open grow area or grow chambers - benefits 4 cooling?

hi all

long winded question here... needs some background...

I am setting up my next grow. its been a while and i have nearly collect all my grow gear back under one roof. I have a room that i grow in which is 75 sq ft and 593 cubic feet.

I ONLY grow in a small area. Basically its the room closet where I grow because its easier for hanging lights etc. It starts in one corner runs 4ft along the wall. Usually the closet is not sealed off from the rest of the room when I grow so its all open.

I am confident that heat has been a major factor in problems with hermies etc. I have applied no cooling except oscilating fan. Could be genetics but I sorted that for this grow by picking up some known seeds.

So I was at my local grow shop and talking about temp control. They suggested that I reduce my grow space into a grow chamber if you like. Something like putting up walls (2) around the closet and a roof. I was thinking of constructing just out of PVC and panda film.

From what they were saying the idea is to control the exchange of air more effectively, cause the room is too big to effectively change the air, you then need to reduce the volume of air you are moving.

does this sound right to you?

I am keen to put together some kind of cool tube or use a cooled hood. Been looking around for a suitable tube. I wonder if I did that how much lower would the tempterature be and would it alleviate the need to use additional cooling?

what are your thoughts? Do cool tubes make such a difference that extra cooling is not needed?

If I use chambers instead of an open room will I have the ability to have better control over cooling?

thanks
treb

I have since gone and found some more info. This is probably what my local was getting at rather than only cooling, air exchange gives additional benefit in co2.

FANS AND AIR FLOW


WITHOUT FRESH AIRFLOW MOVING THROUGH YOUR GROWROOM YOUR PLANTS CANNOT BREATH .

PLANTS HOWEVER DO NOT BREATH IN OXYGEN IN THE SAME WAY THAT WE DO , THEY BREATH OUT OXYGEN .

PLANTS BREATH IN CARBON DIOXIDE , WHICH DEPLETES FAIRLY RAPIDLY IN A GROWROOM WITH INSUFFICIENT AIRFLOW .

WHEN THIS OCCURS THE PLANT DOES NOT HAVE THE MATERIAL IT NEEDS TO CREATE THE BASIS FOR GROWTH OR CELL DIVISION .

WHEN WORKING OUT WHAT OUR FAN REQUIREMENTS ARE , IT IS IMPORTANT TO KNOW THE CUBIC VOLUME OF THE GROWROOM .

YOU WILL NEED A FAN WITH THE CAPACITY TO PURGE THE VOLUME OF THE ROOM APPROXIMATELY EVERY 5 MINUTES

( IN GROWROOMS WITH PROBLEMS OF EXCESS HEAT , FAN CAPACITY WILL NEED TO BE INCREASED )

Its in caps I know...

the whole explanation about working out how big your room is and what size fans you need is here:
http://www.hygrow.net/products.php?category_id=2&product_id=18

they say all air should be changed every 5 minutes. measurements/conversions are metric but works ok for me.

So for me my room is 2.5m x 2.8m x 2.4m = 16.8m3 x 12 (change air X times per hour - every 5 mins) = 201.

Divide 201 by 3.6 (litres conversion) = fan must pump 55.8 litres per second. Litres dont mean anything to me. I always thought it was CFM or cubic feet per minute.

To do CFM I think it calculates out like this:
Room 2.5m x 2.8m 2.4m(h) - 16.8m3 x 12 (change air X times per hour - every 5 mins) = 201 m3/hr

201/60 (mins/hr) = 3.35 m3/min. This converts to 117 cubic feet per minute (CFM)

So in my current open room I need to a fan capable of 117 CFM

either way..... I look at fan capacities and even the smallest 150mm inline fan is cable of shifting more than 100 litres/sec

I cant see it being enough for the space ... either I got the math wrong or I need to see how much air these things can really push...

can anyone vouch for the correctness of the calcs I have used?

thanks
treb

You will need a good exhuast fan that will ventilate your grow space 3-4 times every MINUTE for adequate ventilation.


What are the parameters of the grow space?Length width and height.

He said 2.5m x 2.8m x 2.4m are the dimensions. So that would make it, roughly, 8 x 9 x 8.

I'll take a stab at this. But we're going to need to know the size of the grow. One 600w? 4 kilowatts?

I think that, if it will be a small grow, then you could probably get away with a 6" 449cfm Vortex fan and good air circulation (oscillating fans). If you plan on using the whole room to grow, then you'll need some heavy-duty ventilation.

Now, the best solution would be to get an appropriate fan with a speed controller and build a wall out of poly or a tent out of pvc & poly. The more you can reduce the size of the grow-space, the better.

thanks for the replies

the room is big but my grow is small. I'm running a single 400 w hps in the closet of that room. its not a permanent grow room unfortunately.

originally i figured with that much space heat would be spread/dissapate and not be a prob... but I am learning that being able to control more and more apsects of the grow is gonna turn up better results.

Dr FeelG & d4herb what you suggest on the walls is right on the money I think, given the position of the closet, 2 walls is all I need to put up.

Like Jnugg says, venting the whole room seems necessary but if i can reduce it I can keep things reasonable in terms of a fan, noise etc

will poly do the trick? i guess it will..
plenty of those grow boxes out there made of mylar or someother stuff... whatever it is.....I'm just using panda film for light tightness. Its pretty thick film.

I wish I could run the whole room but its too much to pull down once a year. meybe when in my own place.

thanks for the input.. was wondering if anyone had anything to add on what fan capacity I'm likely to need... 449 cfm seems like a lot to me Dr FG

treb

your panda film is probably 6 mil which is perfect thickness.

449 cfm is based on a 8 x 9 x 8 space. If you want better watts per sq. ft. for your 400w:

3 x 3 x 5 = 45 sq. ft. x 3 or 5 (air changes per minute) = 135 to 225 cfm.

They were saying above to err on the side of too high with a speed control, so that you can easily adjust when space or heat requires....excellent advice. So that being said 225 cfm or a little more would be fantastic in a 3x3x5 space.

449 cfm seems like a lot to me Dr FG

Click to expand...

It might be too much. That's what the fan controller is for. And, if you ever decide to make your grow larger, then you have more ventilation at the ready.

Good luck!

Excellent!.... DR FG thanks very much for your input... i will put it to the test and see.. the fan controller...... of course

Aeric .... again... thanks for working the calcs...having more airflow available is better than not enough for sure

Treb

I have started a grow diary now. you can see it here:

http://www.icmag.com/ic/showthread.php?p=438188#post438188

Thanks to Dr FG, aeric, d4 herb and Jnugg. I will put into practice the info/knowledge you have provided and we will see what results there is.

thx
Treb

Glad I could help. Good luck!

i have a 7'x5' room with a 7' ceiling was wondering if my 8" 500cfm fan blowing through my 2 400w hps and a 6" 250cfm inline to boost out the room through the window

my whole thing is do you thing this is enough air and i am only really worried about cooling the lights cause a ac unit will be place in the room soon...

btw today was day 2 of temp testing and it stood around 80 degrees and 34% humidity with the oscilating fans and light fans all on...

sound about right?

Hey Coloradro

I set up my grow space using the info I picked up here. I chose a 6" 203CFM inline fan and some ducting for my cooling. I also only cool my light which is 400watt. If you check out my grow you can see how I rigged the duct up to the lamp

its here: http://www.icmag.com/ic/showthread....8188#post438188

I was getting temps at about 100F without the lights being cooled(in an 15sq ft space). After rigging up my modest cooling solution, I am gettting temps that are about 23 - 25 F better. So we are down at about 77F now.

I use a 2 probe thermometer. One that is made for inside and outside measurements. It has a small probe on a 3 meter cable that you can poke out through a window or something. I hang this probe near my lamp and place the actual thermometer unit down on the bench near the plants. The unit has a second temp guage in it to measure "indoor" temps.

I also have a small button type thermometer I place on a shelf in the room my grow enclosure is in but it is outside the grow enclosure. This gives me the rooms ambient temp. This is important as well because if the rooms ambient is high and you are using this air and not drawing in air from outside your grow space (like me) this will reduce the cooling affect as the air being sucked through by the fan is already a bit warm.

I would say that from your perspective a 500cfm fan per 400 watts should work really well. I would have thought your temps would be a bit lower than that. Perhaps the ducting could be lined up closer to your lamps or something to improve draw?

I played around with the positioning of the duct opening near my lamp and I found it did make a difference of at least 4 or 5 F.

I think your temps are right. They are within a fraction of mine and I think that this is much improved over what they were for me before I introduced the fan.

I also found that the way the ducting was laid out affected performance quite a bit. I now try and run the ducting as straight or with as gentle a bend as I can manage. I did have 2 fairly sharp bends in the ducting. This change also positively affected cooling performance by reducing temps further by about 10F.

perhaps that might help you tweak your setup a bit but I think your probly on the money there.

cheers
treb