Specifications

48 Catalog WSC/WDC-4
Unit Selection
Many combinations of compressor configuration
and condensers and evaporators are available for a
given capacity. The units range from low first cost
and relatively high kW per ton (COP) to high first
cost and low kW per ton (COP). A graphic display
of the optional performance available is shown at
the right. The COP curve would be mirrored and is
not shown for clarity. Optimum unit selection for
maximum operating return on the invested first cost
is in the area identified by the X.
Actual optimum unit selection will vary with
building application and system design.
Applications with minimal hours of operation
cannot justify a very low kW per ton (COP) unit.
Applications with high hours of operation will
justify high part load as well as full load efficiency units. For optimum selection an energy
analysis is available through your local McQuay Sales Representative.
Basic unit selections
All McQuay centrifugal chillers are computer selected to optimize the cooling output and total
kW. Computer selection allows for the specification of leaving chilled water temperature, entering
condenser water temperature, evaporator and condenser flow rates, number of passes, and fouling
factors. Glycol applications can also be specified.
Glycol operation
The addition of glycol to the chilled water system for freeze protection can be required for special
applications. Glycol solutions are required where the evaporating temperatures are below 33°F
(1°C).
ARI Certification
McQuay International has an on-going commitment to supply chillers that perform as specified.
To this extent, McQuay centrifugal chillers are part of the ARI Certification. On-going
performance verification of chiller capacity and power input plus ARI certified computerized
selection output provide the owner with specified performance in accordance with the latest
version of ARI Standard 550/590.
All chillers that fall within the scope of the certification program have an ARI certification label at
no cost to the owner. Equipment covered by the ARI certification program include all water-
cooled centrifugal and screw water chilling packages rated up to 2000 tons (7,000 kW) for 60
Hertz service at ARI standard rating conditions, hermetic or open drive, with electric driven motor
not exceeding 5000 volts, and cooling water (not glycol). For 50 hertz application the capacity
range covered is 200 to 1,000 tons (700 to 3500 kW).
Published certified ratings verified through testing by ARI include:
• Capacity, tons (kW) • Power, kW/ton (COP) • Pressure drops, ft. of water (kPa)
• Integrated Part Load Value (IPLV) or Non-Standard Part Load Value (NPLV)
As part of the ARI certification program, ARI has the McQuay computer selection program used
to select and rate chillers. The certified computer program version number and issue date for all
manufacturers is listed in the ARI Directory of Certified Applied Air-Conditioning Products
available on www.ari.org.