Hamilton Home Products Residential Duct Sizing Guide
ADVERTISEMENT
1Residential Duct Sizing Guide
The following duct sizes are based on a fraction drop of .10 inches per 100 feet of lineal duct.
This "Equal-Friction" method of duct sizing should be adequate for normal residential furnace
heating and air conditioning applications. Larger volumes or higher static pressures should be
dealt with on an individual job basis.
Rectangular and Round Duct
Air Volume
Rectangular Duct Height (inches)
Equivalent Round
Air Volume
CFM
Duct (inches)
CFM
4"
6"
8"
10"
12"
50
6 x 4
5
50
75
6 x 4
6
75
100
8 x 4
6 x 6
6
100
125
10 x 4
6 x 6
7
125
150
10 x 4
8 x 6
7
150
175
12 x 4
8 x 6
8
175
200
14 x 4
8 x 6
8
200
225
16 x 4
10 x 6
8
225
250
16 x 4
10 x 6
9
250
275
12 x 6
8 x 8
9
275
300
12 x 6
8 x 8
9
300
400
14 x 6
10 x 8
10
400
500
18 x 6
12 x 8
10 x 10
11
500
600
20 x 6
14 x 8
12 x 10
12
600
700
24 x 6
16 x 8
12 x 10
12
700
800
26 x 6
18 x 8
14 x 10
12 x 12
13
800
900
30 x 6
20 x 8
16 x 10
12 x 12
14
900
1000
22 x 8
16 x 10
14 x 12
14
1000
1100
24 x 8
18 x 10
16 x 12
15
1100
1200
26 x 8
20 x 10
16 x 12
15
1200
1300
28 x 8
20 x 10
18 x 12
16
1300
1400
30 x 8
22 x 10
18 x 12
16
1400
1500
24 x 10
20 x 12
16
1500
1600
24 x 10
20 x 12
17
1600
1700
26 x 10
22 x 12
17
1700
1800
28 x 10
22 x 12
18
1800
1900
30 x 10
22 x 12
18
1900
2000
24 x 10
18
2000
HELPFUL BASIC INFORMATION:
When Cooling: You must have 400 CFM of air flow per Ton of A/C (1 Ton equals 12,000 BTU)
Approximately 1 CFM of air is required to heat or cool 1 to 1.25 sq. ft. of floor area.
Duct Work
Supplies are located on outside walls.
Returns are located on inside walls. They should not be located in the same area as the furnace, nor
should they be located by moisture sources such as kitchens or bathrooms.
Return Air CFM must be equal or greater than Supply Air CFM.
Wyes commonly reduce.
Tees split, but do not reduce, and an appropriate reducer must be added.
Dampers on take-off duct runs allow for adjustments of air distribution.
In order to maintain velocity, reduce duct size.
Never locate ducts at the end of the trunk line run. Last take-off run to be located 12" - 18" from end.
Always stagger take-off ducts by 12" to maintain pressure.
Use insulated duct or duct board in unheated spaces.
Flexible duct work must be stretched tightly for maximum air flow.
Information provided is to be used as a guideline only.
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Life