Toby Posted November 19, 2014 Share Posted November 19, 2014 Hi guys, I thought ill share what I have come up with going through tons of websites trying to work out a formula for air circulation. The general rule is that your exhaust should be extract 2-3 times the amount of air that is being let in via an inlet to maintain negative pressure. Most of us will use an extractor / inline fan to extract the air out of our space. The hole is usually round, ie. 6"/15cm, 4"/10cm, etc. How many and what size holes do I need for my given extractor size? That is the question that got me? After much considerations and various trial and error formulas, I am using area()² as the measurement factor. I have set up an excel spread sheet that you are welcome to download and insert your info. Basically you will be inserting the diameter of your fan and the number holes required. It will produce the size of the holes. An example Fan size 15cm 9 holes required 7cm holes So for a 15cm fan I need make 9 holes at 7cm per hole. The area of the 9 holes should be = to double the area of the 15cm? I hope I am making sense? Please feel free to analyse my findings and provide input if you feel I have overlooked certain variables? input_vs_exhaust_calculator.xlsx Quote Link to comment Share on other sites More sharing options...
420SA Posted November 20, 2014 Share Posted November 20, 2014 Hi Toby Are these holes going to be in your cab or what? Also what's gonna go through these holes? Besides air obviously Quote Link to comment Share on other sites More sharing options...
Guest Maxwell Posted November 20, 2014 Share Posted November 20, 2014 Imo all you need is an exhaust with two passive inlets the same size, or slightly smaller. Smaller would be better to force the negative pressure and get the RH down. Too many holes means more light/pest leaks and of course more work. If you can find a 15cm hole saw for under half a grand let me know!! First prize is an active intake.... Quote Link to comment Share on other sites More sharing options...
Toby Posted November 20, 2014 Author Share Posted November 20, 2014 Hi Toby Are these holes going to be in your cab or what? Also what's gonna go through these holes? Besides air obviously The holes will be in the floor as passive intakes. The intention for my setup is to have a fake floor. The base will have the calculated intake holes with filter to prevent insects and other elements getting into my box. The first shelf about 4cm away will be the floor for my plants also with intake holes. There will no light leaking through. To add to the equation, I will be running a 400HID with a DIY vented hood + scrubber. Im in the construction phase at the moment. I shall post pics when complete. Imo all you need is an exhaust with two passive inlets the same size, or slightly smaller. Smaller would be better to force the negative pressure and get the RH down. Too many holes means more light/pest leaks and of course more work. If you can find a 15cm hole saw for under half a grand let me know!! First prize is an active intake.... Thanks for input Maxwell. Like you said finding the right tool for the job can be expensive. My formula basically let you calculate the number of holes that will make up the area of 15cm but doubled. So a lot of small holes that equals the one big hole. A basic example. If you want a 15cm hole its not the same a making 15 1cm holes. The total area of the 15 holes is not the same as the area of the 15cm hole. Quote Link to comment Share on other sites More sharing options...
Dabtzar Posted November 20, 2014 Share Posted November 20, 2014 One intake on the lower level and one exhaust above your light is sufficient. Like Max said, too many holes and entry points, make it a bugs life. Quote Link to comment Share on other sites More sharing options...
Toby Posted November 20, 2014 Author Share Posted November 20, 2014 One intake on the lower level and one exhaust above your light is sufficient. Like Max said, too many holes and entry points, make it a bugs life. Cool thanks, I have mod my spread sheet to include rectangular dimensions for circle sizes. So instead of intake holes I can make intake strips. Either or same effect just based on what tools are available. Quote Link to comment Share on other sites More sharing options...
storm_shadow786 Posted April 3, 2015 Share Posted April 3, 2015 intake strips,hmmm interesting thought can you give more details? Quote Link to comment Share on other sites More sharing options...
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