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DUCTWORK <br />Section 15890 <br />15-1207 <br />B. Fabricate Ducts with minimum gauges and joint reinforcement as follows: <br />Duct Dimension <br />Minimum <br />Gauge <br />Joint Reinforcement <br />per CMC <br />Up through <br />12" <br />26 <br />Not Required <br />13" through <br />18" <br />24 <br />Not Required <br />19" through <br />30" <br />24 <br />C/4 <br />31" through <br />42" <br />22 <br />E/4 <br />43" through <br />54" <br />22 <br />F/2 <br />55" through <br />60" <br />20 <br />G/4 <br />61" through <br />84" <br />20 <br />1/2 <br />85" through <br />96" <br />20 <br />J/2 <br />Over 96" <br />18 <br />K/2 <br />C. Fabricate duct fittings to match adjoining ducts and to comply with duct requirements as <br />applicable to fittings. Fabricate elbows with center -line radius equal to 1.5 times associated <br />duct width. Fabricate to include single thickness turning vane in elbows where space does <br />not permit the above radius or where square elbows are shown. <br />D. Fabricate round supply connections at rectangular, plenum type fittings using spin -in type <br />fittings, complete with extractor and volume control damper. <br />E. Provide drive slip or equivalent flat seams for ducts exposed in the condition space or where <br />necessary due to space limitations. On ducts with flat seams, provide standard reinforcing <br />on inside of duct. Duct connection to outlet on exposed duct shall be full size of outer <br />perimeter of outlet flange. <br />2.05 ROUND/OVAL DUCT CONSTRUCTION: <br />A. Spiral lock seam prefabricated factory -built round and oval duct and fittings shall be used <br />wherever possible. Shop fabricated ducts shall be used only where retangular shaped ducts <br />are shown on plans or where transitions and special fittings cannot be prefabricated by <br />factory. Provide couplings to join each length of duct. <br />B. Fabricate duct fittings to match adjoining ducts and comply with duct requirements as <br />applicable to fittings. Except as noted otherwise, fabricate elbows as follows: <br />1. Center -line radius to be equal to 1.5 times associated duct width. <br />2. Provide two-piece, die stamped, 45 degree to 90 degree elbows for sizes up to 12 <br />inches. <br />3. Provide 5 piece 90 degree elbows for sizes 12" and above, conical tees, and conical <br />laterals. <br />4. All reducers to be located after tap. Reducers shall be long -taper style. Reducing <br />tees shall not be allowed. <br />11 <br />