Overall Health

Chiller 2 performance is generally healthy, with COP 6.49 versus expected 6.14, indicating that overall efficiency remains above expectation under the observed operating conditions.

Overall Condition: MONITOR

• Average cooling effect is approximately 1,056 kW, with average chiller loading of 33%, confirming that a significant proportion of operation occurs at part load.
• The four refrigeration systems provide broadly comparable cooling capacity, but differences are evident in efficiency and operating stability.
• Evaporator approach and suction superheat are generally within acceptable operating ranges, indicating fundamentally stable refrigerant-side operation.
• SYS4 demonstrates the strongest overall performance, while SYS2 presents the clearest efficiency improvement opportunity.
• No correlated multi-parameter deterioration signature currently indicates progressive whole-chiller mechanical degradation, major refrigerant loss or imminent compressor failure.
• The principal watch items are SYS2 efficiency, SYS3 high-load evaporator approach, SYS2/SYS3 part-load stability, high accumulated starts and intermittent telemetry anomalies.

Key Findings

Overall performance is satisfactory, but SYS2 efficiency, SYS3 high-load evaporator performance and SYS2/SYS3 part-load control stability require targeted investigation and continued monitoring.

• SYS4 is the strongest overall performer, delivering approximately 342 kW cooling with 31 kW input and COP ~11, while maintaining comparatively stable evaporator and superheat behaviour.
• SYS2 is the weakest efficiency performer, producing approximately 344 kW cooling with 41 kW input and COP ~8, despite similar average loading.
• SYS3 shows the strongest load-dependent evaporator concern, with approach increasing from 3.87°C at 25% load to 6.83°C at 100% load.
• SYS1 remains generally healthy, although evaporator approach variance increases to 2.50°C² at 100% loading, warranting continued observation during peak duty.
• SYS2 and SYS3 show their greatest suction-superheat variability at 25% loading, indicating reduced evaporator-control stability during minimum-load operation.
• Each refrigeration system has accumulated approximately 3,000 starts, making cycling frequency an important reliability and maintenance consideration.
• Importantly, these individual deviations are not presently accompanied by a simultaneous decline in COP, cooling capacity and refrigerant-control stability, reducing evidence of an active major mechanical deterioration process.

Historical Trends & Predictive Assessment

Long-term performance remains stable with no sustained COP decline, although persistent part-load instability and high cycling exposure could contribute to gradual control-component wear and future efficiency loss.

• COP has generally remained stable or improved across the historical period, including during several higher-load operating conditions.
• Strong efficiency during elevated loading reduces concern over significant progressive compressor or heat-exchanger deterioration.
• Most evaporator and superheat runtime occurs at 25–50% compressor loading, making part-load behaviour particularly important for long-term equipment condition.
• SYS2/SYS3 low-load instability should therefore be treated as a developing optimisation and reliability watch item, rather than evidence of an immediate mechanical fault.
• SYS3 evaporator approach should be trended at equivalent loading and operating conditions. A persistent upward shift at 75–100% load would strengthen evidence of developing heat-transfer deterioration.
• SYS2 COP should similarly be compared against SYS4 under matched load, water-temperature and operating-lift conditions before concluding that the efficiency difference represents mechanical degradation.
• The most credible future deterioration mechanism is currently gradual efficiency reduction, increased cycling stress and control-component wear, rather than imminent major compressor failure.

Unusual Behaviour & Event Trace

• 26 April 2025: LCHW reached approximately 37.1°C while the setpoint remained near 9°C. This is incompatible with normal cooling operation and suggests an enabled-but-not-cooling state, compressor staging issue or invalid temperature telemetry. Check chiller enable, compressor enable/current and ECHW/LCHW signals.
• 14 September 2025: COP fell to approximately 0.70 versus 5.37 expected. The isolated collapse is more consistent with low-load operation, invalid cooling/power calculation or an operating-state transition than sustained mechanical deterioration.
• 24 November 2025: COP fell to approximately 0.71 versus 4.82 expected. Correlate cooling effect, input power, compressor current, loading and chilled-water temperatures for this period.
• 28 November 2025: Calculated cooling reached approximately −1,785 kW with non-zero power. This is non-physical and strongly indicates reversed temperature difference, flow-signal error, timestamp misalignment or invalid operating-state filtering.
• 30 November 2025: LCHW reached approximately 30.3°C while the setpoint remained near 9°C. Confirm whether the chiller was enabled while all compressors were stopped or minimum-load locked out.
• 31 December 2025: Calculated cooling reached approximately −1,615 kW. Verify CHW flow, ECHW/LCHW measurement order, calculation sign convention and timestamp alignment.
• 4 January 2026: LCHW increased to approximately 23.3–25.5°C despite a setpoint near 9°C. Trace the enable command, compressor current feedback, staging status and temperature sensors.
• 21 January 2026: COP decreased to approximately 3.73 versus 5.89 expected, coinciding with abnormal chilled-water behaviour. Treat this as an operational or telemetry event unless confirmed across related parameters.
• 16 February, 18 May, 21 June, 10 July, 13 July and 1 August 2026: Repeated leaving-water/setpoint errors greater than approximately 7–15°C indicate recurring enabled-but-not-cooling periods, minimum-load lockout, control-sequencing problems or invalid status mapping.
• 19 May and 21 June 2026: Negative or near-zero calculated cooling occurred with non-zero power. Validate cooling-effect calculations and operating-state filters before treating these periods as equipment deterioration.
• 2 August 2026: LCHW again reached approximately 23.3–25.5°C while the setpoint remained near 9°C, confirming that the unusual high-temperature condition is recurring rather than unique.
• Engineering Trace Requirement: For every event, retrieve a window covering at least 15 minutes before and after the occurrence and compare chiller enable, compressor enable/current, system loading, ECHW, LCHW, setpoint, CHW flow, cooling effect, input power and COP.

Sensor & Telemetry Deviations

Telemetry is generally coherent, but non-physical cooling values, abnormal temperature excursions and intermittent low-load signal instability require validation before being classified as genuine equipment faults.

• Historical periods contain negative or near-zero calculated cooling effect despite non-zero power, which is inconsistent with normal refrigeration operation.
• Some periods show significantly elevated leaving chilled-water temperature while the chiller remains recorded as enabled, suggesting either genuine failure-to-cool events or enabled-but-not-producing-cooling operating states.
• SYS2 evaporator approach exhibits unusually wide scatter at low load, including occasional non-physical values.
• SYS3 shows transient suction-superheat excursions at 25% loading followed by rapid recovery toward normal conditions.
• These deviations may originate from sensor noise, calculation timing, operating-state transitions, signal mapping or expansion-control instability and should not automatically trigger mechanical fault classification.
• No consistent long-term sensor bias is currently evident across all four refrigeration systems.
• Compressor-off, start-up/stabilisation and invalid telemetry periods should be excluded from condition baselines where appropriate so that transient states do not distort COP, evaporator approach or suction-superheat diagnostics.
• Abnormal telemetry should be validated and appropriately filtered before being incorporated into automated predictive-maintenance decisions.

Performance Analysis

Cooling capacity remains well balanced across all four systems, while SYS4 provides the strongest overall efficiency and SYS2 represents the greatest performance optimisation opportunity.

• Whole-chiller COP 6.49 versus expected 6.14 is approximately 5.7% above the expected efficiency benchmark under the observed operating conditions.
• Average system cooling capacities are closely grouped at approximately SYS1 345 kW, SYS2 344 kW, SYS3 337 kW and SYS4 342 kW, indicating no obvious sustained capacity loss in any individual system.
• Average evaporator approaches remain close to expected: SYS1 4.25°C vs 4.4°C expected; SYS2 4.19°C vs 4.0°C; SYS3 4.44°C vs 4.4°C; SYS4 4.23°C vs 4.3°C.
• These averages do not indicate severe evaporator degradation; however, loading-specific analysis identifies SYS3’s elevated approach at 75–100% load as an important condition-monitoring parameter.
• Suction superheat remains approximately 6–7 K across all systems and loading stages, which does not strongly support major refrigerant undercharge or persistent evaporator overfeeding.
• SYS4 currently provides the best combination of COP, evaporator performance and refrigerant-control stability and should therefore be used as the internal benchmark for comparative diagnostics.
• Performance comparisons should be made at equivalent load and operating conditions wherever possible to separate genuine equipment deterioration from changes caused by operating lift, water temperatures or plant demand.

Engineering Interpretation

The combined evidence indicates localised efficiency, heat-transfer, control and telemetry issues rather than progressive whole-chiller mechanical deterioration.

• SYS2: Persistent lower COP despite comparable average cooling output identifies a circuit-specific efficiency deviation. Confirm this under matched loading, entering-water temperature and operating-lift conditions before assigning a mechanical root cause.
• SYS3: Evaporator approach increases materially with loading, reaching 6.83°C at 100% load. This adverse load-dependent pattern warrants verification of chilled-water flow, evaporator heat-transfer condition, refrigerant distribution and associated temperature measurements.
• SYS2/SYS3: Elevated suction-superheat variance at 25% loading is consistent with part-load TXV/EEV hunting or control instability. Normalisation at higher loading makes a major refrigerant-charge problem less strongly supported by the current evidence.
• SYS1: Overall operation remains satisfactory, although increased full-load evaporator variance should continue to be monitored.
• SYS4: Stable thermal and control behaviour makes this system the most appropriate benchmark circuit for comparison with SYS1–SYS3.
• No correlated multi-parameter deterioration signature is currently present: COP remains strong, cooling capacity is maintained and suction superheat remains generally controlled.
• Isolated abnormal parameters should therefore not be classified as developing mechanical faults unless they become persistent and are corroborated by related performance indicators.
• The strongest current maintenance opportunity is targeted system investigation, control optimisation and telemetry validation rather than broad mechanical component replacement.

Preventative Maintenance

Preventative maintenance should focus on SYS2 performance verification, SYS3 high-load evaporator behaviour, SYS2/SYS3 low-load control stability, cycling reduction and telemetry validation before intrusive mechanical intervention.

• SYS2: Conduct matched-condition performance testing against SYS4, comparing COP, input power, evaporator approach, suction/discharge conditions and cooling output.
• SYS3: Verify chilled-water flow, evaporator condition and refrigerant distribution during 75–100% loading, and compare approach temperature before and after any maintenance intervention.
• SYS2/SYS3: Inspect and optimise TXV/EEV operation at 25% loading, including superheat setpoints, actuator response and PID/step-control behaviour.
• Validate SYS3 suction temperature/pressure measurements and SYS2 evaporator temperature measurements before treating transient excursions as confirmed equipment faults.
• Verify ECHW, LCHW, chilled-water flow, cooling-effect and electrical-power measurements, including sensor calibration, scaling, sign convention, timestamp alignment and calculation logic.
• Cross-check chiller enable command against compressor enable and current feedback to identify enabled-but-not-cooling periods.
• Review lead/lag sequencing, anti-recycle timers, minimum runtime and chilled-water control deadband to reduce unnecessary cycling.
• Continue routine evaporator/condenser inspection, water-treatment verification, refrigerant checks, oil assessment and compressor condition monitoring.
• Record post-maintenance baseline values so future changes in COP, approach, superheat, cooling output and input power can be evaluated against equivalent operating conditions.

Maintenance Priority

Maintenance should prioritise SYS2 efficiency first, SYS3 high-load evaporator performance second, followed by low-load control optimisation, telemetry validation and cycling reduction.

• Priority 1 — SYS2 Performance: Confirm and investigate its persistent efficiency disadvantage relative to SYS1 and SYS4 under matched operating conditions.
• Priority 2 — SYS3 Evaporator: Investigate elevated approach at 75–100% loading and verify water-side, refrigerant-side and measurement conditions.
• Priority 3 — SYS2/SYS3 Low-Load Control: Diagnose 25% superheat variability and optimise expansion-valve control.
• Priority 4 — Telemetry & Controls: Resolve non-physical cooling values, abnormal temperature events and operating-state inconsistencies to improve predictive-diagnostic reliability.
• Priority 5 — Cycling Reduction: Review staging, lead/lag and start/stop strategy to reduce unnecessary compressor starts and associated wear.
• Priority 6 — SYS1/SYS4: Continue condition monitoring and planned preventative maintenance, with SYS4 retained as the current performance benchmark.

Risk Level

Overall risk remains LOW–MODERATE / MONITOR, with no correlated evidence of imminent mechanical failure but moderate efficiency, control, cycling and data-integrity risks requiring continued attention.

• Mechanical Failure Risk: LOW — current COP, cooling capacity and suction-superheat behaviour do not indicate imminent compressor or major refrigerant-system failure.
• Efficiency Risk: MODERATE — SYS2 consistently underperforms the stronger circuits and represents the clearest energy-optimisation opportunity.
• Heat-Transfer Risk: MODERATE for SYS3 — elevated evaporator approach at high load requires trending and investigation but does not currently confirm severe fouling or capacity deterioration.
• Control Risk: MODERATE for SYS2/SYS3 — elevated part-load superheat variability combined with substantial 25% runtime could increase control-component wear and reduce part-load stability.
• Cycling/Wear Risk: MODERATE — approximately 3,000 starts per system warrant review of staging and anti-cycle control.
• Data-Integrity Risk: MODERATE — non-physical cooling and abnormal temperature events could create false predictive-maintenance alarms or obscure genuine developing faults.
• Overall Prognosis: Chiller 2 remains serviceable and thermodynamically efficient, with no correlated evidence of progressive whole-machine deterioration. Current findings support targeted condition-based maintenance and control optimisation rather than urgent overhaul. SYS2 efficiency, SYS3 high-load evaporator approach and SYS2/SYS3 low-load control stability should remain the principal watch items. Escalation from MONITOR to WARNING should be considered if deterioration becomes persistent under equivalent operating conditions and is corroborated across multiple parameters—particularly falling COP, rising evaporator approach, increasing superheat instability, declining cooling output and increasing input power. That combined deterioration signature is not currently evident.