General
The 19XL hermetic centri fugal liquid chiller con tains a microprocessor - ba sed control center
that monitors and controls all operations of the ma chine. The microprocessor control system
matches the cooling capac i ty of the machine to the cooli ng load while providing st ate-of-the-art
machine protection. The system controls cooling load within the set point plus the deadband by
sensing the leavi ng chilled water or brine temperatur e, and regulating the inlet guide vane via a
mechanically linked actuator motor. The guid e v ane is a variable flow prewhir l as s e mbly that
controls the refrigera tion effect in the cool er by r egu lating the amount of refr ig erant vapor flow
into the compressor. A n inc r e ase in guide vane opening inc r ea ses capacity. A decreas e in
guide vane opening d ecreases capacity. Ma chine protection is pr ovided by the processor which
monitors the digital and analog inputs and execut es c ap acity overrides or safet y shutdowns, if
required.
PIC System Components
The Product Integrated Control (PIC) is the control system on the machine. See Table 1. The
PIC controls the operat io n of the machine by monito r ing all operating condition s. The PIC can
diagnose a problem and let the operator know what th e pr ob lem is and what to check. It
promptly positions th e guide vanes to maintain lea ving chilled water temp erature. It can
interface with auxiliary equipm ent such as pum ps and cooling t ower fans to t urn them on onl y
when required. It continually checks all safeties to prevent any unsafe operating condition. It