scale removal chemicals and isolation pressure taps to determine pressure
drop and water flow. Performance shall be based on an allowable water
velocity not less than 0.9 m/s 3 fps nor more than 3 m/s 10 fps with a
fouling factor of [0.001] [0.0005].
2.5.3
Evaporatively-Cooled Section
The evaporative section shall be a packaged component of the unitary
equipment. Unit shall be the counter-flow blow-through design, with
single-side air entry. Unit shall have fan assemblies built into the unit
base, with all moving parts factory mounted and aligned. Primary
construction of the pan section, the cabinet, etc. shall be not lighter
than 16-gauge steel, protected against corrosion by a zinc coating. The
zinc coating shall conform to ASTM A 153/A 153M and ASTM A 123/A 123M, as
applicable and a minimum coating thickness of 0.76 kg/square meter 2.5
ounces/square foot of surface. Cut edges shall be given a protective
coating of zinc-rich compound. After assembly, the manufacturer's standard
zinc chromatized aluminum or epoxy paint finish shall be applied to the
exterior of the unit.
2.5.3.1
Pan Section
The pan shall
be watertight and be provided with drain, overflow, and
make-up water
connections. Standard pan accessories shall include circular
access doors,
a lift-out strainer of anti-vortexing design and a brass
make-up valve
with float ball.
2.5.3.2
Fan Section
Fan shall be the [centrifugal] [propeller] type in accordance with
paragraph "Fans". Fan and fan motor shall not be located in the discharge
airstream of the unit. Motors shall have [open] [splashproof] [totally
enclosed] enclosure and be suitable for the indicated service. The unit
design shall prevent water from entering into the fan section.
2.5.3.3
Condensing Coil
**************************************************************************
NOTE: Delete the copper or aluminum tubes and the
0.076 mm (3 mil) coating except in corrosive
environments.
**************************************************************************
Coils shall have [nonferrous] [copper or aluminum] tubes of 10 mm 3/8 inch
minimum diameter without fins. Coils shall be protected with a minimum
0.076 mm 3 mil thick [phenolic] [or] [vinyl] coating. Casing shall be
galvanized steel or aluminum. Contact of dissimilar metals shall be
avoided. Coils shall be tested in accordance with ASHRAE 15 at the factory
and be suitable for the working pressure of the installed system.
2.5.3.4
Water Distribution System
Water shall be distributed uniformly over the condensing coil to ensure
complete wetting of the coil at all times. Spray nozzles shall be brass,
stainless steel, or high-impact plastic. Nozzles shall be the cleanable,
nonclogging, removable type. Nozzles shall be designed to permit easy
disassembly and be arranged for easy access.
SECTION 15700A
Page 19
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