Fans (technical)

[racked]

Hey skywalker ,

Noticed you said you dont necc need intake fans,

 

Am bilding gr mself 1.3 x 1.1 x 2.3 hav 2x250mm ex fans .

 

Should i run 2 ex fans and 2 passv inlets from windo vent or 1 ex fan and 1 intake fan?

Light is a 600hps.will be runnin lites at night.

[Luke Skywalker]

I'd run a single, large extraction fan, but not a cheap one. I would go get a centrifugal extraction fan designed for moving large volumes of air constantly. The size of fan you need is determined to a large degree by local conditions, but the rule of all the air volume removed in 1 minute or so is a good avg to go for.

 

You could have one, or many, passive intakes, just ensure that the intakes are at the lowest possible point in the growroom and the extraction fan will pull the air from this point. Keep the passive inlet on the other side of the room if you can as well, or decrease the size of the ones which are closer to the fans, as opposed to the ones at the farthest points, to ensure that even airflow is had across the room.

 

Best bet I'd say is a couple of inlets at the opposite end of the room to the fan, ensure that the room is airtight, and a large extraction fan running constantly. Spend the money on a decent fan, it's worth it in strength, cfm and longevity. Your crop will DIE if the only main extraction fan fails, and cheap fans which are not designed to run continuously are liable to do this.

 

Oh, and the reason I don't advocate intake fans is that they're not necessary in the first place, if the room is airtight at all other points then the air can only come into the growroom at that point, and if it's far away from the extractor and low in the room, then the room will be fully evacuated. If you use a couple of fans, you're risking one fan straining the other, even if they're seemingly identical fans. If the intake is more powerful than the exhaust, then the exhaust will be straining to keep up and the intake will be straining to push air into a room which is already full... likewise if the intake is weak, but the only entry point for air, and the exhaust is strong, you'll end up straining the exhaust because it's trying to pull out more air than is being brought in, and the intake fan will be strained by the exhaust fan pulling out more than it can push through...

 

So yeah, don't bother with an intake fan, just have a passive vent at a low, far away point from the exhaust and use a good exhaust fan, and you should be fine.

 

Hope that helps.

[States Zone]

I'd run a single, large extraction fan, but not a cheap one. I would go get a centrifugal extraction fan designed for moving large volumes of air constantly. The size of fan you need is determined to a large degree by local conditions, but the rule of all the air volume removed in 1 minute or so is a good avg to go for.

 

You could have one, or many, passive intakes, just ensure that the intakes are at the lowest possible point in the growroom and the extraction fan will pull the air from this point. Keep the passive inlet on the other side of the room if you can as well, or decrease the size of the ones which are closer to the fans, as opposed to the ones at the farthest points, to ensure that even airflow is had across the room.

 

Best bet I'd say is a couple of inlets at the opposite end of the room to the fan, ensure that the room is airtight, and a large extraction fan running constantly. Spend the money on a decent fan, it's worth it in strength, cfm and longevity. Your crop will DIE if the only main extraction fan fails, and cheap fans which are not designed to run continuously are liable to do this.

 

Oh, and the reason I don't advocate intake fans is that they're not necessary in the first place, if the room is airtight at all other points then the air can only come into the growroom at that point, and if it's far away from the extractor and low in the room, then the room will be fully evacuated. If you use a couple of fans, you're risking one fan straining the other, even if they're seemingly identical fans. If the intake is more powerful than the exhaust, then the exhaust will be straining to keep up and the intake will be straining to push air into a room which is already full... likewise if the intake is weak, but the only entry point for air, and the exhaust is strong, you'll end up straining the exhaust because it's trying to pull out more air than is being brought in, and the intake fan will be strained by the exhaust fan pulling out more than it can push through...

 

So yeah, don't bother with an intake fan, just have a passive vent at a low, far away point from the exhaust and use a good exhaust fan, and you should be fine.

 

Hope that helps.

hey skywalker would you still suggest no intake fans on small grow boxes??

[Luke Skywalker]

Yes.

[States Zone]

ok, thanks for the information

 

-much appeciated

[Luke Skywalker]

[F420]

but thats only Lukes opinion,

 

Personally I do use an inlet fan and this helps ALOT in the grow room,

It acts as the Osc fan, and it sucks air from out side via ducting in to the grow box.

[racked]

Thanks skywalker , i wood neva have thoght about the 2 fans stressin each other out thanks for pointin that out.

 

I have allready bought the 2 ex fans they just your average bathroom ex fan but they are rated for cotinuous running (2yr warr)

so i think ill just use the 2 fans for exhaust and run 2 x 250mm passive intakes from window vent.

Just 1 thing should i have the passive inlets coming in at pot level or little higher? so the pots dont get chilled by night air(will be runnin lite at night)

 

thanks again.

[Luke Skywalker]

The cold air should come in at the lowest possible point. If you're running the lights at night, the extra heat they produce should help out with the air temps inside, evening things out a bit.

 

But you should install your inlets as low as is practical. This is to set up a circulation effect, removing all the air entirely. If you have the intake too high, you end up with a pool of cold air staying at the base of the grow space, as it's only going to travel the shortest possible distance it can to get out. If you have the exhaust lower than the intake, you'll end up with a pool of very, very hot and humid air above this point, so it's important to keep the cycle of air moving upwards and out.

 

Hope that helps.

[LoveMeBucket]

just thought i'd add that u know if u have good ventilation if your plants are "dancing" that is, gently shaking due to the fresh air thats being pulled over them by your wikkid ventilation

 

cheers,

bucket