Unit Controls And Operation - York RecipPak YEAZ88DR6 Installation Operation & Maintenance

FIG. 8 – MICROCOMPUTER CONTROL CENTER
INTRODUCTION
The YORK MicroComputer Control Center is a micro-
processor based control system capable of multi-circuit
control to maintain chilled liquid temperature.
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 set-
points, pressures, temperatures, motor current, cutouts,
daily schedule, options, and fault information is provided.
A master ON/OFF switch is available to activate or
de-activate the chiller system. Separate system (SYS)
switches for each refrigerant system (up to 4) are pro-
vided on the Microprocessor Board.
Remote cycling, unloading, and chilled water tempera-
ture reset can be accomplished by user supplied dry
contacts.
YORK INTERNATIONAL

UNIT CONTROLS AND OPERATION

YORK MICROCOMPUTER CONTROL CENTER
Compressor starting/stopping and loading/unloading de-
cisions are performed by the Microprocessor to main-
tain leaving water temperatures. These decisions are a
function of temperature deviation from setpoint and rate
of change of temperature.
MICROPROCESSOR BOARD
The Microprocessor Board is the controller and decision
maker in the control panel. System inputs from pres-
sure transducers, temperature sensors, and C.T.'s are
connected directly to the Microprocessor Board. The
Microprocessor Board circuitry multiplexer these ana-
log inputs, digitizes them, and constantly scans them
to keep a constant watch on the chiller operating condi-
tions. From this information, the Microprocessor then
issues commands to the Relay Output Board to control
contactors, solenoids, etc. for water temperature con-
trol and to react to safety conditions.
Keypad commands are acted upon by the micro to
change setpoints, Cut-outs, scheduling, operating re-
quirements, and to provide displays.
FORM 150.60-NM4
26572A(D)
23