York YK M3 M3 G4 THRU YK S6 S4 J2, YK LB LB G4 THRU YK SE SC J4 SOLID STATE STARTER Optional

age to the Micro Board that represents this level (0% = empty; 100% = full). Under program control, the Micro Board modulates a variable orifice to control the con- denser refrigerant level to a programmed setpoint. Other setpoints affect the control sensitivity and response. These setpoints must be entered at chiller commis- sioning by a qualified service technician. Only a quali- fied service technician may modify these settings. Manual operation of the refrigerant level control can be selected. This allows the prerotation vanes keypad keys to manually control the variable orifice. This manual control can also be used to position the variable orifice in a fixed position. Instructions for selecting manual level control and entering the level control setpoints are contained in the “Special Setpoints and Program- ming Procedures” section of Service manual, Form 160.49-M3.

While the chiller is shut down, the orifice will be in the fully open position causing the sensed level to be ap- proximately 0%. When the chiller is started, after the vane motor end switch (VMS) opens when entering “SYSTEM RUN”, if actual level is less than the level setpoint, a linearly increasing ramp is applied to the level setpoint. This ramp causes the setpoint to go from the initial refrigerant level (approximately 0%) to the programmed setpoint over a period of 15 minutes. While this ramp is in effect,

PULLDN LEVEL = XXX%; SETP = XXX%; ACTUAL = XXX% is

one of the scrolled messages under the DISPLAY DATA key. “PULLDN LEVEL” is the ramping setpoint that will ramp up to the programmed setpoint “SETP”. “SETP” is the level setpoint programmed by the service tech- nician. “ACTUAL” is the present refrigerant level in the condenser. After the 15 minute pulldown period has elapsed, this message is replaced by

ACTUAL LEVEL = XXX%; LEVEL SETP = XXX% .

If the actual level is greater than the setpoint when the VMS opens, there is no pulldown period, it immedi- ately begins to control to the programmed setpoint.

While the chiller is running, the refrigerant level is nor- mally controlled to the level setpoint. However, any- time the vanes fully close (VMS closes), normal level control is terminated, any refrigerant level setpoint pulldown in effect is cancelled and the outputs to the level control will be opposite that which is supplied to the vane motor (i.e., when a close pulse is applied to the vane motor, an open pulse is applied to the level

FORM 160.49-O2

control, etc.). When the VMS opens, if the refrigerant level is less than the level setpoint, a refrigerant level setpoint pulldown is initiated as described above. Oth- erwise, the level is controlled to the programmed setpoint.

If the refrigerant level sensor output ever goes to greater than 4.4VDC, indicating a level greater than 100%,

WARNING-REFRIGERANT LEVEL OUT OF RANGE is dis- played and the level control actuator is driven open until the level has decreased to a level within range. When within range, the warning message is automati- cally cleared and normal control is resumed.

MICROCOMPUTER CONTROL CENTER (See Section 2)

The MicroComputer Control Center is factory mounted, wired and tested. The electronic panel automatically controls the operation of the unit in meeting system cooling requirements while minimizing energy usage. For detailed information on the Control Center, refer to “Section 2” of this manual.

SOLID STATE STARTER (Optional)

The Solid State Starter is a reduced voltage starter that controls and maintains a constant current flow to the motor during start-up. It is mounted on the chiller. Power and control wiring between the starter and chiller are factory installed. Available for 380-600 volts, the starter enclosure is NEMA-1 with a hinged access door with lock and key. Electrical lugs for incoming power wiring are provided.

VARIABLE SPEED DRIVE (Optional)

A 460V – 3-Ph – 60/50Hz Variable Speed Drive can be factory packaged with the chiller. It is designed to vary the compressor motor speed and prerotation vane po- sition by controlling the frequency and voltage of the electrical power to the motor. Operational information is contained in Form 160.00-O1. The control logic au- tomatically adjusts motor speed and compressor prerotation vane position for maximum part load effi- ciency by analyzing information fed to it by sensors located throughout the chiller.

YORK INTERNATIONAL 41