air exchange

[Mr Blah]

My room is 4.10'w x 9.10'L x 6.10' tall= 228 cubic'.
I want to exchange the air 2x a min.
I have 3x 600Hps in 3 yield master II hoods being vented out using a 6" 400cfm fan.
I also have another 6" 400cfm fan venting the room.


My question is how much more air am I going to vent with the 3-600's?
Also how big do my intakes have to be? I got 2-6" holes all ready?

 

[anon0988]

I would say using your setup with the two fans I'd have 1 fan run the cooling for lights, and one exchange air in the tent through a carbon filter. As long as you don't have lots of extra flexible ducting hanging down from the connection points and keep the pathing relatively direct through the cooltubes, 1 fan should be enough. In that setup I would note that you would want the fan blowing INTO the system and pushing air over the lights and out, that way you're not sucking 3x hot air into your fan. Also that way the cooling setup for the lights will have positive system pressure and you won't have to worry about smells getting out through there. Then for the exhaust do a similar setup with the other fan. Something like filter->fan->ducting out. That way you again take advantage of the positive system pressure inside the exhaust so smells don't leak. As long as the filter is inside the tent you'll have negative system pressure which pull enough air into the tent to prevent smells from leaking. Keep in mind that a carbon filter diminishes the airflow capacity of a fan. I don't have any numbers to back it up but a good rule of thumb I've heard is to figure a filter reduces throughput by 50%. So given your 228 cu/ft size and the desire to swap air twice a minute, using that rule you'd need roughly 456 cfm. I would personally say that as long as your filter is decently rated for cfm it will probably work and be 'good enough'. Yeah you could have more airflow but you'd have to buy another fan. As far as how big to make the intake, from what I hear go 2:1 to the exhaust size. So for you having 1 6" exhaust, open 2 6" holes on the bottom.

 

[RM - aquagrower]

General rule for passive intakes is 2x the active exhaust. A 6" hole (your fan size) is 28.26 "net free inches" times 2 fans is 56.52 times 2 equals 113.04" passive intake if using both fans for exhaust.

If you are using 1 fan/filter combo to vent the room and 1 fan to cool the hoods, then the 2 6" intakes should be good. If you are going this rout, ya should "blow" thru the hoods because you will have odor leaks otherwise.

Keep in mind that there will be cfm losses due to restrictions in the system (carbon filter and turns in duct work).

 

[Mr Blah]

No filter needed.
I all ready have 2-6" holes at the bottom (opposite side).
There is going to be 2-400cfm inline fans; one sucking air from (in order) room-hood-hood-hood-elbow-inline fan-out of room.
the other; (in order) room-inline fan-out of room.

The only restriction will be the elbow in the hood line up.
In this room I am really aiming for 2x air exchange to see if it helps with any positive gain.

 

[anon0988]

If you don't want to filter that's fine, but you should still push the air through the cool tubes rather than suck it through the fan. 3 bulbs will have some hot air travelling through there and it will improve the life of your fan if you push rather than pull.

 

[Mr Blah]

If you don't want to filter that's fine, but you should still push the air through the cool tubes rather than suck it through the fan. 3 bulbs will have some hot air travelling through there and it will improve the life of your fan if you push rather than pull.

Are you talking about a passive system?
If I push, aren't I still sucking hot grow room air through the fan before it travels across the bulbs?

 

[anon0988]

I'm saying you want to be pushing fan over the bulbs and out, not sucking air through then to the fan, then out. The higher air temps are bad for your fan. Here's a picture:

 

[Granger2]

I'd rather pull the air thru. More efficient. The temps should have little effect on the life of a centrifugal fan. If you're worried about smell leaks, make sure everything is sealed. Tape. Good luck. -granger

 

[anon0988]

I'd rather pull the air thru. More efficient. The temps should have little effect on the life of a centrifugal fan. If you're worried about smell leaks, make sure everything is sealed. Tape. Good luck. -granger

Why exactly is it more efficient to pull it through the tubes rather than push it? Don't you think the heat would be an issue for the fan with 3 lights in the same airway? I seem to remember that these style of fans have a max recommended intake air temp of something like 120 degrees F. Also with pushing the air over the bulbs then out you're creating positive pressure so any leaks are into the tent, not into the vent and then out which can cause odor issues.

 

[Mr Blah]

Also with pushing the air over the bulbs then out you're creating positive pressure so any leaks are into the tent, not into the vent and then out which can cause odor issues.

I don't need to mask the odor.

On the fence about pushing or pulling.
Where did you read that about the 120 degrees is the fan max temp?

 

[anon0988]

I got to looking today to figure out where I'd heard about the intake air temps. After a while of looking I noticed none of the growing type fans listed it for them. Then I remembered I also sourced fans on Grainger, here's a link to a list there. If you'll notice when you click on all of the fans that are the same style as the Hydrofarm or ActiveAir, they all list 140 degrees as max intake temperature. Grainger is a supplier of business/commercial grade parts for just about anything, the stuff is quality and there's a lot more data about their products because of the demanding environments they're used in. I would assume 140+ is bad for the motor and bearings. That's why I was recommending you push air through, rather than pull.

 

[mack 10]

good info.

 

[castout]

thanks for the info