Maximum Flow rate thru round air ducts

size, dia.

CFM


size,

inches

 cubic feet/minute

mm

     

4

40

100

6

100

150

8

200

200

10

400

250

12

600

300

14

1,000

350

16

1,400

400

20

2,400

500

24

5,000

600

30

8,000

760

36

11,000

900

48

25,000

1,200

60

42,000

1,500

Friction loss of 0.08 inch of water per 100 feet of duct.

Reference: ASHRAE Fundamentals 32.7

For low noise commercial/ residential hvac ducts

R. Caldwell 1-9-98 revised 10-11-2003

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