Overall Health

Chiller 1 remains serviceable and broadly stable, with COP 5.82 versus expected 5.91, approximately 1.5% below expectation under the observed operating conditions. Recurring chilled-water excursions, load-dependent evaporator deviations, part-load control instability, telemetry inconsistencies and high compressor-start counts justify continued monitoring.

Overall Condition: MONITOR

• Average cooling effect is approximately 798 kW, with average chiller loading of 28%, confirming predominantly part-load operation.
• Average entering and leaving chilled-water temperatures are 11.04°C and 9.31°C, with an average leaving-water/setpoint error of only 0.36°C.
• Average performance is generally acceptable, but system behaviour is uneven: SYS1 has the highest calculated efficiency, SYS3 the lowest average system COP, and SYS4 the clearest evaporator concern.
• Condenser performance is generally satisfactory. SYS2–SYS4 remain below their expected condenser-approach benchmarks, while SYS1 is moderately above expected.
• No correlated whole-chiller deterioration signature currently combines falling COP, declining cooling capacity, increasing power and worsening refrigerant-control behaviour.
• Principal watch items are SYS4 evaporator performance, SYS3 high-load approach/superheat, SYS2 low-load instability, chilled-water temperature excursions, telemetry integrity and compressor cycling.
• Current evidence supports targeted condition-based maintenance and control optimisation rather than urgent overhaul.

 

Key Findings

Overall operation remains serviceable, but SYS4 evaporator performance, SYS3 full-load refrigerant behaviour, SYS2 low-load control and recurring chilled-water anomalies require engineering attention.

• SYS1: Approximately 299 kW cooling, 25 kW input, 28% loading and calculated COP 12.11. It is the strongest calculated efficiency performer, subject to verification of system-level power allocation.
• SYS2: Produces the highest average cooling output at approximately 327 kW, with 39 kW input, 27% loading and COP 8.29.
• SYS3: Produces approximately 297 kW cooling with 40 kW input, 28% loading and COP 7.35, making it the lowest average efficiency performer.
• SYS4: Produces approximately 293 kW cooling with 31 kW input, 28% loading and COP 9.42, but has the most significant evaporator concern.
• SYS4 evaporator approach increases from 5.41°C at 25% to 8.37°C at 100% loading, generating an ALERT at full load.
• SYS3 provides a stronger correlated high-load signature: evaporator approach reaches 7.91°C, while suction superheat simultaneously reaches 8.74 K with 4.00°C² variance.
• SYS2 behaves differently: evaporator approach decreases from 6.81°C at 25% to 2.85°C at 100%, while superheat variance decreases from 11.51°C² to 0.37°C². This identifies a predominantly low-load control issue.
• Compressor starts are high at approximately 3,990 / 3,995 / 4,179 / 4,135 for SYS1–SYS4, with SYS3 having the highest count.
• Whole-chiller trends also contain high LCHW, near-zero COP, unusual power/cooling relationships and enable-status inconsistencies requiring event-level investigation.

 

Historical Trends & Predictive Assessment

Long-term operation does not currently demonstrate confirmed progressive whole-machine deterioration, but several load-dependent and operational trends provide useful predictive watch points.

• Whole-chiller COP fluctuates around its expected benchmark rather than showing a sustained decline. The average 1.5% deficit alone does not confirm mechanical degradation.
• The low 28% average loading means part-load operation, cycling and transitional states strongly influence historical averages.
• The chilled-water setpoint appears to have reduced from approximately 9°C to 7°C during June 2025. Comparisons before and after this change should account for the resulting change in operating lift.
• The displayed month-to-month cooling trend reduces during parts of the assessment period; however, unrestricted averages cannot distinguish capacity deterioration from changes in demand, loading, water temperatures, staging or runtime.
• Peak cooling of approximately 1,716 kW on 26 May 2026 confirms that substantial whole-chiller capacity remained available during the assessment period.
• More recent high-load days sometimes deliver less than 1,600 kW at comparable recorded current. This should be treated as a predictive watch item until confirmed under matched loading, water-temperature, flow and operating-lift conditions.
• SYS1, SYS3 and SYS4 show rising evaporator approach with increasing loading. The strongest deviation is SYS4, reaching 8.37°C at full load.
• SYS4 also shows indications of increasing evaporator approach during higher-load periods between spring 2025 and summer 2026. Confirming deterioration requires comparison at equivalent cooling output, water flow and entering-water temperature.
• SYS2’s approach and superheat variability improve markedly as loading increases, indicating that its principal limitation is minimum-load stability rather than full-load heat-transfer capability.
• SYS3’s simultaneous high-load approach and superheat elevation represents the strongest corroborated refrigerant-side watch signature.
• No present evidence demonstrates simultaneous deterioration in whole-chiller COP, cooling capacity, power consumption and refrigerant-control stability.

 

Unusual Behaviour & Event Trace

The following dated events should be traced against the underlying 10-second telemetry. They should not be classified as confirmed equipment faults until operating state, signal quality and related parameters have been checked.

• 20 March 2025 – SYS3 unusually high COP: Calculated SYS3 COP reached approximately 12.42 at 25% loading.
  Classification: Telemetry/calculation or unusual boundary-condition event.
  Trace: Verify system cooling allocation, system power allocation, compressor current, water temperatures and operating lift.
• 26 April 2025 – Extreme leaving chilled-water temperature: LCHW reached approximately 34.78°C, compared with the normal 8–9°C setpoint range.
  Classification: Operational/control/telemetry event.
  Trace: Check chiller enable, compressor enable and current feedback, CHW flow, pump operation, bypass-valve position and LCHW sensor validity.
• 30 June and 11–12 August 2025 – Near-full-load efficiency imbalance: During near-100% loading, SYS2/SYS3 COP reportedly reduced towards approximately 4–5 / 3–4, while SYS1/SYS4 generally remained higher.
  Classification: Possible matched-load system efficiency deviation.
  Trace: Compare system power, cooling, evaporator/condenser approach, superheat and operating lift at equivalent loading.
• 11 August 2025 – SYS4 electrical/thermal outlier: SYS4 recorded an input-power outlier of approximately 86.39 kW and a higher condenser approach of approximately 3.87°C.
  Classification: High-load event or possible metering anomaly.
  Trace: Verify electrical metering, condenser-water temperatures/flow, loading and discharge pressure.
• 7 October 2025 – SYS2 low COP: SYS2 COP fell to approximately 2.98 as an isolated event.
  Classification: Transitional operation, control deviation or invalid cooling/power relationship.
  Trace: Check system loading, cooling output, input power, compressor state and water temperatures before and after the event.
• 25 December 2025 – SYS4 unusually high COP: SYS4 COP reached approximately 11.65 at 25% loading.
  Classification: Possible low-load calculation distortion, atypical lift condition or power-allocation error.
  Trace: Validate system power, cooling allocation and condenser/evaporator temperatures.
• 28 January 2026 – Severe setpoint deviation: LCHW/setpoint error reached approximately 16.4°C.
  Classification: Failure-to-cool, enable/status mismatch, hydronic-control event or temperature-signal anomaly.
  Trace: Correlate enable command, compressor current, CHW flow, pump/valve status, ECHW, LCHW and setpoint.
• 19 May 2026 – SYS2 unusually high COP: SYS2 COP reached approximately 9.1, substantially above its normal historical band.
  Classification: Possible favourable operating lift or calculation/metering outlier.
  Trace: Compare cooling, system power, loading and condenser-water conditions.
• 26 May 2026 – Peak cooling reference: Whole-chiller cooling reached approximately 1,716 kW.
  Classification: Valid high-capacity reference event unless contradicted by telemetry.
  Trace: Preserve this event as a matched-condition reference for future capacity comparisons.
• 8 July 2026 – Near-full-load system comparison: High loading again exposed lower calculated efficiency on SYS2/SYS3 relative to SYS1/SYS4.
  Classification: Recurrent system efficiency imbalance.
  Trace: Compare with the June/August 2025 high-load events under equivalent lift and water temperatures.
• 1 August 2026 – Enable-status anomaly: The chiller enable signal unexpectedly recorded a low/off state while associated performance or temperature behaviour remained inconsistent with a clean shutdown.
  Classification: Status mapping, timing or control-sequence anomaly.
  Trace: Cross-check command status, feedback status, compressor enables, current and timestamp alignment.
• For each event, retrieve at least 15 minutes before and after the occurrence and compare enable status, compressor current, system loading, ECHW, LCHW, setpoint, CHW flow, cooling effect, input power, COP, evaporator approach and superheat.
• Record whether each event is isolated, intermittent or recurring, and whether it occurs during start-up, shutdown, minimum-load operation or steady loading.

 

Sensor & Telemetry Deviations

Telemetry is adequate for high-level performance assessment, but several operating-state and derived-value inconsistencies reduce confidence in fine refrigerant diagnostics.

• Severe LCHW and setpoint-error excursions are inconsistent with the much lower long-term averages and require separation of genuine failure-to-cool periods from shutdowns, bypass operation and sensor anomalies.
• Several periods show near-zero COP with substantial current, or non-zero calculated cooling with very low or zero system input power.
• Extended zero-power periods with non-zero system cooling indicate possible system-power allocation, signal mapping, aggregation or timestamp-alignment errors.
• Isolated unusually high COP values at low loading are more likely to reflect boundary conditions or calculation distortion than extraordinary compressor efficiency.
• Chiller and compressor enable signals occasionally appear inconsistent with temperature, current or cooling behaviour, suggesting command/status mismatch or logging misalignment.
• Some instantaneous evaporator-approach and superheat values are negative, near zero or extremely high. These should be treated as invalid or transitional unless supported by stable related measurements.
• Intermittent zero DP or flow readings while compressors appear active require range, scaling and operating-state verification.
• Auxiliary telemetry contains some incomplete records, but the principal water-temperature, pressure, electrical and compressor-state signals appear broadly available.
• Compressor-off, start-up, stabilisation, insufficient-current and invalid-loading periods should be excluded from performance baselines.
• Predictive alarms should require persistence and corroboration across multiple related parameters, rather than responding to one abnormal measurement.

 

Performance Analysis

Cooling capacity remains reasonably balanced across the four circuits, but efficiency and refrigerant-side behaviour differ materially.

• Whole-chiller COP 5.82 versus expected 5.91 represents approximately 1.5% below benchmark under the observed operating conditions.
• Average cooling capacities are approximately SYS1 299 kW, SYS2 327 kW, SYS3 297 kW and SYS4 293 kW, indicating no sustained gross capacity collapse in any circuit.
• Calculated system COP values are approximately SYS1 12.11, SYS2 8.29, SYS3 7.35 and SYS4 9.42.
• SYS1’s exceptionally high calculated COP should remain a provisional internal benchmark until system-level power allocation and zero-power/non-zero-cooling periods have been validated.
• Average evaporator approaches are:
  
  • SYS1: 4.71°C versus 4.4°C expected
  • SYS2: 5.06°C versus 4.3°C expected
  • SYS3: 4.88°C versus 4.6°C expected
  • SYS4: 5.94°C versus 4.9°C expected
• SYS4 has the largest average evaporator-approach excess and the highest full-load value at 8.37°C.
• SYS3’s full-load approach of 7.91°C is accompanied by 8.74 K suction superheat, making it a stronger correlated condition signature than an isolated high approach.
• SYS2’s low-load approach and superheat variance fall substantially as load increases, identifying part-load control instability rather than a high-load thermal limitation.
• Condenser approaches are approximately:
  
  • SYS1: 2.8°C versus 2.4°C expected
  • SYS2: 2.3°C versus 4.1°C expected
  • SYS3: 2.2°C versus 3.1°C expected
  • SYS4: 2.4°C versus 3.9°C expected
• Current thermal concerns are therefore concentrated primarily on the evaporator/refrigerant-control side, rather than a common condenser restriction.
• All system comparisons should be normalised for loading, entering-water temperatures, flow and operating lift before assigning mechanical efficiency loss.

 

Engineering Interpretation

The combined evidence indicates localised load-dependent evaporator, control, hydronic and telemetry deviations rather than a common progressive whole-chiller fault.

• SYS1: Provides the highest calculated COP and generally stable operation. Its approach nevertheless increases from 3.82°C at 25% to 7.62°C at 100%, so high-load heat-transfer performance should remain under observation.
• SYS2: Exhibits the strongest low-load instability. Falling approach and superheat variance with increasing loading support investigation of expansion-valve control, sensor stability and operating transitions rather than full-load fouling.
• SYS3: Requires attention at full load because elevated approach and superheat occur together. Possible causes include refrigerant distribution, expansion-valve limitation, liquid-line restriction, evaporator flow imbalance or associated sensor error.
• SYS4: Represents the clearest evaporator concern. Its above-expected average approach, 8.37°C full-load approach and superheat alerts across the loading range justify targeted investigation.
• Some extreme SYS4 approach and SYS3 superheat points are too large or inconsistent to be accepted as physical conditions without telemetry validation.
• Condenser side: No common condenser restriction is evident. SYS1 warrants observation because its average approach is moderately above expected, but current evidence does not confirm severe fouling.
• Extreme LCHW events are unlikely to be explained by gradual heat-exchanger deterioration alone. They more strongly suggest enable/staging problems, pump or bypass-valve behaviour, minimum-load lockout, shutdown states or temperature-signal anomalies.
• The displayed downward cooling trend is not sufficient to confirm capacity degradation because operating conditions have not been normalised.
• No correlated evidence presently confirms major refrigerant loss, imminent compressor failure or progressive whole-machine deterioration.
• The strongest maintenance opportunity is targeted system investigation, control optimisation, telemetry correction and matched-condition verification, not broad component replacement.

 

Preventative Maintenance

Preventative maintenance should address SYS4/SYS3 refrigerant-side behaviour, dated chilled-water events, SYS2 low-load control, telemetry quality and compressor cycling.

• SYS4: Verify chilled-water flow, evaporator cleanliness, strainers, water balance, refrigerant distribution and temperature/pressure measurements at 75–100% loading.
• Confirm whether SYS4’s 8.37°C full-load approach and superheat alerts remain repeatable under equivalent loading and water conditions.
• Inspect SYS4 expansion-valve actuator response, valve authority, control tuning and possible liquid-line or distribution restrictions.
• SYS3: Conduct a controlled full-load test correlating approach, superheat, suction pressure, cooling output, input power and expansion-valve position.
• SYS2: Inspect TXV/EEV behaviour at 25% loading, including actuator response, superheat setpoint, PID/step-control stability and operating transitions.
• SYS1: Continue routine maintenance and verify high-load evaporator approach. Confirm system-level power allocation before using its calculated COP as the performance benchmark.
• Investigate every dated high-LCHW event using enable command, compressor current, pump status, bypass/valve position, water flow and temperature signals.
• Verify ECHW, LCHW, CHW flow, cooling-effect and power measurements, including calibration, scaling, sign convention and timestamp alignment.
• Validate derived approach, superheat, saturated-temperature and subcooling calculations against refrigerant property data and correctly mapped sensors.
• Review lead/lag sequencing, minimum runtime, anti-recycle timers, capacity staging and chilled-water control deadband to reduce unnecessary cycling.
• Continue routine evaporator/condenser inspection, water-treatment verification, refrigerant assessment, oil checks and compressor-condition monitoring.
• Do not mechanically or chemically clean an exchanger solely because Copilot identified a declining trend. First confirm the deviation through matched-condition testing or physical inspection.
• Establish post-maintenance baseline values for COP, approach, superheat, cooling and power at each loading stage.

 

Maintenance Priority

Maintenance should prioritise SYS4 evaporator performance and SYS3 full-load behaviour, while treating chilled-water event tracing and telemetry verification as essential supporting actions.

• Priority 1 — SYS4 Evaporator and Control: Investigate the above-expected average approach, 8.37°C full-load approach, superheat alerts, water flow, expansion control and sensor validity.
• Priority 2 — SYS3 High-Load Operation: Investigate the correlated 7.91°C evaporator approach and 8.74 K suction superheat at 100% loading.
• Priority 3 — Chilled-Water Event Investigation: Trace the dated high-LCHW/setpoint-error events and confirm enable, compressor, pump and bypass-valve behaviour.
• Priority 4 — Telemetry and Calculation Integrity: Resolve zero-power/non-zero-cooling periods, enable-status mismatches, invalid derived values and timestamp inconsistencies.
• Priority 5 — SYS2 Low-Load Control: Diagnose high 25% approach/superheat variance and optimise expansion-valve control.
• Priority 6 — Cycling Reduction: Review staging and anti-cycle strategy, particularly for SYS3/SYS4 with 4,179 and 4,135 starts.
• Priority 7 — Matched-Condition Verification: Confirm system COP rankings and any cooling-capacity trend before diagnosing compressor or heat-exchanger degradation.
• Priority 8 — SYS1 Routine Monitoring: Continue planned maintenance and use SYS1 as a provisional efficiency reference only after power-metering validation.

 

Risk Level

Overall risk remains MODERATE / MONITOR. The principal risks concern evaporator performance, control stability, hydronic events, cycling and diagnostic reliability—not imminent whole-chiller mechanical failure.

• Mechanical Failure Risk: LOW — cooling remains available across all four systems, with no correlated evidence of imminent compressor or major refrigerant-system failure.
• Efficiency Risk: LOW–MODERATE — whole-chiller COP is only approximately 1.5% below expected, although system efficiency differences require matched-condition validation.
• SYS4 Evaporator Risk: MODERATE–HIGH — average and full-load approach exceed expectation, with an ALERT at 100% loading and persistent superheat concerns.
• SYS3 High-Load Risk: MODERATE — simultaneous approach and superheat elevation provides a correlated condition signature requiring investigation.
• SYS2 Control Risk: MODERATE — pronounced 25% approach and superheat variance indicates part-load control instability.
• Hydronic/Operational Risk: MODERATE — severe LCHW and setpoint-error events could result in temporary loss of cooling or comfort if they represent genuine enabled-but-not-cooling operation.
• Condenser Risk: LOW overall — SYS2–SYS4 remain below expected approach benchmarks; SYS1 warrants observation but does not indicate severe degradation.
• Cycling/Wear Risk: MODERATE — approximately 4,000–4,200 starts per system warrant staging and anti-cycle optimisation.
• Data-Integrity Risk: MODERATE — signal and calculation anomalies can generate false alarms or conceal real developing faults.
• Fine-Diagnostic Confidence Risk: MODERATE–HIGH until approach, superheat, saturated-temperature, power-allocation and operating-state calculations are verified.
• Overall Prognosis: Chiller 1 remains serviceable with broadly stable whole-machine performance, but its condition is not uniform across the four refrigeration systems. Current evidence supports targeted condition-based maintenance and control/telemetry optimisation rather than urgent overhaul.
• SYS4 evaporator performance, SYS3 high-load approach/superheat, SYS2 low-load stability and the dated chilled-water excursions should remain the principal watch items.
• Escalation from MONITOR to WARNING should occur if deviations become persistent under equivalent operating conditions and are corroborated across multiple parameters—particularly falling COP, declining cooling capacity, increasing approach, worsening superheat instability, rising input power or repeated failure to maintain LCHW setpoint while compressors are confirmed operating.
• That combined progressive deterioration signature is not currently established.