York 371-01200-010, Operating & Maintenance

FORM 160.52-O1

7

YORK INTERNATIONAL

INTRODUCTION

The YORK MicroComputer Control Center is a micro-

processor based control system for R134a centrifugal

chillers. It controls the leaving chilled water tempera-

ture via pre-rotation vane control and has the ability to

limit motor current via control of the pre-rotation vanes.

Further, it is compatible with YORK Solid State Starter

(optional), Variable Speed Drive (optional), and elec-

tromechanical starter applications.

The Control Center can be equipped with an optional

Chinese language display, either as a field retrofit or

factory supplied option on new units. This display

mounts on the control center door, directly above the

standard display. Both the standard and Chinese dis-

play will be present, providing display messages simul-

taneously in both English and Chinese language. (The

Control Center must be configured for Chinese display

by a qualified service technician. Instructions are con-

tained in YORK service manual, Form 160.49-M2.)

A keypad mounted on the front of the Control Center

(see Fig. 3) allows the operator to display system oper-

ating parameters on a 40 character alphanumeric dis-

play that is part of the keypad. These readings are dis-

played via “Display” keypad as follows:  (In the English

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 – PUMP SPEED
 • CONDENSER LIQUID TEMPERATURES – OP-

TIONAL FIELD INSTALLED – LEAVING AND RE-

TURN

 * HIGH SPEED THRUST POSITION – HIGH SPEED

THRUST OIL TEMPERATURE

 • 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

PRESSURE

 • SOLID STATE STARTER MOTOR CURRENT /

VOLTS (When Supplied)

 • CONDENSER REFRIGERANT LEVEL

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)
 • % CURRENT LIMIT
 • PULLDOWN DEMAND LIMIT
 • CLOCK (TIME-OF-DAY)
 • DAILY SCHEDULE (7 DAY TIME-CLOCK PRO-

GRAMMING)

 • HOLIDAY
 • REMOTE RESET TEMPERATURE RANGE
 • DATA LOGGER
 • CONDENSER REFRIGERANT LEVEL

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 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

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

signal)

4. Remote Current Limit Setpoint (Pulse Width Modu-

lated 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 (0 to 5.5°C) or 0 to 20°F (0 to 11.1°C)

setpoint offset and/or remote current limit setpoint in-

terface 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.