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DUCT ACCESSORIES <br />Section 15910 <br />15-1207 <br />6. Ceiling Cup, rotary cable, and worm gear shall be furnished as one piece for <br />installation with no linkage adjustment required or small parts to get lost on site. <br />Positive, direct, two-way damper control shall be provided with no sleeves, springs, <br />or screw adjustments. <br />7. Cable operated dampers shall be Metropolitan Air Technology, or equal Model #RT - <br />250 with model RT -CCR ceiling cup. <br />D. Rectangular Dampers with either height or width less than 16 inches: <br />1. Butterfly type damper with 18 -gauge steel or duct casing angle reinforced as <br />required. <br />2. Provide single thickness 16 -gauge minimum, galvanized steel blades, welded or <br />permanently bolted to continuous solid 3/8" minimum square shaft. Permanently <br />mark end shaft to indicate blade position and fit with a locking quadrant mounted on <br />outside of frame. Bearings shall be pressed into frame and designed for dynamic <br />requirements <br />E. Rectangular Dampers with either height or width greater than or equal to 16 inches: <br />1. Frame with 5" by 1 ", 16 -gauge galvanized steel channel. Blades to be 8" maximum <br />width, extruded aluminum, airfoil blade, opposed blade, having shafts/bearings <br />designed to meet dynamic requirements, positively locked to shafts. <br />2. Control shafts to be 3/8" square, plated steel, permanently marked to indicate blade <br />position and fitted with locking quadrant mounted on outside of frame. <br />3. Provide single thickness 16 -gauge minimum, galvanized steel blades, welded or <br />permanently bolted to 1/2" minimum diameter through shaft. Permanently mark end <br />shaft to indicate blade position and fit with a locking quadrant mounted on outside of <br />frame. Bearings shall be pressed into frame and designed for dynamic requirements <br />F. Round Dampers: <br />1. Frame shall be 20 gauge galvanized steel or duct casing reinforced. <br />2. Provide single thickness 18 gauge galvanized steel blade, welded or permanently <br />bolted to 3/8" minimum diameter through shaft. Permanently mark end shaft to <br />indicate blade position and fit with a locking quadrant mounted on outside of frame. <br />Damper to be provided with end bearing plates. <br />G. Backdraft Dampers: <br />1. Provide dampers with parallel blades, constructed of 16-ga. aluminum; provide <br />1/2 -inch diameter ball bearings, 1/2 -inch diameter steel axles spaced on 9 -inch <br />centers. Construct frame of 2 inches by 1/2 -inch by 1/8 -inch steel channel for face <br />areas 25 sq. ft. and under; 4 inches by 1-1/4 inches by 16-ga. channel for face areas <br />over 25 sq. ft. Provide galvanized steel finish on frame with aluminum touch-up. <br />H. Acceptable Manufacturers: <br />1. Air Balance Inc. <br />2. Ruskin Manufacturing Company <br />3. Greenheck <br />KI <br />