Orange County NC Website
Browse       Search
DocuSign Envelope ID: E9612703-F25B-492D-9C8C-EC3F9728ECE6 <br /> All ducts larger than 24" in either dimension shall be provided with stiffeners which may be either <br /> transverse joints or angle bracing as indicated above. The center to center spacing of stiffeners shall <br /> not be over 4'-0" for ducts not exceeding 60". Bracing angles shall be galvanized iron. <br /> All rectangular ducts over 10" wide shall be cross-broken between joints. <br /> F. Turning Vanes: <br /> All square elbows shall have factory made double thickness turning vanes. Where space permits, <br /> long radius elbows may be used in lieu of square elbows with turning vanes. Inside radius of long <br /> radius elbows shall be equal to V2 duct width. Vaned turns shall be Barber-Colman "air turns" or <br /> Tuttle and Bailey "duct turns" or approved equal. <br /> G. Clearances: <br /> In the design and sizing of ducts concealed in ceiling spaces, an attempt has been made to allow <br /> clearances for light fixtures,piping,structure,and suspended ceiling system. However,the HVAC <br /> Contractor shall,in all cases,take field measurements before any duct is fabricated to insure that duct <br /> sizes shown will fit into available space without interferences with lighting fixtures, structures, <br /> piping, and ceiling systems. In case of conflict, notify Architect/Engineer before proceeding for <br /> instructions for installation and relocate and/or resize as required and directed without additional cost <br /> to contract. <br /> H. Flexible Duct Sections: <br /> All duct connections to fans and air handler units shall be made with U.L. approved flame proof <br /> flexible connectors, sewed and sealed air tight. <br /> Flexible duct for connections between diffusers and branch ducts shall be a factory fabricated <br /> assembly consisting of an inner sleeve, insulation and an outer moisture barrier. The inner sleeve <br /> shall be constructed of a continuous vinyl-coated spring steel wire helix fused to a continuous layer <br /> of vinyl-coated fiberglass mesh. A 1-1/4"thick insulating blanket of fiberglass wool shall encase the <br /> inner sleeve and be sheathed with an outer moisture barrier of a reinforced metalized mylar/neoprene <br /> laminate of low permeability,and shall be listed by the Underwriters'Laboratories. The flexible duct <br /> shall be Thermaflex II Type NIKE or approved equal and shall not exceed 6 feet in length. All <br /> connectors, and accessories shall be manufactured by duct supplier and all components suitable for <br /> use on a system of these pressures and velocities. Duct shall be installed strictly per manufacturer's <br /> instructions,with factory made fittings and accessories,spin-ins with dampers shall be used for each <br /> take-off connection. <br /> Flexible ductwork to be run as straight as possible with squashing and kinking limited so that free <br /> area is not restricted below 80%. Any turn in excess of 45°to be a metal section,or a boxed plenum <br /> at grill connection. <br /> 15H-27 <br />