System components - YORK - Centrifugal

See Figure 1, Figure 2, and Figure 3 for YVAM1500 and YVAM1650 (mod level B) chiller components.

Figure 1. YVAM1500, and YVAM1650 (mod level B) control panel side view

Figure 2. YVAM1500, and YVAM1650 (mod level B) compressor side view

Figure 3. YVAM1500, and YVAM1650 (mod level B) VSD end view

The compressor is a single-stage centrifugal type powered by a hermetic electric motor, on a common shaft with a cast aluminum, fully shrouded impeller. The compressor has no inlet guide vanes and uses a variable geometry diffuser (VGD) for capacity control.

The compressor motor is a hermetic, permanent magnet, high-speed design with magnetic bearings. The compressor impeller is overhung from the end of the motor shaft and has no bearings.

The motor includes angular contact ball bearings that only engage with the rotor shaft during shutdown after rotation stops or during shutdown due to a loss of power to the magnetic bearings.

The bearing control center maintains correct shaft position in the magnetic bearings.

The evaporator shell is fabricated from rolled carbon steel plates with fusion welded seams. The heat exchanger tubes are internally enhanced type.

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 5 cm (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.

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.

The removable compact waterboxes are fabricated of steel. The design working pressure is 10 barg (145 psig). 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 1.9 cm (3/4 in.) drain and vent connections are provided in each waterbox.

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.

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.

The optional service isolation valves include two on the discharge lines to each condenser section and one on the liquid line to the evaporator. If your chiller is equipped with these optional service isolation valves, they must remain fully open during operation. These valves are used for isolating the refrigerant charge in the condenser to allow service access to the evaporator and compressor side of the system. A refrigerant recovery unit is required to isolate the refrigerant.

The YORK OptiView Control Center LCD graphic display and keypad is the interface for starting, stopping, configuring, monitoring, and commanding the chiller controls. The control center is a microprocessor-based system for centrifugal chillers. It controls the leaving chilled liquid temperature (LCHLT) and maintains safe operation. It is factory-mounted, wired, and tested.

The graphic display presents the operating parameters in logical groups on screens and can trend data to show a graphical representation of present or historical operation of the chiller. The locations of various chiller parameters are clearly and intuitively marked. Instructions for specific operations are provided on many of the screens. For information on the screens and navigation, see OptiView Control Center functions and navigation.

Eight buttons on the right side of the panel are primarily used for navigation between the system screens. Five additional buttons are located at the base of the display. The button functions are redefined based on the currently displayed screen. The area to the right of the keypad is used for data entry and a standard numeric keypad is provided for programming system setpoints and limits.

Figure 1. OptiView Control Center

The graphic display can also display numerical information in both imperial mode, where temperatures are in °F and pressures are in psig, and metric mode, where temperatures are in °C and pressures are in kPa. It can also display many languages.

The control center continually monitors the system operation and records the cause of any shutdowns, including Safety, Cycling, or Normal. This information is recorded in memory and is preserved even through a power failure condition. The user can recall it for viewing at any time. During operation, the user is continually advised of the operating conditions by various status and warning messages. In addition, it can be configured to notify the user of certain conditions using alarms. A complete listing of shutdown, status, and warning messages is provided in Display messages.

The control center includes capabilities for remote control and communications. Common networking protocol through the Building Automation System (BAS) provides increased remote control of the chiller, including 24-hour performance monitoring by a remote site. An optional circuit board called the SC-EQUIP provides Johnson Controls and YORK mechanical equipment such as the YVAM chiller with BAS networking connectivity.

The chiller also maintains the standard digital remote capabilities. Both of these remote control capabilities allow for the following standard energy management system (EMS) interfaces. The actual connection details are in the Field Connections section of Form 160.88-PW3 for YVAM Mod B.

• Remote run/stop
• Cooling setpoint: Local BAS coms, analog signal of 0 VDC to 10 VDC or 4 mA to 20 mA, or pulse width modulation (PWM)
• Current limit setpoint: Local BAS coms, analog signal of 0 VDC to 10 VDC or 4 mA to 20 mA, or pulse width modulation (PWM)
• Remote ready to start contacts
• Safety shutdown contacts
• Cycling shutdown contacts

The OptiView panel can be used to control the customer chilled liquid flow. A set of contacts exists to initiate the evaporator flow. Details are in the Field Connections section Form 160.88-PW3 for YVAM Mod B. The chilled water pump contacts close immediately upon execution of a chiller start command. They open at the same time with the receipt of a stop command or a fault other than the following faults:

1. LEAVING CHILLED LIQUID - LOW TEMPERATURE cycling shutdown.
2. MULTIUNIT CYCLING - CONTACTS OPEN or SYSTEM CYCLING - CONTACTS OPEN (Only if Chilled Liquid Pump Operation is set to Enhanced)
3. LEAVING CHILLED LIQUID FLOW SWITCH OPEN cycling shutdown

Some screens, displayed values, programmable setpoints, and manual controls exist for service technician use only. They are only displayed when logged in at the service access level or higher. The setpoints and parameters displayed on these screens are explained in detail in YORK YVAM Service Manual (Form 160.88-M2). These parameters affect chiller operation and must never be modified by anyone other than a qualified service technician. The advanced diagnostics and troubleshooting information for service technicians is included in YORK YVAM Service Manual (Form 160.88-M2). Also included in the service manual are detailed descriptions of chiller features, such as capacity control, refrigerant level control, variable geometry diffuser, and magnetic bearing controller.

The chiller operating program resides in the OptiView Control Center microboard. Software versions (Y.OPT.20.xx.yyy) are alphanumeric codes that represent the application, language package, and revision levels as follows. Each time the controls portion or language section is revised, the respective revision level increments.

• Y: Commercial chiller
• OPT: OptiView
• 20: Product code, for example YVAM
• xx: Controls revision level, for example 00, 01
• y: Language package (0=English only, 1=NEMA, 2=CE, 3=NEMA/CE )

Software upgrades must only be performed by a service technician.