Grow Room Design & Setup
Intake/exhaust ratio?? in the
The Grow Room forums; Hey guys, I'm building a stacked 50 gal rubbermaid grow box..
I have 9 diesel ryders in veg right now ...
Hey guys, I'm building a stacked 50 gal rubbermaid grow box..
I have 9 diesel ryders in veg right now at about 2 weeks.
I am planning on putting them all in 1 gallon bags in the the box (it will fit). I have plenty of CFL light, and have a 4" inline fan with carbon filter on the way.
with that size exhaust, what size fan should i use as an active intake? I would like to use. 3 smaller ones strategically placed, rather than one larger.
will three of these be okay?
i always heard that its better to have slightly more exhaust then intake for the negative pressure.. but if your looking to do small intake fans. look into a cheep pc power supply about 130watts or so you can pin them to turn on with out being hooked up to a pc. with this you can hook up a decent amount of 80mm or 120mm pc fans if im not mistakin the 120mm fans put out around 87cfm or so. this is what im setting up for my air intake and to circulate air inside the box as these are much smaller and draw much less power then most 120v fans.
Last edited by Trunk5; 04-06-2009 at 10:20 AM.
Bro you wanna have a bigger exhaust than the intake. 2:1 ratio would be pretty good to go for.
yea i thought so too at first, I got mixed up along the way.
that 4" inline fan with filter will be strong enough to deal with heat and odor issues right? I had planned on getting pc fans but didnt feel like waiting for them to be shipped. i guess I will use two of these fans bc they arent very strong anyway.
ur saying I can use multiple small pc fans..
is it cool if I use 3 pc fans? I want the fans to be positioned so that I can focus on the lower portion of the box and on the buds at the top..
two 80mm fans on top bin and one 120mm fan on the lower bin.
is that too much?
off of 130watt power supply i ran 5 80mm and 3 120mm with no problems and i know im not evan close to maxing out the power supply. for my new set up im gunna run 6 to 8 120mm and 4 80mm.
im not worried about power supply.. im discussing ratio of fans.. i have a 4" inline fan.. how many 80mm fans can i use?
All the fans you need to draw in fresh air in less then 5 minutes and you should be good.
Your intake fan has to be smaller then your outtake fan or else you will be blowing the extra amount of air out where you dont want it.
As long as you have enough air movement in there where the leaves flutter, it doesnt need to be a hurricane in there.
ok pc fans are out!..
sparks flew.. im no electrician.
i need to use these small fans i have in the pic.. two should be okay.
the inline fan is far stronger than these.
Originally Posted by KillHit
Haha thats pretty funny. Hope you didn't fry your fans.
Take a look on the labels of your pc fans there should be a voltage rating and an amperage rating. Thats what you want to match your power supply to. The really important number is the voltage. Most are 12v. The amperage doesn't matter as much as long as your power supply is capable of giving at least the fans base amperage. So say you fan is labeled 12v and 0.5A you would need a power supply that can give 12v and at least 0.5A, a power supply that gives 12v and 1.0A would be sufficient as well. You MUST match voltage if you don't thats when things start to fry, the amperage on the other hand can be greater than what is specified on the fan as that is only what the power supply can provide and not what it will actually be sending to the fan, the fan will draw only as much current as it needs.
That said go to your local thrift, electronic, or you junk drawer and pick up an old cellphone charger or similar transformer that is rated to match the base specifications of your fans. Then strip off its connector down to the bare wires. Do the the same with the fan. Then wire the negative wire of the power supply to the negative wire of the fan and the positive to positive. The negative wires of both the fan and the power supply are usually marked by either a colored line or the wire will be red. Cover up the connections with electrical tape or wire nuts and plug in (if the bare wires touch when plugged in there will be sparks and you could risk frying everything so make sure they are covered). If you have matched everything right it will fire up just fine.
I picked up my 12v 3.0A transformer (old game cube transformer) for a dollar at a thrift store and run 3 pc fans off of it and have ran up to 5 with no problems.
You can use an underpowered transformer but the fans will not run as fast. So say you have a 10 volt transformer it will run the fan just fine just at a slower speed (good way of speed controlling a fan with out a speed controller). However if you have a transformer that is underpowered on the current side the fan will not run. Meaning that if your fan requires 0.5A and your transformer only supplies 0.4A the fan will not run and you run the chance of frying the transformer.
1000 mA = 1.0A just in case the transformer is labled in "mA" in stead of "A"
I exhaust my 24 cubic ft grow room with two light traps and a cool tube with just two 120 mm pc fans. I'm using 150w hps and 60w of fluoro tubes. So even one pc fan could drastically improve you're ventilation in such a small box.
You want to maintain a higher rate exhaust to intake ratio so as to create a negative pressure grow box so that no dank smelling air escapes. More air out, less air in. The pc fans pushing in will essentially act as duct boosters. In a negative pressure grow box any air leaks that you may have missed will function as passive intakes and you will be certain that all that dirty air is passing through your carbon scrubber.
Those small desk fans that you have are great and i have seen them used with great success. I opted not to use them as i couldn't find them (wrong season), and pc fans tend to be a lot quieter and allow for more versatility in placement.
The idea you have placing the the pc fans to blow on the plants is a great one it will make the plant much stronger and keep them enveloped in fresh air. Just make sure you don't kill them with too much air flow. Do some tests and adjust their positioning as per your observations.
Sweet looking tape job and box. Clean tape job and light mounting, very nice. Be weary of the aluminum foil tape though as i found it acts more as a heat reflector than a light reflector. What i used for reflective material was a mylar table cloth that i surprisingly came across in a party store. It was $2 for a 6' x 10' table clothe. You should plan for more exhaust than you would initially estimate because of this fact.
Oh also some useful information on wiring:
When wiring in series voltage doubles, when wiring in parallel amperage doubles.
Therefore if you were to wire up two pc fans with a rating of 12v and 0.5A to one power supply in series you would need a transformer that is rated for 24v and at least 0.5A because voltage doubles in series wiring. However if you were to wire the same two fans in parallel your would need a transformer that is rated for 12v and at least 1.0A because amperage doubles.
Wiring in series involves wiring the negative wire of the transformer to the negative wire of pc fan 1, then the positive wire of pc fan 1 to the negative wire of pc fan 2, then the positive wire of pc fan 2 to the positive wire of the transformer.
Wiring in parallel involves wiring the negative wires from the transformer, pc fan 1 and pc fan 2 together, then wiring the positive wires from the transformer, pc fan 1 and pc fan 2 together.
Good luck and keep it green. Let me know if you have any questions.
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