insulated ducts.
2.10.4.3
Closure Collars
Collars shall be fabricated of galvanized sheet metal not less than 100 mm
4 inches wide, unless otherwise indicated, and shall be installed on
exposed ducts on each side of walls or floors where sleeves or prepared
openings are provided. Collars shall be installed tight against surfaces.
Collars shall fit snugly around the duct or insulation. Sharp edges of the
collar around insulated duct shall be ground smooth to preclude tearing or
puncturing the insulation covering or vapor barrier. Collars for round
ducts 375 mm 15 inches in diameter or less shall be fabricated from 1.0 mm
(20 gauge) 20 gauge galvanized steel. Collars for round duct larger than
375 mm 15 inches and all square, and rectangular ducts shall be fabricated
from 1.3 mm (18 gauge) 18 gauge galvanized steel. Collars shall be
installed with fasteners on maximum 150 mm 6 inch centers, except that not
less than 4 fasteners shall be used.
2.10.5
Diffusers, Registers, and Grilles
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NOTE: Refer to TM 5-805-4, Noise and Vibration
Control, for noise criteria. Sound power levels
required should be included in the appropriate
schedule on the drawings.
If diffusers or registers or grilles are not
required, reference to omitted items will be
deleted. Specified performance characteristics
peculiar to the omitted items will be deleted. If
any one or two of the three types of units are
omitted, the corresponding subparagraph will be
deleted.
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Units shall be factory-fabricated of steel, corrosion-resistant steel, or
aluminum and shall distribute the specified quantity of air evenly over
space intended without causing noticeable drafts, air movement faster than
0.25 m/s 50 fpm in occupied zone, or dead spots anywhere in the conditioned
area. Outlets for diffusion, spread, throw, and noise level shall be as
required for specified performance. Sound power level shall be as
indicated. Diffusers and registers shall be provided with volume damper
with accessible operator, unless otherwise indicated; or if standard with
the manufacturer, an automatically controlled device will be acceptable.
Volume dampers shall be opposed blade type for all diffusers and registers,
except linear slot diffusers. Linear slot diffusers shall be provided with
round or elliptical balancing dampers. Where the inlet and outlet openings
are located less than 2 m 7 feet above the floor, they shall be protected
by a grille or screen in accordance with NFPA 90A.
2.10.5.1
Diffusers
Diffuser types shall be as indicated. Ceiling mounted units shall be
furnished with antismudge devices, unless the diffuser unit minimizes
ceiling smudging through design features. Diffusers shall be provided with
air deflectors of the type indicated. Air handling troffers or combination
light and ceiling diffusers shall conform to the requirements of UL Elec
Const Dir for the interchangeable use as cooled or heated air supply
diffusers or return air units. Ceiling mounted units shall be installed
SECTION 15566A
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