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sy100276

An intake question.

I am planning my wardrobe project and have come across the intake options, and hoped I could get an answer here (if you would be so kind).

My space will be 200cm H, 50cm D, 100cm W. In side will be a 250w hps under a 5"filter and fan. But when it comes to the intake i am a bit confused, passive did seem the way to go with, and I thought maybe 2 x 120mm vents at the bottom?, and a couple of pc fans inside. In order to move the air. But earlier i had a thought, maybe i could loose the passive intakes and just install 1 or 2 pc fans, either 120mm or 140mm instead.

Could anyone help point me in the right direction, as I have so much to learn.

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just go with a light leak baffled passive, try 1.5 X the cross section of your extraction duct. The light leak proof bit is important though

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Thanks for the reply, so if i have got it right. I will just have passive intakes (which i will baffle with hood filters).

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the baffle design is up to you, I use a thin long box with a slot up close to one end and another on the oposite side & opposite end, with the inside blackened, just as long as when you are in your grow you can't see light coming you have cracked it

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Thanks, just waiting for it to be delivered and my work can begin. Oh and that reminds me......need to send subs!!!!

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@@sy100276

Hiya, I adapated an old fridge and got round the light issue using cooker hood filter (B&Q/Homebase)

there is a formula somewhere on here which gives the ratio which size intake to the fan size,

I would go for a higher power extractor and passive intake, rather than less power and fan intake. Less to go wrong and it can be difficult balancing the intake and outtakes to maintain negative pressure. You can always add an intake later if it warrants.

My main tip is to concentrate on the ventilation above all else, nothing works if you don't get it right

good luck my friend

atb

stu

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Thanks for the tip. I will get the idea RIGHT out of my head. Just passive intakes.

5" extraction, 2 x passive intakes. I think your right about the formula being about stu, I think I read that it is 2 x the extraction. (might be wrong).

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Thanks for the tip. I will get the idea RIGHT out of my head. Just passive intakes.

5" extraction, 2 x passive intakes. I think your right about the formula being about stu, I think I read that it is 2 x the extraction. (might be wrong).

It's 4 times the area of the extraction hole for proper passive intake

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withnailed cause i was wrong and a bell.

Edited by Sancho Panza

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It's 4 times the area of the extraction hole for proper passive intake

Proper?

It works for me at just above 1.5x, I have used more without issue.. I suppose it depends on how good your fan is, as it is about m3/hr in and m3/hr out and how much negative pressure you feel is sensible and keeps you secure rather than the cross sections of the holes

ETA I grow in the attic so there is no restriction for the atmosphere getting in as fast as it can, in an airtight house the pressure gradients from outside to the extraction may be quite different

Edited by distracted

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It's 4 times the area of the extraction hole for proper passive intake

Thanks for clearing that up. So really i could do with 4 x 120mmx120mm passive vents? (my maths are not that great)

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try 2x and see where you get with that, nothing wrong with anythink I have grown with 1.5 x passive intake.

2x your 5" duct area is 244 cm2 square so a 120mm x 200mm hole should be perfect, if you aren't happy you can enlarge it but cutting 4no 120mm x 120mm holes in your growroom inho is too much by far, you have kilometres of atmosphere pressing down, lower the pressure in the room and it will rush in to equalise the pressure, provided the house isn't completly airtight

Edited by distracted

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try 2x and see where you get with that, nothing wrong with anythink I have grown with 1.5 x passive intake.

2x your 5" duct are is 244 cm2 square so a 120mm x 200mm hole should be perfect, if you aren't happy you can enlarge it but cutting 4no 120mm x 120mm holes in your growroom inho is too much by far, you have kilometres of atmosphere pressing down, lower the pressure in the room and it will rush in to equalise the pressure, provided the house isn't completly airtight

Thanks for clearing that up for me distracted. Sending subs in the morning so full steam ahead. :yahoo:

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