Controls; Definitions; General; Pic 5+ System Components - Carrier 19DV Series Installation, Operation And Maintenance Instructions

2.6 – CONTROLS

2.6.1 Definitions

ANALOG SIGNAL — An analog signal varies in proportion to the monitored source. It quantifies values between
operating limits. (Example: A temperature sensor is an analog device because its resistance changes in proportion
to the temperature, generating many values.)
DISCRETE SIGNAL — A discrete signal is a 2-position representation of the value of a monitored source.
(Example: A switch produces a discrete signal indicating whether a value is above or below a set point or
boundary by generating an on/off, high/low, or open/closed signal.)

2.6.2 General

The 19DV centrifugal liquid chiller contains a microprocessor-based control center that monitors and controls all
operations of the chiller. The microprocessor control system matches the cooling capacity of the chiller to the
cooling load while providing state-of-the-art chiller protection.
The system controls cooling load within the set point plus the deadband by sensing the leaving chilled water or
brine temperature and regulating the inlet guide vanes and compressor speed. The guide vane is a variable flow
pre-whirl assembly that controls the refrigeration effect in the cooler by regulating the amount of refrigerant vapor
flow into the compressor. An increase in guide vane opening increases capacity. A decrease in guide vane
opening decreases capacity. The microprocessor-based control center
protects the chiller by monitoring the digital and analog inputs and executing capacity overrides or safety
shutdowns, if required. The variable frequency drive (VFD) allows compressor start-up and capacity control by
modulating the motor frequency based on the operation condition.

2.6.3 PIC 5+ system components

The chiller control system is called the PIC5+ (Product Integrated Control 5).
As with previous PIC versions, the PIC5+ system controls the operation of the chiller by monitoring all operating
conditions. The PIC5+ control system can diagnose a problem and let the operator know what the problem is and
what to check. It positions the guide vanes and VFD speed to maintain leaving chilled water temperature. It
controls the refrigerant pump providing compressor bearing lubrication and can interface with auxiliary equipment
such as pumps and cooling tower fans to turn them on when required.
It continually checks all safeties to prevent any unsafe operating condition. It regulates the envelope control
valve for stabilized aerodynamic operation, if installed. The PIC5+ controls offer an operator trending function to
help the operator monitor the chiller status more easily and for critical compressor motor protection. The PIC5+
system provides open protocols to support the competitive BMS system and can be integrated into Carrier's
Lifecycle System Management for remote monitoring and data management.
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