PMP-098
Oil Furnaces
–
Furnace Manual
10
11/13
1.10
CONNECT SUPPLY AND RETURN DUCTS (continued)
1.10.1
Duct sizing (continued)
Table 4: Typical duct sizing for systems not over 100 feet equivalent length – round or flat oval galvanized
Do not apply this table for duct systems over approximately 100 equivalent feet length. For longer systems or
systems using other duct materials, refer to ACCA Manual D. Incorrectly sizing duct systems can result in unsafe or
uncomfortable operation.
Round
duct
diameter
3
4
5
6
7
8
9
10
12
14
16
18
20
(inches)
x
x
x
x
x
x
x
x
x
x
x
x
x
45
4
6
5
-
-
-
-
-
-
-
-
-
-
-
65
5
8
6
-
-
-
-
-
-
-
-
-
-
-
100
6
11
8
7
-
-
-
-
-
-
-
-
-
-
150
7
16
11
9
8
-
-
-
-
-
-
-
-
-
200
8
21
15
11
10
8
-
-
-
-
-
-
-
-
250
9
26
18
14
11
10
9
-
-
-
-
-
-
-
300
9
30
20
16
13
11
10
-
-
-
-
-
-
-
400
10
40
26
20
16
14
12
11
-
-
-
-
-
-
500
12
49
32
24
19
16
14
13
12
-
-
-
-
-
600
12
59
38
28
22
19
16
15
13
-
-
-
-
-
700
12
69
44
32
25
21
18
16
15
13
-
-
-
-
800
14
-
50
36
29
24
20
18
16
14
-
-
-
-
900
14
-
56
41
32
26
22
20
18
15
-
-
-
-
1000
16
-
63
45
35
29
24
22
19
17
15
-
-
-
1100
16
-
69
49
38
31
26
23
21
18
16
-
-
-
1200
16
-
75
53
41
33
28
25
22
19
17
-
-
-
1300
16
-
-
58
44
36
30
26
24
20
18
-
-
-
1400
18
-
-
62
47
38
32
28
25
21
18
17
-
-
1500
18
-
-
66
50
41
34
30
26
22
19
18
-
-
1600
18
-
-
71
54
43
36
31
28
23
20
18
-
-
1700
18
-
-
-
57
46
38
33
29
24
21
19
-
-
1800
18
-
-
-
60
48
40
35
31
25
22
20
-
-
1900
20
-
-
-
63
50
42
36
32
26
23
21
19
-
2000
20
-
-
-
67
53
44
38
33
27
24
21
20
-
2200
20
-
-
-
73
58
48
41
36
29
25
23
21
-
2400
22
-
-
-
-
63
52
44
39
32
27
24
22
21
2600
22
-
-
-
-
68
56
48
42
34
29
25
23
22
2800
22
-
-
-
-
-
60
51
44
36
30
27
24
23
3000
22
-
-
-
-
-
64
54
47
38
32
28
26
24
3500
24
-
-
-
-
-
-
63
54
43
36
32
28
26
4000
26
-
-
-
-
-
-
71
61
48
40
35
31
29
Typical duct sizing
(For approximately 0.10 inch w.c. in a typical residential installation of galvanized metal duct)
CFM
Flat oval duct equivalent sizes
Minimum width
(inches)
for duct heights
(inches)
of :
