without attached ductwork; use centrifugal fans with
attached ductwork.
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a.
Propeller Fan: Direct-drive propeller fan with all welded frame
and statically-dynamically balanced aluminum blades. The exterior
and interior of the fan shall be epoxy primed prior to the
application of a baked enamel finish. The fan motor shall be
totally enclosed with permanently lubricated ball bearings.
b.
Centrifugal Fan: Belt-drive or direct-drive centrifugal fan with
forward curved blades. Construct scrolls, wheels, and inlet cones
of [steel] [or] [aluminum] with corrosion resistant finish.
Attach the fan to a welded steel frame designed to support the
entire fan and motor assembly. Select V-belt sheaves based on a
minimum of 1.3 times the motor nameplate power. Provide these
sheaves to have critical speed at least 20 percent higher than the
maximum operating speed.
2.2.1.5
Filter Rack
Water resistant permanent frame with 50 mm 2 inch thick disposable
fiberglass or equivalent medium.
2.2.1.6
Component Casing
Construct casing of minimum 14 gage galvanized steel panels secured to a
welded steel angle frame. Exterior panels shall be removable to permit
access to any interior component. Coat with epoxy on frame members, sump
drains, entire casing bottom and interior wet surfaces. Exterior steel
surfaces shall be primed with epoxy and finished with baked enamel.
Terminate all exterior wiring in a weathertight junction box located
outside of the casing. Provide hoisting lug for installation.
2.2.2
Direct Section
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NOTE: For two-stage evaporative cooling systems,
major manufacturers often use direct evaporative
coolers.
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Except as modified, direct evaporative cooler [Drip-type with stationary
wetted pad] [Rotary-type] with revolving drum or disk. [Washer (eliminator
type)].
2.2.2.1
Evaporative Media
Refined cellulose fibers. [Impregnate fibers with copper 8-quino
linolate.] [Rotary filters with maximum 3 m/s 600 fpm and 2 1/2 percent
by-pass water flow through the rotary assemblies and minimum 127 mm 5 inch
depth of rotary sections.] [Washer media consisting of self-cleaning,
centrifugal brass spray nozzles, brass flooding nozzles, [copper] [or]
[galvanized steel] water piping, centrifugal water pump, strainers, and a
minimum 24 gage [galvanized steel] [or] [aluminum] eliminator with minimum
four surfaces and three bends in the airflow direction.]
SECTION 15721N
Page 10
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