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PROJECT NO. #######
PROJECT TITLE
CONTRACT TITLE
SECTION 15890
DUCTWORK
PART I - GENERAL
1.01 WORK INCLUDED
A. Types of ductwork required for this project include the following:
1. Sheet Metal Ductwork
2. Flexible Ductwork
3. Air Plenums
B. Construct all ductwork located between air handling unit and variable air volume boxes
for 4” w.g. pressure class per SMACNA requirements and as listed herein.
C. Construct all other ductwork for 2” w.g. pressure class, except as noted, per SMACNA
requirements.
1.02 QUALITY ASSURANCE
A. Installer: A firm with at least three years of successful installation experience on projects
similar to that required for this work.
1. For work on fiberglass ductwork provide statement from manufacturer indicating
that the manufacturer accepts this fabricator to be a qualified fabricator.
2. No fiberglass ductwork; no fiberglass in air stream.
B. SMACNA Compliance: Comply with applicable portions of Sheet Metal and Air
Conditioning Contractor's National Association (SMACNA) for all work in this section.
C. ASHRAE Standards: Comply with American Society of Heating, Refrigerating and Air
Conditioning Engineers, Inc. (ASHRAE) recommendations, latest edition, for all work in
this section.
D. NFPA Compliance: Comply with ANSI/NFPA 90A, "Standard for the Installation of Air
Conditioning and Ventilating Systems," and ANSI/NFPA 90B, "Standard for the
Installation of Warm Air Heating and Air Conditioning Systems."
E. Patch, repair or replace ductwork as required. All ductwork shall be made airtight with
1% maximum or less leakage of design flow. Repair or replace ducts and joints as
required to the satisfaction of the University's Representative.
1.03 SUBMITTALS
A. Product Data: Submit manufacturer's specifications on manufactured products and
factory-fabricated ductwork, used for work of this section.
B. Record Drawings: At project close-out, submit Record Drawings of installed ductwork,
duct accessories, and outlets and inlets in accordance with requirements of Division 1.
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PROJECT TITLE
CONTRACT TITLE
PART II - MATERIALS
2.01 GENERAL
A. All standing seams and transverse joints in ALL sheet metal ductwork shall be covered
with 4” wide strip of 6-ounce canvas and lagging adhesive to assure airtight joints.
Pressure-sensitive tapes not acceptable.
B. No interior duct liner accepted.
2.02 TWO-INCH PRESSURE CLASS DUCTWORK MATERIALS
A. Sheet Metal Ductwork: Except as otherwise indicated, fabricate ductwork with
commercial grade of galvanized steel.
B. External Duct Lining:
1. Provide external duct lining only:
2. Oversize duct to maintain low pressure.
C. Round supply ductwork shall be of the same materials, gauges, and construction as that
indicated for 4” pressure class ductwork.
D. Ductwork Support Materials: Except as otherwise indicated, provide hot-dipped
galvanized steel fasteners, anchors, rods, straps, trim, and angles for support of
ductwork.
2.03 TWO-INCH PRESSURE CLASS FABRICATION
A. Shop fabricate ductwork in 4-, 8-, 10- or 12-foot lengths, unless otherwise indicated or
required, to complete runs. Pre-assemble work in shop to greatest extent possible, so as
to minimize field assembly of systems. Disassemble systems only to extent necessary
for shipping and handling. Match-mark sections for reassembly and coordinated
installation.
B. Shop fabricate ductwork of gauges and reinforcement complying with SMACNA HVAC
Duct Construction Standards, latest edition.
C. Fabricate duct fittings to match adjoining ducts and to comply with duct requirements as
applicable to fittings. Except as otherwise indicated, fabricate elbows with center-line
radius equal to 1.5 times associated duct width and fabricate to include turning vanes in
elbows where shorter radius is necessary. Limit angular tapers to 30º for contracting
tapers and 20º for expanding tapers.
D. Fabricate ductwork with accessories installed during fabrication to the greatest extent
possible. Refer to Division 15, Section 15910 – Duct Accessories for accessory
requirements.
E. Fabricate round supply connections at rectangular, plenum-type fittings using spin-in type
fittings, complete with extractor and volume control damper.
1. Provide spiral-lock seam prefabricated duct, as specified for 4” pressure class.
Longitudinal seam duct shall not be used.
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2.04 FOUR-INCH PRESSURE CLASS
A. Sheet Metal: Except as otherwise indicated, fabricate ductwork with commercial grade of
galvanized sheet steel.
2.05 FACTORY-FABRICATED, FOUR-INCH PRESSURE CLASS
A. Spiral lock seam prefabricated factory-build round and oval duct and fittings shall be used
wherever possible. Shop-fabricated ducts shall be used only where rectangular shaped
ducts are shown on plans or where transitions and special fittings cannot be
prefabricated by factory.
B. Round Ductwork: Construct of galvanized sheet steel complying with ANSI/ASTM A 527
by the following methods and in minimum gauges listed.
1. DIAMETER MINIMUM GAUGE METHOD OF MANUFACTURE
3" to 14" 26 Spiral Lockseam
15" to 26" 24 Spiral Lockseam
27" to 36" 22 Spiral Lockseam
37" to 50" 20 Spiral Lockseam
51" to 60" 18 Spiral Lockseam
Over 60" 16 Longitudinal Seam
C. Provide locked seams for spiral duct; fusion-welded butt seam for longitudinal seam duct.
D. Fittings and Couplings: Construct of minimum gauges listed. Provide continuous welds
along seams.
1. DIAMETER MINIMUM GAUGE
3" to 36" 20
38" to 50" 18
Over 50" 16
E. Flat-Oval Ductwork: Construct of galvanized sheet steel complying with ANSI/ASTM A
527, of spiral lockseam construction, in minimum gauges listed.
1. MAXIMUM WIDTH MINIMUM GAUGE
Under 25" 24
25" to 48" 22
49" to 70" 20
Over 70" 18
F. Fittings and Couplings: Construct of minimum gauges listed. Provide continuous weld
along seams.
1. MAXIMUM WIDTH MINIMUM GAUGE
Under 37" 20
37" to 50" 18
Over 50" 16
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G. Manufacturers:
1. MANUFACTURER PRODUCT
United Sheet Metal Div., United Magill Corp. Uniseal
Semco Manufacturing Incorporated
Air Systems Incorporated - Las Vegas
Or equal
2.06 MISCELLANEOUS DUCTWORK MATERIALS
A. Provide miscellaneous materials and products of types and sizes indicated, and where
not otherwise indicated, provide requirements as listed in the latest SMACNA manuals,
including proper connection of ductwork and equipment.
B. Fittings: Unless otherwise shown on Drawings, following fittings shall be used: two-piece,
die-stamped, 45º to 90º elbows for sizes up to 8”; five-piece, 90º elbows for sizes over 8”;
conical tees; and conical laterals. All reducers shall be placed after a tap has been made
on the duct main. Reducers shall be long-taper style.
C. Duct Sealant: Non-hardening, non-migrating mastic or liquid elastic sealant as
compounded and recommended by manufacturer specifically for sealing joints and
seams in ductwork.
D. Duct Joints: Joint and seal prefabricated, factory-built ducts, fittings, and couplings in
strict accordance with duct manufacturer's instructions. Install duct sealers, pop rivets or
sheet metal screws and canvas and apply adhesive sealant, Foster SEALFAST,
Hardcast Flex-Grip, Childers Chil-Perm or equal, on each joint. Duct sealer shall be fire
retardant. Sheet metal screw for joints shall be minimum #10 size galvanized.
E. Duct Access: Provide access panel sections in prefabricated, factory-built ducts for
access to fire dampers, control equipment, etc. as specified in Duct Accessories Section.
Access panel size shall be duct diameter wide by duct diameter high for all ducts under
24”. Ducts over 24” in diameter shall have 24” x 18” access panels. Minimum size access
panels shall be 6” x 6”.
2.07 FLEXIBLE DUCTS
A. Flexible ducts may be used in concealed areas only.
B. Factory insulate all flexible ducts with 1” thick, one- pound density fiberglass insulation
and wrap with factory-installed vapor barrier jacket. Ducts shall be UL approved and
tested and meet Class 1 requirements of NFPA 90A. Make elbows to maintain R/W-1.5.
C. Flexible ducts from rigid runouts to registers shall be Thermaflex M-KE, or equal, with
maximum length of seven (7) feet. Flexible duct shall have no bends greater than 45º.
D. Flexible ducts shall consist of an exterior reinforced laminated vapor barrier, 1-½” thick
fiberglass insulation (K= .25 @ 75ºF), encapsulated spring steel wire Helix and
impervious, smooth, non-perforated interior vinyl liner. Individual lengths of flexible ducts
shall contain factory-fabricated steel connection collars.
1. Make connections to rigid duct and units with draw band and sealer, and then
duct tape over outside of sheath.
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