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The microprocessor and all supporting logic circuits, along
with the memory devices containing the op er at ing pro gram,
reside on the Microboard. All chiller op er at ing de ci sions
are made here. It receives analog and dig i tal in puts from
the chiller and remote devices. The analog in puts are
con nect ed directly to the Microboard. The dig i tal in puts
are received via the I/O Board (see de scrip tion be low).
Un der Program control, the Microboard op er ates the
re lays and triacs that are lo cat ed on the I/O Board.
The I/O Board acts as an input/output device for the
Microboard. It conditions the digital input signals for
the Microboard and contains relays and triacs that are
con trolled by the Microboard to control solenoids,
mo tor contactors and actuators. The 115VAC digital
in puts from switch and relay contacts are converted to
logic level voltages by Opto-Couplers. The relays have
+12VDC coils that are energized and de-energized by
the Microboard. The contacts of these relays control the
115VAC system solenoids, relays and motor contactors.
The triacs are turned on and off by the Microboard. The
outputs of these triacs control ac tu a tors.
A front panel-mounted Keypad allows Operator and
Ser vice Technician user interface. Membrane keys are
used to display chiller and system parameters, enter
setpoints and perform chiller and OptiView Control
Center di ag nos tics. It also contains a START-RUN-
STOP/RE SET Switch that is used to locally start and
stop the chill er and per form manual reset functions.
A front panel mounted liquid crystal Display allows
graph ic animated display of the chiller, chiller sub sys-
tems and system parameters. The chiller and work ing
com po nents of the chiller are displayed, along with
chiller operating pressures and temperatures. The Key-
pad is used to select displays showing increasing levels
of de tail of chiller working components.
A self-contained Power Supply supplies the nec es sary
DC volt ag es for all the components within the OptiView
Control Cen ter.
Chillers equipped with "P" compressors and all style
"F" and later chillers have a different Condenser High
Pressure Safety Cutout Switch (HPCO) than sup plied on
other compressor ap pli ca tions. This switch is mount ed
YORK INTERNATIONAL
on the condenser shell but has a different wiring in-
terface to the I/O Board and Motor Controller circuit.
Re fer to the I/O Board section of this book. Also, "P"
compressor applications and style "F" and later chillers
with "G" and "H5-8" compressors are equipped with a
High Speed Thrust Bearing Limit Switch instead of the
Proximity Probe supplied on other com pres sors. This
device detects abnormal bearing po si tion through probe
contact instead of distance mea sure ment as performed
with the Proximity Probe.
Style C and earlier chillers are equipped with fi xed speed
oil pumps. Style D and later chillers are equipped with
Variable Speed Oil Pumps.
Style F (and later) chillers require Flash Memory card
version C.MLM.01.07.xxx and later and are supplied
with factory-mounted Flow Sensors on the evapora-
tor and condenser. These are electronic thermal-type
sensors. The operating principle of the sensor is thermal
conductivity. It uses the cooling effect of a fl owing liq-
uid to sense fl ow. The temperature of the heated sensor
tip is sensed by a thermistor located in the tip. A second
thermistor, located higher in the tip in a non-heated area,
is only affected by changes in liquid temperature. The
temperatures sensed by the thermistors are compared.
Flowing liquid carries heat away from the heated sensor
tip, lowering its temperature. The lower temperature dif-
ferential between the two thermistors indicates the liquid
is fl owing. A higher differential indicates no fl ow. These
sensors are interfaced to Microboard analog inputs. Re-
fer to the SECTION 3 for a detailed explanation of this
fl ow sensor and interface.
If equipped with Flash Memory Card version
C.MLM.01.07.xxx (and later), the chiller Style/Com-
pressor combination must be entered using the Chiller
Style/Compressor Setpoint (refer to SECTION 23).
Once the applicable chiller style/compressor combina-
tion is entered, the program automatically bundles the
functionality and chiller control per the entered chiller
style/compressor requirements. The various chiller
style/compressor combinations are equipped differently
and have different control requirements. The variables
include:
• High Speed Thrust bearing proximity sensing
– Proximity Probe or Limit Switch
FORM 160.54-M1(503)
2
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