I've had a decent closet going for a while now, but today I decided to rework a couple things in the interest of cutting down on some of the hum from the closet. I have a Hurricane 600+ CFM inline fan, a CAN 66 filter, and a 400w HPS/Halide in a Cool Tube 6. This was the previous setup: LEGEND: = 4 inch duct, + ceiling, * 6 inch duct ===++==***COOLTUBE*****FAN directly connected to filter The setup I went to today moves the fan to the attic: FAN===++===***COOLTUBE*******filter We're talking about probably 50/50 4 inch duct to 6 inch duct, I have to use 4 inch because of the clearances in my ceiling to attic transition, because of an upstairs room. The total duct is probably 20 feet. I'm mostly wondering if anyone else has this type of setup, with nothing on the exhaust side of the inline fan. I'm not sure if the pull better with some pressure on both sides or if it's cool like this. I know the squirrel cage type of blowers will kind of "spin out" with a bunch of back pressre on the intake and nothing on the exhuast. So far the temps are nearly identical to the previous setup, so I'm pretty confident that I'm ok, but I'd like to leverage the experience we have at grasscity just to be sure!
I think you're better off with the new configuration. Inline fans like to suck better than blow(!). You're cool with no downstream head losses. Your fan will probably last longer. Do you have a fan speed controller?
No controller, but I can tell it's not pulling as strong right at the filter, which might not be a bad thing at all. Air moving slower through the filter can be better for scrubbing odor from what I understand. I have the fan sitting on the attic floor right now and I can hear it inside some, but I'm going to hang it a couple inches off of the floor tomorrow and that should kill what little noise I have. The main thing I'm looking at is the temps, and so far so good, been about 3 hours now and no heat build up. I have intake and exhaust fans in the attic now. The intake is connected to a duct from one of the bathroom vents, so it always gets air from an air conditioned/heated part of the house, and the exhaust is as described above.
Sounds good. I highly recommend a fan speed controller ($20). It allows you to adjust your cfm's for best temp/humidity control and least noise. I now have my filter relocated to the attic and the fan blowing into it instead of sucking from it. There is a good article, originally from Urban Grower, here that make an excellent argument that blowing into a filter (vs sucking) increases its effectiveness and prolongs its useful life.
I considered this, but I live in the south and I figure my attic for +80% humidity a lot of the summer, and higher in my attic. That would kill a very expensive filter a lot faster than my 30% humitidy in the flowering room. My veg box has slower air and CFLs, so with some creative water placement I can keep it a nice 50-60%. So far humidity hasn't caused me any problems, but that's not to say that perfecting it wouldn't yeirld better results.