Doggone amateurs…

Someone on LE writes with a good question:

I have a “barley box” being made up for me and need to know the CFM’s necessary for proper ventilation. I can’t figure out these CFM calculators I’ve seen on some other sites.

The box is 17″ deep, 30″ wide and 30″ tall. I’m working on a Cheetah.

One of the new “know-it-alls” writes back in response:

… – this is the calculation for a 17×30 hood:

17 x 30 = 510 / 144 = 3.54 x 125 = 443 CFM

Since you will have the sides enclosed, you can use the 100 multiplier instead of 125, thus 354 CFM

So you need a fan between 354 and 443 CFM.

Ummmmm…the opening of the box is 30″ x 30″. The 17″ is the depth (or how deep from front to back) the box measures.

The correct calculations are:

30 x 30 = 900 / 144 = 6.25 x 100 = 625 CFM. Size the fan with a minimum 625 CFM fan, up to about 10% over (or about 700 CFM).

 

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