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SECTION 15891 HVAC SHEET METAL DUCTWORK

PART 1 - GENERAL 1.01 RELATED DOCUMENTS A. Drawings and general provisions of Contract including General and Supplementary Conditions, Division 1 Specification Sections, and the Mechanical General Requirements Section 15050 apply to work of this Section, as if repeated herein.

1.02

DEFINITIONS A. Ductwork sizes on Drawings state inside clear dimensions. For acoustically lined and internally insulated ductwork, maintain ductwork sizes inside lining or insulation.

1.03

REFERENCES A. Fabricate ductwork in accordance with latest edition of SMACNA HVAC Duct Construction Standards and ASHRAE handbooks unless more stringently detailed. Construct ductwork to conform to NFPA 90 A, Air Conditioning and Ventilating Systems and NFPA 96, Standard for the Installation of Equipment for the Removal of Smoke and Grease-Laden Vapors from Commercial Cooking Equipment, latest edition. Ductwork shall be seismically supported and braced per the SMACNA "Guidelines for Seismic Restraints of Mechanical Systems and Plumbing Piping Systems."

B.

[C.

1.04

SUBMITTALS A. B. Submit in accordance with Division 1 and Section 15050. Submit typical shop standards and/or SMACNA details for each class of duct specified, including particulates such as gauge sizes, welds, joint details, and fitting configurations prior to start of work.

C.

Submit written report confirming ductwork has been fabricated and installed in accordance with SMACNA standards. Submit shop drawings of ductwork only when it is necessary to deviate from the design drawings.

D.

1.05

FLOW DIAGRAMS A. Predicated upon Project magnitude, Construction Documents may include flow diagrams as a part of the working Drawings. These flow diagrams are not for the purpose of giving physical dimensions or locations but rather to make clear the interconnections, by the duct systems, of the various units of the process. If an item is shown on either the flow diagram or the Drawings, but not on both, it will be assumed that the contractor has included such item in his estimate of the cost of the work and that he shall provide same.

PART 2 - PRODUCTS 2.01 ACCEPTABLE MANUFACTURERS A. Manufactured Round and Oval Ductwork: 1. 2. 3. 4. 5. 6. 2.02 MATERIALS A. Galvanized Ductwork: Fabricated using galvanized steel sheet of lock forming quality, having zinc coating of 1.25 ounces per square foot for each side per ASTM A 525, G 90. All ductwork, supports, and reinforcement to be galvanized unless otherwise noted. Steel ductwork (kitchen grease removal): 16 gauge, welded steel. Support Materials: Provide galvanized angle iron, channels, stays, and rods. Do not use raw steel. Fasteners: Use galvanized rivets and bolts throughout; sheet metal screws are acceptable on low pressure ducts only. Buckley Spiral Metal Corporation United Sheet Metal Metal Manufacturing PAR, Inc. Spiro-Fab, Inc.

B. C.

D.

E.

Proprietary Duct Joint Systems: "Ductmate 35" consisting entirely of metal components. PVC components will not be acceptable. Sealant Material: Water and fire resistant, compatible with mating

F. materials. 2.03

DUCT CONSTRUCTION CLASSIFICATIONS A. General: Construct and seal ductwork in accordance with SMACNA pressure classifications and seal classes listed for ductwork systems involved. Rectangular Ductwork: 1. +1" WG Class with Seal Class C: Supply air ductwork downstream of fan coils. +2" WG Class with Seal Class B: Return air ductwork, general exhaust ductwork.

B.

2.

C.

Round or Oval Ductwork: Same as rectangular ductwork except do not use round ductwork in negative static pressure greater than -2" WG or oval ductwork in any negative static pressure applications whatsoever. Materials: Use galvanized steel sheet for all applications listed except use steel in constructing ductwork for kitchen hood exhaust systems. Provide kitchen hood exhaust system per NFPA 96.

D.

2.04

SHEET METAL PLENUMS A. Construct plenums and equipment casings in accordance with Section 6 of SMACNA standards except that sheet metal shall be 16 gauge minimum throughout.

PART 3 - EXECUTION 3.01 FABRICATION A. No variation of duct configuration or sizes permitted except by written permission of the Architect. Complete metal ducts within themselves with no single partition between ducts. Open corners are not acceptable.

B.

C.

Lap metal ducts in direction of air flow. Hammer down edges and slips to leave smooth duct interior. Fabricate tees, bends, and elbows with radius of not less than 1-1/2 times width of duct on center line. Where rectangular elbows are used, provide turning vanes. All mitered elbows shall have single thickness turning vanes; dual wall airfoil type blades are not acceptable. Increase duct sizes gradually, not exceeding 15" divergence wherever possible. Maximum divergence upstream of equipment to be 30" and 45" convergence downstream. Rigidly construct metal ducts with joints mechanically tight, substantially airtight, braced and stiffened so as not to breathe, rattle, vibrate, or sag. Seal duct joints and connections with sealant as ducts are being assembled. Provide necessary baffling in mixed air plenums to ensure good mixed air temperature. Fabricate round and oval duct fittings with spiral or continuously welded seams. Joints shall be 4" slip type, cemented, brazed, or electric welded. Prime coat welded joints. Fabricate elbows of 5-piece construction. Provide standard 45 degree takeoffs unless otherwise indicated. Reinforce plenum or casing door frames with galvanized steel angles tied to horizontal and vertical plenum supporting angles. Install hinged access doors for access to equipment, for cleaning, and inspection. Fabricate seams and joints in kitchen hood exhaust and dishwasher exhaust ductwork liquid tight with continuous external welds.

D.

E.

F.

G.

H.

I.

J.

3.02

INSTALLATION A. Provide openings in ductwork to accommodate thermometers and controllers. Provide pitot tube openings for testing of systems, complete with metal cam with spring device or screw to ensure against air leakage. Where openings are provided in insulated ductwork, install insulation material inside a metal ring.

B.

Mount duct-type smoke detectors on the ductwork under this Section of the Specifications. All mounting arrangements, holes cut into ductwork, sealing of openings along with ceiling and access doors for each duct-type detector shall be provided under this Section of the Specifications. Duct detectors along with all sampling tubes and accessories shall be furnished under Division 16. Clean ductwork as it is installed to remove dirt and dust. During installation, close duct openings and open ends with temporary covers to keep construction duct out of the duct systems. Construct ductwork with sufficient clearance around equipment to allow normal operating and maintenance activities of equipment. At each point where ducts pass through partitions, seal joints around duct with noncombustible material. Where manufactured duct joint systems such as "Ductmate" are employed, install components in strict accordance with the manufacturer's recommendations. Bolt metal corner pieces except where bolting access is restricted, in which case metal corner clips shall be used. Install ducts and supports in accordance with SMACNA standards. Adequately attach hangers to the building structure. Refer to Section 15090. Prior to operation or test and balance, clean duct systems with high power vacuum machines. Protect equipment which may be harmed by excessive dirt with filters, or bypass during cleaning. Provide adequate access into ductwork for cleaning purposes.

C.

D.

E.

F.

G.

H.

**END OF SECTION**

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