Provide air deflectors at all duct mounted supply outlets, at takeoff or
extension collars to supply outlets, at duct branch takeoff connections,
and at 90 degree elbows, as well as at locations as indicated on the
drawings or otherwise specified. Conical branch connections or 45 degree
entry connections may be used in lieu of deflectors or extractors for
branch connections. Furnish all air deflectors, except those installed in
90 degree elbows, with an approved means of adjustment. Adjustment shall
be made from easily accessible means inside the duct or from an adjustment
with sturdy lock on the face of the duct. When installed on ducts to be
thermally insulated, external adjustments shall be provided with stand-off
mounting brackets, integral with the adjustment device, to provide
clearance between the duct surface and the adjustment device not less than
the thickness of the thermal insulation. Air deflectors shall be
factory-fabricated units consisting of curved turning vanes or louver
blades designed to provide uniform air distribution and change of direction
with minimum turbulence or pressure loss. Air deflectors shall be factory
or field assembled. Blade air deflectors, also called blade air
extractors, shall be approved factory fabricated units consisting of
equalizing grid and adjustable blade and lock. Adjustment shall be easily
made from the face of the diffuser or by position adjustment and lock
external to the duct. Stand-off brackets shall be provided on insulated
ducts and are described herein. Fixed air deflectors, also called turning
vanes, shall be provided in 90 degree elbows.
2.6.3
Plenums and Casings for Field-Fabricated Units
**************************************************************************
NOTE: If field-fabricated air handling units are
not used, delete this paragraph entirely. Delete
inapplicable sentences or items. Delete the
push-button station if not required.
**************************************************************************
2.6.3.1
Plenum and Casings
Fabricate and erect plenums and casings as shown in SMACNA HVAC Duct Const
Stds, as applicable. Construct system casing of not less than 1.6 mm 16
gauge galvanized sheet steel. Furnish cooling coil drain pans with 25 mm 1
inch threaded outlet to collect condensation from the cooling coils.
Fabricate drain pans from not lighter than 1.6 mm 16 gauge steel,
galvanized after fabrication or of 1.3 mm 18 gauge corrosion-resisting
sheet steel conforming to ASTM A 167, Type 304, welded and stiffened.
Thermally insulate drain pans exposed to the atmosphere to prevent
condensation. Insulation shall be coated with a flame resistant
waterproofing material. Provide separate drain pans for each vertical coil
section, and a separate drain line for each pan. Size pans to ensure
capture of entrained moisture on the downstream-air side of the coil. Seal
openings in the casing, such as for piping connections, to prevent air
leakage. Size the water seal for the drain to maintain a pressure of at
least 500 Pa 2 inch water gauge greater than the maximum negative pressure
in the coil space.
2.6.3.2
Casing
Terminate casings at the curb line and bolt each to the curb using
galvanized angle, as indicated in SMACNA HVAC Duct Const Stds.
SECTION 15895
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