Handbook of air conditioning and refrigeration / Shan K

17.15
TABLE 17.2 Rectangular Ferrous Metal Duct Construction for Commercial Buildings
Minimum galvanized steel thickness, in. (gauge)
0.0575 (16) 0.0466 (18) 0.0356 (20) 0.0296 (22) 0.0236 (24) 0.0187 (26)
Duct
dimensions,
Pressure, in. WG
in.
Up through 10
�2 �3 �1 �2 �3 �1 �2 �3 �0.5 �1 �2 �3 �0.5 �1 �2 �3 �0.5 �1 �2
12 A-8 A-8
14 A-8 A-8 A-5 A-10 A-5
16 A-8 A-10 A-8 A-10 A-8 A-5 A-8 A-5
18 A-8 A-10 A-8 A-10 A-8 A-5 A-8 A-5
20 B-10 B-10 B-8 A-10 B-8 A-5 A-10 A-5 A-5 A-10 A-8 A-5
22 B-10 C-10 A-10 B-10 B-8 A-10 B-8 A-5 A-10 A-10 A-5 B-5 A-10 A-5 A-5
24 C-10 C-10 B-10 C-10 B-5 B-10 C-8 B-5 A-10 B-10 B-5 B-5 A-10 A-5 B-5
26 C-10 D-10 C-10 D-10 B-10 C-10 C-5 A-10 B-10 C-8 C-5 A-10 B-8 B-5 C-5 A-10 A-5 B-5
28 C-10 D-10 C-10 C-10 D-10 C-10 C-8 C-5 B-10 C-10 C-5 C-5 B-10 C-8 C-5 C-4 B-8 B-5 B-4
30 D-10 D-10 C-10 D-10 D-8 C-10 D-8 C-5 B-10 C-10 C-5 C-5 B-10 C-8 C-5 C-4 B-8 B-5 C-4
36 E-10 E-8 D-10 E-8 E-5 D-10 D-5 E-5 C-10 D-8 D-5 D-4 C-8 C-5 D-4 D-4 C-5 C-5 —
42 E-8 E-5 E-10 E-5 E-5 D-8 E-5 E-5 D-8 D-5 E-5 E-4 D-8 D-5 E-4 E-3 D-5 D-4 —
48 G-8 G-5 E-8 F-5 G-5 E-5 F-5 F-4 D-8 E-5 E-4 E-3 D-5 E-5 E-3 E-2.5 D-5 D-4 —
54 G-5 H-5 F-8 G-5 H-5 E-5 F-4 G-3 D-5 E-5 F-3 G-3 D-5 E-4 F-3 E-2.5 D-5 — —
60 H-5 H-5 G-8 H-5 H-4 F-5 G-4 G-3 E-5 F-5 G-3 G-2.5 E-5 F-4 G-2.5 G-2.5 E-4 — —
72 I-5 I-4 H-5 H-4 H-3 G-4 H-3 H-3 F-5 G-4 H-3 H-2.5 F-4 H-2 H-2 H-2 — — —
84 J-4 J-3 I-5 J-4 J-3 H-4 I-3 J-2.5 H-5 — — — G-4 — — — — — —
96 K-4 L-3 I-4 K-3 K-2.5 I-3 J-2.5 J-2 H-4 — — — — — — — — — —
Over 96 H-2.5 H-2.5 H-2.5 H-2.5 H-2.5 — — — — — — — — — — — — — —
plus plus plus plus plus
rods rods rods rods rods
Note: For a given duct thickness, letters indicate type (rigidity class) of duct reinforcement (see Table 17.3); numbers indicate maximum spacing (ft) between duct reinforcement. Use the same
metal duct thickness on all duct sides.
Source: Adapted with permission from SMACNA, HVAC Duct Construction Standards—Metal and Flexible. Refer to this standard for complete details.