McQuay WDC

26 Product Manual PM WSC/WDC
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 identified as point X.
Actual optimum unit selection will vary with building
application and system design. Applications with
minimal hours of operation may not 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 recommended 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 may also be
specified.
Glycol operation
The addition of glycol to the chilled water system for freeze protection may 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 assure the owner of specified
performance in accordance with 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 at ARI standard rating conditions, hermetic or open drive, 60 Hz, with
electric driven motor below 5000 volts, cooling water (not glycol).
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 approved 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 published biannually.