best fan for a stealth set up?

Contributed by: Flowerman
Images archived: 2001

Just for fun, I wanted to show how easy it is to turn a PC fan into an intake, or into an exhaust fan. The fan I am using is quite small, but the objective is still the same. The first step is to find or buy a 12v DC plug adapter. This fan here is rated at 80cfm, which will work for a small box set-up.

Here's is some info on the 12v DC adapter: (Model 420A4141)

Output (DC) 12.0V @ 500mA
Output Voltage VDC(1)
Input 108VAC
Output Volts @ 100% Load 10.20
Input 132VAC
Output Volts @ 100% Load 13.60
Input 132VAC
Output Volts @ 10% Load 17.40
UL(2) UL*
CSA(3) L
Plug(4) 1



Simply cut the wires at the end, and strip down about a ¼ inch of bare wire is showing.

If you don’t know which wire to wire up, for instance they’re all black wires, don’t worry, it will only work one way, and if wired wrong, will simply not work at all. But the idea is, black to black, red to red. This one here that I used, had one black and one red coming from the fan, and from the adapter, one black and one black and white. The black and white wire from the adapter got wired to the all black wire from the fan. And the all black wire from the adapter, gets wired to the all red wire from the fan.

To add another fan, just connect the wires of the same together. All black goes with black, all red goes with red. So you would still only use 2 connectors all together. Here’s a few more pictures. But for the most part, I just wanted to show how simple it is. Make sure you get an adapter which is rated DC for the output.



Finished


Testing


Also a worthwhile consideration is places like radio shack and grainger also have nice 4" muffin fans that move as much as 200 cfm and more, which run on 110 vac. They come with a handy power cord that has a special connector on one end for the fan and a plug on the other end for plugging into the wall socket or humistat / thermostat.


How much ventilation do I need in my grow room?

Each fan has a rating that tells you how many cubic feet of air per minute (CFM) it will move. When dealing with above average temperatures you will want your fan to exchange the grow room air 3-5 times in one minute, so for a room that is 40 cubic feet, a fan that is capable of moving 120-200 cfm (cubic feet per minute) is recommended. If you only want to replace depleted levels of co2 and are growing in a closet using fluorescents, one room change per five minutes (divide room size by 5) will be adequate.

To calculate your room size, multiply Width by Length by Height, this will give you the CFM rating required for one room change per minute.

Air that’s exhausted will be replaced by fresh air, which is drawn from Passive Intakes-
located opposite the exhaust at the floor of your grow room (Recommended for closet grows) or forced in using another blower (recommended for larger grow rooms).

For internal circulation oscillating fans are In my opinion the most efficient devices for circulating air in a room. The gentle back and forth sway of the fan is very beneficial for the developing plants. These fans tend to keep anaerobic moulds down by constantly freshening any potentially stagnant air. Home improvement centres carry a large array of various types and styles of air-moving fans, there are wall-mounted styles available and most are relatively inexpensive.

NOTE: To convert CFM to CMH use the folowing formula CFM X 0.03 X 60 = CMH

To help maintain a lower room temperature follow this link detailing how to construct a DIY- Air-cooled Reflector​