Specifications

90 Catalog WSC/WDC-4
Provide and install as shown on the plans a factory assembled, charged, and run-tested water-cooled
packaged chiller. Each unit shall be complete with two single-stage hermetic centrifugal
compressors each having independent lubrication and control systems, factory mounted starters, and
isolation valves. The evaporator, condenser, and refrigerant control device of each unit shall be
common to the compressors. The chiller unit shall be capable of running on one compressor with
the other compressor or any of its auxiliaries removed.
2.3 DESIGN REQUIREMENTS
A. General: Provide a complete water-cooled dual hermetic compressor centrifugal water
chiller as specified herein. Machine shall be provided according to standards, Section 1.2.
In general, unit shall consist of two compressors, refrigerant condenser and evaporator, two
lubrication systems, two starters and two control systems.
Note: Chillers shall be charged with a refrigerant such as HFC-134a, not subject to the
Montreal Protocol and the U. S. Clean Air Act.
B. Performance: Refer to schedule on the drawings. The chiller shall be capable of stable
operation to five percent of full load with standard ARI entering condensing water relief
without hot gas bypass.
C. Acoustics: Sound pressure for the unit shall not exceed the following specified levels.
Provide the necessary acoustic treatment to chiller as required. Sound data shall be
measured according to ARI Standard 575-87and shall be in dB. Data shall be the highest
levels recorded at all load points. Test shall be in accordance with ARI Standard 575.
Octave Band
63 125 250 500 1000 2000 4000 8000 dba
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2.4 CHILLER COMPONENTS
A. Compressors:
1. Unit shall have two single-stage hermetic centrifugal compressors. Casing design
shall ensure major wearing parts, main bearings and thrust bearings are accessible for
maintenance and replacement. Lubrication system shall protect machine during coast
down resulting from a loss of power.
2. Impeller shall be statically and dynamically balanced. The compressor shall be
vibration tested and not exceed 0.14 IPS.
3. Movable inlet guide vanes actuated by an internal oil pressure driven piston shall
accomplish unloading. Compressors using an unloading system that requires
penetrations of the compressor housing or linkages, or both, that must be lubricated
and adjusted are acceptable provided the manufacturer provides a five-year inspection
agreement consisting of semi-annual inspection, lubrication, and annual changeout of
compressor seals. A statement of inclusion must accompany any quotations.
4. If compressors are not equipped with guide vanes for each stage and movable
discharge diffusers, then furnish hot gas bypass and select chillers at 5% lower kW/ton
than specified to compensate for bypass inefficiency at low loads.
B. Lubrication System: Each compressor shall have an independent lubrication system to
provide lubrication to all parts requiring oil. Provide a heater in the oil sump to maintain
oil at sufficient temperature to minimize affinity of refrigerant, and a thermostatically
controlled water-cooled oil cooler. Coolers located inside the evaporator or condenser are
not acceptable due to inaccessibility. A positive displacement submerged oil pump shall be
powered through the unit control transformer.
C. Refrigerant Evaporator and Condenser:
1. Evaporator and condenser shall be of the shell-and-tube type, designed,
constructed, tested and stamped according to the requirements of the ASME Code,
Section VIII. Regardless of the operating pressure, the refrigerant side of each
vessel will bear the ASME stamp indicating compliance with the code and
indicating a test pressure of 1.3 times the working pressure but not less than 100
psig. Provide intermediate tube supports at a maximum of 18 inch spacing.