Wish I found this 2 mths ago

[micmac]

take a tape and measure (in meters) the length, width and height of your grow tent – this will give you the cubic area of the tent

then multiply this figure by 60 (the number of minutes in an hour) which is how many times you want the area exchanged in a hour

here’s an example:

 

my grow tent is 1.2 M x 1.2 M x 2M

 

so 1.2 x 1.2 x2= 2.8 cubic meters in total

 

2.8 X 60 =172.8 cubic meters an hour needed

 

and here’s a quick approximate guide to the size of fan for what size area you are growing in

 

Sizes:

 

4″/100mm – 175m3/hour

5″/125mm – 225m3/hour

6″/150mm – 420m3/hour

8″/200mm – 750m3/hour

10″/250mm – 1000m3/hour

12″/315mm – 1300m3/hour

 

 

 

 

 

However! any 90º bend in the ducting means that you will need to add a 30% power increase due to resistance –

172m3 X 1.3=223.6m3

Would have saved me a lot of grief have 6" with no bends when I only needed 4" more than twice the air exchange I needed bloody hydro shop guy!

[nici]

What type of fan are you running? You could always dial it back to what you need.

[micmac]

What type of fan are you running? You could always dial it back to what you need.

yeah nici I am trying that now I have 2.5 metres ducting between filter and fan it's also coiled it still drops temperature and humidity significantly I just opened vents you can see the air rushing in over plants and going out the top vent just hope this is enough j

[Gazza2001au]

Those figures only work if u have the same size fan on the intake, if your running one exhaust fan there are a lot of factors plus different types of fans, axle, mixed flow and centrifugal, i ran a 100mm centrifugal fan thru a 1x1x2 meter tent using the intake vents and that little fan sucked harder than my 150mm mixed flow on a .9x.5x1.8m

 

i would pick a centrifugal fan over any other type if they were not so loud, a centrifugal fan's Pa/pressure ratings on smaller 100-125mm fans is almost double over a mixed flow fan of same size

 

plus there are a lot of crap fans on the market i have only ever came across one good 150mm axle fan and as far as i know it was only sold by Hydro Experts for i think $100 its the only rated axle fan for a carbon filter or does two cooltubes at one time

[micmac]

Those figures only work if u have the same size fan on the intake, if your running one exhaust fan there are a lot of factors plus different types of fans, axle, mixed flow and centrifugal, i ran a 100mm centrifugal fan thru a 1x1x2 meter tent using the intake vents and that little fan sucked harder than my 150mm mixed flow on a .9x.5x1.8m

 

i would pick a centrifugal fan over any other type if they were not so loud, a centrifugal fan's Pa/pressure ratings on smaller 100-125mm fans is almost double over a mixed flow fan of same size

 

plus there are a lot of crap fans on the market i have only ever came across one good 150mm axle fan and as far as i know it was only sold by Hydro Experts for i think $100 its the only rated axle fan for a carbon filter or does two cooltubes at one time

do you think too much flow could cause plants to dry out my soil dries well some seem to be going better than others even if I move them around I just noticed the fan has switched on the temp went from 24.5 to 19 and the humidity from 65% to 44% and dropping this driving me crazy

[nici]

It would play a small part but unless your using geopots it wouldnt be too much I would think.

[Gazza2001au]

Let me get this strait your growing in a 1.2x1.2m tent with a 600w HPS and with the fan turned off your temps are 24c? mate how are u measuring your temps? i cant even see this happening in tassie, your temps would be really high in a closed tent with the fan off

[micmac]

Let me get this strait your growing in a 1.2x1.2m tent with a 600w HPS and with the fan turned off your temps are 24c? mate how are u measuring your temps? i cant even see this happening in tassie, your temps would be really high in a closed tent with the fan off

yeah Gazza I know you're right I think temp meter isn't reading correctly put both sensors together and they read different I dialled back fan moved the light from .8m to 1m put a smaller oscillating fan everything seems to be ok the new growth looks to be fine and the burn and yellow leaves seems to have stopped should have stayed with the 4 leds like I did with the first batch thought I'd go to hps to solve heat problems this is what I got before

[Gazza2001au]

You grew those under led and changed lights? the 600w hps will give much bigger and denser buds but looks like your led was doing fine

 

some people are going led because the hps and mh are a fire hazard

[pedro de pacas]

You grew those under led and changed lights? the 600w hps will give much bigger and denser buds but looks like your led was doing fine

 

some people are going led because the hps and mh are a fire hazard