York YCAS0098EB, Installation Operation & Maintenance, Page: 123 / 184

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JOHNSON CONTROLS
FORM 201.18-NM7
1. INTRODUCTION & PHYSICAL DESCRIPTION
29023A
1.1 GENERAL
The YORK Screw Chiller Control Panel is a micro-
processor based control system fitted to YCAS liq -
uid chillers. It is capable of multi-refrigerant system
control to maintain chilled liquid temperature within
programmed limits and to provide safety control of the
chiller. The microprocessor monitors leaving chilled
liquid temperature deviation from setpoint and the rate
of change of this temperature to start, stop, load and
unload compressors as required.
User interface is via a touch keypad and a liquid crystal
display allowing access to operating and programmed
data. Information can be displayed in English (Imperi-
al) units or SI (Metric) units (Section 8.1). Conversion
tables are provided at the back of this manual.
A master ON/OFF rocker switch is provided on the
chiller control panel to activate or deactivate the com-
plete chiller, while switches to activate or deactivate
individual refrigerant systems are provided on the Mi-
croprocessor Board(s).
External interface is available for control of the chiller
via a YORK ISN System or YORK Remote Control
Center. In addition, EMS/BAS System connections are
provided for remote cycling, current limiting, remote
temperature setpoint reset and alarm annunciation.
YCAS chillers each have a single split circuit evapora-
tor serving 2 independent refrigerant systems. YCAS 2
system chillers are configured as a single self contained
section with a single control panel controlling the two
refrigerant systems.
1.2 KEYPAD & DISPLAY
An operator keypad allows complete control of the
chiller from a central location. The keypad offers a
multitude of commands available to access displays,
program setpoints, and initiate system commands. Keys
are grouped and color coded for clarity and ease of use.
A 40 Character Liquid Crystal Display (2 lines of 20
characters) is used for displaying system parameters
and operator messages. The display has a lighted back-
ground for night viewing as well as a special feature
which intensifies the display for viewing in direct
sunlight.
Displays will be updated every two seconds by the
microprocessor.
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