ventilation

Trojan46312

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I'm looking to buy some fans to suck the dead hot air from the flower room and would like to know if there's a such thing as too much negative pressure? I ask because I want to hook a fan to the lamps to cool them and place another in the room with a carbon filter for smell. Will that much negative pressure harm the plants?
 
T

The Hemp Goddess

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If you are going to use a separate fan to cool the light and not use a carbon filter, you are going to want to pull cool air from outside your grow room so that you do not pick up the smells from your room with the exhaust. If you are pulling air from outside the space, this will not create any negative pressure in the room. The only negative pressure will be created by the fan with the filter that is pulling air from the grow room.
 

kiksroks

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Now if you have nothing going in, even with the fans, do you think anything is going to be coming out?

Think about this man. . .


No i don't think you could create enough negative pressure, with inline fans anyways, to hurt the plants. Although at some point I imagine they would just explode, like when you catch cod out of deep water and their eyeballs pop out when you get them to the surface.

You will be fine just make sure the fan sucking through the light is in taking from out side your tent other wise it will be exhausting stinky air as THG said.
 
W

woodydude

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There is another issue, depending on you ambient climate and that is relative humidity.
By having massive negative pressure, you are suching the humidity out of the room too.
If you drop the rh below 30%, depending on temperature, you could have problems.

(I could be wrong about that figure as I aim for 40% flowering, 70% veg) I am far from being an expert here, just repeating what I have read in "The Urban Gardner" magazine, someone else may know more.
Peace W
 
T

The Hemp Goddess

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Trojan46312 said:
Can I get away with no intake and exhaust only?
If you are asking if you can get away with no intake FAN, the answer is yes, but you need somewhere for the exhaust fan to draw air from, so you do need some kind of intakes, however they can be passive. Most of us run passive intakes with centrifuge type fans for exhaust. The inexpensive inline duct booster fans will not do the job, so don't waste your money, get a centrifuge fan like Vortex, Eclipse, Can, etc.
 

Trojan46312

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The Hemp Goddess said:
If you are asking if you can get away with no intake FAN, the answer is yes, but you need somewhere for the exhaust fan to draw air from, so you do need some kind of intakes, however they can be passive. Most of us run passive intakes with centrifuge type fans for exhaust. The inexpensive inline duct booster fans will not do the job, so don't waste your money, get a centrifuge fan like Vortex, Eclipse, Can, etc.
I'm sorry but when you say passive intake do you mean something like an air conditioner?
 

nova564t

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Just let air in, a hole, open door, just dont seal your room.
 
T

The Hemp Goddess

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Passive intake is basically just a vent or a hole that air can flow through from another source. For example I have 2 4" holes cut in the floor that go into my crawl space. I have a piece of screen across to keep out bugs and/or rodents. When the exhaust fan is on, it pulls air from the crawl space to cool the room (think of it like sucking through a straw). In the winter, the hot air is exhausted back into the house. In the summer, it is exhausted under the deck.
 

Hushpuppy

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Yu may have already figured this out but anytime yu want to remove air from a given room, yu have to have another place that allows air to come into the room to replace the air that is leaving. for a given grow room yu must replace the air with either fresh (outside) air or find some way to exchange the oxygen given off by the plants with carbon dioxide that the plants need. If yer grow room is sealed very tight and yu try to exaust the air, yu will not move much air. Yu must allow air in for air out. If yu put yer fan on the exaust then it is an active exaust and the air in through the other opening is passive airflow as it is not being driven. I have my lights being cooled by active air in through flex hose to the lights and back out again, while my grow space air is refreshed separately through multiple means. Hope this helps.
 

Trojan46312

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The Hemp Goddess said:
Passive intake is basically just a vent or a hole that air can flow through from another source. For example I have 2 4" holes cut in the floor that go into my crawl space. I have a piece of screen across to keep out bugs and/or rodents. When the exhaust fan is on, it pulls air from the crawl space to cool the room (think of it like sucking through a straw). In the winter, the hot air is exhausted back into the house. In the summer, it is exhausted under the deck.
Ok I get it. Thanks alot. The way you did it is clever by the way.
 

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