:
How much can you slow a fan down ie. 75%, 50%, 20%?
The main reason I want a slow fan is because, according to the growroom calculator
, my space (0.33m3) needs 15m3/hr (minimum).
Every AC extrator I've seen is at least four times more powerful than I need.
I do remember seeing a DC squirrel cage fan, it came out of an old, valve PA, but that was about 25 years ago!
oh right, TOTALLY ignore the growroom calculator, the ventilation rates it puts up are for replacement co2 for the plants to breath. and doesn't in anyway count for the rate of extraction you'll need when you take into account the heat for your lights, also humidity and air circulation in general.
as a general rule of thumb, 4" inline fan will do a 250w HID, 5" high powered inline fan for a 400w and a 6" fan for a 600w, all these sizes are more than enough to cope with the assigned lights, and so give a bit of headroom to slow the fan down, which helps with noise issues and/or temps.
personally i use a high powered 5" fan with a 600w, ensuring i only have the lights on at night, and have a very short ducting run etc, and it just about copes all year round.
also, you can slow an inline fan down to virtually nothing