Round: 22 gauge spiral duct from the fan to 28 gauge spiral ducts for the end
branch ducts, No extra reinforcement required with beaded sleeve joints.
. . . A light weight system
Flat Oval: 20 gauge flat oval duct from the fan to 28 gauge spiral round ducts
for the end branch ducts, F-20 reinforcement is used on 4 foot centers
for only the flat surfaces.
. . . A medium weight system
Rectangular: 18 gauge duct from the fan with H-48 reinforcement plus F+rod intermediate
reinforcement to 22 gauge with no reinforcement or 26 gauge with
A-26 reinforcement on 5 foot centers for the end branch ducts.
. . . A heavy weight system
