Williamson-Thermoflo SCH High Boy, Manual Manual, Page: 7 / 39

SCH & SCL
Oil Furnaces
– Furnace Manual
670-000-006-1007
3 Connect supply and return ducts
(continued)
Duct sizing
(continued)
Table 4 Typical duct sizing for systems not over 100 feet equivalent length – round or rectangular galvanized
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 :
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. WARNING
7