Specifications

4 YORK INTERNATIONAL
SECTION 1
DESCRIPTION OF SYSTEM AND OPERATIONAL
FUNDAMENTALS
ing through the condenser tubes absorbs heat from
the refrigerant vapor, causing it to condense. The con-
denser water is supplied to the chiller from an external
source, usually a cooling tower. The condensed refrig-
erant drains from the condenser into the flow control
chamber, where the flow restrictor meters the flow
of liquid refrigerant to the cooler to complete the
refrigerant circuit.
The major components of a chiller are selected to
handle the refrigerant which would be evaporated at
full load design conditions. However, most systems
will be called upon to deliver full load capacity for only
a relatively small part of the time the unit is in opera-
tion.
CAPACITY CONTROL
The major components of a chiller are selected for full
load capacities; therefore, capacity must be controlled
to maintain a constant chilled liquid temperature leav-
ing the cooler. Prerotation vanes (PRV), located at the
entrance to the compressor impeller, compensate for
variation in load. (See Fig. 3 Detail A)
The position of these vanes is automatically controlled
through a lever arm attached to an electric motor lo-
cated outside the compressor housing. The automatic
adjustment of the vane position in effect provides the
performance of many different compressors to match
various load conditions from full load with vanes wide
open to minimum load with vanes completely closed.
For Variable Speed Drive units, the capacity is controlled
by speed modulation as well as prerotation vane con-
trol. The Variable Speed Drive selects the combination
of compressor motor speed and prerotation vane open-
ing for the most efficient operation. (See Form 160.00-O1)
SYSTEM OPERATION DESCRIPTION
YORK Millenium chillers are commonly applied to large
air conditioning systems, but may be used on other ap-
plications. The unit consists of an open motor mounted
to a compressor (with integral speed increasing gears)
condenser with purge unit, sub-cooler, cooler and flow
control chamber.
The chiller is controlled by a modern state of the art
MicroComputer Control Center which monitors its
operation. The control center is programmed by the
operator to suit job specifications. Automatic timed start-
ups and shutdowns are also programmed to suit
nighttime, weekends, and holidays. The operating sta-
tus, temperatures, pressures, and other information
pertinent to operation of the chiller are automatically
displayed and read on a 40 character alphanumeric
message display. Other displays can be observed by
pressing the keys as labeled on the control center.
The chiller with the MicroComputer Control Center is
applied with an Electro-Mechanical Starter, a factory
packaged YORK Solid State Starter or a factory pack-
aged Variable Speed Drive that produces even greater
efficiency and energy savings.
In operation, a liquid (water or brine) to be chilled flows
through the cooler, where refrigerant, boiling at low pres-
sure and temperature, absorbs heat from the water. The
chilled liquid is then piped to fan coil units or other air
conditioning terminal units, where it flows through finned
coils, absorbing heat from the air. The warmed liquid is
then returned to the chiller to complete the chilled liquid
circuit.
The refrigerant vapor, which is produced by the boiling
action in the cooler, flows to the compressor where the
rotating impeller increases its pressure and tempera-
ture and discharges it into the condenser. Water flow-