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Ask a Grower

Ask-a-Grower #82

How can I tell what combo of fan and carbon filter size are right for my growing space?

First you are going to want to determine the cubic feet of your growing space. You can calculate that by multiplying the height by the width by the length of your area.

For example: 8′ high x 10′ long x 10′ wide = 800 cubic feet

It is recommended that your fan have the ability to exchange the air in the room every 1-3 minutes. Now divide the cubic foot of the room by the number of minutes you would like it to take for the fan to exchange the air in the room. This will give you your minimum CFM (cubic feet per minute) rating

For example: 800 cubic feet divided by 2 minutes equals 400 CFM of exhaust needed.

At San Diego Hydroponics we recommend CAN Fans and Filters. All their fans display the output in CFM on the side of the box and the filters display their minimum and maximum CFM ratings. Take the number you arrived at earlier, in this case 400 CFM, and find a filter with a LOWER minimum CFM rating. Now pair that filter with any fan that has a CFM rating between the filters minimum and maximum CFM ratings.

For example: You need 400 CFM of exhaust. The CAN 75 has a minimum rating of 300 CFM and a maximum rating of 600 CFM. This would be a good choice of filter. Now you will need to find a fan that produces between 300 a 600 CFM of exhaust. The CAN 8″ RS produces 483 CFM and would be a great choice to go with the CAN 75.

Other factors could influence the size of fan you would need. One could be the amount of heat producing equipment you have in the growing space.

For example an 8×10 room with (2) 1000 watt lights would require less CFM of exhaust than the same size room with (4) 1000 watt lights.

Another external factor could be ambient outside air temperature. The temperature of the fans intake air will directly affect it’s cooling ability.

For example if the intake air was 50 degrees Fahrenheit it will do a much better job of cooling than if the intake air was 80 degrees Fahrenheit.

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