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YORK INTERNATIONAL
*These keys provide a print-out when the customer connects a compatible printer to the Micro Board RS-232 serial port. (See Form 160.60-N2.)
The YORK MicroComputer Control Center is a micro-
processor based control system for R-134A centrifugal
chillers. It controls the leaving chilled water temperature
via prerotation vane and engine speed control and has
the ability to limit engine loading via control of the
prerotation vanes.
A keypad mounted on the front of the Control Center (See
Fig. 4) allows the operator to display system operating
parameters on a 40 character alphanumeric display that
is part of the keypad. These readings are displayed via
Display keypad as follows: (In the English mode; tem-
peratures 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 COMPRESSOR OIL PRESSURE
CONDENSER LIQUID TEMPERATURES LEAVING
AND RETURN
PRINT*
HISTORY PRINT*
SATURATION TEMPERATURES EVAPORATOR
AND CONDENSER
DISCHARGE TEMPERATURE
COMPRESSOR OIL TEMPERATURE
HIGH & LOW OIL PRESSURE TRANSDUCER
PRESSURE
ENGINE RPM % VANES
% ENGINE LOADING
% OPERATING HOURS/START COUNTER
ENGINE DATA
CHILLER DATA
The system setpoints (See Fig. 5) are operator entered
on the front control center
SETPOINTS
keypad. These
setpoints can also be displayed on the 40 character al-
phanumeric display. The system setpoints are:
CHILLED LIQUID TEMPERATURE (LCWT)
% ENGINE LOAD LIMIT
PULLDOWN DEMAND LIMIT
CLOCK (TIME-OF-DAY)
DAILY SCHEDULE (7 DAY TIME-CLOCK
PROGRAMMING)
HOLIDAY
REMOTE RESET TEMPERATURE RANGE
DATA LOGGER
SERVICE INTERVAL
The cause of all system shutdowns (safety or cycling) is
preserved (until the system is reset or restarts) in the
MicroComputers memory for subsequent viewing on the
keypad display. The operator is continually advised of
system operating conditions by various background 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 com-
patible 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
signal)
4. Remote Engine Load 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
8. System Run Contacts
As an enhancement to the standard EMS features, an
optional card file with plug-in printed circuit boards is avail-
able. These optional cards will accept a remote LCWT 0°
to 10°F or 0° to 20°F setpoint offset and/or remote engine
load limit setpoint interface from three user input choices:
1. 4-20mA
2. 0-10VDC
3. contact closures
INTRODUCTION
