Ventilation help with true cfm's?

[Yeti]

Just curious if any ventilation experts could help? I have venting from outside through 4 rows of 3 lights and into a vacuum box There is a vacuum created by two 8" Ecoplus inline fans (740 cfm each) intaking from two carbon scrubbers that enter a 8"-8"-10" Y to exhaust through 10".

My question is if cfm's are simply additive or if they overlap and are not necessarily adding directly. Would it be beneficial to increase to one larger more effective 10" fan or are the two 8" fans optimal or do you have a better suggestion.

Thank you, any and all helps.

Yeti

 

[Shafto]

One larger fan will be much better.

If at all possible you should never use two fans in parallel. They just fight each other.

"true CFM" can be measured by building yourself a manometer out of some plastic tubing, very easy. You can then measure the static pressure in your ducting system. You have to measure before the fan to see what the negative pressure is, and after the fan to see what the positive pressure is. Add them up and then look at the manufacturer's chart for the fan. It will show actual airflow at different static pressures (SP).