SECTION 15890

DUCTWORK

PART 1 GENERAL

WORK INCLUDED

Low pressure ducts.

Medium and high pressure ductwork.

Casings.

Fibrous glass ductwork.

Buried ducts.

Kitchen hood ductwork.

Duct cleaning.

RELATED WORK

Section 09900 - Painting: Weld priming, weather resistant, paint or coating.

Section 15140 - Supports and Anchors: Sleeves.

Section 15250 - Duct Insulation.

Section 15910 - Ductwork Accessories.

Section [____] - Air Terminal Units.

Section 15932 - Terminal High Velocity Units.

Section 15936 - Air inlets and Outlets.

Section 15990 - Testing, Adjusting and Balancing.

REFERENCES

ASHRAE - Handbook 1981 Fundamentals; Chapter 33 - Duct Design.

ASHRAE - Handbook 1983 Equipment; Chapter 1 - Duct Construction.

ASTM A 90 - Weight of Coating on Zinc-Coated (Galvanized) Iron or Steel Articles.

ASTM A 167 - Stainless and Heat-Resisting Chromium-Nickel Steel Plate, Sheet, and Strip.

ASTM A 525 - General Requirements for Steel Sheet, Zinc-

Coated (Galvanized) by the Hot-Dip Process.

ASTM A 527 - Steel Sheet, Zinc-Coated (Galvanized) by Hot-Dip Process, Lock Forming Quality.

ASTM B209 - Aluminum and Aluminum Alloy Sheet and Plate.

ASTM C 14 - Concrete Sewer, Storm Drain, and Culvert Pipe.

ASTM C 443 - Joints for Circular Concrete Sewer and Culvert Pipe, Using Rubber Gaskets.

NFPA 90A - Installation of Air Conditioning and Ventilating Systems.

NFPA 90B - Installation of Warm Air Heating and Air Conditioning Systems.

NFPA 96 - Installation of Equipment for the Removal of Smoke and Grease-Laden Vapors from Commercial Cooling Equipment.

SMACNA - Low Pressure Duct Construction Standards.

SMACNA - High Pressure Duct Construction Standards.

SMACNA - Fibrous Glass Duct Construction Standards.

UL 181 - Factory-Made Air Ducts and Connectors.

DEFINITIONS

Duct Sizes: Inside clear dimensions.	For lined ducts, maintain sizes inside lining.

Low Pressure: Three pressure classifications: 1/2 inch WG (125 Pa) positive or negative static pressure and velocities less than 2,000 fpm (10 m/sec); 1 inch WG (250 Pa) positive or negative static pressure and velocities less than 2,500 fpm (12.7 m/sec) and 2 inch WG (500 Pa) positive or negative static pressure and velocities less than 2,500 fpm (12.7 m/sec).

Medium Pressure: Three pressure classifications: 3 inch WG (750 Pa) positive or negative static pressure and velocities less than 4,000 fpm (20 m/sec), 4 inch WG (1,000 Pa) positive static pressure and velocities greater than 2,000 fpm (10 m/sec), 6 inch WG (1,500 Pa) positive static pressure and velocities greater than 2,000 fpm (10 m/sec) and

High Pressure: 10 inch WG (4300 Pa) positive static pressure and velocities greater than 2,000 fpm (10 m/sec).

REGULATORY REQUIREMENTS

Construct ductwork to [NFPA 90A] [and] [NFPA 90B] [and]

[NFPA 96] standards.

SUBMITTALS

Submit [shop drawings] [and] [product data] under provisions of Section [01300.] [01340.]

Indicate duct fittings, particulars such as gages, sizes, welds, and configuration prior to start of work for [low pressure] [medium and high pressure] [kitchen hood exhaust] [glass fiber duct] [________] systems.

Submit samples under provisions of Section [01300.] [01340.]

Submit [two] [________] samples of typical shop fabricated [medium or high pressure duct fittings.] [________.]

Submit manufacturer's installation instructions for glass fiber ducts under provisions of Section [01300.] [01340.]

Submit manufacturer's certificate under provisions of Section [01400] [01405] that installation of glass fiber ducts meets or exceeds recommended fabrication and installation requirements.

DELIVERY, STORAGE, AND HANDLING

Deliver products to site under provisions of Section [01600.] [01610.]

Store and protect products under provisions of Section [01600.] [01620.]

Protect [________] from [____________] by [____________.]

PART 2 PRODUCTS

ACCEPTABLE MANUFACTURERS

[_________________________________.]

[_________________________________.]

[_________________________________.]

Substitutions: Under provisions of Section [01600.] [01630.]

MATERIALS

General: Non-combustible or conforming to requirements for Class 1 air duct materials, or UL 181.

Steel Ducts: [ASTM A525] [or] ASTM A527] galvanized steel sheet, lock-forming quality, having zinc coating of 1.25 oz per sq ft (382 g/sq m) for each side in conformance with ASTM A90.

Aluminum Ducts: ANSI/ASTM B209; aluminum sheet, alloy 3003-H14. Aluminum Connectors and Bar Stock: Alloy 6061-T6 or of equivalent strength.

Flexible Ducts: [Interlocking spiral of galvanized steel or aluminum construction] [or] [fabric supported by helically wound spring steel wire or flat steel bands]; rated to [2 inches WG (500 Pa) positive and 1.5 inches WG (375 Pa) negative for low pressure ducts] [and 15 inches WG (3.75 kPa) positive or negative for medium high pressure ducts.]

Insulated Flexible Ducts: Flexible duct wrapped with flexible glass fiber insulation, enclosed by seamless aluminum pigmented plastic vapor barrier jacket; maximum 0.23 K value at 75 degrees F (0.034 KSI at 24 degrees C).

Fibrous Glass Ducts: UL 181; [one inch (25 mm)] [1-1/2 inch (40 mm)] thick rigid glass fiber with aluminum foil, glass scrim and kraft or plastic jacket vapor barrier; maximum 0.23 K value at 75 degrees F (0.034 KSI at 24 degrees C).

Stainless Steel Ducts: ASTM A167, Type [304.] [____.]

Glass Fiber Reinforced Plastic Ducts: [________________.]

Coating For Buried Ducts: Asphalt base, [________], manufactured by [____________.]

Concrete Ducts: ASTM C14; hub and spigot concrete sewer pipe with ANSI/ASTM C443 joints, rubber gaskets.

Fasteners: Rivets, bolts, or sheet metal screws.

Sealant: Non-hardening, water resistant, fire resistive, compatible with mating materials; liquid used alone or with tape, or heavy mastic.

Hanger Rod: Steel, galvanized; threaded both ends, threaded one end, or continuously threaded.

LOW PRESSURE DUCTWORK

Fabricate and support in accordance with SMACNA Low Pressure Duct Construction Standards and ASHRAE handbooks, except as indicated. Provide duct material, gages, reinforcing, and sealing for operating pressures indicated.

Size round ducts installed in place of rectangular ducts in accordance with ASHRAE table of equivalent rectangular and round ducts. No variation of duct configuration or sizes permitted except by written permission.

Construct T's, bends, and elbows with radius of not less than 1-1/2 times width of duct on centerline. Where not possible and where rectangular elbows are used, provide [air foil] turning vanes. Where acoustical lining is indicated, provide turning vanes of perforated metal with glass fiber insulation.

Increase duct sizes gradually, not exceeding 15 degrees divergence wherever possible. Divergence upstream of equipment shall not exceed 30 degrees; convergence downstream shall not exceed 45 degrees.

Provide easements where low pressure ductwork conflicts with piping and structure. Where easements exceed 10 percent duct area, split into two ducts maintaining original duct area.

Connect flexible ducts to metal ducts with [adhesive only,] [liquid adhesive plus tape.] [draw bands.] [adhesive plus sheet metal screws.]

Use crimp joints with or without bead for joining round duct sizes [8] [__] inch ([200] [__] mm) and smaller with crimp in direction of air flow.

Use double nuts and lock washers on threaded rod supports.

MEDIUM AND HIGH PRESSURE DUCTS

Fabricate and support in accordance with SMACNA High Pressure Duct Construction Standards and ASHRAE handbooks, except as indicated. Provide duct material, gages, reinforcing, and sealing for operating pressures indicated.

Construct T's, bends, and elbows with radius of not less than 1-1/2 times width of duct on centerline. Where not possible and where rectangular elbows are used, provide [air foil] turning vanes. Where acoustical lining is required, provide turning vanes of perforated metal with glass fiber insulation. Weld in place.

Transform duct sizes gradually, not exceeding 15 degrees divergence and 30 degrees convergence.

Fabricate continuously welded medium and high pressure round and oval duct fittings two gages heavier than duct gages indicated in SMACNA Standard. Joints shall be minimum 4 inch (100 mm) cemented slip joint, brazed or electric welded. Prime coat welded joints.

Provide standard 45 degree lateral wye takeoffs unless otherwise indicated where 90 degree conical tee connections may be used.

CASINGS

Fabricate casings in accordance with SMACNA Low Pressure Duct Construction Standards and SMACNA High Pressure Duct Construction Standards and construct for operating pressures indicated.

Mount floor mounted casings on [4] [__] inch ([100] [__] mm) high concrete curbs. At floor, rivet panels on 8 inch (200 mm) centers to angles. Where floors are acoustically insulated, provide liner of 18 gage (1.20 mm) galvanized expanded metal mesh supported at 12 inch (300 mm) centers, turned up 12 inches (300 mm) at sides with sheet metal shields.

Reinforce door frames with steel angles tied to horizontal and vertical plenum supporting angles. Install hinged access doors where indicated or required for access to equipment for cleaning and inspection. [Provide clear wire glass observation ports, minimum 6 X 6 inch (150 X 150 mm) size.]

Fabricate acoustic casings with reinforcing turned inward. Provide 16 gage (1.50 mm) back facing and 22 gage (0.80 mm) perforated front facing with 3/32 inch (2.4 mm) diameter holes on 5/32 inch (4 mm) centers. Construct panels 3 inches (75 mm) thick packed with 4.5 lb/cu ft (72 kg/cu m) minimum glass fiber media, on inverted channels of 16 gage (1.50 mm).

FIBROUS GLASS DUCTS

Fabricate and install in accordance with SMACNA Fibrous Glass Duct Construction Standards, except as indicated.

Machine fabricate fibrous glass ducts and fittings. Make only minor on site manual adjustments.

Staple duct joints and tape with [3 inch (75 mm) wide 2 mil (0.05) thick or 2 inch (50 mm) wide 3 mil (0.75 mm) thick aluminum pressure sensitive tape, UL approved.] [2 inch (50 mm) wide pressure sensitive tape, UL approved.] [3 inch (75 mm) wide heat activated chemical bonding tape.]

Do not use fibrous glass ducts within 12 inches (300 mm) of electric or fuel fired heaters.

BURIED UNDERGROUND DUCTS

Buried ducts may be [concrete encased sheet metal] [PVC jacketed sheet metal] [fiber glass reinforced plastic] [concrete] as indicated.

Fabricate metal ductwork in accordance with SMACNA Low Pressure Duct Construction Standards, except as indicated. Fabricate using two gages heavier material than indicated for 2 inch WG (500 Pa) pressure class.

KITCHEN HOOD EXHAUST DUCTWORK

Fabricate in accordance with SMACNA Low Pressure Duct Construction Standards, High Pressure Duct Construction Standards, and NFPA 96.

Construct of 16 gage (1.37 mm) carbon steel or 18 gage (1.09 mm) stainless steel, using continuous external welded joints.

PART 3 EXECUTION

INSTALLATION

Obtain manufacturer's inspection and acceptance of fabrication and installation of glass fiber ductwork at beginning of installation.

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

Locate ducts with sufficient space around equipment to allow normal operating and maintenance activities.

Slope underground ducts to plenums or low pumpout points at l:500. Provide access doors for inspection.

Coat buried, metal ductwork without factory jacket with one coat [and seams and joints with additional coat] of asphalt base protective coating.

Insulate buried supply duct runs over [70] [__] feet ([20] [__] m) long with one inch (25 mm) thick insulation covered with plastic vapor barrier.

Encase buried metal ductwork in 3 inch (75 mm) minimum of concrete. Provide adequate tie-down points to prevent ducts from floating during concrete placement. Introduce no heat into ducts for 20 days following placement of concrete.

Set plenum doors 6 to 12 inches (150 to 300 mm) above floor. Arrange door swings so that fan static pressure holds door in closed position.

Connect terminal units to medium or high pressure ducts [directly or] with one foot (300 mm) maximum length of flexible duct. Do not use flexible duct to change direction.

Connect diffusers or troffer boots to low pressure ducts with 5 feet (1.5 m) maximum length of flexible duct. Hold

in place with strap or clamp.

Provide residue traps in kitchen hood exhaust ducts at base of vertical risers with provisions for cleanout. Use stainless steel [or painted galvanized steel] for ductwork exposed to view and stainless steel or galvanized steel for ducts where concealed.

Fibrous glass ductwork may be substituted for internally or externally insulated or uninsulated low pressure sheet metal ductwork.

During construction provide temporary closures of metal or taped polyethylene on open ductwork to prevent construction dust from entering ductwork system.

DUCTWORK APPLICATION SCHEDULE

AIR_SYSTEM______________________MATERIAL___________________

Low Pressure Supply	Steel, Aluminum, Fibrous

(Heating Systems)	Glass

Low Pressure Supply	Steel, Aluminum, Fibrous

(System with Cooling Coils	Glass

Buried Supply or Return	Steel, Concrete, Glass Fiber

Reinforced Plastic

Medium and High Pressure	Steel

Supply

Return and Relief	Steel, Aluminum

General Exhaust	Steel, Aluminum

Kitchen Hood Exhaust	Steel, Stainless Steel

Dishwasher Exhaust	Steel, Stainless Steel, Glass Fiber

Reinforced Plastic

Fume Hood Exhaust	Stainless Steel, Glass Fiber

Reinforced Plastic

Outside Air Intake	Steel

Combustion Air	Steel

Evaporative Condenser	Steel

Intake and Exhaust

Emergency Generation	Steel

Ventilation

ADJUSTING AND CLEANING

Clean duct system and force air at high velocity through duct to remove accumulated dust. To obtain sufficient air, clean half the system at a time. Protect equipment which may be harmed by excessive dirt with temporary filters, or bypass during cleaning.

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.

END OF SECTION