Heat exchangers
The evaporator shell is fabricated from rolled carbon steel plates with fusion welded seams. The
heat exchanger tubes are internally enhanced type.
Evaporator
The evaporator is a shell and tube, hybrid falling film, and flooded type heat exchanger. A
distributor trough provides uniform distribution of refrigerant over the tubes in the falling film
section. Residual refrigerant floods the tubes in the lower section. Suction baffles are located above
the tube bundle to prevent liquid refrigerant carryover into the compressor. A 2 in. liquid level sight
glass is located on the side of the shell. The evaporator shell has a pressure relief valve for safety.
Optional dual relief valves are also available.
Condenser
The condenser sections have a microchannel design and consist of a flat aluminum tube and fin
design. Each condenser section has two cooling fans that are speed controlled from the chiller
control panel and use variable speed drive technology to operate the fans. Refrigerant sub-cooling
is accomplished in the condenser section. Refrigerant relief valves are located on the system
discharge piping that feeds the condenser sections with refrigerant isolation valves as standard
options.
Waterboxes
The removable compact waterboxes are fabricated of steel. The design working pressure is 150
psig (1,034 kPa) and the boxes are tested at 225 psig (1,551 kPa). Integral steel water baffles
provide the required pass arrangements. Stub-out water nozzle connections with grooved
connections, which are a standard option, are welded to the waterboxes. These nozzle connections
are suitable for groove type couplings, welding, or flanges, and are capped for shipment. Plugged
3/4 in. drain and vent connections are provided in each waterbox.
Refrigerant flow control
Refrigerant flow to the evaporator is controlled by the condenser drain valve. The control panel
monitors the condenser subcooling value as the control point for the condenser drain valve.
Under program control, the control panel modulates the condenser drain valve to control the
condenser refrigerant level to the programmed subcooling setpoint. Other setpoints modify the
control sensitivity and response. Only a qualified service technician can change these settings. The
subcooling setpoint must be verified at chiller commissioning by a qualified service technician.
While the chiller is shut down, the condenser drain valve is pre-positioned to anticipate run. When
the chiller is started, if the subcooling value is less than the setpoint, a linearly increasing ramp is
applied to the subcooling setpoint. This ramp causes the setpoint to go from the initial subcooling
value to the programmed setpoint over a programmable period of time. If the actual subcooling
value is greater than the setpoint upon run, it immediately begins to control to the programmed
setpoint.
While the chiller is running, the refrigerant level is normally controlled to the subcooling setpoint.
Variable speed compressor drive
The HYP model variable speed drive is factory packaged with the chiller. It is designed to vary the
compressor motor speed by controlling the frequency and voltage of the electrical power to the
motor. The control logic automatically adjusts motor speed as required to suit lift and capacity
requirements.
21YVAM with OptiView Control Center
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