Hey guys! this thread has a lot of info and input, seems like a common problem for a lot of different people with different set ups. I have a grow box that I built myself out of material I had laying around at home. It's 4 ft tall and 2.5 ft sq. I'm 99% confident that my box is sealed because my 4 inch intake hole at the bottom pulls air when the fan is on creating negative pressure. Please correct me if I'm wrong. I plan to run a 150w hps, 2x 65w cfls for side lighting all on timers. I have a 4 inch inline fan for out take hooked to a carbon scrubber and fan controller blowing all the box heat outside. Pulling air from my garage. Last night I ran a test run and I'm a bit concerned about my temp and humidity. Please keep in mind that I had the fan set to medium because my box is only 28 sq ft unless I calculated wrong. I plan to start growing in 3 weeks trying to make sure my set up is working properly before I throw a plant in it. My question is should I make another intake hole? Honestly I don't think I should. Should I turn the fan up? At that point I think I would be moving to much air to fast through the carbon filter due to the size of my grow box. Or should I buy another fan for intake? Don't think I need to because I can feel the air being pulled through the 4 inch hole. I'm open to any suggestions and am not in a hard spot because I haven't even popped a seed yet. Thank you for any input you have. New thought an hour after posting - humidity dropped into the 30s when tempatures dropped could I Balance this by hanging a damp wash rag in the grow box. Maybe I'll try that tonight. What do you guys think?
Hey guys, i am running a single 600w HPS in a 5'x6'x6' room and a 4" Centrifugal fan/Carbon filter temps are stable at about 77deg. I am wanting to add another 600w HPS to the room as i have too many girls on the go, how much of a rise in temps should i expect ? and do you think the fan i am running will cope ? Any help appreciated. Cheers from NZ
I have a 7.5x11.5x7.5 shed... should I use a 6 or 8 inch inline fan? I'm using two sun system lec 630s.
Wondering if someone could help me with a question I have.... I just more than doubled my room size. I have a 8" fan and figure I need to go to 12" miniumm. My issue is that the noise from the 12" will just be way too much. I'm wanting to add another fan...I was thinking a 6" or maybe a 4"... Will 2 fans still allow for air flow if they're in different parts of my grow? Just didn't know if this would affect negative pressure...I know I'll have heat issues with the extra lights...was planning on running both fans when the lights where on and then turn the smaller fan off when the lights are out... Thank you for any responses GC!
Okay so I have a ghetto setup for ventilation lol I have a grow tent and I put it up against a window fan and cut holes in it where the fans are one of my fans won’t work so I got a another fan and cut a hole for the fan to blow out into my room. Just wondering if that will work I haven’t seen anyone else that has something like it first pic is the window fan blowing in and the second is blowing out my grow tent is 4 ft long 2ft wide and 6ft tall and the window fan blowing in is 6in I thing and the one blowing is bigger not sure how much.
Starting a perpetual 1 or 2 plants per grow. However the owner of the house I'm in wants STEALTH! Instantly hit up Google. Some AWESOME hydro n dirt grow boxes out there I'm sorry I never pay over 1500 for a grow space unless it like yielded platinum coated nugs lol. Always LED. 48" tall 16.5" width 14" depth. May go with a slightly bigger one.. Here's the kicker.. The exhaust systems on those look mighty budget.. After numerous tent grows w a 490cfm turbine. Im hoping these cooler months down here will help. I can always improve on the fan.. I jus have to have. EVERYTHING completely enclosed in the box. No visible vents,etc. Iv heard good things about SOME brands. Terrors about others. I'll be dropping over 5 bills . it guarantees up to 5 lbs PER YEAR assuming u can harvest 3 or 4 times a year indoors. A HP per grow would b lovey. I got the juice 2x 50w cree cxb 3590s a 315w 3 knob tuneable LEDgle LED. 415w total. With 189w I hit 118g. If Ivan manage to bend and train her enough I'll atleast yield 236g dry per harvest. That'd be sweet.
just wondering if a cheap way to cool down your tent/air intake is to place a 50w fan blowing towards the end of the ducting obviously for indoor growers. would this work I'm just planning for worse case scenario lol.
I have a 4" 200 CFM in line fan to run a heat sink in my greenhouse I was just wondering how much 4" PVC pipe(duct) I can attach to it or if it matters. also I was thinking I would pull air from the top of my greenhouse have a fan in the middle and then blow the air into the ground(heat sink) good idea/bad idea?? cause I read here that it is easier on the fan to pull air. so should I pull the air through the whole thing?
That would depend on the fans static pressure capability. The longer the duct the more static pressure that is required to move the air through the duct. This typically would depend on the size of the motor and the fan curve of the specific fan (usually available from the manufacturer). A good rule of thumb is to assume a 0.1" static pressure drop for every 100' of straight duct. Having elbows in the system will also increase the static pressure requirement of the fan. Each one would be equivalent to about 15' of straight duct. Also be sure that you have at least 5' of straight duct on the connection to the fan. Having a fitting to close to the fan can have a very large negative effect on its ability to move air. Once you have determined the pressure drop of the duct system you can use the fan curve to determine the actual air flow your fan would produce.
In looking at my DUCULATOR a 4" duct moving 200 CFM would require 2.2" static pressure for every 100' feet of duct. I would recommend using at least a 6" duct as the SP requirements drops to 0.3"/100'
I have recently been looking at some bathroom fans as they are nice and quiet. I would adapt these charts based on how long my fan is running daily, they also seem to be very efficient at longer runs when needed.
Not to sound to much like a mechanical engineer (I am), cubic volume of the space has nothing to do with the amount of air that can be effectively drawn threw a 4" duct, but has to do with the number of air changes per hour. In a bathroom you would be looking for a minimum air change rate of 12/hr. In the commercial grow rooms that I design we are looking for an change rate of 20/hr. I have read in other post that an air change rate of 12/hr (1 every 5 minutes) should be achieved. This is help remove the humidity from the air and to help in combating mold growth. Duct sizing is the same as pipe sizing for water, just uses different constants. Trying to get 400 CFM through a 4" duct would be the same as trying to get 15 GPM though a 1/2" pipe, just requires more pressure. Increasing the duct size would reduce the air resistance (static pressure drop) through the system and thereby allow more air through. Here is a picture of the pressure drop for the 4" duct. The outer blue band is the flow rate (CFM). Typical duct sizing is set for a pressure drop of no more than 0.08" of friction head (pressure drop) per 100' of duct. This would equate to a 8" duct, but using a 6" would drop the loss to 0.3". Most fart fans (bathroom fans) have a maximum static pressure capability of about 0.6" external static pressure (pressure available to move the air through the duct) and still move the fans rated air flow. The next picture is a of a fan curve for a typical fart fan. As you can see as the pressure increase to the flow rate decreases. Each fan has a different curve, so you need to know the specific make and model of the fan in order to determine how many feet of 4" duct can you add to a 200 CFM fan.
Fans and blowers have different characteristics , I am not an engineer and don't need to debate or question this manufactures calculations . But I have pushed much more air thru a 4" duct over much greater distances with a blower. With a mining background typically under 8' round working area, the typical 12" vent fans were useless over a 500' even with installing them every 100'. A blower with an intake of 6" and an outlet of 4". Easily blew air in between the 500' to 1000' mark and this was the max we were required to tunnel. The air flow was needed as we were running a diesel skid steer in this space. I am guessing as I am not an engineer that the bathroom fan is housed in manner to act more like a blower than a fan.
It all comes down to the motor horsepower put behind the fan/blower. I would assume that the blowers used in mine ventilation have a much larger motor than the fractional horsepower fans used for cultivation purposes.
A hanging scrog in my 5'x5' tent. 4 cmh 315's. 10gal fiber pots are in saucers on pedestals with drain tubes to a tub in the middle. 6" exhaust out the top and dedicated window unit ac. I've been building this for 2 1/2 years and raised dozens of plants but the cmh lights made all the difference. It's sunshine in your grow space.
Can I cycle my inline fan with my lighting ? I’m doing a 20 and 4 scheldue. Reasoning is too give it a rest and save some power. Or should I leave it run 24.7?
I have three passive intakes on my tent, two 8in and one 6in. Problem is the tent's walls still get sucked in pretty hard and I don't feel like spending money on an intake fan. I suppose a fan controller could do the trick but are there work-arounds that would keep me from sacrificing air flow? *When I put my hand on the passive intakes I barely feel any air getting sucked in...? **To give you an idea I can literally lean on the walls from inside and they won't budge because of all the tension.