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Passive Intake Question

burner

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The cabinet I'm going to be using is: 19"x15"x28" tall (1.97 sq. ft.)

I'm most likely going to have a 150watt HPS enclosed ballast/hood with glass setup. I can make it a remote ballast if I have too.

(2) 80cfm 120mm (4.7") PC fans for exhaust. Possibly hook another up to the hood as well.

Basically i'm not sure if ...(4) 2" holes on the bottom (with 2 90 deg. elbows for light traps) will be sufficient for my intake. Maybe I should add a 40-50 cfm PC fan for intake or use that instead of the passive.
 
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dman1234

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You may need to do a test run watch the temps with no plants and add more holes if needed, i think passive is the way too go, but see what others say.
 

Hamster Lewis

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I like passive intakes the best....but I also use an inline fan to pull the air from my grow space and let the cool fresh air enter through the passive intakes along the bottom...I wld go with dman and do a test run to see what your temps look like and expand then passive intakes if needed. Jmo
 

burner

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Thanks guys, I'll do that and see what the temps look like. I don't have much space to expand the holes anymore depending on the pot size, but I'll figure something out
 
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burner said:
The cabinet I'm going to be using is: 19"x15"x28" tall (1.97 sq. ft.)

I'm most likely going to have a 150watt HPS enclosed ballast/hood with glass setup. I can make it a remote ballast if I have too.

(2) 80cfm 120mm (4.7") PC fans for exhaust. Possibly hook another up to the hood as well.

Basically i'm not sure if ...(4) 2" holes on the bottom (with 2 90 deg. elbows for light traps) will be sufficient for my intake. Maybe I should add a 40-50 cfm PC fan for intake or use that instead of the passive.
How are you setting the 2 exhaust fans up? I would advise against the intake fan. If your intake fan is substantially smaller than your exhaust, it can actually impede air movement. Four 2" holes equal about the same square inches as a single 4" hole. If you are going to have 2 4" or larger exhaust fans running, you either need more intakes or one of them needs to pull air from outside the cabinet.

I see some real problems with only 28" in height. Is there any way this can be made taller? I don't think I would attempt a grow in less than 3' and even that is really quite tricky. What is the depth of your light? of your pots? How much room is left for plants?

I think you should remotely locate the ballast if you can. They do put out some heat.
 

burner

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THG, the 2 fans will be right behind the light. I can modify the size of the box width wise, I was going to block off half to keep my space the right size, but I can change that if I need to.

Height wise it will be a problem. I was thinking of actually sinking the pot in the floor of the cab, I can save 5" that way.

The depth of the light hood is 5", so if I sink the put I'm looking at 20"+/-
grow height.

I got the cab for free from a friend, I really wanted to go taller, I'm hoping I can make this work, but it may be more trouble than it's worth.

Photo_1000E4F8-0483-7427-0ED6-3E10E7C8EDCF.jpg
 

Mutt

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You can grow fine in that thing. Sinking the pot down and using 2gallon size with a 4-5week veg. You can easily do a small SOG. or larger pot size and a scrog. 150w HPS would be about it for that box. if you did a cool tube you might be able to squeeze a 250w HPS in a Scrog.
I would not just do passive intake. I would have a comp fan or two, with a higher rated output fans.
 

burner

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I've seen a lot of grows with 150s about this size, so maybe I'm over worrying. I'm gonna be exhausting 160cfm, I have an extra 30-40ish cfm PC fan maybe I could throw that in the floor as well as the passive holes
 
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I would absolutely be for cutting out the bottom of the cabinet and taking advantage of the space in the toe kick area.
 

burner

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My original plan to box it off at 19" is gonna change. I'm going to make it a little longer and make room for a big enough passive intake or two and supplement that with a pc fan in a light trap/duct

Kind of hard to explain, but here it goes.

Off the passive intake hole, I'll make a makeshift duct (either out of black poster board or something easy to work with and paint it black), so off the hole i'll atleast have one 90 deg. turn and some straight length after that. I'll stick a fan on the long end of the duct so it will draw air in from the toe kick space and up thru the duct into the cabinet.

get it?
 

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