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FIG. 18 – Millennium CONTROL CENTER
INTRODUCTION
The YORK Millennium Computer Control Center is a
microprocessor based control system capable of multi-
circuit control to maintain chilled liquid temperature and
provide safety control.
A 40 character display (2 lines of 20 characters) allows the
operator to display system operating parameters as well
as access programmed information already in memory. A
keypad for programming and accessing setpoints,
pressures, temperatures, motor current, cutouts, daily
schedule, options, and fault information is provided.
A master switch is available to activate or de-activate the
chiller system. Separate system (SYS) switches for each
refrigerant system (up to 4) are provided on the
Microprocessor Board.
Remote cycling, current limiting, and chilled water
temperature reset can be accomplished by user supplied
dry contacts.
72
UNIT CONTROLS AND OPERATION
Compressor starting, stopping, loading and unloading
decisions are performed by the Microprocessor to
maintain leaving water temperatures. These decisions
are a function of temperature deviation from setpoint and
the rate of change of temperature.
MICROPROCESSOR BOARD
The Microprocessor Board is the controller and decision
maker in the control panel. System inputs from pressure
transducers and temperature sensors are connected
directly to the Microprocessor Board. Other inputs from
the I/O Expansion Board such as slide valve position, oil
temperature, etc. are multiplexed on the Expansion Board
and are also sent to the Microprocessor Board. The
Microprocessor Board circuitry multiplexes all of these
analog inputs, digitizes them, and constantly scans them
to keep a constant watch on chiller operating conditions.
From this information, the Microprocessor then issues
commands to the Relay Output Board to activate and de-
activate contactors, solenoids, etc. for chilled liquid
control and safety control.
28164A
YORK INTERNATIONAL
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