PLB-112
Oil Furnaces
–
Furnace Manual
8
11/13
1.9
CONNECT SUPPLY AND RETURN DUCTS (continued)
1.9.1 Duct sizing (continued)
Table 3: Typical duct sizing for systems not over 100 feet equivalent length – round or rectangular 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
4
5
6
7
8
9
10
12
14
16
18
20
22
24
26
28
30
(inches)
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
45
4
4
4
4
-
-
-
-
-
-
-
-
-
-
-
-
-
-
65
5
6
5
4
4
-
-
-
-
-
-
-
-
-
-
-
-
-
100
6
8
6
5
5
4
4
-
-
-
-
-
-
-
-
-
-
-
150
7
12
9
7
6
5
5
5
4
4
-
-
-
-
-
-
-
-
200
8
14
11
9
8
7
6
6
5
4
4
-
-
-
-
-
-
-
250
9
18
13
10
9
8
7
6
6
5
5
4
4
-
-
-
-
-
300
9
20
15
12
10
9
8
7
6
6
5
5
4
4
-
-
-
-
400
10
26
19
15
13
11
10
9
8
7
6
6
5
5
5
4
4
-
500
12
32
23
18
15
13
12
11
9
8
7
6
6
6
5
5
5
5
600
12
38
28
22
18
15
13
12
10
9
8
7
7
6
6
6
5
5
700
12
46
32
25
20
17
15
14
11
10
9
8
7
7
7
6
6
6
800
14
52
36
28
23
19
17
15
13
11
10
9
8
8
7
7
6
6
900
14
58
41
31
25
21
19
17
14
12
11
10
9
8
8
7
7
7
1000
16
64
45
34
28
23
20
18
15
13
11
10
9
9
8
8
7
7
1100
16
72
49
38
30
25
22
19
16
14
12
11
10
9
9
8
8
7
1200
16
-
54
41
33
27
24
21
17
15
13
12
11
10
9
9
8
8
1300
16
-
58
44
35
29
25
22
18
16
14
12
11
10
10
9
9
8
1400
18
-
63
47
38
31
27
24
19
16
14
13
12
11
10
10
9
9
1500
18
-
68
51
40
34
29
25
20
17
15
14
12
12
11
10
10
9
1600
18
-
72
54
43
36
30
27
21
18
16
14
13
12
11
11
10
9
1700
18
-
-
58
45
38
32
28
23
19
17
15
14
13
12
11
10
10
1800
18
-
-
61
48
40
34
29
24
20
17
16
14
13
12
11
11
10
1900
20
-
-
64
51
42
35
31
25
21
18
16
15
14
13
12
11
11
2000
20
-
-
68
53
44
37
32
26
22
19
17
15
14
13
12
12
11
2200
20
-
-
-
59
48
41
35
28
23
20
18
16
15
14
13
12
12
2400
22
-
-
-
64
52
44
38
30
25
22
19
17
16
15
14
13
12
2600
22
-
-
-
69
56
47
41
32
27
23
21
19
17
16
15
14
13
2800
22
-
-
-
-
61
51
44
34
29
25
22
20
18
17
15
15
14
3000
22
-
-
-
-
65
54
47
37
30
26
23
21
19
17
16
15
14
3500
24
-
-
-
-
-
63
54
42
34
29
26
23
21
19
18
17
16
4000
26
-
-
-
-
-
72
61
47
39
33
29
26
23
21
20
19
18
Typical duct sizing
(For approximately 0.10 inch w.c. in a typical residential installation of galvanized metal duct)
CFM
Rectangular duct equivalent sizes
Minimum width
(inches)
for duct heights
(inches)
of :
