ventilation size?

[ranneG]

Hi just a quick question. I building a small cab for a 400watt bulb. Im not sure how much air flow i need. I have a cab about 3 m3 big, what do I need? Was thinking about gettin one of these: S&P TD160 - 160m3/hr - 100mm Outlet/ Inlet

Too much too little?

Peace

 

[SpoCannabis]

Just do the math basic on your cubic meters and cfm of fan.

Taken from OG's FAQ's:
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


Basically you are only exchanging the air in your cab about once per minute, which is not quite enough - specially since you are in a small cab. IMO, you should get a stronger fan. Hope this helps... Good luck ;-)

 

[FreezerBoy]

Readers Digest version- Intake is double the exhaust. Example, one 4 inch exhaust requires two 4 inch intakes. Note: Four 1 inch holes do NOT a 4 inch hole make.




Long Version fan-intake calculator

I'm with Spo in thinking a 160 is too small but, I haven't worked the math.

 

[SpoCannabis]

Readers Digest version- Intake is double the exhaust. Example, one 4 inch exhaust requires two 4 inch intakes. Note: Four 1 inch holes do NOT a 4 inch hole make.

Never thought of it that way...makes sense lol. I just make sure I have PLENTY of passive intakes heh.

Arrrgh... "You must spread some Reputation around before giving it to FreezerBoy again."

 

[FreezerBoy]

"You must spread some Reputation around before giving it to FreezerBoy again."

Just as well. I stole this from HoosierDaddy, who wrote it up with formulas and everything. I just consolidated the info into a single graphic. Hammers the idea home, don't it?

Understanding Airflow

 

[SpoCannabis]

Indeed. Good work soldier!

 

[ranneG]

Thanks guys nice link up, usefull. The td160 might be a little small, but im in a cold climate. Also the last grow in same cab but with an open door was ok temps. Now i've moved the cab, it has to be closed due to light contamination (on me hehe). Anyway venting+bigass cold intakes+ new hydro system=weed deluxe.
Thanks