Chrysler LLC Construction Standards

12/17/04

SECTION 15815 - METAL DUCTS

PART 1 - GENERAL

1.1  SUMMARY

  1. This Section includes rectangular, round, and flat-oval metal ducts and plenums for heating, ventilating, and air-conditioning systems in pressure classes from minus 4 to plus 10-inch wg.
  2. Related Sections include the following:
  3. Division7 Section "Joint Sealants" for fire-resistant sealants for use around duct penetrations and fire-damper installations in fire-rated floors, partitions, and walls.
  4. Division8 Section "Access Doors" for wall- and ceiling-mounted access doors for access to concealed ducts.
  5. Division10 Section "Louvers and Vents" for intake louvers and vents connected to ducts and installed in exterior walls.
  6. Division15 Section "Duct Insulation" for duct insulation.
  7. Division15 Section "Duct Accessories" for dampers, sound-control devices, duct-mounted access doors and panels, turning vanes, and flexible ducts.
  8. Division15 Section "Diffusers, Registers, and Grilles."
  9. Division15 Section "Testing, Adjusting, and Balancing" for air balancing and final adjusting of manual-volume dampers.

1.2  SYSTEM DESCRIPTION

  1. Duct system design, as indicated, has been used to select and size air-moving and air distribution equipment and other components of air system. Changes to layout or configuration of duct system must be specifically approved in writing by Architect/Engineer. Accompany requests for layout modifications with calculations showing that proposed layout would provide original design results without increasing system total pressure, decreasing air distribution performance, or increasing noise levels.

1.3  SUBMITTALS

  1. Product Data: For duct liner and sealing materials.
  2. Shop Drawings: Submit shop drawings for the ductwork layout, fabrication and installation of the Work. Prepare layouts in plan at not less than 1/8" = I'-0" and Equipment Room plans at not less than 1/4" = 1'-0". Prepare plan, elevation, section, and assembly details at not less than 1/2" = 1'-0" scale. Show sleeve placement locations at not less than 1/16" = 1'-0". Show typical details for critical areas, special conditions, anchorage, and support in the system. Include the following:
  3. Louver layouts, elevations, dimensions and tolerances. Provide head and jamb details including blade configuration and spacing. Provide details indicating method of anchorage to openings.
  4. Show details of the following:
  5. Fabrication, assembly, and installation, including plans, elevations, sections, components, and attachments to other work.
  6. Duct layout indicating pressure classifications and sizes on plans.
  7. Fittings.
  8. Reinforcement and spacing.
  9. Seam and joint construction.
  10. Penetrations through fire-rated and other partitions.
  11. Hangers and supports, including methods for building attachment, vibration isolation, and duct attachment.
  12. Coordination Drawings: Reflected ceiling plans drawn to scale and coordinating penetrations and ceiling-mounted items. Show the following:
  13. Other systems installed in same space as ducts.
  14. Ceiling- and wall-mounted access doors and panels required to provide access to dampers, valves, and other operating devices.
  15. Coordination with ceiling-mounted items, including lighting fixtures, diffusers, grilles, speakers, sprinkler heads, access panels, structural framing, and special moldings.
  16. Welding Certificates: Copies of certificates indicating welding procedures and personnel comply with requirements in "Quality Assurance" Article.
  17. Field Test Reports: Indicate and interpret test results for compliance with performance requirements.
  18. Record Drawings: Indicate actual routing, fitting details, reinforcement, support, and installed accessories and devices.
  19. Provide fully coordinated CAD shop drawings in format required by Owner. Sheet metal ductwork layouts shall serve as the base sheets for the Contractor Coordination Drawings, and indicate the coordination by the Contractor with sprinkler piping, other mechanical and electrical services, and the Structural and Architectural requirements. Ductwork joint, connection, reinforcing and elbow details shall be submitted prior to the first ductwork Shop Drawing submittal. At the completion of the project the Contractor shall submit to the Owner diskettes showing all mechanical record drawings.

1.4  QUALITY ASSURANCE

  1. Comply with NFPA90A, "Installation of Air Conditioning and Ventilating Systems," unless otherwise indicated.
  2. Comply with NFPA90B, "Installation of Warm Air Heating and Air Conditioning Systems," unless otherwise indicated.
  3. Comply with SMACNA Duct and fitting fabrication and installation standards.
  4. Welding Standards: Qualify welding procedures and welding personnel to perform welding processes for this Project according to AWS D1.1, "Structural Welding Code--Steel," for hangers and supports; AWSD1.2, "Structural Welding Code--Aluminum," for aluminum supporting members; and AWSD9.1, "Sheet Metal Welding Code," for duct joint and seam welding.

1.5  DELIVERY, STORAGE, AND HANDLING

  1. Deliver sealant and firestopping materials to site in original unopened containers or bundles with labels indicating manufacturer, product name and designation, color, expiration period for use, pot life, curing time, and mixing instructions for multicomponent materials.
  2. Store and handle sealant and firestopping materials according to manufacturer's written recommendations.

PART 2 - PRODUCTS

2.1  SHEET METAL MATERIALS

  1. Galvanized, Sheet Steel: Lock-forming quality; ASTMA653/A653M, G90 coating designation; mill-phosphatized finish for surfaces of ducts exposed to view.
  2. Stainless Steel: ASTMA480/A480M, Type316, sheet form with No.4 finish for surfaces of ducts exposed to view; and Type304, sheet form with No.1 finish for concealed ducts.
  3. Aluminum Sheets: ASTMB209Alloy3003, TemperH14, sheet form with standard, one-side bright finish for ducts exposed to view and with mill finish for concealed ducts.
  4. Reinforcement Shapes and Plates: Galvanized steel reinforcement where installed on galvanized, sheet metal ducts, compatible materials for aluminum and stainless-steel ducts.
  5. Tie Rods: Galvanized steel, 1/4-inch minimum diameter for 36-inch length or less; 3/8-inch minimum diameter for lengths longer than 36 inches

2.2  SEALANT MATERIALS

  1. Joint and Seam Sealants, General: The term "sealant" is not limited to materials of adhesive or mastic nature but includes tapes and combinations of open-weave fabric strips and mastics. Provide sealant as required so that the leakage rates specified are not exceeded. Duct sealant shall be applied in strict accordance with the manufacturer's written instructions.
  2. Products: Unless otherwise directed by the Owner, provide products by one of the following:
  3. For Use In Longitudinal Duct Seams

1)  Hard Cast CS-1001

2)  RectorSeal "Air-Lock"

3)  Ductmate 5511 M

  1. For External Application On Ductwork Joints

1)  Hard Cast IG-601

2)  Kingco 10-526

3)  Air Seal #11

4)  Foster 32-50.

  1. Joint and Seam Tape: 2 inches wide; glass-fiber fabric reinforced.
  2. Tape Sealing System: Woven-fiber tape impregnated with a gypsum mineral compound and a modified acrylic/silicone activator to react exothermically with tape to form a hard, durable, airtight seal.
  3. Joint and Seam Sealant: One-part, non-sag, solvent-release-curing, polymerized butyl sealant, formulated with a minimum of 75 percent solids.
  4. Flanged Joint Mastics: One-part, acid-curing, silicone, elastomeric joint sealants, complying with ASTMC920, TypeS, GradeNS, Class25, UseO.

2.3  HANGERS AND SUPPORTS

  1. Building Attachments: Concrete inserts, powder-actuated fasteners (where allowed by Owner) or structural-steel fasteners appropriate for building materials.
  2. Use powder-actuated concrete fasteners for standard-weight aggregate concrete or for slabs more than 4 inches thick.
  3. Exception: Do not use powder-actuated concrete fasteners for lightweight-aggregate concrete or for slabs less than 4 inches thick.
  4. Hanger Materials: Galvanized, sheet steel or round, threaded steel rod.
  5. Hangers Installed in Corrosive Atmospheres: Electrogalvanized, all-thread rod or galvanized rods with threads painted after installation.
  6. Straps and Rod Sizes: Comply with SMACNA's "HVAC Duct Construction Standards--Metal and Flexible" for sheet steel width and thickness and for steel rod diameters.
  7. Duct Attachments: Sheet metal screws, blind rivets, or self-tapping metal screws; compatible with duct materials.
  8. Trapeze and Riser Supports: Steel shapes complying with ASTMA36/A36M.
  9. Supports for Galvanized-Steel Ducts: Galvanized steel shapes and plates.
  10. Supports for Stainless-Steel Ducts: Stainless-steel support materials.
  11. Supports for Aluminum Ducts: Aluminum support materials, unless materials are electrolytically separated from ductwork.

2.4  RECTANGULAR DUCT FABRICATION

  1. General: Fabricate ducts, elbows, transitions, offsets, branch connections, and other construction with galvanized, sheet steel, according to the drawings and SMACNA's "HVAC Duct Construction Standards--Metal and Flexible." Comply with requirements for metal thickness, reinforcing types and intervals, tie-rod applications, and joint types and intervals.
  2. Lengths: Fabricate rectangular ducts in lengths appropriate to reinforcement and rigidity class required for pressure classification.
  3. Materials: Free from visual imperfections such as pitting, seam marks, roller marks, stains, and discolorations.
  4. Static-Pressure Classifications: Unless otherwise indicated, construct ducts to the following:

1.  Supply Ducts: 4-inch wg.

  1. Return Ducts: 2-inch wg, negative pressure.
  2. Toilet and General Exhaust Ducts: 2-inch wg, negative pressure.
  3. Cross Breaking or Cross Beading: Cross break or cross bead duct sides 19 inches and larger and 0.0359 inch thick or less, with more than 10 sq. ft. of unbraced panel area, unless ducts are lined.
  4. Regulators mounted on externally insulated ductwork shall have 16 gage elevated platform at least 1/8 inch higher than the thickness of the insulation. Damper shaft shall have Ventlok No. 607 bearing mounted on ductwork within elevated platform. If duct is enclosed in a furring, or in an inaccessible ceiling, extend the operating handle and install the regulator on the face of the ceiling. Where regulators are exposed in finished areas of the building, they shall be concealed type, Ventlok No. 666 with off-white round flush-mounted coverplate. Areas with inaccessible ceiling construction shall be adjusted prior to ceiling installation as specified in Division 15 Section "Testing, Adjusting And Balancing." Concealed damper regulators shall not be installed in any area without the written permission of the Architect/Engineer.
  5. Provide a manual volume damper in all spin-in or other duct connections to all supply devices and air exhaust devices not equipped with a damper.

2.5  AUXILIARY DRAIN PANS

  1. Furnish and install auxiliary drain pans under any piping, equipment, etc., for which a pan is shown on the Drawings and under all suspended horizontal air handling or fan-coil units, duct mounted hot water coils located above ceilings and under piping located over electrical equipment. The auxiliary drain pan shall be at least 6 inches larger in both dimensions than the equipment it is serving, and at least 2 inches deep.
  2. Drain pans shall be constructed of 18 gauge galvanized steel with all joints brazed. Pans shall be watertight and have hemmed edges.
  3. Drain pans shall have drain pipe connections of at least 3/4 inch, or as shown on the Drawings. Unless otherwise shown on the Drawings, route a 3/4 inch IPS galvanized steel or Type "L" copper tube to the nearest equipment room floor or hub drain independent of any air handling unit drains, etc.

2.6  ROUND DUCT FABRICATION

  1. Round Ducts: Fabricate supply ducts of galvanized steel according to SMACNA's "HVAC Duct Construction Standards--Metal and Flexible."
  2. Exposed round ducts shall be spiral duct with inside insulation.
  3. Double-Wall (Insulated) Ducts: Fabricate double-wall (insulated) ducts with an outer shell and an inner liner. Dimensions indicated on internally insulated ducts are inside dimensions.
  4. Thermal Conductivity (k-Value): 0.26 at 75 deg F mean temperature.
  5. Outer Shell: Base outer-shell metal thickness on actual outer-shell dimensions. Fabricate outer-shell lengths 2 inches longer than inner shell and insulation, and in metal thickness specified for single-wall duct.
  6. Insulation: 1-inch thick fibrous-glass insulation, unless otherwise indicated. Terminate insulation where internally insulated duct connects to single-wall duct or uninsulated components. Terminate insulation and reduce outer duct diameter to inner liner diameter.
  7. Perforated Inner Liner: Fabricate round and flat-oval inner liners with sheet metal having 3/32-inch diameter perforations, with an overall open area of 23 percent. Use the following sheet metal thicknesses and seam construction:
  8. Ducts 3 to 8 Inches in Diameter: 0.019 inch with standard spiral seam construction.
  9. Ducts 9 to 42 Inches in Diameter: 0.019 inch with single-rib spiral seam construction.
  10. Ducts 44 to 60 Inches in Diameter: 0.022 inch with single-rib spiral seam construction.
  11. Ducts 62 to 88 Inches in Diameter: 0.034 inch with standard spiral seam construction.
  12. Maintain concentricity of liner to outer shell by mechanical means. Retain insulation from dislocation by mechanical means.

2.7  ROUND SUPPLY AND EXHAUST FITTING FABRICATION

  1. 90-Degree Tees and Laterals and Conical Tees: Fabricate to comply with SMACNA's "HVAC Duct Construction Standards--Metal and Flexible," with metal thickness specified for longitudinal seam straight duct. Provide conical 90-degree tees at all take-offs to diffusers, unless noted otherwise.
  2. Diverging-Flow Fittings: Fabricate with a reduced entrance to branch taps with no excess material projecting from body onto branch tap entrance.
  3. Elbows: Fabricate in die-formed, gored, pleated, or mitered construction. Fabricate bend radius of die-formed, gored, and pleated elbows one and one-half times elbow diameter. Unless elbow construction type is indicated, fabricate elbows as follows:
  4. Mitered-Elbow Radius and Number of Pieces: Welded construction complying with SMACNA's "HVAC Duct Construction Standards--Metal and Flexible," unless otherwise indicated.
  5. Round Mitered Elbows: Welded construction with the following metal thickness for pressure classes from 2- to 10-inch wg.
  6. Ducts 3 to 14 Inches in Diameter: 0.028 inch.
  7. Ducts 15 to 26 Inches in Diameter: 0.034 inch.
  8. Ducts 27 to 50 Inches in Diameter: 0.040 inch.
  9. Round Elbows, 8 Inches and Smaller: Fabricate die-formed elbows for 45- and 90-degree elbows and pleated elbows for 30, 45, 60, and 90 degrees only. Fabricate nonstandard bend-angle configuration or nonstandard diameter elbows with gored construction.
  10. Round Elbows, 9 through 14 Inches: Fabricate gored or pleated elbows for 30, 45, 60, and 90 degrees, unless space restrictions require a mitered elbow. Fabricate nonstandard bend-angle configuration or nonstandard diameter elbows with gored construction.
  11. Round Elbows, Larger Than 14 Inches: Fabricate gored elbows, unless space restrictions require a mitered elbow.
  12. Die-Formed Elbows for Sizes through 8 Inches and All Pressures: 0.040 inch thick with two-piece welded construction.
  13. Round Gored-Elbow Metal Thickness: Same as non-elbow fittings specified above.
  14. Pleated Elbows for Sizes through 14 Inches and Pressures through 10-Inch wg, 0.022 inch.

2.8  SOUND ABSORBING SECTIONS

  1. The casing shall be constructed of a minimum 22 gage lock-forming galvanized steel with seams mastic filled to withstand 8 inch water gauge pressure differential. The interior partitions shall be made of minimum 24 gage perforated galvanized steel. Filler material shall be of 2 inch thick rigid inorganic mineral or glass fiber with 3.0 pound density. The filler shall be packed under not less than 5 percent compression to eliminate voids due to vibration. The casings of the absorbing device shall be double walled. The sizes indicated on the Drawings are minimum inside dimensions.

PART 3 - EXECUTION

3.1  DUCT INSTALLATION, GENERAL

  1. Drawings indicate arrangement of ducts, fittings, and accessories.
  2. Construct and install each duct system for the specific duct pressure classification indicated.
  3. Install round ducts in lengths not less than 12 feet unless interrupted by fittings.
  4. Install ducts with fewest possible joints.
  5. Install fabricated fittings for changes in directions, changes in size and shape, and connections.
  6. Install couplings tight to duct wall surface with a minimum of projections into duct.
  7. Install ducts, unless otherwise indicated, vertically and horizontally, parallel and perpendicular to building lines; avoid diagonal runs.
  8. Install ducts close to walls, overhead construction, columns, and other structural and permanent enclosure elements of building.
  9. Install ducts with a clearance of 1 inch plus allowance for insulation thickness.
  10. Conceal ducts from view in finished spaces. Do not encase horizontal runs in solid partitions, unless specifically indicated.
  11. Coordinate layout with suspended ceiling, fire dampers, pipe routing, lighting layouts, and similar finished work.
  12. Non-Fire-Rated Partition Penetrations: Where ducts pass through interior partitions and exterior walls, and are exposed to view, conceal space between construction opening and duct or duct insulation with sheet metal flanges of same metal thickness as duct. Overlap opening on four sides by at least 1-1/2 inches.
  13. Fire-Rated Partition Penetrations: Where ducts pass through interior partitions and exterior walls, install appropriately rated fire damper, sleeve, and firestopping sealant. Fire and smoke dampers are specified in Division15 Section "Duct Accessories." Firestopping materials and installation methods are specified in Division7 Section "Firestopping."

3.2  INSTALLATION OF ACOUSTIC INSULATION