the Microboard modulates a variable orifice to control the condenser refrigerant level to a
programmed setpoint. Other setpoints affect the control sensitivity and response. These setpoints
must be entered at chiller commissioning by a qualified service technician. Only a qualified service
technician may modify these settings.
While the chiller is shut down, the orifice is in the fully open position causing the sensed level to be
approximately 0%. When the chiller is started, after the vane motor end switch (VMS) opens when
entering SYSTEM RUN, if actual level is less than the level setpoint, a linearly increasing ramp is
applied to the level setpoint. This ramp causes the setpoint to go from the initial refrigerant level
(approximately 0%) to the programmed setpoint over a programmable period of time.
If the actual level is greater than the setpoint when the VMS opens, there is no pulldown period, it
immediately begins to control to the programmed setpoint.
While the chiller is running, the refrigerant level is normally controlled to the level setpoint.
However, anytime the vanes fully close (VMS closes), normal level control is terminated, any
refrigerant level setpoint in effect is cancelled and the outputs to the level control are constant
open.
Optional service isolation valves
If your chiller is equipped with optional service isolation valves on the discharge and liquid line,
these valves must remain open during operation. These valves are used for isolating the refrigerant
charge in either the evaporator or condenser to allow service access to the system. A refrigerant
pump-out unit will be required to isolate the refrigerant.
CAUTION
Isolation of the refrigerant in this system must be performed by a qualified service technician.
Optional hot gas bypass
Hot gas bypass is optional and is used to eliminate compressor surge during light load or high
head operation. The OptiView
™
control panel automatically modulates the hot gas valve open
and closed as required. Adjustment of the hot gas control valve must be performed by a qualified
service technician following the hot gas set-up procedure.
Note: Changes in chilled water flow require readjustment of the hot gas control to insure
correct operation.
OptiView
™
Control Center
The OptiView
™
Control Center is factory-mounted, wired and tested. The electronic panel
automatically controls the operation of the unit in meeting system cooling requirements while
minimizing energy usage. For detailed information on the Control Center, see System operating
procedures.
Solid state starter (optional)
The Solid State Starter is a reduced voltage starter that controls and maintains a constant current
flow to the motor during start-up. It is mounted on the chiller. Power and control wiring between
the starter and chiller are factory installed. The starter enclosure is NEMA-1 with a hinged access
door with lock and key. Electrical lugs for incoming power wiring are provided.
Model YK (Style H), R-134a and R-513A22
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