Specifications

Catalog WSC/WDC-4 37
Options and Accessories
Vessels
Marine water boxes
Provides tube access for inspection, cleaning, and removal without dismantling water piping.
Flanges (Victaulic® connections are standard)
ANSI raised face flanges on either the evaporator or condenser. Mating flanges are by others.
0.028 or 0.035 in. tube wall thickness
For applications with aggressive water conditions requiring thicker tube walls.
Cupro-nickel or titanium tube material
For use with corrosive water conditions, includes clad tube sheets and epoxy coated water heads.
Water-side vessel construction of 300 psi (150 psi is standard)
For high pressure water systems, typically high-rise building construction.
Water differential pressure switches
This option provides evaporator and condenser water pressure differential switches as a factory
mounted and wired option. A proof-of-flow device is mandatory in both the chilled water and
condenser water systems.
Single insulation, ¾-inch, on evaporator, suction piping, and motor barrel
For normal machine room applications.
Double insulation, 1-½ inch, on evaporator, suction piping, and motor barrel
For high humidity locations and ice making applications.
Electrical
Optional starters for factory or field mounting
See details in the Motor Starter section of this manual and catalog PM Starter.
Variable frequency drives (VFD)
Efficiency: The variable frequency drive option is a technology that has been used for decades to
control motor speed on a wide variety of motor-drive applications. When applied to centrifugal
compressor motors, significant gains in compressor part load performance can be realized. The
improvement in efficiency and reduction of annual energy cost is maximized when there are long
periods of part load operation, combined with low compressor lift (lower condenser water
temperatures). When atmospheric conditions permit, McQuay chillers equipped with VFDs can
operate with entering condenser as low as 50°F (10°C), which results in extremely low kW/ton
values.
Combining the attributes of VFD drives and the extremely efficient McQuay WDC Dual
Centrifugal Chiller produces the industry's most efficient chiller based on the all-important IPLV
value. See “IPLV/NPLV Defined” on page 49 for details on the ARI IPLV efficiency rating.
Water-Side Economizers: Free cooling systems utilizing cold cooling tower water to remove heat
from the chilled water system through a heat exchanger are becoming popular because the ability
of a chiller to move seamlessly from mechanical cooling to the free cooling mode is an important
operational feature. When equipped with a VFD, McQuay chillers can operate with condenser
water down to 50°F (10°C) at which point the economizer heat exchanger can be activated and the
free cooling can go into effect.
Starting Inrush: The use of a VFD on centrifugal chillers also provides an excellent method of
reducing motor starting inrush, even better than solid state starters. Starting current can be closely
controlled since both the frequency and voltage are regulated. This can be an important benefit to
a building's electrical distribution system.
Sound: The sound level of centrifugal compressors is largely dependent on the impeller tip speed.
By reducing compressor speed the sound level is also reduced.