2.10
EVAPORATIVE COOLERS
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NOTE: Drip type evaporative coolers are the most
widely used; pads are uniformly and sufficiently
wetted to reduce scale buildup. Indirect
evaporative coolers are used when the designer
wishes to add no moisture to the supply air. Two
stage coolers incorporate both indirect and direct
sections to provide lower supply temperatures, a
degree of humidity control. In general, a blow
through unit can provide discharge air that is
slightly cooler than a comparable draw through
units. In addition, the fan and motor in a blow
through unit is not located in the saturated air
stream, as is typically the case with draw through
units.
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Units shall be a self-contained [direct] [indirect] [indirect/direct]
[multi-stage], weather resistant [drip,] [rotary,] [slinger] type, [blow
through] [draw through] and shall conform to UL 507 and UL 746C. Unit
shall be the [side] [or] [vertical downblast] discharge type as indicated.
A guillotine type manual winterizing damper complete with holding rack
shall be provided on the discharge side of each unit. Holding rack shall
retain damper during operating season.
2.10.1
Fan Unit
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NOTE: Inapplicable motor enclosures, motor
starters, and starter enclosures will be deleted.
In areas where severe sand and dust conditions
exist, totally enclosed motors will be considered.
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The unit shall be the centrifugal type and shall be complete with motor,
drive equipment, and vibration-isolation supports between motor and fan
housing. Water distributor or rotary wheel motor shall be [synchronized to
start and stop with the fan unit] [separately controlled] [provided with a
time delay in the fan circuit to allow media to be thoroughly wetted before
air flow starts]. Manual or automatic reset type thermal overload
protection shall be provided in the starter or shall be integral with the
motor. Motor starters shall be [manual] [magnetic] across-the-line type
with [general purpose] [weather resistant] enclosure. [Remote manual
switch with pilot indicating light shall be provided where indicated.] Fan
scroll and wheel shall be constructed of galvanized steel, aluminum,
stainless steel, or polymeric material with stainless steel, hot-dip zinc
coated steel or cadmium coated steel shaft. Fan scroll may be made of a
different material than the wheel. Bearings shall be sleeve type,
self-aligning and self-oiling with oil reservoirs, or precision
self-aligning roller or ball-type with accessible grease fittings or
permanently lubricated type. Grease fittings shall be connected to tubing
and serviceable from a single accessible point. Bearing life shall be L50
rated at not less than 200,000 hours as defined by ABMA 9 and ABMA 11.
2.10.1.1
Fan Rating
Evaporative cooler fans shall have air delivery ratings based on AMCA 210
SECTION 15690A
Page 11
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