The chiller control system based on the PR205 provides coordinated, efficient, and protected operation of cooling equipment with up to four compressors, electronically controlled expansion valves, and a condenser fan. Designed for reliability and operational clarity, the system manages all essential refrigeration processes, monitors critical pressures and temperatures, and ensures safe and optimized performance in all operating conditions.
At startup, the system remains in standby until a remote start command is received. It then automatically performs a safety check of all monitored conditions. Operation begins only if no alarm is active; otherwise, the system alerts the operator to the fault and remains locked until manually reset. This ensures that the chiller never begins operation under unsafe or unknown conditions.
During normal operation, the controller continuously evaluates cooling demand and activates compressors in stages. Each compressor is started only after a defined delay, and the controller always selects the unit with the lowest accumulated running hours to promote balanced wear. As demand increases, additional compressors are engaged sequentially; as demand decreases, the system identifies and shuts down the compressor with the highest operating hours, but only when the load has fallen sufficiently below its stage threshold. This approach minimizes cycling, extends service life, and adapts output to real-time load conditions.
The electronic expansion valve is regulated through a dedicated control algorithm that maintains stable superheat and protects the compressor. Valve opening is adjusted dynamically based on cooling conditions and the number of active compressors. The controller automatically selects optimal control parameters depending on whether the system’s superheat is within its normal range, above it, or below it. In cases where suction pressure rises excessively, the system switches to a protective control mode to stabilize operation and prevent potential compressor damage.
Condenser fan operation is likewise optimized. The fan engages only when discharge pressure exceeds a defined threshold and then modulates its speed proportionally to maintain safe and efficient condenser conditions. This reduces unnecessary energy consumption and maintains consistent operational stability.
To further protect the system, a high-pressure warning stage is implemented. When discharge pressure approaches a critical limit, the controller issues a visual warning and temporarily reduces the cooling output request, lowering compressor load enough to bring pressures back into safe range. This preventive action avoids unnecessary system shutdowns and reduces thermal stress on the refrigeration circuit.
If any monitored parameter — such as suction pressure, discharge pressure, or compressor superheat — exceeds its allowable range for longer than the permitted delay, the system enters a locked-out state. In this condition all operation stops, an alarm is raised, and manual acknowledgment is required before the chiller can be restarted. Special handling is included for superheat monitoring during compressor startup to avoid nuisance alarms.
Together, these functions form a robust and intelligent control platform that ensures reliable cooling performance, balanced utilization of mechanical components, and comprehensive protection of the refrigeration system. The PR205-based architecture delivers operational transparency, predictable behavior, and long-term system stability — making it a strong foundation for modern chiller applications in commercial and industrial environments.
