6
YORK INTERNATIONAL
The YORK MicroComputer Control Center is a micro-
processor based control system for R-22 or R134a
centrifugal chillers. It controls the leaving chilled water
temperature via pre-rotation vane control and has the
ability to limit motor current via control of the pre-rota-
tion vanes. Further, it is compatible with YORK Solid
State Starter (optional) and electro-mechanical starter
applications.
A keypad mounted on the front of the Control Center
(see Fig. 3) allows the operator to display system op-
erating parameters on a 40 character alphanumeric
display that is part of the keypad. These readings are
displayed via “Display” keypad as follows: (In the En-
glish mode; temperatures in °F, pressures in (PSIG)
(in the metric mode, temperatures in °C, Pressures in
kPa).
• CHILLED LIQUID TEMPERATURES – LEAVING AND
RETURN
• REFRIGERANT PRESSURES – EVAPORATOR AND
CONDENSER
• DIFFERENTIAL OIL PRESSURE
• CONDENSER LIQUID TEMPERATURES –
OPTIONAL FIELD INSTALLED – LEAVING AND
RETURN
• OPTIONS
• PRINT *
• HISTORY PRINT *
• MOTOR CURRENT IN % OF FULL LOAD AMPS
• SATURATION TEMPERATURES – EVAPORATOR
AND CONDENSER
• DISCHARGE TEMPERATURE
• OIL TEMPERATURE
• HIGH & LOW OIL PRESSURE TRANSDUCER PRES-
SURE
• SOLID STATE STARTER MOTOR CURRENT / VOLTS
(When Supplied)
The system setpoints (see Fig. 3) are operator entered
on the front control center Setpoints keypad. These
setpoints can also be displayed on the 40 character
alphanumeric display. The system setpoints are:
• CHILLED LIQUID TEMPERATURE (LCWT)
INTRODUCTION
• % CURRENT LIMIT
• PULLDOWN DEMAND LIMIT
• CLOCK (TIME-OF-DAY)
• DAILY SCHEDULE (7 DAY TIME-CLOCK PROGRAM-
MING)
• HOLIDAY
• REMOTE RESET TEMPERATURE RANGE
• DATA LOGGER
The cause of all system shutdowns (safety or cycling)
is preserved (until the system is reset or restarts) in
the microcomputer’s memory for subsequent viewing
on the keypad display. The operator is continually ad-
vised of system operating conditions by various back-
ground and warning messages. The keypad contains
special service keys for use by the service technician
when performing system troubleshooting.
The MicroComputer Control Center is designed to be
compatible with most Energy
Management Systems
(EMS) in use today. The standard design allows for the
following EMS interface:
1. Remote Start
2. Remote Stop
3. Remote LCWT Setpoint (Pulse Width Modulated sig-
nal)
4. Remote Current Limit Setpoint (Pulse Width Modulated
signal)
5. A “Remote Mode Ready to Start” Status Contacts
6. Safety Shutdown Status Contacts
7. Cycling Shutdown Status Contacts
As an enhancement to the standard EMS features, an
optional card file with plug-in printed circuit boards is
available. These optional cards will accept a remote
LCWT 0 to 10°F or 0 to 20°F (0 to 5.56°C or 0 to
11.1°C) setpoint offset and/or remote current limit
setpoint interface from three user input choices:
1. 4-20mA
2. 0-10VDC
3. Contact Closures
* These keys provide a print-out when the customer connects a compatible printer to
the Micro Board RS-232 serial port. (See Form 160.49-N2.)
