SECTION 15841 LOW PRESSURE STEEL DUCTWORK PART 1 GENERAL 1.01 SUMMARY A. Related Sections: 1. 15180 - Mechanical Systems Insulation. 2. 15940 - Outlets (HVAC). 3. 15991 - Testing and Balancing. 1.02 SUBMITTALS A. Properly identified manufacturer's data and shop drawings before starting work. 1.03 REFERENCES A. Sheet Metal and Air-conditioning Contractors National Association (SMACNA) Low Velocity Duct Manual. B. National Fire Protection Association (NFPA) 90-A Standard for Air-conditioning and Ventilating Systems. PART 2 PRODUCTS 2.01 EQUIPMENT A. Ductwork: 1. Galvanized steel ductwork, designed according to the latest Edition of SMACNA, Low Velocity Duct Manual and as shown on drawings. a. Cross-break flat areas over 18 inches in duct dimension. 2. Gage Stamp: Fabricated ductwork shall have manufacturer's gage stamp intact. ****** ***** **** *** ** * ** *** **** ***** ****** NOTE TO SPECIFIER: Choose either the paragraph above or below that best meets project conditions. ****** ***** **** *** ** * ** *** **** ***** ****** B. Ductwork: Project No. SPECIFICATION GUIDELINES 15841-1
1. Includes supply ductwork from air handling units, ventilating units and exhaust, outside and return air ductwork. 2. Construction: a. Galvanized steel, designed and constructed according to the more stringent requirements of either the latest edition of SMACNA Low Velocity Duct Construction Standards or as specified. 1) Ductwork gages shall comply with the following: Greatest Dimension US Gage 0" to 12" 26 13" to 30" 24 31" to 60" 22 61" to 90" 20 over 90" 18 2) Ductwork dimensions shown on the drawings are clear inside dimensions. b. Flexible Collar Connections: Make connections to and from units with flexible collars not less than 4 inches long, secured by peripheral strap iron, using 30 ounce neoprene coated glass fabric by Ventglas or accepted equivalent. c. Hangers: 1) Hang horizontal ducts at intervals not exceeding 8 feet, with hangers of 16 gage by 1 inch wide galvanized band iron on ducts up to and including 30 inches wide and 12 gage by 1-1/2" wide galvanized band iron on ducts over 30 inches wide. 2) Extend hangers down and fasten underneath duct in addition to both sides of duct. d. Splitters and Dampers: 1) Provide as necessary for proper regulation of air distribution system. a) Locate splitters and dampers to be easily adjustable after work is completed. Provide a set screw locking device for each splitter or damper. b) On insulated ducts, place locking device on Project No. SPECIFICATION GUIDELINES 15841-2
a bracket so set screw is on surface of insulation and is easily operable. c) Use Ventlock or Young Regulator. 2) Sheet Metal Gage: Construct splitters and dampers of galvanized steel 1 gage heavier than installed duct. e. Standing Seams: 1) 1 inch on widths of 24 inches to 48 inches. 2) 1-1/2" on widths over 48 inches. 3) Provide reinforcing bars or angles on widths of 60 inches and over. f. Longitudinal Seams and Transverse Joints: Make flat and smooth inside. g. Slip Joints: Make flat and smooth and in direction of air flow. h. Exhaust, Supply, and Return Duct System Joint Sealing Tape: Permaceil #691AF. i. Plenums: 1) Construct, design, and test plenums according to SMACNA as specified. 2) Make joints angle reinforced pocket type and provide fully gasketed joints between plenums and filter sections. 3) Internally line surfaces of plenums as specified in Section 15180. C. Grilles, Registers, and Diffusers: 1. Aluminum construction complete with specified accessories and baked enamel finish. 2. Acceptable Manufacturers: a. Air Guide. b. Carnes. c. Krueger. d. Metalaire. e. Price. f. Titus. D. Joint Sealant: Flexomastic No.210 with fiberglass membrane for weatherproofing as manufactured by Weatherproofing Products, Inc. or accepted equivalent. E. Ductwork Supports and Hangers: Project No. SPECIFICATION GUIDELINES 15841-3
1. Supports: Galvanized steel angles or channels. a. Provide minimum support sizes as follows: Duct Width Angle Size To 24" 1-1/4" X 1-1/4" X 1/8" 25" to 36" 1-1/2" X 1-1/2" X 1/8" 37" to 54" 2" X 2" X 3/16" Above 54" 2" X 2" X 1/4" 2. Hangers: Galvanized steel straps. F. Fire Dampers: Provide fire dampers as indicated on Construction Documents for ducts penetrating fire separations. 1. Construct dampers and install according to UL 555 and NFPA 90-A. 2.02 FABRICATION a. Fire Dampers: 100 percent free area, blade out of airstream type unless otherwise indicated, UL listed. b. Fire Dampers for Vertical Air Flow: Actuate by 2 stainless steel springs exerting force 2-1/2 times greater than required to close damper. c. Provide access doors. A. Fabricate work according to SMACNA manuals, except as otherwise indicated. B. Seams and Joints: Make airtight as possible. Seal joints with 4 inch wide cloth tape with bonding agent, except ductwork exposed to weather shall have joints sealed with specified joint sealant. PART 3 EXECUTION 3.01 INSPECTION A. Do not proceed with the work of this section until conditions detrimental to the proper and timely completion of the work have been corrected in an acceptable manner. 3.02 INSTALLATION A. Install ductwork materials and accessories according to the Project No. SPECIFICATION GUIDELINES 15841-4
latest edition of SMACNA Low Velocity Duct Construction Standards as specified. These written specifications shall take precedence in case of conflict. B. Thoroughly clean ductwork before attempting test and balance. C. Where interferences arise during construction, make transition or division of ductwork on a basis of pressure drop equivalent to the original size. Obtain acceptance from A/E before fabrication. D. Apply cloth tape with bonding agent to joints of ductwork installed in interior spaces. E. Apply Flexomastic weatherproofing with smooth finish to joints of ductwork exposed to weather as recommended by joint sealant manufacturer, with at least 2 final coats of No.210. F. Install strap hangers from inserts, clip angles, or clamps secured to structure. 1. Do not hang from expansion bolts in tension. 2. Bend hangers under ductwork at least 2 inches. 3. Secure hangers for ducts 48 inches wide and over to bottom and sides of duct at 6 inches on center. G. Support vertical ducts at each floor with minimum of 2 angle or channel supports secured to duct and spanning shaft opening. 1. Fasten structural members to floor in a manner acceptable to A/E. END OF SECTION Project No. SPECIFICATION GUIDELINES 15841-5