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61 - 84 20 20 1-1/2 x 18 ga. 1-1/2 x 1-1/2 x 1/8 • <br /> Angle <br /> 85 - 96 18 20 1-1/2 x 18 ga. 1-1/2 x 1-1/2 x 3/16 <br /> Angle <br /> Over 96 18 20 2 x 18 ga. 2 x 2 x 1/4 Angle <br /> C. Duct dimensions on drawings indicate"inside clear' dimensions. <br /> Maintain "inside clear" dimensions. <br /> D. In addition to the requirements above, add supplemental bracing as <br /> necessary to prevent sagging, drumming, and vibration. <br /> E. Round prefabricated 26 gauge slip joint duct may be used on <br /> exhaust and return duct 12" and smaller and for runout duct to <br /> boxes, diffusers, registers, and grilles. <br /> 1. Secure duct sections and fittings with sheet metal screws. <br /> 2. Make connections of round duct to rectangular duct using <br /> "spin-in" collars with manual volume damper. <br /> 3. Transverse and longitudinal slip joints shall be sealed`��ith <br /> approved sealer. • <br /> F. Provide transverse joints of"S" and drive construction at least <br /> every eight feet on duct whose larger side is less than 18". Sea1 all <br /> transverse joints with joint sealant material. <br /> G. Provide transverse joints, or equivalent supplemental angle <br /> reinforcing on 4 foot centers on duct whose larger side is b eate-r <br /> than 18". At the contractor's option, duct mate or equal joint system <br /> may be substituted for "s" and drive construction. Seal all <br /> transverse joints with joint sealant material. <br /> H. Longitudinal seams shall be Pittsburg Lock or grooved seams <br /> closed tightly and evenly. Button punch snap lock longitudinal <br /> seam construction are not allowed. Seal longitudinal joints which <br /> prove to leak with joint sealant material. <br /> I. Cross break ductwork over 10" dimension, either side. <br /> J. Do not exceed 20 dea ee angle of slope for increase-in-area <br /> transitions. <br /> • <br /> ICT 99184 <br /> 15890 - 4 <br />