In general selection of the duct, thickness is related to more than one main parameter, but in the case of the max coil length will be around 1.2 m selecting the duct gauge according to SMACNA standards is related to the duct ESP made by the equipment in some cases it is right to choose 0.6 mm thickness duct another time it’s a must to choose a 1.5 mm or above according to the duct most critical dimensions also.
