15840-3
DUCTWORK AND DEVICES
locking setscrew and bushing. Two rods are required on splitters over 8 inches.
Manual volume-control dampers shall be operated by locking type quadrant
operators. Dampers and splitters shall be two gages heavier than duct in which
installed. Unless otherwise indicated, multi-leaf damper shall be opposed blade type
with maximum blade width of 4 inches. Access doors or panels shall be provided
for all concealed damper operators and locking setscrews. Unless otherwise
indicated, provide the locking type quadrant operators for dampers, when installed
on ducts to be thermally insulated, with stand-off mounting brackets, bases or
adapters to provide clearance between the duct surface and the operator not less than
the thickness of the insulation. Stand-off mounting items shall be integral with the
operator or standard accessory of the damper manufacturer. Provide volume
dampers where shown on the Drawings.
Air Deflectors: Provide air deflectors in all square elbows, duct-mounted supply
outlets, takeoff or extension collars to supply outlets, and tap-in branch-takeoff
connections. Air deflectors shall be factory-fabricated and factory- or field-
assembled units consisting of curved turning vanes or louver blades for uniform air
distribution and change of direction with minimum turbulence and pressure loss.
Provide square elbows with curved vanes as shown on the Drawings. Devices shall
be of the same material as ductwork.
Fire Dampers: Provide fire dampers in all ducts penetrating fire walls and slabs, and
where duct systems serve two or more floors in accordance with the National Fire
Protection Association Standard No. 90A. Install dampers with sufficient tension to
prevent rattling or vibration. Fire dampers shall conform to the requirements of
Under-writers' Laboratories, Inc. Provide dampers where shown on the Drawings.
Duct Access Doors: Provide hinged doors at all automatic dampers, fire dampers,
coils, thermostats, temperature controllers, and other apparatus requiring service and
inspection in the duct system. Doors shall be 12 by 12 inches unless otherwise
shown on the Drawings. Where size of duct will not accommodate this size, make
the doors as large as practical. Install doors not less than 24 by 24 inches on each
side of each air-handling unit. Doors shall be rigid, and shall be provided with
airtight felt gaskets. Provide doors with hinges, pins and two fasteners of the same
material as the adjacent duct. Provide doors 24 by 24 inches or larger with fasteners
operable from both sides. Doors in insulated ducts shall be of the insulated type.
Unless otherwise shown on the Drawings, doors shall swing so that fan pressure or
suction holds the door closed.
Duct Sleeves and Prepared Openings:
1. Round ducts - 15 inches in diameter or less: Provide duct sleeves for all round
ducts 15 inches diameter or less passing through floors, walls, ceiling, or roof.
Install ducts larger than 15 inches diameter and all square and rectangular
ducts passing through floors, walls, ceilings or roof. Sleeves shall conform to
the requirements of Section 15092 except as noted below:
a. Sleeve shall provide one-inch clearance between the duct and the sleeve,
or one inch clearance between the insulation and the sleeve for insulated
ducts, except at grilles, registers, and diffusers.
2. Round ducts larger than 15 inches diameter and all rectangular ducts:
13089K
