Duct Installation Design Charts

Equivalent Resistance in ft.

ø in
Elbow 90° 1.5 Elbow 90° 2.5 Elbow 30° Branch
3 2.5 1.75 2
4 3.5 2.5 2.5
5 4.5 3.25 3.5
6 5.5 4 4
7 6.5 5 5
8 8 5.5 6
9 9 6.5 7
10 10.25 7.25 8
11 11.5 8 9
12 13 9 10
13 14.5 10 11
14 15.5 11 12
16 18.5 13
14
18 21.5 15
16
20 24 17
18
22 27 19
21
24 30
21
23
26 33 23.5
25
28 37
25.5
27
30 40
28
30
32 43
30
32
34 46
32
35
36 49
35
37
38 53
37
40
40 56
40
42
42 60
43
45
44 64
45
47
46 67
47
50
48 70
49
53

 

Elbow Friction Factor Chart

R. No. of Dia.
  Loss Factor
Elbow 30° Branch
1.0 D   0.33
1.5 D   0.24
2.0 D   0.19
2.5 D   .17